Merge remote-tracking branch 'origin/upstream'platform-tools-35.0.1sdk-releasebusytown-mac-infra-releasebuild-tools-release

Import b/327672730

31 files changed, 4872 insertions, 0 deletions

diff --git a/Android.bp b/Android.bp
new file mode 100644
index 0000000..e510112
--- /dev/null
+++ b/Android.bp
@@ -0,0 +1,48 @@
+// This file is generated by cargo_embargo.
+// Do not modify this file as changes will be overridden on upgrade.
+
+// TODO: Add license.
+rust_test {
+    name: "dashmap_test_src_lib",
+    host_supported: true,
+    crate_name: "dashmap",
+    cargo_env_compat: true,
+    cargo_pkg_version: "5.5.3",
+    srcs: ["src/lib.rs"],
+    test_suites: ["general-tests"],
+    auto_gen_config: true,
+    test_options: {
+        unit_test: true,
+    },
+    edition: "2018",
+    rustlibs: [
+        "libcfg_if",
+        "libhashbrown",
+        "liblock_api",
+        "libonce_cell",
+        "libparking_lot_core",
+    ],
+}
+
+rust_library {
+    name: "libdashmap",
+    host_supported: true,
+    crate_name: "dashmap",
+    cargo_env_compat: true,
+    cargo_pkg_version: "5.5.3",
+    srcs: ["src/lib.rs"],
+    edition: "2018",
+    rustlibs: [
+        "libcfg_if",
+        "libhashbrown",
+        "liblock_api",
+        "libonce_cell",
+        "libparking_lot_core",
+    ],
+    apex_available: [
+        "//apex_available:platform",
+        "//apex_available:anyapex",
+    ],
+    product_available: true,
+    vendor_available: true,
+}
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..cb7480b
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,73 @@
+# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO
+#
+# When uploading crates to the registry Cargo will automatically
+# "normalize" Cargo.toml files for maximal compatibility
+# with all versions of Cargo and also rewrite `path` dependencies
+# to registry (e.g., crates.io) dependencies.
+#
+# If you are reading this file be aware that the original Cargo.toml
+# will likely look very different (and much more reasonable).
+# See Cargo.toml.orig for the original contents.
+
+[package]
+edition = "2018"
+rust-version = "1.65"
+name = "dashmap"
+version = "5.5.3"
+authors = ["Acrimon <joel.wejdenstal@gmail.com>"]
+description = "Blazing fast concurrent HashMap for Rust."
+homepage = "https://github.com/xacrimon/dashmap"
+documentation = "https://docs.rs/dashmap"
+readme = "README.md"
+keywords = [
+    "atomic",
+    "concurrent",
+    "hashmap",
+]
+categories = [
+    "concurrency",
+    "algorithms",
+    "data-structures",
+]
+license = "MIT"
+repository = "https://github.com/xacrimon/dashmap"
+
+[package.metadata.docs.rs]
+features = [
+    "rayon",
+    "raw-api",
+    "serde",
+]
+
+[dependencies.arbitrary]
+version = "1.3.0"
+optional = true
+
+[dependencies.cfg-if]
+version = "1.0.0"
+
+[dependencies.hashbrown]
+version = "0.14.0"
+default-features = false
+
+[dependencies.lock_api]
+version = "0.4.10"
+
+[dependencies.once_cell]
+version = "1.18.0"
+
+[dependencies.parking_lot_core]
+version = "0.9.8"
+
+[dependencies.rayon]
+version = "1.7.0"
+optional = true
+
+[dependencies.serde]
+version = "1.0.188"
+features = ["derive"]
+optional = true
+
+[features]
+inline = ["hashbrown/inline-more"]
+raw-api = []
diff --git a/Cargo.toml.orig b/Cargo.toml.orig
new file mode 100644
index 0000000..602ea9c
--- /dev/null
+++ b/Cargo.toml.orig
@@ -0,0 +1,31 @@
+[package]
+name = "dashmap"
+version = "5.5.3"
+authors = ["Acrimon <joel.wejdenstal@gmail.com>"]
+edition = "2018"
+rust-version = "1.65"
+license = "MIT"
+repository = "https://github.com/xacrimon/dashmap"
+homepage = "https://github.com/xacrimon/dashmap"
+description = "Blazing fast concurrent HashMap for Rust."
+readme = "README.md"
+documentation = "https://docs.rs/dashmap"
+keywords = ["atomic", "concurrent", "hashmap"]
+categories = ["concurrency", "algorithms", "data-structures"]
+
+[features]
+raw-api = []
+inline = ["hashbrown/inline-more"]
+
+[dependencies]
+lock_api = "0.4.10"
+parking_lot_core = "0.9.8"
+hashbrown = { version = "0.14.0", default-features = false }
+serde = { version = "1.0.188", optional = true, features = ["derive"] }
+cfg-if = "1.0.0"
+rayon = { version = "1.7.0", optional = true }
+once_cell = "1.18.0"
+arbitrary = { version = "1.3.0", optional = true }
+
+[package.metadata.docs.rs]
+features = ["rayon", "raw-api", "serde"]
diff --git a/LICENSE b/LICENSE
new file mode 100644
index 0000000..5a8b9ef
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,21 @@
+MIT License
+
+Copyright (c) 2019 Acrimon
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
diff --git a/METADATA b/METADATA
new file mode 100644
index 0000000..e63fbc9
--- /dev/null
+++ b/METADATA
@@ -0,0 +1,20 @@
+name: "dashmap"
+description: "Blazing fast concurrent HashMap for Rust."
+third_party {
+  identifier {
+    type: "crates.io"
+    value: "dashmap"
+  }
+  identifier {
+    type: "Archive"
+    value: "https://static.crates.io/crates/dashmap/dashmap-5.5.3.crate"
+    primary_source: true
+  }
+  version: "5.5.3"
+  license_type: NOTICE
+  last_upgrade_date {
+    year: 2024
+    month: 3
+    day: 6
+  }
+}
diff --git a/MODULE_LICENSE_MIT b/MODULE_LICENSE_MIT
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/MODULE_LICENSE_MIT
diff --git a/OWNERS b/OWNERS
new file mode 100644
index 0000000..5a2b844
--- /dev/null
+++ b/OWNERS
@@ -0,0 +1 @@
+include platform/prebuilts/rust:main:/OWNERS
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..2eb721e
--- /dev/null
+++ b/README.md
@@ -0,0 +1,67 @@
+# DashMap
+
+Blazingly fast concurrent map in Rust.
+
+DashMap is an implementation of a concurrent associative array/hashmap in Rust.
+
+DashMap tries to implement an easy to use API similar to `std::collections::HashMap`
+with some slight changes to handle concurrency.
+
+DashMap tries to be very simple to use and to be a direct replacement for `RwLock<HashMap<K, V>>`.
+To accomplish these goals, all methods take `&self` instead of modifying methods taking `&mut self`.
+This allows you to put a DashMap in an `Arc<T>` and share it between threads while still being able to modify it.
+
+DashMap puts great effort into performance and aims to be as fast as possible.
+If you have any suggestions or tips do not hesitate to open an issue or a PR.
+
+[![version](https://img.shields.io/crates/v/dashmap)](https://crates.io/crates/dashmap)
+
+[![documentation](https://docs.rs/dashmap/badge.svg)](https://docs.rs/dashmap)
+
+[![downloads](https://img.shields.io/crates/d/dashmap)](https://crates.io/crates/dashmap)
+
+[![minimum rustc version](https://img.shields.io/badge/rustc-1.65-orange.svg)](https://crates.io/crates/dashmap)
+
+## Cargo features
+
+- `serde` - Enables serde support.
+
+- `raw-api` - Enables the unstable raw-shard api.
+
+- `rayon` - Enables rayon support.
+
+- `inline` - Enables `inline-more` feature from the `hashbrown` crate. Can lead to better performance, but with the cost of longer compile-time.
+
+- `arbitrary` - Enables support for the `arbitrary` crate.
+
+## Contributing
+
+DashMap gladly accepts contributions!
+Do not hesitate to open issues or PR's.
+
+I will take a look as soon as I have time for it.
+
+That said I do not get paid (yet) to work on open-source. This means
+that my time is limited and my work here comes after my personal life.
+
+## Performance
+
+A comprehensive benchmark suite including DashMap can be found [here](https://github.com/xacrimon/conc-map-bench).
+
+## Special thanks
+
+- [Jon Gjengset](https://github.com/jonhoo)
+
+- [Yato](https://github.com/RustyYato) 
+
+- [Karl Bergström](https://github.com/kabergstrom)
+
+- [Dylan DPC](https://github.com/Dylan-DPC)
+
+- [Lokathor](https://github.com/Lokathor)
+
+- [namibj](https://github.com/namibj)
+
+## License
+
+This project is licensed under MIT.
diff --git a/cargo_embargo.json b/cargo_embargo.json
new file mode 100644
index 0000000..c8842d1
--- /dev/null
+++ b/cargo_embargo.json
@@ -0,0 +1,4 @@
+{
+  "run_cargo": false,
+  "tests": true
+}
diff --git a/rust-toolchain.toml b/rust-toolchain.toml
new file mode 100644
index 0000000..a32876a
--- /dev/null
+++ b/rust-toolchain.toml
@@ -0,0 +1,4 @@
+[toolchain]
+channel = "1.65"
+components = ["rustfmt", "clippy"]
+profile = "minimal"
diff --git a/src/arbitrary.rs b/src/arbitrary.rs
new file mode 100644
index 0000000..a760964
--- /dev/null
+++ b/src/arbitrary.rs
@@ -0,0 +1,13 @@
+use arbitrary::{Arbitrary, Unstructured};
+use core::hash::BuildHasher;
+
+impl<'a, K, V, S> Arbitrary<'a> for crate::DashMap<K, V, S>
+where
+    K: Eq + std::hash::Hash + Arbitrary<'a>,
+    V: Arbitrary<'a>,
+    S: Default + BuildHasher + Clone,
+{
+    fn arbitrary(u: &mut Unstructured<'a>) -> arbitrary::Result<Self> {
+        u.arbitrary_iter()?.collect()
+    }
+}
diff --git a/src/iter.rs b/src/iter.rs
new file mode 100644
index 0000000..ce50e73
--- /dev/null
+++ b/src/iter.rs
@@ -0,0 +1,315 @@
+use super::mapref::multiple::{RefMulti, RefMutMulti};
+use super::util;
+use crate::lock::{RwLockReadGuard, RwLockWriteGuard};
+use crate::t::Map;
+use crate::util::SharedValue;
+use crate::{DashMap, HashMap};
+use core::hash::{BuildHasher, Hash};
+use core::mem;
+use hashbrown::hash_map;
+use std::collections::hash_map::RandomState;
+use std::sync::Arc;
+
+/// Iterator over a DashMap yielding key value pairs.
+///
+/// # Examples
+///
+/// ```
+/// use dashmap::DashMap;
+///
+/// let map = DashMap::new();
+/// map.insert("hello", "world");
+/// map.insert("alex", "steve");
+/// let pairs: Vec<(&'static str, &'static str)> = map.into_iter().collect();
+/// assert_eq!(pairs.len(), 2);
+/// ```
+pub struct OwningIter<K, V, S = RandomState> {
+    map: DashMap<K, V, S>,
+    shard_i: usize,
+    current: Option<GuardOwningIter<K, V>>,
+}
+
+impl<K: Eq + Hash, V, S: BuildHasher + Clone> OwningIter<K, V, S> {
+    pub(crate) fn new(map: DashMap<K, V, S>) -> Self {
+        Self {
+            map,
+            shard_i: 0,
+            current: None,
+        }
+    }
+}
+
+type GuardOwningIter<K, V> = hash_map::IntoIter<K, SharedValue<V>>;
+
+impl<K: Eq + Hash, V, S: BuildHasher + Clone> Iterator for OwningIter<K, V, S> {
+    type Item = (K, V);
+
+    fn next(&mut self) -> Option<Self::Item> {
+        loop {
+            if let Some(current) = self.current.as_mut() {
+                if let Some((k, v)) = current.next() {
+                    return Some((k, v.into_inner()));
+                }
+            }
+
+            if self.shard_i == self.map._shard_count() {
+                return None;
+            }
+
+            //let guard = unsafe { self.map._yield_read_shard(self.shard_i) };
+            let mut shard_wl = unsafe { self.map._yield_write_shard(self.shard_i) };
+
+            let hasher = self.map._hasher();
+
+            let map = mem::replace(&mut *shard_wl, HashMap::with_hasher(hasher));
+
+            drop(shard_wl);
+
+            let iter = map.into_iter();
+
+            //unsafe { ptr::write(&mut self.current, Some((arcee, iter))); }
+            self.current = Some(iter);
+
+            self.shard_i += 1;
+        }
+    }
+}
+
+unsafe impl<K, V, S> Send for OwningIter<K, V, S>
+where
+    K: Eq + Hash + Send,
+    V: Send,
+    S: BuildHasher + Clone + Send,
+{
+}
+
+unsafe impl<K, V, S> Sync for OwningIter<K, V, S>
+where
+    K: Eq + Hash + Sync,
+    V: Sync,
+    S: BuildHasher + Clone + Sync,
+{
+}
+
+type GuardIter<'a, K, V, S> = (
+    Arc<RwLockReadGuard<'a, HashMap<K, V, S>>>,
+    hash_map::Iter<'a, K, SharedValue<V>>,
+);
+
+type GuardIterMut<'a, K, V, S> = (
+    Arc<RwLockWriteGuard<'a, HashMap<K, V, S>>>,
+    hash_map::IterMut<'a, K, SharedValue<V>>,
+);
+
+/// Iterator over a DashMap yielding immutable references.
+///
+/// # Examples
+///
+/// ```
+/// use dashmap::DashMap;
+///
+/// let map = DashMap::new();
+/// map.insert("hello", "world");
+/// assert_eq!(map.iter().count(), 1);
+/// ```
+pub struct Iter<'a, K, V, S = RandomState, M = DashMap<K, V, S>> {
+    map: &'a M,
+    shard_i: usize,
+    current: Option<GuardIter<'a, K, V, S>>,
+}
+
+impl<'i, K: Clone + Hash + Eq, V: Clone, S: Clone + BuildHasher> Clone for Iter<'i, K, V, S> {
+    fn clone(&self) -> Self {
+        Iter::new(self.map)
+    }
+}
+
+unsafe impl<'a, 'i, K, V, S, M> Send for Iter<'i, K, V, S, M>
+where
+    K: 'a + Eq + Hash + Send,
+    V: 'a + Send,
+    S: 'a + BuildHasher + Clone,
+    M: Map<'a, K, V, S>,
+{
+}
+
+unsafe impl<'a, 'i, K, V, S, M> Sync for Iter<'i, K, V, S, M>
+where
+    K: 'a + Eq + Hash + Sync,
+    V: 'a + Sync,
+    S: 'a + BuildHasher + Clone,
+    M: Map<'a, K, V, S>,
+{
+}
+
+impl<'a, K: Eq + Hash, V, S: 'a + BuildHasher + Clone, M: Map<'a, K, V, S>> Iter<'a, K, V, S, M> {
+    pub(crate) fn new(map: &'a M) -> Self {
+        Self {
+            map,
+            shard_i: 0,
+            current: None,
+        }
+    }
+}
+
+impl<'a, K: Eq + Hash, V, S: 'a + BuildHasher + Clone, M: Map<'a, K, V, S>> Iterator
+    for Iter<'a, K, V, S, M>
+{
+    type Item = RefMulti<'a, K, V, S>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        loop {
+            if let Some(current) = self.current.as_mut() {
+                if let Some((k, v)) = current.1.next() {
+                    let guard = current.0.clone();
+
+                    return unsafe { Some(RefMulti::new(guard, k, v.get())) };
+                }
+            }
+
+            if self.shard_i == self.map._shard_count() {
+                return None;
+            }
+
+            let guard = unsafe { self.map._yield_read_shard(self.shard_i) };
+
+            let sref: &HashMap<K, V, S> = unsafe { util::change_lifetime_const(&*guard) };
+
+            let iter = sref.iter();
+
+            self.current = Some((Arc::new(guard), iter));
+
+            self.shard_i += 1;
+        }
+    }
+}
+
+/// Iterator over a DashMap yielding mutable references.
+///
+/// # Examples
+///
+/// ```
+/// use dashmap::DashMap;
+///
+/// let map = DashMap::new();
+/// map.insert("Johnny", 21);
+/// map.iter_mut().for_each(|mut r| *r += 1);
+/// assert_eq!(*map.get("Johnny").unwrap(), 22);
+/// ```
+pub struct IterMut<'a, K, V, S = RandomState, M = DashMap<K, V, S>> {
+    map: &'a M,
+    shard_i: usize,
+    current: Option<GuardIterMut<'a, K, V, S>>,
+}
+
+unsafe impl<'a, 'i, K, V, S, M> Send for IterMut<'i, K, V, S, M>
+where
+    K: 'a + Eq + Hash + Send,
+    V: 'a + Send,
+    S: 'a + BuildHasher + Clone,
+    M: Map<'a, K, V, S>,
+{
+}
+
+unsafe impl<'a, 'i, K, V, S, M> Sync for IterMut<'i, K, V, S, M>
+where
+    K: 'a + Eq + Hash + Sync,
+    V: 'a + Sync,
+    S: 'a + BuildHasher + Clone,
+    M: Map<'a, K, V, S>,
+{
+}
+
+impl<'a, K: Eq + Hash, V, S: 'a + BuildHasher + Clone, M: Map<'a, K, V, S>>
+    IterMut<'a, K, V, S, M>
+{
+    pub(crate) fn new(map: &'a M) -> Self {
+        Self {
+            map,
+            shard_i: 0,
+            current: None,
+        }
+    }
+}
+
+impl<'a, K: Eq + Hash, V, S: 'a + BuildHasher + Clone, M: Map<'a, K, V, S>> Iterator
+    for IterMut<'a, K, V, S, M>
+{
+    type Item = RefMutMulti<'a, K, V, S>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        loop {
+            if let Some(current) = self.current.as_mut() {
+                if let Some((k, v)) = current.1.next() {
+                    let guard = current.0.clone();
+
+                    unsafe {
+                        let k = util::change_lifetime_const(k);
+
+                        let v = &mut *v.as_ptr();
+
+                        return Some(RefMutMulti::new(guard, k, v));
+                    }
+                }
+            }
+
+            if self.shard_i == self.map._shard_count() {
+                return None;
+            }
+
+            let mut guard = unsafe { self.map._yield_write_shard(self.shard_i) };
+
+            let sref: &mut HashMap<K, V, S> = unsafe { util::change_lifetime_mut(&mut *guard) };
+
+            let iter = sref.iter_mut();
+
+            self.current = Some((Arc::new(guard), iter));
+
+            self.shard_i += 1;
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::DashMap;
+
+    #[test]
+    fn iter_mut_manual_count() {
+        let map = DashMap::new();
+
+        map.insert("Johnny", 21);
+
+        assert_eq!(map.len(), 1);
+
+        let mut c = 0;
+
+        for shard in map.shards() {
+            c += shard.write().iter_mut().count();
+        }
+
+        assert_eq!(c, 1);
+    }
+
+    #[test]
+    fn iter_mut_count() {
+        let map = DashMap::new();
+
+        map.insert("Johnny", 21);
+
+        assert_eq!(map.len(), 1);
+
+        assert_eq!(map.iter_mut().count(), 1);
+    }
+
+    #[test]
+    fn iter_count() {
+        let map = DashMap::new();
+
+        map.insert("Johnny", 21);
+
+        assert_eq!(map.len(), 1);
+
+        assert_eq!(map.iter().count(), 1);
+    }
+}
diff --git a/src/iter_set.rs b/src/iter_set.rs
new file mode 100644
index 0000000..619a5b5
--- /dev/null
+++ b/src/iter_set.rs
@@ -0,0 +1,71 @@
+use crate::setref::multiple::RefMulti;
+use crate::t::Map;
+use core::hash::{BuildHasher, Hash};
+
+pub struct OwningIter<K, S> {
+    inner: crate::iter::OwningIter<K, (), S>,
+}
+
+impl<K: Eq + Hash, S: BuildHasher + Clone> OwningIter<K, S> {
+    pub(crate) fn new(inner: crate::iter::OwningIter<K, (), S>) -> Self {
+        Self { inner }
+    }
+}
+
+impl<K: Eq + Hash, S: BuildHasher + Clone> Iterator for OwningIter<K, S> {
+    type Item = K;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.inner.next().map(|(k, _)| k)
+    }
+}
+
+unsafe impl<K, S> Send for OwningIter<K, S>
+where
+    K: Eq + Hash + Send,
+    S: BuildHasher + Clone + Send,
+{
+}
+
+unsafe impl<K, S> Sync for OwningIter<K, S>
+where
+    K: Eq + Hash + Sync,
+    S: BuildHasher + Clone + Sync,
+{
+}
+
+pub struct Iter<'a, K, S, M> {
+    inner: crate::iter::Iter<'a, K, (), S, M>,
+}
+
+unsafe impl<'a, 'i, K, S, M> Send for Iter<'i, K, S, M>
+where
+    K: 'a + Eq + Hash + Send,
+    S: 'a + BuildHasher + Clone,
+    M: Map<'a, K, (), S>,
+{
+}
+
+unsafe impl<'a, 'i, K, S, M> Sync for Iter<'i, K, S, M>
+where
+    K: 'a + Eq + Hash + Sync,
+    S: 'a + BuildHasher + Clone,
+    M: Map<'a, K, (), S>,
+{
+}
+
+impl<'a, K: Eq + Hash, S: 'a + BuildHasher + Clone, M: Map<'a, K, (), S>> Iter<'a, K, S, M> {
+    pub(crate) fn new(inner: crate::iter::Iter<'a, K, (), S, M>) -> Self {
+        Self { inner }
+    }
+}
+
+impl<'a, K: Eq + Hash, S: 'a + BuildHasher + Clone, M: Map<'a, K, (), S>> Iterator
+    for Iter<'a, K, S, M>
+{
+    type Item = RefMulti<'a, K, S>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.inner.next().map(RefMulti::new)
+    }
+}
diff --git a/src/lib.rs b/src/lib.rs
new file mode 100644
index 0000000..34e5d8b
--- /dev/null
+++ b/src/lib.rs
@@ -0,0 +1,1465 @@
+#![allow(clippy::type_complexity)]
+
+#[cfg(feature = "arbitrary")]
+mod arbitrary;
+pub mod iter;
+pub mod iter_set;
+mod lock;
+pub mod mapref;
+mod read_only;
+#[cfg(feature = "serde")]
+mod serde;
+mod set;
+pub mod setref;
+mod t;
+pub mod try_result;
+mod util;
+
+#[cfg(feature = "rayon")]
+pub mod rayon {
+    pub mod map;
+    pub mod read_only;
+    pub mod set;
+}
+
+#[cfg(not(feature = "raw-api"))]
+use crate::lock::{RwLock, RwLockReadGuard, RwLockWriteGuard};
+
+#[cfg(feature = "raw-api")]
+pub use crate::lock::{RawRwLock, RwLock, RwLockReadGuard, RwLockWriteGuard};
+
+use cfg_if::cfg_if;
+use core::borrow::Borrow;
+use core::fmt;
+use core::hash::{BuildHasher, Hash, Hasher};
+use core::iter::FromIterator;
+use core::ops::{BitAnd, BitOr, Shl, Shr, Sub};
+use iter::{Iter, IterMut, OwningIter};
+use mapref::entry::{Entry, OccupiedEntry, VacantEntry};
+use mapref::multiple::RefMulti;
+use mapref::one::{Ref, RefMut};
+use once_cell::sync::OnceCell;
+pub use read_only::ReadOnlyView;
+pub use set::DashSet;
+use std::collections::hash_map::RandomState;
+pub use t::Map;
+use try_result::TryResult;
+
+cfg_if! {
+    if #[cfg(feature = "raw-api")] {
+        pub use util::SharedValue;
+    } else {
+        use util::SharedValue;
+    }
+}
+
+pub(crate) type HashMap<K, V, S> = hashbrown::HashMap<K, SharedValue<V>, S>;
+
+// Temporary reimplementation of [`std::collections::TryReserveError`]
+// util [`std::collections::TryReserveError`] stabilises.
+// We cannot easily create `std::collections` error type from `hashbrown` error type
+// without access to `TryReserveError::kind` method.
+#[non_exhaustive]
+#[derive(Clone, PartialEq, Eq, Debug)]
+pub struct TryReserveError {}
+
+fn default_shard_amount() -> usize {
+    static DEFAULT_SHARD_AMOUNT: OnceCell<usize> = OnceCell::new();
+    *DEFAULT_SHARD_AMOUNT.get_or_init(|| {
+        (std::thread::available_parallelism().map_or(1, usize::from) * 4).next_power_of_two()
+    })
+}
+
+fn ncb(shard_amount: usize) -> usize {
+    shard_amount.trailing_zeros() as usize
+}
+
+/// DashMap is an implementation of a concurrent associative array/hashmap in Rust.
+///
+/// DashMap tries to implement an easy to use API similar to `std::collections::HashMap`
+/// with some slight changes to handle concurrency.
+///
+/// DashMap tries to be very simple to use and to be a direct replacement for `RwLock<HashMap<K, V, S>>`.
+/// To accomplish this, all methods take `&self` instead of modifying methods taking `&mut self`.
+/// This allows you to put a DashMap in an `Arc<T>` and share it between threads while being able to modify it.
+///
+/// Documentation mentioning locking behaviour acts in the reference frame of the calling thread.
+/// This means that it is safe to ignore it across multiple threads.
+pub struct DashMap<K, V, S = RandomState> {
+    shift: usize,
+    shards: Box<[RwLock<HashMap<K, V, S>>]>,
+    hasher: S,
+}
+
+impl<K: Eq + Hash + Clone, V: Clone, S: Clone> Clone for DashMap<K, V, S> {
+    fn clone(&self) -> Self {
+        let mut inner_shards = Vec::new();
+
+        for shard in self.shards.iter() {
+            let shard = shard.read();
+
+            inner_shards.push(RwLock::new((*shard).clone()));
+        }
+
+        Self {
+            shift: self.shift,
+            shards: inner_shards.into_boxed_slice(),
+            hasher: self.hasher.clone(),
+        }
+    }
+}
+
+impl<K, V, S> Default for DashMap<K, V, S>
+where
+    K: Eq + Hash,
+    S: Default + BuildHasher + Clone,
+{
+    fn default() -> Self {
+        Self::with_hasher(Default::default())
+    }
+}
+
+impl<'a, K: 'a + Eq + Hash, V: 'a> DashMap<K, V, RandomState> {
+    /// Creates a new DashMap with a capacity of 0.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashMap;
+    ///
+    /// let reviews = DashMap::new();
+    /// reviews.insert("Veloren", "What a fantastic game!");
+    /// ```
+    pub fn new() -> Self {
+        DashMap::with_hasher(RandomState::default())
+    }
+
+    /// Creates a new DashMap with a specified starting capacity.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashMap;
+    ///
+    /// let mappings = DashMap::with_capacity(2);
+    /// mappings.insert(2, 4);
+    /// mappings.insert(8, 16);
+    /// ```
+    pub fn with_capacity(capacity: usize) -> Self {
+        DashMap::with_capacity_and_hasher(capacity, RandomState::default())
+    }
+
+    /// Creates a new DashMap with a specified shard amount
+    ///
+    /// shard_amount should greater than 0 and be a power of two.
+    /// If a shard_amount which is not a power of two is provided, the function will panic.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashMap;
+    ///
+    /// let mappings = DashMap::with_shard_amount(32);
+    /// mappings.insert(2, 4);
+    /// mappings.insert(8, 16);
+    /// ```
+    pub fn with_shard_amount(shard_amount: usize) -> Self {
+        Self::with_capacity_and_hasher_and_shard_amount(0, RandomState::default(), shard_amount)
+    }
+
+    /// Creates a new DashMap with a specified capacity and shard amount.
+    ///
+    /// shard_amount should greater than 0 and be a power of two.
+    /// If a shard_amount which is not a power of two is provided, the function will panic.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashMap;
+    ///
+    /// let mappings = DashMap::with_capacity_and_shard_amount(32, 32);
+    /// mappings.insert(2, 4);
+    /// mappings.insert(8, 16);
+    /// ```
+    pub fn with_capacity_and_shard_amount(capacity: usize, shard_amount: usize) -> Self {
+        Self::with_capacity_and_hasher_and_shard_amount(
+            capacity,
+            RandomState::default(),
+            shard_amount,
+        )
+    }
+}
+
+impl<'a, K: 'a + Eq + Hash, V: 'a, S: BuildHasher + Clone> DashMap<K, V, S> {
+    /// Wraps this `DashMap` into a read-only view. This view allows to obtain raw references to the stored values.
+    pub fn into_read_only(self) -> ReadOnlyView<K, V, S> {
+        ReadOnlyView::new(self)
+    }
+
+    /// Creates a new DashMap with a capacity of 0 and the provided hasher.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashMap;
+    /// use std::collections::hash_map::RandomState;
+    ///
+    /// let s = RandomState::new();
+    /// let reviews = DashMap::with_hasher(s);
+    /// reviews.insert("Veloren", "What a fantastic game!");
+    /// ```
+    pub fn with_hasher(hasher: S) -> Self {
+        Self::with_capacity_and_hasher(0, hasher)
+    }
+
+    /// Creates a new DashMap with a specified starting capacity and hasher.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashMap;
+    /// use std::collections::hash_map::RandomState;
+    ///
+    /// let s = RandomState::new();
+    /// let mappings = DashMap::with_capacity_and_hasher(2, s);
+    /// mappings.insert(2, 4);
+    /// mappings.insert(8, 16);
+    /// ```
+    pub fn with_capacity_and_hasher(capacity: usize, hasher: S) -> Self {
+        Self::with_capacity_and_hasher_and_shard_amount(capacity, hasher, default_shard_amount())
+    }
+
+    /// Creates a new DashMap with a specified hasher and shard amount
+    ///
+    /// shard_amount should be greater than 0 and a power of two.
+    /// If a shard_amount which is not a power of two is provided, the function will panic.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashMap;
+    /// use std::collections::hash_map::RandomState;
+    ///
+    /// let s = RandomState::new();
+    /// let mappings = DashMap::with_hasher_and_shard_amount(s, 32);
+    /// mappings.insert(2, 4);
+    /// mappings.insert(8, 16);
+    /// ```
+    pub fn with_hasher_and_shard_amount(hasher: S, shard_amount: usize) -> Self {
+        Self::with_capacity_and_hasher_and_shard_amount(0, hasher, shard_amount)
+    }
+
+    /// Creates a new DashMap with a specified starting capacity, hasher and shard_amount.
+    ///
+    /// shard_amount should greater than 0 and be a power of two.
+    /// If a shard_amount which is not a power of two is provided, the function will panic.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashMap;
+    /// use std::collections::hash_map::RandomState;
+    ///
+    /// let s = RandomState::new();
+    /// let mappings = DashMap::with_capacity_and_hasher_and_shard_amount(2, s, 32);
+    /// mappings.insert(2, 4);
+    /// mappings.insert(8, 16);
+    /// ```
+    pub fn with_capacity_and_hasher_and_shard_amount(
+        mut capacity: usize,
+        hasher: S,
+        shard_amount: usize,
+    ) -> Self {
+        assert!(shard_amount > 1);
+        assert!(shard_amount.is_power_of_two());
+
+        let shift = util::ptr_size_bits() - ncb(shard_amount);
+
+        if capacity != 0 {
+            capacity = (capacity + (shard_amount - 1)) & !(shard_amount - 1);
+        }
+
+        let cps = capacity / shard_amount;
+
+        let shards = (0..shard_amount)
+            .map(|_| RwLock::new(HashMap::with_capacity_and_hasher(cps, hasher.clone())))
+            .collect();
+
+        Self {
+            shift,
+            shards,
+            hasher,
+        }
+    }
+
+    /// Hash a given item to produce a usize.
+    /// Uses the provided or default HashBuilder.
+    pub fn hash_usize<T: Hash>(&self, item: &T) -> usize {
+        let mut hasher = self.hasher.build_hasher();
+
+        item.hash(&mut hasher);
+
+        hasher.finish() as usize
+    }
+
+    cfg_if! {
+        if #[cfg(feature = "raw-api")] {
+            /// Allows you to peek at the inner shards that store your data.
+            /// You should probably not use this unless you know what you are doing.
+            ///
+            /// Requires the `raw-api` feature to be enabled.
+            ///
+            /// # Examples
+            ///
+            /// ```
+            /// use dashmap::DashMap;
+            ///
+            /// let map = DashMap::<(), ()>::new();
+            /// println!("Amount of shards: {}", map.shards().len());
+            /// ```
+            pub fn shards(&self) -> &[RwLock<HashMap<K, V, S>>] {
+                &self.shards
+            }
+
+            /// Provides mutable access to the inner shards that store your data.
+            /// You should probably not use this unless you know what you are doing.
+            ///
+            /// Requires the `raw-api` feature to be enabled.
+            ///
+            /// # Examples
+            ///
+            /// ```
+            /// use dashmap::DashMap;
+            /// use dashmap::SharedValue;
+            ///
+            /// let mut map = DashMap::<i32, &'static str>::new();
+            /// let shard_ind = map.determine_map(&42);
+            /// map.shards_mut()[shard_ind].get_mut().insert(42, SharedValue::new("forty two"));
+            /// assert_eq!(*map.get(&42).unwrap(), "forty two");
+            /// ```
+            pub fn shards_mut(&mut self) -> &mut [RwLock<HashMap<K, V, S>>] {
+                &mut self.shards
+            }
+
+            /// Consumes this `DashMap` and returns the inner shards.
+            /// You should probably not use this unless you know what you are doing.
+            ///
+            /// Requires the `raw-api` feature to be enabled.
+            ///
+            /// See [`DashMap::shards()`] and [`DashMap::shards_mut()`] for more information.
+            pub fn into_shards(self) -> Box<[RwLock<HashMap<K, V, S>>]> {
+                self.shards
+            }
+        } else {
+            #[allow(dead_code)]
+            pub(crate) fn shards(&self) -> &[RwLock<HashMap<K, V, S>>] {
+                &self.shards
+            }
+
+            #[allow(dead_code)]
+            pub(crate) fn shards_mut(&mut self) -> &mut [RwLock<HashMap<K, V, S>>] {
+                &mut self.shards
+            }
+
+            #[allow(dead_code)]
+            pub(crate) fn into_shards(self) -> Box<[RwLock<HashMap<K, V, S>>]> {
+                self.shards
+            }
+        }
+    }
+
+    cfg_if! {
+        if #[cfg(feature = "raw-api")] {
+            /// Finds which shard a certain key is stored in.
+            /// You should probably not use this unless you know what you are doing.
+            /// Note that shard selection is dependent on the default or provided HashBuilder.
+            ///
+            /// Requires the `raw-api` feature to be enabled.
+            ///
+            /// # Examples
+            ///
+            /// ```
+            /// use dashmap::DashMap;
+            ///
+            /// let map = DashMap::new();
+            /// map.insert("coca-cola", 1.4);
+            /// println!("coca-cola is stored in shard: {}", map.determine_map("coca-cola"));
+            /// ```
+            pub fn determine_map<Q>(&self, key: &Q) -> usize
+            where
+                K: Borrow<Q>,
+                Q: Hash + Eq + ?Sized,
+            {
+                let hash = self.hash_usize(&key);
+                self.determine_shard(hash)
+            }
+        }
+    }
+
+    cfg_if! {
+        if #[cfg(feature = "raw-api")] {
+            /// Finds which shard a certain hash is stored in.
+            ///
+            /// Requires the `raw-api` feature to be enabled.
+            ///
+            /// # Examples
+            ///
+            /// ```
+            /// use dashmap::DashMap;
+            ///
+            /// let map: DashMap<i32, i32> = DashMap::new();
+            /// let key = "key";
+            /// let hash = map.hash_usize(&key);
+            /// println!("hash is stored in shard: {}", map.determine_shard(hash));
+            /// ```
+            pub fn determine_shard(&self, hash: usize) -> usize {
+                // Leave the high 7 bits for the HashBrown SIMD tag.
+                (hash << 7) >> self.shift
+            }
+        } else {
+
+            pub(crate) fn determine_shard(&self, hash: usize) -> usize {
+                // Leave the high 7 bits for the HashBrown SIMD tag.
+                (hash << 7) >> self.shift
+            }
+        }
+    }
+
+    /// Returns a reference to the map's [`BuildHasher`].
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// use dashmap::DashMap;
+    /// use std::collections::hash_map::RandomState;
+    ///
+    /// let hasher = RandomState::new();
+    /// let map: DashMap<i32, i32> = DashMap::new();
+    /// let hasher: &RandomState = map.hasher();
+    /// ```
+    ///
+    /// [`BuildHasher`]: https://doc.rust-lang.org/std/hash/trait.BuildHasher.html
+    pub fn hasher(&self) -> &S {
+        &self.hasher
+    }
+
+    /// Inserts a key and a value into the map. Returns the old value associated with the key if there was one.
+    ///
+    /// **Locking behaviour:** May deadlock if called when holding any sort of reference into the map.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashMap;
+    ///
+    /// let map = DashMap::new();
+    /// map.insert("I am the key!", "And I am the value!");
+    /// ```
+    pub fn insert(&self, key: K, value: V) -> Option<V> {
+        self._insert(key, value)
+    }
+
+    /// Removes an entry from the map, returning the key and value if they existed in the map.
+    ///
+    /// **Locking behaviour:** May deadlock if called when holding any sort of reference into the map.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashMap;
+    ///
+    /// let soccer_team = DashMap::new();
+    /// soccer_team.insert("Jack", "Goalie");
+    /// assert_eq!(soccer_team.remove("Jack").unwrap().1, "Goalie");
+    /// ```
+    pub fn remove<Q>(&self, key: &Q) -> Option<(K, V)>
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized,
+    {
+        self._remove(key)
+    }
+
+    /// Removes an entry from the map, returning the key and value
+    /// if the entry existed and the provided conditional function returned true.
+    ///
+    /// **Locking behaviour:** May deadlock if called when holding any sort of reference into the map.
+    ///
+    /// ```
+    /// use dashmap::DashMap;
+    ///
+    /// let soccer_team = DashMap::new();
+    /// soccer_team.insert("Sam", "Forward");
+    /// soccer_team.remove_if("Sam", |_, position| position == &"Goalie");
+    /// assert!(soccer_team.contains_key("Sam"));
+    /// ```
+    /// ```
+    /// use dashmap::DashMap;
+    ///
+    /// let soccer_team = DashMap::new();
+    /// soccer_team.insert("Sam", "Forward");
+    /// soccer_team.remove_if("Sam", |_, position| position == &"Forward");
+    /// assert!(!soccer_team.contains_key("Sam"));
+    /// ```
+    pub fn remove_if<Q>(&self, key: &Q, f: impl FnOnce(&K, &V) -> bool) -> Option<(K, V)>
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized,
+    {
+        self._remove_if(key, f)
+    }
+
+    pub fn remove_if_mut<Q>(&self, key: &Q, f: impl FnOnce(&K, &mut V) -> bool) -> Option<(K, V)>
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized,
+    {
+        self._remove_if_mut(key, f)
+    }
+
+    /// Creates an iterator over a DashMap yielding immutable references.
+    ///
+    /// **Locking behaviour:** May deadlock if called when holding a mutable reference into the map.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashMap;
+    ///
+    /// let words = DashMap::new();
+    /// words.insert("hello", "world");
+    /// assert_eq!(words.iter().count(), 1);
+    /// ```
+    pub fn iter(&'a self) -> Iter<'a, K, V, S, DashMap<K, V, S>> {
+        self._iter()
+    }
+
+    /// Iterator over a DashMap yielding mutable references.
+    ///
+    /// **Locking behaviour:** May deadlock if called when holding any sort of reference into the map.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashMap;
+    ///
+    /// let map = DashMap::new();
+    /// map.insert("Johnny", 21);
+    /// map.iter_mut().for_each(|mut r| *r += 1);
+    /// assert_eq!(*map.get("Johnny").unwrap(), 22);
+    /// ```
+    pub fn iter_mut(&'a self) -> IterMut<'a, K, V, S, DashMap<K, V, S>> {
+        self._iter_mut()
+    }
+
+    /// Get an immutable reference to an entry in the map
+    ///
+    /// **Locking behaviour:** May deadlock if called when holding a mutable reference into the map.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashMap;
+    ///
+    /// let youtubers = DashMap::new();
+    /// youtubers.insert("Bosnian Bill", 457000);
+    /// assert_eq!(*youtubers.get("Bosnian Bill").unwrap(), 457000);
+    /// ```
+    pub fn get<Q>(&'a self, key: &Q) -> Option<Ref<'a, K, V, S>>
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized,
+    {
+        self._get(key)
+    }
+
+    /// Get a mutable reference to an entry in the map
+    ///
+    /// **Locking behaviour:** May deadlock if called when holding any sort of reference into the map.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashMap;
+    ///
+    /// let class = DashMap::new();
+    /// class.insert("Albin", 15);
+    /// *class.get_mut("Albin").unwrap() -= 1;
+    /// assert_eq!(*class.get("Albin").unwrap(), 14);
+    /// ```
+    pub fn get_mut<Q>(&'a self, key: &Q) -> Option<RefMut<'a, K, V, S>>
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized,
+    {
+        self._get_mut(key)
+    }
+
+    /// Get an immutable reference to an entry in the map, if the shard is not locked.
+    /// If the shard is locked, the function will return [TryResult::Locked].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashMap;
+    /// use dashmap::try_result::TryResult;
+    ///
+    /// let map = DashMap::new();
+    /// map.insert("Johnny", 21);
+    ///
+    /// assert_eq!(*map.try_get("Johnny").unwrap(), 21);
+    ///
+    /// let _result1_locking = map.get_mut("Johnny");
+    ///
+    /// let result2 = map.try_get("Johnny");
+    /// assert!(result2.is_locked());
+    /// ```
+    pub fn try_get<Q>(&'a self, key: &Q) -> TryResult<Ref<'a, K, V, S>>
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized,
+    {
+        self._try_get(key)
+    }
+
+    /// Get a mutable reference to an entry in the map, if the shard is not locked.
+    /// If the shard is locked, the function will return [TryResult::Locked].
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashMap;
+    /// use dashmap::try_result::TryResult;
+    ///
+    /// let map = DashMap::new();
+    /// map.insert("Johnny", 21);
+    ///
+    /// *map.try_get_mut("Johnny").unwrap() += 1;
+    /// assert_eq!(*map.get("Johnny").unwrap(), 22);
+    ///
+    /// let _result1_locking = map.get("Johnny");
+    ///
+    /// let result2 = map.try_get_mut("Johnny");
+    /// assert!(result2.is_locked());
+    /// ```
+    pub fn try_get_mut<Q>(&'a self, key: &Q) -> TryResult<RefMut<'a, K, V, S>>
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized,
+    {
+        self._try_get_mut(key)
+    }
+
+    /// Remove excess capacity to reduce memory usage.
+    ///
+    /// **Locking behaviour:** May deadlock if called when holding any sort of reference into the map.
+    pub fn shrink_to_fit(&self) {
+        self._shrink_to_fit();
+    }
+
+    /// Retain elements that whose predicates return true
+    /// and discard elements whose predicates return false.
+    ///
+    /// **Locking behaviour:** May deadlock if called when holding any sort of reference into the map.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashMap;
+    ///
+    /// let people = DashMap::new();
+    /// people.insert("Albin", 15);
+    /// people.insert("Jones", 22);
+    /// people.insert("Charlie", 27);
+    /// people.retain(|_, v| *v > 20);
+    /// assert_eq!(people.len(), 2);
+    /// ```
+    pub fn retain(&self, f: impl FnMut(&K, &mut V) -> bool) {
+        self._retain(f);
+    }
+
+    /// Fetches the total number of key-value pairs stored in the map.
+    ///
+    /// **Locking behaviour:** May deadlock if called when holding a mutable reference into the map.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashMap;
+    ///
+    /// let people = DashMap::new();
+    /// people.insert("Albin", 15);
+    /// people.insert("Jones", 22);
+    /// people.insert("Charlie", 27);
+    /// assert_eq!(people.len(), 3);
+    /// ```
+    pub fn len(&self) -> usize {
+        self._len()
+    }
+
+    /// Checks if the map is empty or not.
+    ///
+    /// **Locking behaviour:** May deadlock if called when holding a mutable reference into the map.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashMap;
+    ///
+    /// let map = DashMap::<(), ()>::new();
+    /// assert!(map.is_empty());
+    /// ```
+    pub fn is_empty(&self) -> bool {
+        self._is_empty()
+    }
+
+    /// Removes all key-value pairs in the map.
+    ///
+    /// **Locking behaviour:** May deadlock if called when holding any sort of reference into the map.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashMap;
+    ///
+    /// let stats = DashMap::new();
+    /// stats.insert("Goals", 4);
+    /// assert!(!stats.is_empty());
+    /// stats.clear();
+    /// assert!(stats.is_empty());
+    /// ```
+    pub fn clear(&self) {
+        self._clear();
+    }
+
+    /// Returns how many key-value pairs the map can store without reallocating.
+    ///
+    /// **Locking behaviour:** May deadlock if called when holding a mutable reference into the map.
+    pub fn capacity(&self) -> usize {
+        self._capacity()
+    }
+
+    /// Modify a specific value according to a function.
+    ///
+    /// **Locking behaviour:** May deadlock if called when holding any sort of reference into the map.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashMap;
+    ///
+    /// let stats = DashMap::new();
+    /// stats.insert("Goals", 4);
+    /// stats.alter("Goals", |_, v| v * 2);
+    /// assert_eq!(*stats.get("Goals").unwrap(), 8);
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// If the given closure panics, then `alter` will abort the process
+    pub fn alter<Q>(&self, key: &Q, f: impl FnOnce(&K, V) -> V)
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized,
+    {
+        self._alter(key, f);
+    }
+
+    /// Modify every value in the map according to a function.
+    ///
+    /// **Locking behaviour:** May deadlock if called when holding any sort of reference into the map.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashMap;
+    ///
+    /// let stats = DashMap::new();
+    /// stats.insert("Wins", 4);
+    /// stats.insert("Losses", 2);
+    /// stats.alter_all(|_, v| v + 1);
+    /// assert_eq!(*stats.get("Wins").unwrap(), 5);
+    /// assert_eq!(*stats.get("Losses").unwrap(), 3);
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// If the given closure panics, then `alter_all` will abort the process
+    pub fn alter_all(&self, f: impl FnMut(&K, V) -> V) {
+        self._alter_all(f);
+    }
+
+    /// Scoped access into an item of the map according to a function.
+    ///
+    /// **Locking behaviour:** May deadlock if called when holding any sort of reference into the map.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashMap;
+    ///
+    /// let warehouse = DashMap::new();
+    /// warehouse.insert(4267, ("Banana", 100));
+    /// warehouse.insert(2359, ("Pear", 120));
+    /// let fruit = warehouse.view(&4267, |_k, v| *v);
+    /// assert_eq!(fruit, Some(("Banana", 100)));
+    /// ```
+    ///
+    /// # Panics
+    ///
+    /// If the given closure panics, then `view` will abort the process
+    pub fn view<Q, R>(&self, key: &Q, f: impl FnOnce(&K, &V) -> R) -> Option<R>
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized,
+    {
+        self._view(key, f)
+    }
+
+    /// Checks if the map contains a specific key.
+    ///
+    /// **Locking behaviour:** May deadlock if called when holding a mutable reference into the map.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashMap;
+    ///
+    /// let team_sizes = DashMap::new();
+    /// team_sizes.insert("Dakota Cherries", 23);
+    /// assert!(team_sizes.contains_key("Dakota Cherries"));
+    /// ```
+    pub fn contains_key<Q>(&self, key: &Q) -> bool
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized,
+    {
+        self._contains_key(key)
+    }
+
+    /// Advanced entry API that tries to mimic `std::collections::HashMap`.
+    /// See the documentation on `dashmap::mapref::entry` for more details.
+    ///
+    /// **Locking behaviour:** May deadlock if called when holding any sort of reference into the map.
+    pub fn entry(&'a self, key: K) -> Entry<'a, K, V, S> {
+        self._entry(key)
+    }
+
+    /// Advanced entry API that tries to mimic `std::collections::HashMap`.
+    /// See the documentation on `dashmap::mapref::entry` for more details.
+    ///
+    /// Returns None if the shard is currently locked.
+    pub fn try_entry(&'a self, key: K) -> Option<Entry<'a, K, V, S>> {
+        self._try_entry(key)
+    }
+
+    /// Advanced entry API that tries to mimic `std::collections::HashMap::try_reserve`.
+    /// Tries to reserve capacity for at least `shard * additional`
+    /// and may reserve more space to avoid frequent reallocations.
+    ///
+    /// # Errors
+    ///
+    /// If the capacity overflows, or the allocator reports a failure, then an error is returned.
+    // TODO: return std::collections::TryReserveError once std::collections::TryReserveErrorKind stabilises.
+    pub fn try_reserve(&mut self, additional: usize) -> Result<(), TryReserveError> {
+        for shard in self.shards.iter() {
+            shard
+                .write()
+                .try_reserve(additional)
+                .map_err(|_| TryReserveError {})?;
+        }
+        Ok(())
+    }
+}
+
+impl<'a, K: 'a + Eq + Hash, V: 'a, S: 'a + BuildHasher + Clone> Map<'a, K, V, S>
+    for DashMap<K, V, S>
+{
+    fn _shard_count(&self) -> usize {
+        self.shards.len()
+    }
+
+    unsafe fn _get_read_shard(&'a self, i: usize) -> &'a HashMap<K, V, S> {
+        debug_assert!(i < self.shards.len());
+
+        &*self.shards.get_unchecked(i).data_ptr()
+    }
+
+    unsafe fn _yield_read_shard(&'a self, i: usize) -> RwLockReadGuard<'a, HashMap<K, V, S>> {
+        debug_assert!(i < self.shards.len());
+
+        self.shards.get_unchecked(i).read()
+    }
+
+    unsafe fn _yield_write_shard(&'a self, i: usize) -> RwLockWriteGuard<'a, HashMap<K, V, S>> {
+        debug_assert!(i < self.shards.len());
+
+        self.shards.get_unchecked(i).write()
+    }
+
+    unsafe fn _try_yield_read_shard(
+        &'a self,
+        i: usize,
+    ) -> Option<RwLockReadGuard<'a, HashMap<K, V, S>>> {
+        debug_assert!(i < self.shards.len());
+
+        self.shards.get_unchecked(i).try_read()
+    }
+
+    unsafe fn _try_yield_write_shard(
+        &'a self,
+        i: usize,
+    ) -> Option<RwLockWriteGuard<'a, HashMap<K, V, S>>> {
+        debug_assert!(i < self.shards.len());
+
+        self.shards.get_unchecked(i).try_write()
+    }
+
+    fn _insert(&self, key: K, value: V) -> Option<V> {
+        let hash = self.hash_usize(&key);
+
+        let idx = self.determine_shard(hash);
+
+        let mut shard = unsafe { self._yield_write_shard(idx) };
+
+        shard
+            .insert(key, SharedValue::new(value))
+            .map(|v| v.into_inner())
+    }
+
+    fn _remove<Q>(&self, key: &Q) -> Option<(K, V)>
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized,
+    {
+        let hash = self.hash_usize(&key);
+
+        let idx = self.determine_shard(hash);
+
+        let mut shard = unsafe { self._yield_write_shard(idx) };
+
+        shard.remove_entry(key).map(|(k, v)| (k, v.into_inner()))
+    }
+
+    fn _remove_if<Q>(&self, key: &Q, f: impl FnOnce(&K, &V) -> bool) -> Option<(K, V)>
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized,
+    {
+        let hash = self.hash_usize(&key);
+
+        let idx = self.determine_shard(hash);
+
+        let mut shard = unsafe { self._yield_write_shard(idx) };
+
+        if let Some((kptr, vptr)) = shard.get_key_value(key) {
+            unsafe {
+                let kptr: *const K = kptr;
+                let vptr: *mut V = vptr.as_ptr();
+
+                if f(&*kptr, &mut *vptr) {
+                    shard.remove_entry(key).map(|(k, v)| (k, v.into_inner()))
+                } else {
+                    None
+                }
+            }
+        } else {
+            None
+        }
+    }
+
+    fn _remove_if_mut<Q>(&self, key: &Q, f: impl FnOnce(&K, &mut V) -> bool) -> Option<(K, V)>
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized,
+    {
+        let hash = self.hash_usize(&key);
+
+        let idx = self.determine_shard(hash);
+
+        let mut shard = unsafe { self._yield_write_shard(idx) };
+
+        if let Some((kptr, vptr)) = shard.get_key_value(key) {
+            unsafe {
+                let kptr: *const K = kptr;
+                let vptr: *mut V = vptr.as_ptr();
+
+                if f(&*kptr, &mut *vptr) {
+                    shard.remove_entry(key).map(|(k, v)| (k, v.into_inner()))
+                } else {
+                    None
+                }
+            }
+        } else {
+            None
+        }
+    }
+
+    fn _iter(&'a self) -> Iter<'a, K, V, S, DashMap<K, V, S>> {
+        Iter::new(self)
+    }
+
+    fn _iter_mut(&'a self) -> IterMut<'a, K, V, S, DashMap<K, V, S>> {
+        IterMut::new(self)
+    }
+
+    fn _get<Q>(&'a self, key: &Q) -> Option<Ref<'a, K, V, S>>
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized,
+    {
+        let hash = self.hash_usize(&key);
+
+        let idx = self.determine_shard(hash);
+
+        let shard = unsafe { self._yield_read_shard(idx) };
+
+        if let Some((kptr, vptr)) = shard.get_key_value(key) {
+            unsafe {
+                let kptr: *const K = kptr;
+                let vptr: *const V = vptr.get();
+                Some(Ref::new(shard, kptr, vptr))
+            }
+        } else {
+            None
+        }
+    }
+
+    fn _get_mut<Q>(&'a self, key: &Q) -> Option<RefMut<'a, K, V, S>>
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized,
+    {
+        let hash = self.hash_usize(&key);
+
+        let idx = self.determine_shard(hash);
+
+        let shard = unsafe { self._yield_write_shard(idx) };
+
+        if let Some((kptr, vptr)) = shard.get_key_value(key) {
+            unsafe {
+                let kptr: *const K = kptr;
+                let vptr: *mut V = vptr.as_ptr();
+                Some(RefMut::new(shard, kptr, vptr))
+            }
+        } else {
+            None
+        }
+    }
+
+    fn _try_get<Q>(&'a self, key: &Q) -> TryResult<Ref<'a, K, V, S>>
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized,
+    {
+        let hash = self.hash_usize(&key);
+
+        let idx = self.determine_shard(hash);
+
+        let shard = match unsafe { self._try_yield_read_shard(idx) } {
+            Some(shard) => shard,
+            None => return TryResult::Locked,
+        };
+
+        if let Some((kptr, vptr)) = shard.get_key_value(key) {
+            unsafe {
+                let kptr: *const K = kptr;
+                let vptr: *const V = vptr.get();
+                TryResult::Present(Ref::new(shard, kptr, vptr))
+            }
+        } else {
+            TryResult::Absent
+        }
+    }
+
+    fn _try_get_mut<Q>(&'a self, key: &Q) -> TryResult<RefMut<'a, K, V, S>>
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized,
+    {
+        let hash = self.hash_usize(&key);
+
+        let idx = self.determine_shard(hash);
+
+        let shard = match unsafe { self._try_yield_write_shard(idx) } {
+            Some(shard) => shard,
+            None => return TryResult::Locked,
+        };
+
+        if let Some((kptr, vptr)) = shard.get_key_value(key) {
+            unsafe {
+                let kptr: *const K = kptr;
+                let vptr: *mut V = vptr.as_ptr();
+                TryResult::Present(RefMut::new(shard, kptr, vptr))
+            }
+        } else {
+            TryResult::Absent
+        }
+    }
+
+    fn _shrink_to_fit(&self) {
+        self.shards.iter().for_each(|s| s.write().shrink_to_fit());
+    }
+
+    fn _retain(&self, mut f: impl FnMut(&K, &mut V) -> bool) {
+        self.shards
+            .iter()
+            .for_each(|s| s.write().retain(|k, v| f(k, v.get_mut())));
+    }
+
+    fn _len(&self) -> usize {
+        self.shards.iter().map(|s| s.read().len()).sum()
+    }
+
+    fn _capacity(&self) -> usize {
+        self.shards.iter().map(|s| s.read().capacity()).sum()
+    }
+
+    fn _alter<Q>(&self, key: &Q, f: impl FnOnce(&K, V) -> V)
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized,
+    {
+        if let Some(mut r) = self.get_mut(key) {
+            util::map_in_place_2(r.pair_mut(), f);
+        }
+    }
+
+    fn _alter_all(&self, mut f: impl FnMut(&K, V) -> V) {
+        self.shards.iter().for_each(|s| {
+            s.write()
+                .iter_mut()
+                .for_each(|(k, v)| util::map_in_place_2((k, v.get_mut()), &mut f));
+        });
+    }
+
+    fn _view<Q, R>(&self, key: &Q, f: impl FnOnce(&K, &V) -> R) -> Option<R>
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized,
+    {
+        self.get(key).map(|r| {
+            let (k, v) = r.pair();
+            f(k, v)
+        })
+    }
+
+    fn _entry(&'a self, key: K) -> Entry<'a, K, V, S> {
+        let hash = self.hash_usize(&key);
+
+        let idx = self.determine_shard(hash);
+
+        let shard = unsafe { self._yield_write_shard(idx) };
+
+        if let Some((kptr, vptr)) = shard.get_key_value(&key) {
+            unsafe {
+                let kptr: *const K = kptr;
+                let vptr: *mut V = vptr.as_ptr();
+                Entry::Occupied(OccupiedEntry::new(shard, key, (kptr, vptr)))
+            }
+        } else {
+            unsafe { Entry::Vacant(VacantEntry::new(shard, key)) }
+        }
+    }
+
+    fn _try_entry(&'a self, key: K) -> Option<Entry<'a, K, V, S>> {
+        let hash = self.hash_usize(&key);
+
+        let idx = self.determine_shard(hash);
+
+        let shard = match unsafe { self._try_yield_write_shard(idx) } {
+            Some(shard) => shard,
+            None => return None,
+        };
+
+        if let Some((kptr, vptr)) = shard.get_key_value(&key) {
+            unsafe {
+                let kptr: *const K = kptr;
+                let vptr: *mut V = vptr.as_ptr();
+
+                Some(Entry::Occupied(OccupiedEntry::new(
+                    shard,
+                    key,
+                    (kptr, vptr),
+                )))
+            }
+        } else {
+            unsafe { Some(Entry::Vacant(VacantEntry::new(shard, key))) }
+        }
+    }
+
+    fn _hasher(&self) -> S {
+        self.hasher.clone()
+    }
+}
+
+impl<K: Eq + Hash + fmt::Debug, V: fmt::Debug, S: BuildHasher + Clone> fmt::Debug
+    for DashMap<K, V, S>
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let mut pmap = f.debug_map();
+
+        for r in self {
+            let (k, v) = r.pair();
+
+            pmap.entry(k, v);
+        }
+
+        pmap.finish()
+    }
+}
+
+impl<'a, K: 'a + Eq + Hash, V: 'a, S: BuildHasher + Clone> Shl<(K, V)> for &'a DashMap<K, V, S> {
+    type Output = Option<V>;
+
+    fn shl(self, pair: (K, V)) -> Self::Output {
+        self.insert(pair.0, pair.1)
+    }
+}
+
+impl<'a, K: 'a + Eq + Hash, V: 'a, S: BuildHasher + Clone, Q> Shr<&Q> for &'a DashMap<K, V, S>
+where
+    K: Borrow<Q>,
+    Q: Hash + Eq + ?Sized,
+{
+    type Output = Ref<'a, K, V, S>;
+
+    fn shr(self, key: &Q) -> Self::Output {
+        self.get(key).unwrap()
+    }
+}
+
+impl<'a, K: 'a + Eq + Hash, V: 'a, S: BuildHasher + Clone, Q> BitOr<&Q> for &'a DashMap<K, V, S>
+where
+    K: Borrow<Q>,
+    Q: Hash + Eq + ?Sized,
+{
+    type Output = RefMut<'a, K, V, S>;
+
+    fn bitor(self, key: &Q) -> Self::Output {
+        self.get_mut(key).unwrap()
+    }
+}
+
+impl<'a, K: 'a + Eq + Hash, V: 'a, S: BuildHasher + Clone, Q> Sub<&Q> for &'a DashMap<K, V, S>
+where
+    K: Borrow<Q>,
+    Q: Hash + Eq + ?Sized,
+{
+    type Output = Option<(K, V)>;
+
+    fn sub(self, key: &Q) -> Self::Output {
+        self.remove(key)
+    }
+}
+
+impl<'a, K: 'a + Eq + Hash, V: 'a, S: BuildHasher + Clone, Q> BitAnd<&Q> for &'a DashMap<K, V, S>
+where
+    K: Borrow<Q>,
+    Q: Hash + Eq + ?Sized,
+{
+    type Output = bool;
+
+    fn bitand(self, key: &Q) -> Self::Output {
+        self.contains_key(key)
+    }
+}
+
+impl<K: Eq + Hash, V, S: BuildHasher + Clone> IntoIterator for DashMap<K, V, S> {
+    type Item = (K, V);
+
+    type IntoIter = OwningIter<K, V, S>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        OwningIter::new(self)
+    }
+}
+
+impl<'a, K: Eq + Hash, V, S: BuildHasher + Clone> IntoIterator for &'a DashMap<K, V, S> {
+    type Item = RefMulti<'a, K, V, S>;
+
+    type IntoIter = Iter<'a, K, V, S, DashMap<K, V, S>>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.iter()
+    }
+}
+
+impl<K: Eq + Hash, V, S: BuildHasher + Clone> Extend<(K, V)> for DashMap<K, V, S> {
+    fn extend<I: IntoIterator<Item = (K, V)>>(&mut self, intoiter: I) {
+        for pair in intoiter.into_iter() {
+            self.insert(pair.0, pair.1);
+        }
+    }
+}
+
+impl<K: Eq + Hash, V, S: BuildHasher + Clone + Default> FromIterator<(K, V)> for DashMap<K, V, S> {
+    fn from_iter<I: IntoIterator<Item = (K, V)>>(intoiter: I) -> Self {
+        let mut map = DashMap::default();
+
+        map.extend(intoiter);
+
+        map
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::DashMap;
+    use std::collections::hash_map::RandomState;
+
+    #[test]
+    fn test_basic() {
+        let dm = DashMap::new();
+
+        dm.insert(0, 0);
+
+        assert_eq!(dm.get(&0).unwrap().value(), &0);
+    }
+
+    #[test]
+    fn test_default() {
+        let dm: DashMap<u32, u32> = DashMap::default();
+
+        dm.insert(0, 0);
+
+        assert_eq!(dm.get(&0).unwrap().value(), &0);
+    }
+
+    #[test]
+    fn test_multiple_hashes() {
+        let dm: DashMap<u32, u32> = DashMap::default();
+
+        for i in 0..100 {
+            dm.insert(0, i);
+
+            dm.insert(i, i);
+        }
+
+        for i in 1..100 {
+            let r = dm.get(&i).unwrap();
+
+            assert_eq!(i, *r.value());
+
+            assert_eq!(i, *r.key());
+        }
+
+        let r = dm.get(&0).unwrap();
+
+        assert_eq!(99, *r.value());
+    }
+
+    #[test]
+    fn test_more_complex_values() {
+        #[derive(Hash, PartialEq, Debug, Clone)]
+
+        struct T0 {
+            s: String,
+            u: u8,
+        }
+
+        let dm = DashMap::new();
+
+        let range = 0..10;
+
+        for i in range {
+            let t = T0 {
+                s: i.to_string(),
+                u: i as u8,
+            };
+
+            dm.insert(i, t.clone());
+
+            assert_eq!(&t, dm.get(&i).unwrap().value());
+        }
+    }
+
+    #[test]
+    fn test_different_hashers_randomstate() {
+        let dm_hm_default: DashMap<u32, u32, RandomState> =
+            DashMap::with_hasher(RandomState::new());
+
+        for i in 0..10 {
+            dm_hm_default.insert(i, i);
+
+            assert_eq!(i, *dm_hm_default.get(&i).unwrap().value());
+        }
+    }
+
+    #[test]
+    fn test_map_view() {
+        let dm = DashMap::new();
+
+        let vegetables: [String; 4] = [
+            "Salad".to_string(),
+            "Beans".to_string(),
+            "Potato".to_string(),
+            "Tomato".to_string(),
+        ];
+
+        // Give it some values
+        dm.insert(0, "Banana".to_string());
+        dm.insert(4, "Pear".to_string());
+        dm.insert(9, "Potato".to_string());
+        dm.insert(12, "Chicken".to_string());
+
+        let potato_vegetableness = dm.view(&9, |_, v| vegetables.contains(v));
+        assert_eq!(potato_vegetableness, Some(true));
+
+        let chicken_vegetableness = dm.view(&12, |_, v| vegetables.contains(v));
+        assert_eq!(chicken_vegetableness, Some(false));
+
+        let not_in_map = dm.view(&30, |_k, _v| false);
+        assert_eq!(not_in_map, None);
+    }
+
+    #[test]
+    fn test_try_get() {
+        {
+            let map = DashMap::new();
+            map.insert("Johnny", 21);
+
+            assert_eq!(*map.try_get("Johnny").unwrap(), 21);
+
+            let _result1_locking = map.get_mut("Johnny");
+
+            let result2 = map.try_get("Johnny");
+            assert!(result2.is_locked());
+        }
+
+        {
+            let map = DashMap::new();
+            map.insert("Johnny", 21);
+
+            *map.try_get_mut("Johnny").unwrap() += 1;
+            assert_eq!(*map.get("Johnny").unwrap(), 22);
+
+            let _result1_locking = map.get("Johnny");
+
+            let result2 = map.try_get_mut("Johnny");
+            assert!(result2.is_locked());
+        }
+    }
+
+    #[test]
+    fn test_try_reserve() {
+        let mut map: DashMap<i32, i32> = DashMap::new();
+        // DashMap is empty and doesn't allocate memory
+        assert_eq!(map.capacity(), 0);
+
+        map.try_reserve(10).unwrap();
+
+        // And now map can hold at least 10 elements
+        assert!(map.capacity() >= 10);
+    }
+
+    #[test]
+    fn test_try_reserve_errors() {
+        let mut map: DashMap<i32, i32> = DashMap::new();
+
+        match map.try_reserve(usize::MAX) {
+            Err(_) => {}
+            _ => panic!("should have raised CapacityOverflow error"),
+        }
+    }
+}
diff --git a/src/lock.rs b/src/lock.rs
new file mode 100644
index 0000000..f2c98c7
--- /dev/null
+++ b/src/lock.rs
@@ -0,0 +1,300 @@
+use core::sync::atomic::{AtomicUsize, Ordering};
+use parking_lot_core::{ParkToken, SpinWait, UnparkToken};
+
+pub type RwLock<T> = lock_api::RwLock<RawRwLock, T>;
+pub type RwLockReadGuard<'a, T> = lock_api::RwLockReadGuard<'a, RawRwLock, T>;
+pub type RwLockWriteGuard<'a, T> = lock_api::RwLockWriteGuard<'a, RawRwLock, T>;
+
+const READERS_PARKED: usize = 0b0001;
+const WRITERS_PARKED: usize = 0b0010;
+const ONE_READER: usize = 0b0100;
+const ONE_WRITER: usize = !(READERS_PARKED | WRITERS_PARKED);
+
+pub struct RawRwLock {
+    state: AtomicUsize,
+}
+
+unsafe impl lock_api::RawRwLock for RawRwLock {
+    #[allow(clippy::declare_interior_mutable_const)]
+    const INIT: Self = Self {
+        state: AtomicUsize::new(0),
+    };
+
+    type GuardMarker = lock_api::GuardNoSend;
+
+    #[inline]
+    fn try_lock_exclusive(&self) -> bool {
+        self.state
+            .compare_exchange(0, ONE_WRITER, Ordering::Acquire, Ordering::Relaxed)
+            .is_ok()
+    }
+
+    #[inline]
+    fn lock_exclusive(&self) {
+        if self
+            .state
+            .compare_exchange_weak(0, ONE_WRITER, Ordering::Acquire, Ordering::Relaxed)
+            .is_err()
+        {
+            self.lock_exclusive_slow();
+        }
+    }
+
+    #[inline]
+    unsafe fn unlock_exclusive(&self) {
+        if self
+            .state
+            .compare_exchange(ONE_WRITER, 0, Ordering::Release, Ordering::Relaxed)
+            .is_err()
+        {
+            self.unlock_exclusive_slow();
+        }
+    }
+
+    #[inline]
+    fn try_lock_shared(&self) -> bool {
+        self.try_lock_shared_fast() || self.try_lock_shared_slow()
+    }
+
+    #[inline]
+    fn lock_shared(&self) {
+        if !self.try_lock_shared_fast() {
+            self.lock_shared_slow();
+        }
+    }
+
+    #[inline]
+    unsafe fn unlock_shared(&self) {
+        let state = self.state.fetch_sub(ONE_READER, Ordering::Release);
+
+        if state == (ONE_READER | WRITERS_PARKED) {
+            self.unlock_shared_slow();
+        }
+    }
+}
+
+unsafe impl lock_api::RawRwLockDowngrade for RawRwLock {
+    #[inline]
+    unsafe fn downgrade(&self) {
+        let state = self
+            .state
+            .fetch_and(ONE_READER | WRITERS_PARKED, Ordering::Release);
+        if state & READERS_PARKED != 0 {
+            parking_lot_core::unpark_all((self as *const _ as usize) + 1, UnparkToken(0));
+        }
+    }
+}
+
+impl RawRwLock {
+    #[cold]
+    fn lock_exclusive_slow(&self) {
+        let mut acquire_with = 0;
+        loop {
+            let mut spin = SpinWait::new();
+            let mut state = self.state.load(Ordering::Relaxed);
+
+            loop {
+                while state & ONE_WRITER == 0 {
+                    match self.state.compare_exchange_weak(
+                        state,
+                        state | ONE_WRITER | acquire_with,
+                        Ordering::Acquire,
+                        Ordering::Relaxed,
+                    ) {
+                        Ok(_) => return,
+                        Err(e) => state = e,
+                    }
+                }
+
+                if state & WRITERS_PARKED == 0 {
+                    if spin.spin() {
+                        state = self.state.load(Ordering::Relaxed);
+                        continue;
+                    }
+
+                    if let Err(e) = self.state.compare_exchange_weak(
+                        state,
+                        state | WRITERS_PARKED,
+                        Ordering::Relaxed,
+                        Ordering::Relaxed,
+                    ) {
+                        state = e;
+                        continue;
+                    }
+                }
+
+                let _ = unsafe {
+                    parking_lot_core::park(
+                        self as *const _ as usize,
+                        || {
+                            let state = self.state.load(Ordering::Relaxed);
+                            (state & ONE_WRITER != 0) && (state & WRITERS_PARKED != 0)
+                        },
+                        || {},
+                        |_, _| {},
+                        ParkToken(0),
+                        None,
+                    )
+                };
+
+                acquire_with = WRITERS_PARKED;
+                break;
+            }
+        }
+    }
+
+    #[cold]
+    fn unlock_exclusive_slow(&self) {
+        let state = self.state.load(Ordering::Relaxed);
+        assert_eq!(state & ONE_WRITER, ONE_WRITER);
+
+        let mut parked = state & (READERS_PARKED | WRITERS_PARKED);
+        assert_ne!(parked, 0);
+
+        if parked != (READERS_PARKED | WRITERS_PARKED) {
+            if let Err(new_state) =
+                self.state
+                    .compare_exchange(state, 0, Ordering::Release, Ordering::Relaxed)
+            {
+                assert_eq!(new_state, ONE_WRITER | READERS_PARKED | WRITERS_PARKED);
+                parked = READERS_PARKED | WRITERS_PARKED;
+            }
+        }
+
+        if parked == (READERS_PARKED | WRITERS_PARKED) {
+            self.state.store(WRITERS_PARKED, Ordering::Release);
+            parked = READERS_PARKED;
+        }
+
+        if parked == READERS_PARKED {
+            return unsafe {
+                parking_lot_core::unpark_all((self as *const _ as usize) + 1, UnparkToken(0));
+            };
+        }
+
+        assert_eq!(parked, WRITERS_PARKED);
+        unsafe {
+            parking_lot_core::unpark_one(self as *const _ as usize, |_| UnparkToken(0));
+        }
+    }
+
+    #[inline(always)]
+    fn try_lock_shared_fast(&self) -> bool {
+        let state = self.state.load(Ordering::Relaxed);
+
+        if let Some(new_state) = state.checked_add(ONE_READER) {
+            if new_state & ONE_WRITER != ONE_WRITER {
+                return self
+                    .state
+                    .compare_exchange_weak(state, new_state, Ordering::Acquire, Ordering::Relaxed)
+                    .is_ok();
+            }
+        }
+
+        false
+    }
+
+    #[cold]
+    fn try_lock_shared_slow(&self) -> bool {
+        let mut state = self.state.load(Ordering::Relaxed);
+
+        while let Some(new_state) = state.checked_add(ONE_READER) {
+            if new_state & ONE_WRITER == ONE_WRITER {
+                break;
+            }
+
+            match self.state.compare_exchange_weak(
+                state,
+                new_state,
+                Ordering::Acquire,
+                Ordering::Relaxed,
+            ) {
+                Ok(_) => return true,
+                Err(e) => state = e,
+            }
+        }
+
+        false
+    }
+
+    #[cold]
+    fn lock_shared_slow(&self) {
+        loop {
+            let mut spin = SpinWait::new();
+            let mut state = self.state.load(Ordering::Relaxed);
+
+            loop {
+                let mut backoff = SpinWait::new();
+                while let Some(new_state) = state.checked_add(ONE_READER) {
+                    assert_ne!(
+                        new_state & ONE_WRITER,
+                        ONE_WRITER,
+                        "reader count overflowed",
+                    );
+
+                    if self
+                        .state
+                        .compare_exchange_weak(
+                            state,
+                            new_state,
+                            Ordering::Acquire,
+                            Ordering::Relaxed,
+                        )
+                        .is_ok()
+                    {
+                        return;
+                    }
+
+                    backoff.spin_no_yield();
+                    state = self.state.load(Ordering::Relaxed);
+                }
+
+                if state & READERS_PARKED == 0 {
+                    if spin.spin() {
+                        state = self.state.load(Ordering::Relaxed);
+                        continue;
+                    }
+
+                    if let Err(e) = self.state.compare_exchange_weak(
+                        state,
+                        state | READERS_PARKED,
+                        Ordering::Relaxed,
+                        Ordering::Relaxed,
+                    ) {
+                        state = e;
+                        continue;
+                    }
+                }
+
+                let _ = unsafe {
+                    parking_lot_core::park(
+                        (self as *const _ as usize) + 1,
+                        || {
+                            let state = self.state.load(Ordering::Relaxed);
+                            (state & ONE_WRITER == ONE_WRITER) && (state & READERS_PARKED != 0)
+                        },
+                        || {},
+                        |_, _| {},
+                        ParkToken(0),
+                        None,
+                    )
+                };
+
+                break;
+            }
+        }
+    }
+
+    #[cold]
+    fn unlock_shared_slow(&self) {
+        if self
+            .state
+            .compare_exchange(WRITERS_PARKED, 0, Ordering::Relaxed, Ordering::Relaxed)
+            .is_ok()
+        {
+            unsafe {
+                parking_lot_core::unpark_one(self as *const _ as usize, |_| UnparkToken(0));
+            }
+        }
+    }
+}
diff --git a/src/mapref/entry.rs b/src/mapref/entry.rs
new file mode 100644
index 0000000..e9e6b91
--- /dev/null
+++ b/src/mapref/entry.rs
@@ -0,0 +1,278 @@
+use super::one::RefMut;
+use crate::lock::RwLockWriteGuard;
+use crate::util;
+use crate::util::SharedValue;
+use crate::HashMap;
+use core::hash::{BuildHasher, Hash};
+use core::mem;
+use core::ptr;
+use std::collections::hash_map::RandomState;
+
+pub enum Entry<'a, K, V, S = RandomState> {
+    Occupied(OccupiedEntry<'a, K, V, S>),
+    Vacant(VacantEntry<'a, K, V, S>),
+}
+
+impl<'a, K: Eq + Hash, V, S: BuildHasher> Entry<'a, K, V, S> {
+    /// Apply a function to the stored value if it exists.
+    pub fn and_modify(self, f: impl FnOnce(&mut V)) -> Self {
+        match self {
+            Entry::Occupied(mut entry) => {
+                f(entry.get_mut());
+
+                Entry::Occupied(entry)
+            }
+
+            Entry::Vacant(entry) => Entry::Vacant(entry),
+        }
+    }
+
+    /// Get the key of the entry.
+    pub fn key(&self) -> &K {
+        match *self {
+            Entry::Occupied(ref entry) => entry.key(),
+            Entry::Vacant(ref entry) => entry.key(),
+        }
+    }
+
+    /// Into the key of the entry.
+    pub fn into_key(self) -> K {
+        match self {
+            Entry::Occupied(entry) => entry.into_key(),
+            Entry::Vacant(entry) => entry.into_key(),
+        }
+    }
+
+    /// Return a mutable reference to the element if it exists,
+    /// otherwise insert the default and return a mutable reference to that.
+    pub fn or_default(self) -> RefMut<'a, K, V, S>
+    where
+        V: Default,
+    {
+        match self {
+            Entry::Occupied(entry) => entry.into_ref(),
+            Entry::Vacant(entry) => entry.insert(V::default()),
+        }
+    }
+
+    /// Return a mutable reference to the element if it exists,
+    /// otherwise a provided value and return a mutable reference to that.
+    pub fn or_insert(self, value: V) -> RefMut<'a, K, V, S> {
+        match self {
+            Entry::Occupied(entry) => entry.into_ref(),
+            Entry::Vacant(entry) => entry.insert(value),
+        }
+    }
+
+    /// Return a mutable reference to the element if it exists,
+    /// otherwise insert the result of a provided function and return a mutable reference to that.
+    pub fn or_insert_with(self, value: impl FnOnce() -> V) -> RefMut<'a, K, V, S> {
+        match self {
+            Entry::Occupied(entry) => entry.into_ref(),
+            Entry::Vacant(entry) => entry.insert(value()),
+        }
+    }
+
+    pub fn or_try_insert_with<E>(
+        self,
+        value: impl FnOnce() -> Result<V, E>,
+    ) -> Result<RefMut<'a, K, V, S>, E> {
+        match self {
+            Entry::Occupied(entry) => Ok(entry.into_ref()),
+            Entry::Vacant(entry) => Ok(entry.insert(value()?)),
+        }
+    }
+
+    /// Sets the value of the entry, and returns a reference to the inserted value.
+    pub fn insert(self, value: V) -> RefMut<'a, K, V, S> {
+        match self {
+            Entry::Occupied(mut entry) => {
+                entry.insert(value);
+                entry.into_ref()
+            }
+            Entry::Vacant(entry) => entry.insert(value),
+        }
+    }
+
+    /// Sets the value of the entry, and returns an OccupiedEntry.
+    ///
+    /// If you are not interested in the occupied entry,
+    /// consider [`insert`] as it doesn't need to clone the key.
+    ///
+    /// [`insert`]: Entry::insert
+    pub fn insert_entry(self, value: V) -> OccupiedEntry<'a, K, V, S>
+    where
+        K: Clone,
+    {
+        match self {
+            Entry::Occupied(mut entry) => {
+                entry.insert(value);
+                entry
+            }
+            Entry::Vacant(entry) => entry.insert_entry(value),
+        }
+    }
+}
+
+pub struct VacantEntry<'a, K, V, S = RandomState> {
+    shard: RwLockWriteGuard<'a, HashMap<K, V, S>>,
+    key: K,
+}
+
+unsafe impl<'a, K: Eq + Hash + Sync, V: Sync, S: BuildHasher> Send for VacantEntry<'a, K, V, S> {}
+unsafe impl<'a, K: Eq + Hash + Sync, V: Sync, S: BuildHasher> Sync for VacantEntry<'a, K, V, S> {}
+
+impl<'a, K: Eq + Hash, V, S: BuildHasher> VacantEntry<'a, K, V, S> {
+    pub(crate) unsafe fn new(shard: RwLockWriteGuard<'a, HashMap<K, V, S>>, key: K) -> Self {
+        Self { shard, key }
+    }
+
+    pub fn insert(mut self, value: V) -> RefMut<'a, K, V, S> {
+        unsafe {
+            let c: K = ptr::read(&self.key);
+
+            self.shard.insert(self.key, SharedValue::new(value));
+
+            let (k, v) = self.shard.get_key_value(&c).unwrap();
+
+            let k = util::change_lifetime_const(k);
+
+            let v = &mut *v.as_ptr();
+
+            let r = RefMut::new(self.shard, k, v);
+
+            mem::forget(c);
+
+            r
+        }
+    }
+
+    /// Sets the value of the entry with the VacantEntry’s key, and returns an OccupiedEntry.
+    pub fn insert_entry(mut self, value: V) -> OccupiedEntry<'a, K, V, S>
+    where
+        K: Clone,
+    {
+        unsafe {
+            self.shard.insert(self.key.clone(), SharedValue::new(value));
+
+            let (k, v) = self.shard.get_key_value(&self.key).unwrap();
+
+            let kptr: *const K = k;
+            let vptr: *mut V = v.as_ptr();
+            OccupiedEntry::new(self.shard, self.key, (kptr, vptr))
+        }
+    }
+
+    pub fn into_key(self) -> K {
+        self.key
+    }
+
+    pub fn key(&self) -> &K {
+        &self.key
+    }
+}
+
+pub struct OccupiedEntry<'a, K, V, S = RandomState> {
+    shard: RwLockWriteGuard<'a, HashMap<K, V, S>>,
+    elem: (*const K, *mut V),
+    key: K,
+}
+
+unsafe impl<'a, K: Eq + Hash + Sync, V: Sync, S: BuildHasher> Send for OccupiedEntry<'a, K, V, S> {}
+unsafe impl<'a, K: Eq + Hash + Sync, V: Sync, S: BuildHasher> Sync for OccupiedEntry<'a, K, V, S> {}
+
+impl<'a, K: Eq + Hash, V, S: BuildHasher> OccupiedEntry<'a, K, V, S> {
+    pub(crate) unsafe fn new(
+        shard: RwLockWriteGuard<'a, HashMap<K, V, S>>,
+        key: K,
+        elem: (*const K, *mut V),
+    ) -> Self {
+        Self { shard, elem, key }
+    }
+
+    pub fn get(&self) -> &V {
+        unsafe { &*self.elem.1 }
+    }
+
+    pub fn get_mut(&mut self) -> &mut V {
+        unsafe { &mut *self.elem.1 }
+    }
+
+    pub fn insert(&mut self, value: V) -> V {
+        mem::replace(self.get_mut(), value)
+    }
+
+    pub fn into_ref(self) -> RefMut<'a, K, V, S> {
+        unsafe { RefMut::new(self.shard, self.elem.0, self.elem.1) }
+    }
+
+    pub fn into_key(self) -> K {
+        self.key
+    }
+
+    pub fn key(&self) -> &K {
+        unsafe { &*self.elem.0 }
+    }
+
+    pub fn remove(mut self) -> V {
+        let key = unsafe { &*self.elem.0 };
+        self.shard.remove(key).unwrap().into_inner()
+    }
+
+    pub fn remove_entry(mut self) -> (K, V) {
+        let key = unsafe { &*self.elem.0 };
+        let (k, v) = self.shard.remove_entry(key).unwrap();
+        (k, v.into_inner())
+    }
+
+    pub fn replace_entry(mut self, value: V) -> (K, V) {
+        let nk = self.key;
+        let key = unsafe { &*self.elem.0 };
+        let (k, v) = self.shard.remove_entry(key).unwrap();
+        self.shard.insert(nk, SharedValue::new(value));
+        (k, v.into_inner())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::DashMap;
+
+    use super::*;
+
+    #[test]
+    fn test_insert_entry_into_vacant() {
+        let map: DashMap<u32, u32> = DashMap::new();
+
+        let entry = map.entry(1);
+
+        assert!(matches!(entry, Entry::Vacant(_)));
+
+        let entry = entry.insert_entry(2);
+
+        assert_eq!(*entry.get(), 2);
+
+        drop(entry);
+
+        assert_eq!(*map.get(&1).unwrap(), 2);
+    }
+
+    #[test]
+    fn test_insert_entry_into_occupied() {
+        let map: DashMap<u32, u32> = DashMap::new();
+
+        map.insert(1, 1000);
+
+        let entry = map.entry(1);
+
+        assert!(matches!(&entry, Entry::Occupied(entry) if *entry.get() == 1000));
+
+        let entry = entry.insert_entry(2);
+
+        assert_eq!(*entry.get(), 2);
+
+        drop(entry);
+
+        assert_eq!(*map.get(&1).unwrap(), 2);
+    }
+}
diff --git a/src/mapref/mod.rs b/src/mapref/mod.rs
new file mode 100644
index 0000000..8897547
--- /dev/null
+++ b/src/mapref/mod.rs
@@ -0,0 +1,3 @@
+pub mod entry;
+pub mod multiple;
+pub mod one;
diff --git a/src/mapref/multiple.rs b/src/mapref/multiple.rs
new file mode 100644
index 0000000..53a8a7e
--- /dev/null
+++ b/src/mapref/multiple.rs
@@ -0,0 +1,107 @@
+use crate::lock::{RwLockReadGuard, RwLockWriteGuard};
+use crate::HashMap;
+use core::hash::BuildHasher;
+use core::hash::Hash;
+use core::ops::{Deref, DerefMut};
+use std::collections::hash_map::RandomState;
+use std::sync::Arc;
+
+pub struct RefMulti<'a, K, V, S = RandomState> {
+    _guard: Arc<RwLockReadGuard<'a, HashMap<K, V, S>>>,
+    k: *const K,
+    v: *const V,
+}
+
+unsafe impl<'a, K: Eq + Hash + Sync, V: Sync, S: BuildHasher> Send for RefMulti<'a, K, V, S> {}
+unsafe impl<'a, K: Eq + Hash + Sync, V: Sync, S: BuildHasher> Sync for RefMulti<'a, K, V, S> {}
+
+impl<'a, K: Eq + Hash, V, S: BuildHasher> RefMulti<'a, K, V, S> {
+    pub(crate) unsafe fn new(
+        guard: Arc<RwLockReadGuard<'a, HashMap<K, V, S>>>,
+        k: *const K,
+        v: *const V,
+    ) -> Self {
+        Self {
+            _guard: guard,
+            k,
+            v,
+        }
+    }
+
+    pub fn key(&self) -> &K {
+        self.pair().0
+    }
+
+    pub fn value(&self) -> &V {
+        self.pair().1
+    }
+
+    pub fn pair(&self) -> (&K, &V) {
+        unsafe { (&*self.k, &*self.v) }
+    }
+}
+
+impl<'a, K: Eq + Hash, V, S: BuildHasher> Deref for RefMulti<'a, K, V, S> {
+    type Target = V;
+
+    fn deref(&self) -> &V {
+        self.value()
+    }
+}
+
+pub struct RefMutMulti<'a, K, V, S = RandomState> {
+    _guard: Arc<RwLockWriteGuard<'a, HashMap<K, V, S>>>,
+    k: *const K,
+    v: *mut V,
+}
+
+unsafe impl<'a, K: Eq + Hash + Sync, V: Sync, S: BuildHasher> Send for RefMutMulti<'a, K, V, S> {}
+unsafe impl<'a, K: Eq + Hash + Sync, V: Sync, S: BuildHasher> Sync for RefMutMulti<'a, K, V, S> {}
+
+impl<'a, K: Eq + Hash, V, S: BuildHasher> RefMutMulti<'a, K, V, S> {
+    pub(crate) unsafe fn new(
+        guard: Arc<RwLockWriteGuard<'a, HashMap<K, V, S>>>,
+        k: *const K,
+        v: *mut V,
+    ) -> Self {
+        Self {
+            _guard: guard,
+            k,
+            v,
+        }
+    }
+
+    pub fn key(&self) -> &K {
+        self.pair().0
+    }
+
+    pub fn value(&self) -> &V {
+        self.pair().1
+    }
+
+    pub fn value_mut(&mut self) -> &mut V {
+        self.pair_mut().1
+    }
+
+    pub fn pair(&self) -> (&K, &V) {
+        unsafe { (&*self.k, &*self.v) }
+    }
+
+    pub fn pair_mut(&mut self) -> (&K, &mut V) {
+        unsafe { (&*self.k, &mut *self.v) }
+    }
+}
+
+impl<'a, K: Eq + Hash, V, S: BuildHasher> Deref for RefMutMulti<'a, K, V, S> {
+    type Target = V;
+
+    fn deref(&self) -> &V {
+        self.value()
+    }
+}
+
+impl<'a, K: Eq + Hash, V, S: BuildHasher> DerefMut for RefMutMulti<'a, K, V, S> {
+    fn deref_mut(&mut self) -> &mut V {
+        self.value_mut()
+    }
+}
diff --git a/src/mapref/one.rs b/src/mapref/one.rs
new file mode 100644
index 0000000..fd38530
--- /dev/null
+++ b/src/mapref/one.rs
@@ -0,0 +1,335 @@
+use crate::lock::{RwLockReadGuard, RwLockWriteGuard};
+use crate::HashMap;
+use core::hash::{BuildHasher, Hash};
+use core::ops::{Deref, DerefMut};
+use std::collections::hash_map::RandomState;
+use std::fmt::{Debug, Formatter};
+
+pub struct Ref<'a, K, V, S = RandomState> {
+    _guard: RwLockReadGuard<'a, HashMap<K, V, S>>,
+    k: *const K,
+    v: *const V,
+}
+
+unsafe impl<'a, K: Eq + Hash + Sync, V: Sync, S: BuildHasher> Send for Ref<'a, K, V, S> {}
+unsafe impl<'a, K: Eq + Hash + Sync, V: Sync, S: BuildHasher> Sync for Ref<'a, K, V, S> {}
+
+impl<'a, K: Eq + Hash, V, S: BuildHasher> Ref<'a, K, V, S> {
+    pub(crate) unsafe fn new(
+        guard: RwLockReadGuard<'a, HashMap<K, V, S>>,
+        k: *const K,
+        v: *const V,
+    ) -> Self {
+        Self {
+            _guard: guard,
+            k,
+            v,
+        }
+    }
+
+    pub fn key(&self) -> &K {
+        self.pair().0
+    }
+
+    pub fn value(&self) -> &V {
+        self.pair().1
+    }
+
+    pub fn pair(&self) -> (&K, &V) {
+        unsafe { (&*self.k, &*self.v) }
+    }
+
+    pub fn map<F, T>(self, f: F) -> MappedRef<'a, K, V, T, S>
+    where
+        F: FnOnce(&V) -> &T,
+    {
+        MappedRef {
+            _guard: self._guard,
+            k: self.k,
+            v: f(unsafe { &*self.v }),
+        }
+    }
+
+    pub fn try_map<F, T>(self, f: F) -> Result<MappedRef<'a, K, V, T, S>, Self>
+    where
+        F: FnOnce(&V) -> Option<&T>,
+    {
+        if let Some(v) = f(unsafe { &*self.v }) {
+            Ok(MappedRef {
+                _guard: self._guard,
+                k: self.k,
+                v,
+            })
+        } else {
+            Err(self)
+        }
+    }
+}
+
+impl<'a, K: Eq + Hash + Debug, V: Debug, S: BuildHasher> Debug for Ref<'a, K, V, S> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("Ref")
+            .field("k", &self.k)
+            .field("v", &self.v)
+            .finish()
+    }
+}
+
+impl<'a, K: Eq + Hash, V, S: BuildHasher> Deref for Ref<'a, K, V, S> {
+    type Target = V;
+
+    fn deref(&self) -> &V {
+        self.value()
+    }
+}
+
+pub struct RefMut<'a, K, V, S = RandomState> {
+    guard: RwLockWriteGuard<'a, HashMap<K, V, S>>,
+    k: *const K,
+    v: *mut V,
+}
+
+unsafe impl<'a, K: Eq + Hash + Sync, V: Sync, S: BuildHasher> Send for RefMut<'a, K, V, S> {}
+unsafe impl<'a, K: Eq + Hash + Sync, V: Sync, S: BuildHasher> Sync for RefMut<'a, K, V, S> {}
+
+impl<'a, K: Eq + Hash, V, S: BuildHasher> RefMut<'a, K, V, S> {
+    pub(crate) unsafe fn new(
+        guard: RwLockWriteGuard<'a, HashMap<K, V, S>>,
+        k: *const K,
+        v: *mut V,
+    ) -> Self {
+        Self { guard, k, v }
+    }
+
+    pub fn key(&self) -> &K {
+        self.pair().0
+    }
+
+    pub fn value(&self) -> &V {
+        self.pair().1
+    }
+
+    pub fn value_mut(&mut self) -> &mut V {
+        self.pair_mut().1
+    }
+
+    pub fn pair(&self) -> (&K, &V) {
+        unsafe { (&*self.k, &*self.v) }
+    }
+
+    pub fn pair_mut(&mut self) -> (&K, &mut V) {
+        unsafe { (&*self.k, &mut *self.v) }
+    }
+
+    pub fn downgrade(self) -> Ref<'a, K, V, S> {
+        unsafe { Ref::new(RwLockWriteGuard::downgrade(self.guard), self.k, self.v) }
+    }
+
+    pub fn map<F, T>(self, f: F) -> MappedRefMut<'a, K, V, T, S>
+    where
+        F: FnOnce(&mut V) -> &mut T,
+    {
+        MappedRefMut {
+            _guard: self.guard,
+            k: self.k,
+            v: f(unsafe { &mut *self.v }),
+        }
+    }
+
+    pub fn try_map<F, T>(self, f: F) -> Result<MappedRefMut<'a, K, V, T, S>, Self>
+    where
+        F: FnOnce(&mut V) -> Option<&mut T>,
+    {
+        let v = match f(unsafe { &mut *(self.v as *mut _) }) {
+            Some(v) => v,
+            None => return Err(self),
+        };
+        let guard = self.guard;
+        let k = self.k;
+        Ok(MappedRefMut {
+            _guard: guard,
+            k,
+            v,
+        })
+    }
+}
+
+impl<'a, K: Eq + Hash + Debug, V: Debug, S: BuildHasher> Debug for RefMut<'a, K, V, S> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("RefMut")
+            .field("k", &self.k)
+            .field("v", &self.v)
+            .finish()
+    }
+}
+
+impl<'a, K: Eq + Hash, V, S: BuildHasher> Deref for RefMut<'a, K, V, S> {
+    type Target = V;
+
+    fn deref(&self) -> &V {
+        self.value()
+    }
+}
+
+impl<'a, K: Eq + Hash, V, S: BuildHasher> DerefMut for RefMut<'a, K, V, S> {
+    fn deref_mut(&mut self) -> &mut V {
+        self.value_mut()
+    }
+}
+
+pub struct MappedRef<'a, K, V, T, S = RandomState> {
+    _guard: RwLockReadGuard<'a, HashMap<K, V, S>>,
+    k: *const K,
+    v: *const T,
+}
+
+impl<'a, K: Eq + Hash, V, T, S: BuildHasher> MappedRef<'a, K, V, T, S> {
+    pub fn key(&self) -> &K {
+        self.pair().0
+    }
+
+    pub fn value(&self) -> &T {
+        self.pair().1
+    }
+
+    pub fn pair(&self) -> (&K, &T) {
+        unsafe { (&*self.k, &*self.v) }
+    }
+
+    pub fn map<F, T2>(self, f: F) -> MappedRef<'a, K, V, T2, S>
+    where
+        F: FnOnce(&T) -> &T2,
+    {
+        MappedRef {
+            _guard: self._guard,
+            k: self.k,
+            v: f(unsafe { &*self.v }),
+        }
+    }
+
+    pub fn try_map<F, T2>(self, f: F) -> Result<MappedRef<'a, K, V, T2, S>, Self>
+    where
+        F: FnOnce(&T) -> Option<&T2>,
+    {
+        let v = match f(unsafe { &*self.v }) {
+            Some(v) => v,
+            None => return Err(self),
+        };
+        let guard = self._guard;
+        Ok(MappedRef {
+            _guard: guard,
+            k: self.k,
+            v,
+        })
+    }
+}
+
+impl<'a, K: Eq + Hash + Debug, V, T: Debug, S: BuildHasher> Debug for MappedRef<'a, K, V, T, S> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("MappedRef")
+            .field("k", &self.k)
+            .field("v", &self.v)
+            .finish()
+    }
+}
+
+impl<'a, K: Eq + Hash, V, T, S: BuildHasher> Deref for MappedRef<'a, K, V, T, S> {
+    type Target = T;
+
+    fn deref(&self) -> &T {
+        self.value()
+    }
+}
+
+impl<'a, K: Eq + Hash, V, T: std::fmt::Display> std::fmt::Display for MappedRef<'a, K, V, T> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        std::fmt::Display::fmt(self.value(), f)
+    }
+}
+
+impl<'a, K: Eq + Hash, V, T: AsRef<TDeref>, TDeref: ?Sized> AsRef<TDeref>
+    for MappedRef<'a, K, V, T>
+{
+    fn as_ref(&self) -> &TDeref {
+        self.value().as_ref()
+    }
+}
+
+pub struct MappedRefMut<'a, K, V, T, S = RandomState> {
+    _guard: RwLockWriteGuard<'a, HashMap<K, V, S>>,
+    k: *const K,
+    v: *mut T,
+}
+
+impl<'a, K: Eq + Hash, V, T, S: BuildHasher> MappedRefMut<'a, K, V, T, S> {
+    pub fn key(&self) -> &K {
+        self.pair().0
+    }
+
+    pub fn value(&self) -> &T {
+        self.pair().1
+    }
+
+    pub fn value_mut(&mut self) -> &mut T {
+        self.pair_mut().1
+    }
+
+    pub fn pair(&self) -> (&K, &T) {
+        unsafe { (&*self.k, &*self.v) }
+    }
+
+    pub fn pair_mut(&mut self) -> (&K, &mut T) {
+        unsafe { (&*self.k, &mut *self.v) }
+    }
+
+    pub fn map<F, T2>(self, f: F) -> MappedRefMut<'a, K, V, T2, S>
+    where
+        F: FnOnce(&mut T) -> &mut T2,
+    {
+        MappedRefMut {
+            _guard: self._guard,
+            k: self.k,
+            v: f(unsafe { &mut *self.v }),
+        }
+    }
+
+    pub fn try_map<F, T2>(self, f: F) -> Result<MappedRefMut<'a, K, V, T2, S>, Self>
+    where
+        F: FnOnce(&mut T) -> Option<&mut T2>,
+    {
+        let v = match f(unsafe { &mut *(self.v as *mut _) }) {
+            Some(v) => v,
+            None => return Err(self),
+        };
+        let guard = self._guard;
+        let k = self.k;
+        Ok(MappedRefMut {
+            _guard: guard,
+            k,
+            v,
+        })
+    }
+}
+
+impl<'a, K: Eq + Hash + Debug, V, T: Debug, S: BuildHasher> Debug for MappedRefMut<'a, K, V, T, S> {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("MappedRefMut")
+            .field("k", &self.k)
+            .field("v", &self.v)
+            .finish()
+    }
+}
+
+impl<'a, K: Eq + Hash, V, T, S: BuildHasher> Deref for MappedRefMut<'a, K, V, T, S> {
+    type Target = T;
+
+    fn deref(&self) -> &T {
+        self.value()
+    }
+}
+
+impl<'a, K: Eq + Hash, V, T, S: BuildHasher> DerefMut for MappedRefMut<'a, K, V, T, S> {
+    fn deref_mut(&mut self) -> &mut T {
+        self.value_mut()
+    }
+}
diff --git a/src/rayon/map.rs b/src/rayon/map.rs
new file mode 100644
index 0000000..ab45e61
--- /dev/null
+++ b/src/rayon/map.rs
@@ -0,0 +1,221 @@
+use crate::lock::RwLock;
+use crate::mapref::multiple::{RefMulti, RefMutMulti};
+use crate::util;
+use crate::{DashMap, HashMap};
+use core::hash::{BuildHasher, Hash};
+use rayon::iter::plumbing::UnindexedConsumer;
+use rayon::iter::{FromParallelIterator, IntoParallelIterator, ParallelExtend, ParallelIterator};
+use std::collections::hash_map::RandomState;
+use std::sync::Arc;
+
+impl<K, V, S> ParallelExtend<(K, V)> for DashMap<K, V, S>
+where
+    K: Send + Sync + Eq + Hash,
+    V: Send + Sync,
+    S: Send + Sync + Clone + BuildHasher,
+{
+    fn par_extend<I>(&mut self, par_iter: I)
+    where
+        I: IntoParallelIterator<Item = (K, V)>,
+    {
+        (&*self).par_extend(par_iter);
+    }
+}
+
+// Since we don't actually need mutability, we can implement this on a
+// reference, similar to `io::Write for &File`.
+impl<K, V, S> ParallelExtend<(K, V)> for &'_ DashMap<K, V, S>
+where
+    K: Send + Sync + Eq + Hash,
+    V: Send + Sync,
+    S: Send + Sync + Clone + BuildHasher,
+{
+    fn par_extend<I>(&mut self, par_iter: I)
+    where
+        I: IntoParallelIterator<Item = (K, V)>,
+    {
+        let &mut map = self;
+        par_iter.into_par_iter().for_each(move |(key, value)| {
+            map.insert(key, value);
+        });
+    }
+}
+
+impl<K, V, S> FromParallelIterator<(K, V)> for DashMap<K, V, S>
+where
+    K: Send + Sync + Eq + Hash,
+    V: Send + Sync,
+    S: Send + Sync + Clone + Default + BuildHasher,
+{
+    fn from_par_iter<I>(par_iter: I) -> Self
+    where
+        I: IntoParallelIterator<Item = (K, V)>,
+    {
+        let map = Self::default();
+        (&map).par_extend(par_iter);
+        map
+    }
+}
+
+// Implementation note: while the shards will iterate in parallel, we flatten
+// sequentially within each shard (`flat_map_iter`), because the standard
+// `HashMap` only implements `ParallelIterator` by collecting to a `Vec` first.
+// There is real parallel support in the `hashbrown/rayon` feature, but we don't
+// always use that map.
+
+impl<K, V, S> IntoParallelIterator for DashMap<K, V, S>
+where
+    K: Send + Eq + Hash,
+    V: Send,
+    S: Send + Clone + BuildHasher,
+{
+    type Iter = OwningIter<K, V, S>;
+    type Item = (K, V);
+
+    fn into_par_iter(self) -> Self::Iter {
+        OwningIter {
+            shards: self.shards,
+        }
+    }
+}
+
+pub struct OwningIter<K, V, S = RandomState> {
+    pub(super) shards: Box<[RwLock<HashMap<K, V, S>>]>,
+}
+
+impl<K, V, S> ParallelIterator for OwningIter<K, V, S>
+where
+    K: Send + Eq + Hash,
+    V: Send,
+    S: Send + Clone + BuildHasher,
+{
+    type Item = (K, V);
+
+    fn drive_unindexed<C>(self, consumer: C) -> C::Result
+    where
+        C: UnindexedConsumer<Self::Item>,
+    {
+        Vec::from(self.shards)
+            .into_par_iter()
+            .flat_map_iter(|shard| {
+                shard
+                    .into_inner()
+                    .into_iter()
+                    .map(|(k, v)| (k, v.into_inner()))
+            })
+            .drive_unindexed(consumer)
+    }
+}
+
+// This impl also enables `IntoParallelRefIterator::par_iter`
+impl<'a, K, V, S> IntoParallelIterator for &'a DashMap<K, V, S>
+where
+    K: Send + Sync + Eq + Hash,
+    V: Send + Sync,
+    S: Send + Sync + Clone + BuildHasher,
+{
+    type Iter = Iter<'a, K, V, S>;
+    type Item = RefMulti<'a, K, V, S>;
+
+    fn into_par_iter(self) -> Self::Iter {
+        Iter {
+            shards: &self.shards,
+        }
+    }
+}
+
+pub struct Iter<'a, K, V, S = RandomState> {
+    pub(super) shards: &'a [RwLock<HashMap<K, V, S>>],
+}
+
+impl<'a, K, V, S> ParallelIterator for Iter<'a, K, V, S>
+where
+    K: Send + Sync + Eq + Hash,
+    V: Send + Sync,
+    S: Send + Sync + Clone + BuildHasher,
+{
+    type Item = RefMulti<'a, K, V, S>;
+
+    fn drive_unindexed<C>(self, consumer: C) -> C::Result
+    where
+        C: UnindexedConsumer<Self::Item>,
+    {
+        self.shards
+            .into_par_iter()
+            .flat_map_iter(|shard| {
+                let guard = shard.read();
+                let sref: &'a HashMap<K, V, S> = unsafe { util::change_lifetime_const(&*guard) };
+
+                let guard = Arc::new(guard);
+                sref.iter().map(move |(k, v)| {
+                    let guard = Arc::clone(&guard);
+                    unsafe { RefMulti::new(guard, k, v.get()) }
+                })
+            })
+            .drive_unindexed(consumer)
+    }
+}
+
+// This impl also enables `IntoParallelRefMutIterator::par_iter_mut`
+impl<'a, K, V, S> IntoParallelIterator for &'a mut DashMap<K, V, S>
+where
+    K: Send + Sync + Eq + Hash,
+    V: Send + Sync,
+    S: Send + Sync + Clone + BuildHasher,
+{
+    type Iter = IterMut<'a, K, V, S>;
+    type Item = RefMutMulti<'a, K, V, S>;
+
+    fn into_par_iter(self) -> Self::Iter {
+        IterMut {
+            shards: &self.shards,
+        }
+    }
+}
+
+impl<K, V, S> DashMap<K, V, S>
+where
+    K: Send + Sync + Eq + Hash,
+    V: Send + Sync,
+    S: Send + Sync + Clone + BuildHasher,
+{
+    // Unlike `IntoParallelRefMutIterator::par_iter_mut`, we only _need_ `&self`.
+    pub fn par_iter_mut(&self) -> IterMut<'_, K, V, S> {
+        IterMut {
+            shards: &self.shards,
+        }
+    }
+}
+
+pub struct IterMut<'a, K, V, S = RandomState> {
+    shards: &'a [RwLock<HashMap<K, V, S>>],
+}
+
+impl<'a, K, V, S> ParallelIterator for IterMut<'a, K, V, S>
+where
+    K: Send + Sync + Eq + Hash,
+    V: Send + Sync,
+    S: Send + Sync + Clone + BuildHasher,
+{
+    type Item = RefMutMulti<'a, K, V, S>;
+
+    fn drive_unindexed<C>(self, consumer: C) -> C::Result
+    where
+        C: UnindexedConsumer<Self::Item>,
+    {
+        self.shards
+            .into_par_iter()
+            .flat_map_iter(|shard| {
+                let mut guard = shard.write();
+                let sref: &'a mut HashMap<K, V, S> =
+                    unsafe { util::change_lifetime_mut(&mut *guard) };
+
+                let guard = Arc::new(guard);
+                sref.iter_mut().map(move |(k, v)| {
+                    let guard = Arc::clone(&guard);
+                    unsafe { RefMutMulti::new(guard, k, v.get_mut()) }
+                })
+            })
+            .drive_unindexed(consumer)
+    }
+}
diff --git a/src/rayon/read_only.rs b/src/rayon/read_only.rs
new file mode 100644
index 0000000..a11448c
--- /dev/null
+++ b/src/rayon/read_only.rs
@@ -0,0 +1,96 @@
+use crate::mapref::multiple::RefMulti;
+use crate::rayon::map::Iter;
+use crate::ReadOnlyView;
+use core::hash::{BuildHasher, Hash};
+use rayon::iter::IntoParallelIterator;
+
+impl<K, V, S> IntoParallelIterator for ReadOnlyView<K, V, S>
+where
+    K: Send + Eq + Hash,
+    V: Send,
+    S: Send + Clone + BuildHasher,
+{
+    type Iter = super::map::OwningIter<K, V, S>;
+    type Item = (K, V);
+
+    fn into_par_iter(self) -> Self::Iter {
+        super::map::OwningIter {
+            shards: self.map.shards,
+        }
+    }
+}
+
+// This impl also enables `IntoParallelRefIterator::par_iter`
+impl<'a, K, V, S> IntoParallelIterator for &'a ReadOnlyView<K, V, S>
+where
+    K: Send + Sync + Eq + Hash,
+    V: Send + Sync,
+    S: Send + Sync + Clone + BuildHasher,
+{
+    type Iter = Iter<'a, K, V, S>;
+    type Item = RefMulti<'a, K, V, S>;
+
+    fn into_par_iter(self) -> Self::Iter {
+        Iter {
+            shards: &self.map.shards,
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::DashMap;
+    use rayon::iter::{IntoParallelIterator, IntoParallelRefIterator, ParallelIterator};
+
+    fn construct_sample_map() -> DashMap<i32, String> {
+        let map = DashMap::new();
+
+        map.insert(1, "one".to_string());
+
+        map.insert(10, "ten".to_string());
+
+        map.insert(27, "twenty seven".to_string());
+
+        map.insert(45, "forty five".to_string());
+
+        map
+    }
+
+    #[test]
+    fn test_par_iter() {
+        let map = construct_sample_map();
+
+        let view = map.clone().into_read_only();
+
+        view.par_iter().for_each(|entry| {
+            let key = *entry.key();
+
+            assert!(view.contains_key(&key));
+
+            let map_entry = map.get(&key).unwrap();
+
+            assert_eq!(view.get(&key).unwrap(), map_entry.value());
+
+            let key_value: (&i32, &String) = view.get_key_value(&key).unwrap();
+
+            assert_eq!(key_value.0, map_entry.key());
+
+            assert_eq!(key_value.1, map_entry.value());
+        });
+    }
+
+    #[test]
+    fn test_into_par_iter() {
+        let map = construct_sample_map();
+
+        let view = map.clone().into_read_only();
+
+        view.into_par_iter().for_each(|(key, value)| {
+            let map_entry = map.get(&key).unwrap();
+
+            assert_eq!(&key, map_entry.key());
+
+            assert_eq!(&value, map_entry.value());
+        });
+    }
+}
diff --git a/src/rayon/set.rs b/src/rayon/set.rs
new file mode 100644
index 0000000..11c06cc
--- /dev/null
+++ b/src/rayon/set.rs
@@ -0,0 +1,121 @@
+use crate::setref::multiple::RefMulti;
+use crate::DashSet;
+use core::hash::{BuildHasher, Hash};
+use rayon::iter::plumbing::UnindexedConsumer;
+use rayon::iter::{FromParallelIterator, IntoParallelIterator, ParallelExtend, ParallelIterator};
+use std::collections::hash_map::RandomState;
+
+impl<K, S> ParallelExtend<K> for DashSet<K, S>
+where
+    K: Send + Sync + Eq + Hash,
+    S: Send + Sync + Clone + BuildHasher,
+{
+    fn par_extend<I>(&mut self, par_iter: I)
+    where
+        I: IntoParallelIterator<Item = K>,
+    {
+        (&*self).par_extend(par_iter);
+    }
+}
+
+// Since we don't actually need mutability, we can implement this on a
+// reference, similar to `io::Write for &File`.
+impl<K, S> ParallelExtend<K> for &'_ DashSet<K, S>
+where
+    K: Send + Sync + Eq + Hash,
+    S: Send + Sync + Clone + BuildHasher,
+{
+    fn par_extend<I>(&mut self, par_iter: I)
+    where
+        I: IntoParallelIterator<Item = K>,
+    {
+        let &mut set = self;
+        par_iter.into_par_iter().for_each(move |key| {
+            set.insert(key);
+        });
+    }
+}
+
+impl<K, S> FromParallelIterator<K> for DashSet<K, S>
+where
+    K: Send + Sync + Eq + Hash,
+    S: Send + Sync + Clone + Default + BuildHasher,
+{
+    fn from_par_iter<I>(par_iter: I) -> Self
+    where
+        I: IntoParallelIterator<Item = K>,
+    {
+        let set = Self::default();
+        (&set).par_extend(par_iter);
+        set
+    }
+}
+
+impl<K, S> IntoParallelIterator for DashSet<K, S>
+where
+    K: Send + Eq + Hash,
+    S: Send + Clone + BuildHasher,
+{
+    type Iter = OwningIter<K, S>;
+    type Item = K;
+
+    fn into_par_iter(self) -> Self::Iter {
+        OwningIter {
+            inner: self.inner.into_par_iter(),
+        }
+    }
+}
+
+pub struct OwningIter<K, S = RandomState> {
+    inner: super::map::OwningIter<K, (), S>,
+}
+
+impl<K, S> ParallelIterator for OwningIter<K, S>
+where
+    K: Send + Eq + Hash,
+    S: Send + Clone + BuildHasher,
+{
+    type Item = K;
+
+    fn drive_unindexed<C>(self, consumer: C) -> C::Result
+    where
+        C: UnindexedConsumer<Self::Item>,
+    {
+        self.inner.map(|(k, _)| k).drive_unindexed(consumer)
+    }
+}
+
+// This impl also enables `IntoParallelRefIterator::par_iter`
+impl<'a, K, S> IntoParallelIterator for &'a DashSet<K, S>
+where
+    K: Send + Sync + Eq + Hash,
+    S: Send + Sync + Clone + BuildHasher,
+{
+    type Iter = Iter<'a, K, S>;
+    type Item = RefMulti<'a, K, S>;
+
+    fn into_par_iter(self) -> Self::Iter {
+        Iter {
+            inner: (&self.inner).into_par_iter(),
+        }
+    }
+}
+
+pub struct Iter<'a, K, S = RandomState> {
+    inner: super::map::Iter<'a, K, (), S>,
+}
+
+impl<'a, K, S> ParallelIterator for Iter<'a, K, S>
+where
+    K: Send + Sync + Eq + Hash,
+    S: Send + Sync + Clone + BuildHasher,
+{
+    type Item = RefMulti<'a, K, S>;
+
+    fn drive_unindexed<C>(self, consumer: C) -> C::Result
+    where
+        C: UnindexedConsumer<Self::Item>,
+    {
+        self.inner.map(RefMulti::new).drive_unindexed(consumer)
+    }
+}
diff --git a/src/read_only.rs b/src/read_only.rs
new file mode 100644
index 0000000..42ee443
--- /dev/null
+++ b/src/read_only.rs
@@ -0,0 +1,271 @@
+use crate::lock::RwLock;
+use crate::t::Map;
+use crate::{DashMap, HashMap};
+use cfg_if::cfg_if;
+use core::borrow::Borrow;
+use core::fmt;
+use core::hash::{BuildHasher, Hash};
+use std::collections::hash_map::RandomState;
+
+/// A read-only view into a `DashMap`. Allows to obtain raw references to the stored values.
+pub struct ReadOnlyView<K, V, S = RandomState> {
+    pub(crate) map: DashMap<K, V, S>,
+}
+
+impl<K: Eq + Hash + Clone, V: Clone, S: Clone> Clone for ReadOnlyView<K, V, S> {
+    fn clone(&self) -> Self {
+        Self {
+            map: self.map.clone(),
+        }
+    }
+}
+
+impl<K: Eq + Hash + fmt::Debug, V: fmt::Debug, S: BuildHasher + Clone> fmt::Debug
+    for ReadOnlyView<K, V, S>
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.map.fmt(f)
+    }
+}
+
+impl<K, V, S> ReadOnlyView<K, V, S> {
+    pub(crate) fn new(map: DashMap<K, V, S>) -> Self {
+        Self { map }
+    }
+
+    /// Consumes this `ReadOnlyView`, returning the underlying `DashMap`.
+    pub fn into_inner(self) -> DashMap<K, V, S> {
+        self.map
+    }
+}
+
+impl<'a, K: 'a + Eq + Hash, V: 'a, S: BuildHasher + Clone> ReadOnlyView<K, V, S> {
+    /// Returns the number of elements in the map.
+    pub fn len(&self) -> usize {
+        self.map.len()
+    }
+
+    /// Returns `true` if the map contains no elements.
+    pub fn is_empty(&self) -> bool {
+        self.map.is_empty()
+    }
+
+    /// Returns the number of elements the map can hold without reallocating.
+    pub fn capacity(&self) -> usize {
+        self.map.capacity()
+    }
+
+    /// Returns `true` if the map contains a value for the specified key.
+    pub fn contains_key<Q>(&'a self, key: &Q) -> bool
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized,
+    {
+        let hash = self.map.hash_usize(&key);
+
+        let idx = self.map.determine_shard(hash);
+
+        let shard = unsafe { self.map._get_read_shard(idx) };
+
+        shard.contains_key(key)
+    }
+
+    /// Returns a reference to the value corresponding to the key.
+    pub fn get<Q>(&'a self, key: &Q) -> Option<&'a V>
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized,
+    {
+        let hash = self.map.hash_usize(&key);
+
+        let idx = self.map.determine_shard(hash);
+
+        let shard = unsafe { self.map._get_read_shard(idx) };
+
+        shard.get(key).map(|v| v.get())
+    }
+
+    /// Returns the key-value pair corresponding to the supplied key.
+    pub fn get_key_value<Q>(&'a self, key: &Q) -> Option<(&'a K, &'a V)>
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized,
+    {
+        let hash = self.map.hash_usize(&key);
+
+        let idx = self.map.determine_shard(hash);
+
+        let shard = unsafe { self.map._get_read_shard(idx) };
+
+        shard.get_key_value(key).map(|(k, v)| (k, v.get()))
+    }
+
+    fn shard_read_iter(&'a self) -> impl Iterator<Item = &'a HashMap<K, V, S>> + 'a {
+        (0..self.map._shard_count())
+            .map(move |shard_i| unsafe { self.map._get_read_shard(shard_i) })
+    }
+
+    /// An iterator visiting all key-value pairs in arbitrary order. The iterator element type is `(&'a K, &'a V)`.
+    pub fn iter(&'a self) -> impl Iterator<Item = (&'a K, &'a V)> + 'a {
+        self.shard_read_iter()
+            .flat_map(|shard| shard.iter())
+            .map(|(k, v)| (k, v.get()))
+    }
+
+    /// An iterator visiting all keys in arbitrary order. The iterator element type is `&'a K`.
+    pub fn keys(&'a self) -> impl Iterator<Item = &'a K> + 'a {
+        self.shard_read_iter().flat_map(|shard| shard.keys())
+    }
+
+    /// An iterator visiting all values in arbitrary order. The iterator element type is `&'a V`.
+    pub fn values(&'a self) -> impl Iterator<Item = &'a V> + 'a {
+        self.shard_read_iter()
+            .flat_map(|shard| shard.values())
+            .map(|v| v.get())
+    }
+
+    cfg_if! {
+        if #[cfg(feature = "raw-api")] {
+            /// Allows you to peek at the inner shards that store your data.
+            /// You should probably not use this unless you know what you are doing.
+            ///
+            /// Requires the `raw-api` feature to be enabled.
+            ///
+            /// # Examples
+            ///
+            /// ```
+            /// use dashmap::DashMap;
+            ///
+            /// let map = DashMap::<(), ()>::new().into_read_only();
+            /// println!("Amount of shards: {}", map.shards().len());
+            /// ```
+            pub fn shards(&self) -> &[RwLock<HashMap<K, V, S>>] {
+                &self.map.shards
+            }
+        } else {
+            #[allow(dead_code)]
+            pub(crate) fn shards(&self) -> &[RwLock<HashMap<K, V, S>>] {
+                &self.map.shards
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+
+mod tests {
+
+    use crate::DashMap;
+
+    fn construct_sample_map() -> DashMap<i32, String> {
+        let map = DashMap::new();
+
+        map.insert(1, "one".to_string());
+
+        map.insert(10, "ten".to_string());
+
+        map.insert(27, "twenty seven".to_string());
+
+        map.insert(45, "forty five".to_string());
+
+        map
+    }
+
+    #[test]
+
+    fn test_properties() {
+        let map = construct_sample_map();
+
+        let view = map.clone().into_read_only();
+
+        assert_eq!(view.is_empty(), map.is_empty());
+
+        assert_eq!(view.len(), map.len());
+
+        assert_eq!(view.capacity(), map.capacity());
+
+        let new_map = view.into_inner();
+
+        assert_eq!(new_map.is_empty(), map.is_empty());
+
+        assert_eq!(new_map.len(), map.len());
+
+        assert_eq!(new_map.capacity(), map.capacity());
+    }
+
+    #[test]
+
+    fn test_get() {
+        let map = construct_sample_map();
+
+        let view = map.clone().into_read_only();
+
+        for key in map.iter().map(|entry| *entry.key()) {
+            assert!(view.contains_key(&key));
+
+            let map_entry = map.get(&key).unwrap();
+
+            assert_eq!(view.get(&key).unwrap(), map_entry.value());
+
+            let key_value: (&i32, &String) = view.get_key_value(&key).unwrap();
+
+            assert_eq!(key_value.0, map_entry.key());
+
+            assert_eq!(key_value.1, map_entry.value());
+        }
+    }
+
+    #[test]
+
+    fn test_iters() {
+        let map = construct_sample_map();
+
+        let view = map.clone().into_read_only();
+
+        let mut visited_items = Vec::new();
+
+        for (key, value) in view.iter() {
+            map.contains_key(key);
+
+            let map_entry = map.get(key).unwrap();
+
+            assert_eq!(key, map_entry.key());
+
+            assert_eq!(value, map_entry.value());
+
+            visited_items.push((key, value));
+        }
+
+        let mut visited_keys = Vec::new();
+
+        for key in view.keys() {
+            map.contains_key(key);
+
+            let map_entry = map.get(key).unwrap();
+
+            assert_eq!(key, map_entry.key());
+
+            assert_eq!(view.get(key).unwrap(), map_entry.value());
+
+            visited_keys.push(key);
+        }
+
+        let mut visited_values = Vec::new();
+
+        for value in view.values() {
+            visited_values.push(value);
+        }
+
+        for entry in map.iter() {
+            let key = entry.key();
+
+            let value = entry.value();
+
+            assert!(visited_keys.contains(&key));
+
+            assert!(visited_values.contains(&value));
+
+            assert!(visited_items.contains(&(key, value)));
+        }
+    }
+}
diff --git a/src/serde.rs b/src/serde.rs
new file mode 100644
index 0000000..6abeb06
--- /dev/null
+++ b/src/serde.rs
@@ -0,0 +1,215 @@
+use crate::{mapref, setref, DashMap, DashSet};
+use core::fmt;
+use core::hash::{BuildHasher, Hash};
+use core::marker::PhantomData;
+use serde::de::{Deserialize, MapAccess, SeqAccess, Visitor};
+use serde::ser::{Serialize, SerializeMap, SerializeSeq, Serializer};
+use serde::Deserializer;
+
+pub struct DashMapVisitor<K, V, S> {
+    marker: PhantomData<fn() -> DashMap<K, V, S>>,
+}
+
+impl<K, V, S> DashMapVisitor<K, V, S>
+where
+    K: Eq + Hash,
+    S: BuildHasher + Clone,
+{
+    fn new() -> Self {
+        DashMapVisitor {
+            marker: PhantomData,
+        }
+    }
+}
+
+impl<'de, K, V, S> Visitor<'de> for DashMapVisitor<K, V, S>
+where
+    K: Deserialize<'de> + Eq + Hash,
+    V: Deserialize<'de>,
+    S: BuildHasher + Clone + Default,
+{
+    type Value = DashMap<K, V, S>;
+
+    fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("a DashMap")
+    }
+
+    fn visit_map<M>(self, mut access: M) -> Result<Self::Value, M::Error>
+    where
+        M: MapAccess<'de>,
+    {
+        let map =
+            DashMap::with_capacity_and_hasher(access.size_hint().unwrap_or(0), Default::default());
+
+        while let Some((key, value)) = access.next_entry()? {
+            map.insert(key, value);
+        }
+
+        Ok(map)
+    }
+}
+
+impl<'de, K, V, S> Deserialize<'de> for DashMap<K, V, S>
+where
+    K: Deserialize<'de> + Eq + Hash,
+    V: Deserialize<'de>,
+    S: BuildHasher + Clone + Default,
+{
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        deserializer.deserialize_map(DashMapVisitor::<K, V, S>::new())
+    }
+}
+
+impl<K, V, H> Serialize for DashMap<K, V, H>
+where
+    K: Serialize + Eq + Hash,
+    V: Serialize,
+    H: BuildHasher + Clone,
+{
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        let mut map = serializer.serialize_map(Some(self.len()))?;
+
+        for ref_multi in self.iter() {
+            map.serialize_entry(ref_multi.key(), ref_multi.value())?;
+        }
+
+        map.end()
+    }
+}
+
+pub struct DashSetVisitor<K, S> {
+    marker: PhantomData<fn() -> DashSet<K, S>>,
+}
+
+impl<K, S> DashSetVisitor<K, S>
+where
+    K: Eq + Hash,
+    S: BuildHasher + Clone,
+{
+    fn new() -> Self {
+        DashSetVisitor {
+            marker: PhantomData,
+        }
+    }
+}
+
+impl<'de, K, S> Visitor<'de> for DashSetVisitor<K, S>
+where
+    K: Deserialize<'de> + Eq + Hash,
+    S: BuildHasher + Clone + Default,
+{
+    type Value = DashSet<K, S>;
+
+    fn expecting(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.write_str("a DashSet")
+    }
+
+    fn visit_seq<M>(self, mut access: M) -> Result<Self::Value, M::Error>
+    where
+        M: SeqAccess<'de>,
+    {
+        let map =
+            DashSet::with_capacity_and_hasher(access.size_hint().unwrap_or(0), Default::default());
+
+        while let Some(key) = access.next_element()? {
+            map.insert(key);
+        }
+
+        Ok(map)
+    }
+}
+
+impl<'de, K, S> Deserialize<'de> for DashSet<K, S>
+where
+    K: Deserialize<'de> + Eq + Hash,
+    S: BuildHasher + Clone + Default,
+{
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        deserializer.deserialize_seq(DashSetVisitor::<K, S>::new())
+    }
+}
+
+impl<K, H> Serialize for DashSet<K, H>
+where
+    K: Serialize + Eq + Hash,
+    H: BuildHasher + Clone,
+{
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        let mut seq = serializer.serialize_seq(Some(self.len()))?;
+
+        for ref_multi in self.iter() {
+            seq.serialize_element(ref_multi.key())?;
+        }
+
+        seq.end()
+    }
+}
+
+macro_rules! serialize_impl {
+    () => {
+        fn serialize<Ser>(&self, serializer: Ser) -> Result<Ser::Ok, Ser::Error>
+        where
+            Ser: serde::Serializer,
+        {
+            std::ops::Deref::deref(self).serialize(serializer)
+        }
+    };
+}
+
+// Map
+impl<'a, K: Eq + Hash, V: Serialize, S: BuildHasher> Serialize
+    for mapref::multiple::RefMulti<'a, K, V, S>
+{
+    serialize_impl! {}
+}
+
+impl<'a, K: Eq + Hash, V: Serialize, S: BuildHasher> Serialize
+    for mapref::multiple::RefMutMulti<'a, K, V, S>
+{
+    serialize_impl! {}
+}
+
+impl<'a, K: Eq + Hash, V: Serialize, S: BuildHasher> Serialize for mapref::one::Ref<'a, K, V, S> {
+    serialize_impl! {}
+}
+
+impl<'a, K: Eq + Hash, V: Serialize, S: BuildHasher> Serialize
+    for mapref::one::RefMut<'a, K, V, S>
+{
+    serialize_impl! {}
+}
+
+impl<'a, K: Eq + Hash, V, T: Serialize, S: BuildHasher> Serialize
+    for mapref::one::MappedRef<'a, K, V, T, S>
+{
+    serialize_impl! {}
+}
+
+impl<'a, K: Eq + Hash, V, T: Serialize, S: BuildHasher> Serialize
+    for mapref::one::MappedRefMut<'a, K, V, T, S>
+{
+    serialize_impl! {}
+}
+
+// Set
+impl<'a, V: Hash + Eq + Serialize, S: BuildHasher> Serialize
+    for setref::multiple::RefMulti<'a, V, S>
+{
+    serialize_impl! {}
+}
+
+impl<'a, V: Hash + Eq + Serialize, S: BuildHasher> Serialize for setref::one::Ref<'a, V, S> {
+    serialize_impl! {}
+}
diff --git a/src/set.rs b/src/set.rs
new file mode 100644
index 0000000..1a56177
--- /dev/null
+++ b/src/set.rs
@@ -0,0 +1,458 @@
+use crate::iter_set::{Iter, OwningIter};
+#[cfg(feature = "raw-api")]
+use crate::lock::RwLock;
+use crate::setref::one::Ref;
+use crate::DashMap;
+#[cfg(feature = "raw-api")]
+use crate::HashMap;
+use cfg_if::cfg_if;
+use core::borrow::Borrow;
+use core::fmt;
+use core::hash::{BuildHasher, Hash};
+use core::iter::FromIterator;
+use std::collections::hash_map::RandomState;
+
+/// DashSet is a thin wrapper around [`DashMap`] using `()` as the value type. It uses
+/// methods and types which are more convenient to work with on a set.
+///
+/// [`DashMap`]: struct.DashMap.html
+pub struct DashSet<K, S = RandomState> {
+    pub(crate) inner: DashMap<K, (), S>,
+}
+
+impl<K: Eq + Hash + fmt::Debug, S: BuildHasher + Clone> fmt::Debug for DashSet<K, S> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Debug::fmt(&self.inner, f)
+    }
+}
+
+impl<K: Eq + Hash + Clone, S: Clone> Clone for DashSet<K, S> {
+    fn clone(&self) -> Self {
+        Self {
+            inner: self.inner.clone(),
+        }
+    }
+
+    fn clone_from(&mut self, source: &Self) {
+        self.inner.clone_from(&source.inner)
+    }
+}
+
+impl<K, S> Default for DashSet<K, S>
+where
+    K: Eq + Hash,
+    S: Default + BuildHasher + Clone,
+{
+    fn default() -> Self {
+        Self::with_hasher(Default::default())
+    }
+}
+
+impl<'a, K: 'a + Eq + Hash> DashSet<K, RandomState> {
+    /// Creates a new DashSet with a capacity of 0.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashSet;
+    ///
+    /// let games = DashSet::new();
+    /// games.insert("Veloren");
+    /// ```
+    pub fn new() -> Self {
+        Self::with_hasher(RandomState::default())
+    }
+
+    /// Creates a new DashMap with a specified starting capacity.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashSet;
+    ///
+    /// let numbers = DashSet::with_capacity(2);
+    /// numbers.insert(2);
+    /// numbers.insert(8);
+    /// ```
+    pub fn with_capacity(capacity: usize) -> Self {
+        Self::with_capacity_and_hasher(capacity, RandomState::default())
+    }
+}
+
+impl<'a, K: 'a + Eq + Hash, S: BuildHasher + Clone> DashSet<K, S> {
+    /// Creates a new DashMap with a capacity of 0 and the provided hasher.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashSet;
+    /// use std::collections::hash_map::RandomState;
+    ///
+    /// let s = RandomState::new();
+    /// let games = DashSet::with_hasher(s);
+    /// games.insert("Veloren");
+    /// ```
+    pub fn with_hasher(hasher: S) -> Self {
+        Self::with_capacity_and_hasher(0, hasher)
+    }
+
+    /// Creates a new DashMap with a specified starting capacity and hasher.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashSet;
+    /// use std::collections::hash_map::RandomState;
+    ///
+    /// let s = RandomState::new();
+    /// let numbers = DashSet::with_capacity_and_hasher(2, s);
+    /// numbers.insert(2);
+    /// numbers.insert(8);
+    /// ```
+    pub fn with_capacity_and_hasher(capacity: usize, hasher: S) -> Self {
+        Self {
+            inner: DashMap::with_capacity_and_hasher(capacity, hasher),
+        }
+    }
+
+    /// Hash a given item to produce a usize.
+    /// Uses the provided or default HashBuilder.
+    pub fn hash_usize<T: Hash>(&self, item: &T) -> usize {
+        self.inner.hash_usize(item)
+    }
+
+    cfg_if! {
+        if #[cfg(feature = "raw-api")] {
+            /// Allows you to peek at the inner shards that store your data.
+            /// You should probably not use this unless you know what you are doing.
+            ///
+            /// Requires the `raw-api` feature to be enabled.
+            ///
+            /// # Examples
+            ///
+            /// ```
+            /// use dashmap::DashSet;
+            ///
+            /// let set = DashSet::<()>::new();
+            /// println!("Amount of shards: {}", set.shards().len());
+            /// ```
+            pub fn shards(&self) -> &[RwLock<HashMap<K, (), S>>] {
+                self.inner.shards()
+            }
+        }
+    }
+
+    cfg_if! {
+        if #[cfg(feature = "raw-api")] {
+            /// Finds which shard a certain key is stored in.
+            /// You should probably not use this unless you know what you are doing.
+            /// Note that shard selection is dependent on the default or provided HashBuilder.
+            ///
+            /// Requires the `raw-api` feature to be enabled.
+            ///
+            /// # Examples
+            ///
+            /// ```
+            /// use dashmap::DashSet;
+            ///
+            /// let set = DashSet::new();
+            /// set.insert("coca-cola");
+            /// println!("coca-cola is stored in shard: {}", set.determine_map("coca-cola"));
+            /// ```
+            pub fn determine_map<Q>(&self, key: &Q) -> usize
+            where
+                K: Borrow<Q>,
+                Q: Hash + Eq + ?Sized,
+            {
+                self.inner.determine_map(key)
+            }
+        }
+    }
+
+    cfg_if! {
+        if #[cfg(feature = "raw-api")] {
+            /// Finds which shard a certain hash is stored in.
+            ///
+            /// Requires the `raw-api` feature to be enabled.
+            ///
+            /// # Examples
+            ///
+            /// ```
+            /// use dashmap::DashSet;
+            ///
+            /// let set: DashSet<i32> = DashSet::new();
+            /// let key = "key";
+            /// let hash = set.hash_usize(&key);
+            /// println!("hash is stored in shard: {}", set.determine_shard(hash));
+            /// ```
+            pub fn determine_shard(&self, hash: usize) -> usize {
+                self.inner.determine_shard(hash)
+            }
+        }
+    }
+
+    /// Inserts a key into the set. Returns true if the key was not already in the set.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashSet;
+    ///
+    /// let set = DashSet::new();
+    /// set.insert("I am the key!");
+    /// ```
+    pub fn insert(&self, key: K) -> bool {
+        self.inner.insert(key, ()).is_none()
+    }
+
+    /// Removes an entry from the map, returning the key if it existed in the map.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashSet;
+    ///
+    /// let soccer_team = DashSet::new();
+    /// soccer_team.insert("Jack");
+    /// assert_eq!(soccer_team.remove("Jack").unwrap(), "Jack");
+    /// ```
+    pub fn remove<Q>(&self, key: &Q) -> Option<K>
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized,
+    {
+        self.inner.remove(key).map(|(k, _)| k)
+    }
+
+    /// Removes an entry from the set, returning the key
+    /// if the entry existed and the provided conditional function returned true.
+    ///
+    /// ```
+    /// use dashmap::DashSet;
+    ///
+    /// let soccer_team = DashSet::new();
+    /// soccer_team.insert("Sam");
+    /// soccer_team.remove_if("Sam", |player| player.starts_with("Ja"));
+    /// assert!(soccer_team.contains("Sam"));
+    /// ```
+    /// ```
+    /// use dashmap::DashSet;
+    ///
+    /// let soccer_team = DashSet::new();
+    /// soccer_team.insert("Sam");
+    /// soccer_team.remove_if("Jacob", |player| player.starts_with("Ja"));
+    /// assert!(!soccer_team.contains("Jacob"));
+    /// ```
+    pub fn remove_if<Q>(&self, key: &Q, f: impl FnOnce(&K) -> bool) -> Option<K>
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized,
+    {
+        // TODO: Don't create another closure around f
+        self.inner.remove_if(key, |k, _| f(k)).map(|(k, _)| k)
+    }
+
+    /// Creates an iterator over a DashMap yielding immutable references.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashSet;
+    ///
+    /// let words = DashSet::new();
+    /// words.insert("hello");
+    /// assert_eq!(words.iter().count(), 1);
+    /// ```
+    pub fn iter(&'a self) -> Iter<'a, K, S, DashMap<K, (), S>> {
+        let iter = self.inner.iter();
+
+        Iter::new(iter)
+    }
+
+    /// Get a reference to an entry in the set
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashSet;
+    ///
+    /// let youtubers = DashSet::new();
+    /// youtubers.insert("Bosnian Bill");
+    /// assert_eq!(*youtubers.get("Bosnian Bill").unwrap(), "Bosnian Bill");
+    /// ```
+    pub fn get<Q>(&'a self, key: &Q) -> Option<Ref<'a, K, S>>
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized,
+    {
+        self.inner.get(key).map(Ref::new)
+    }
+
+    /// Remove excess capacity to reduce memory usage.
+    pub fn shrink_to_fit(&self) {
+        self.inner.shrink_to_fit()
+    }
+
+    /// Retain elements that whose predicates return true
+    /// and discard elements whose predicates return false.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashSet;
+    ///
+    /// let people = DashSet::new();
+    /// people.insert("Albin");
+    /// people.insert("Jones");
+    /// people.insert("Charlie");
+    /// people.retain(|name| name.contains('i'));
+    /// assert_eq!(people.len(), 2);
+    /// ```
+    pub fn retain(&self, mut f: impl FnMut(&K) -> bool) {
+        self.inner.retain(|k, _| f(k))
+    }
+
+    /// Fetches the total number of keys stored in the set.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashSet;
+    ///
+    /// let people = DashSet::new();
+    /// people.insert("Albin");
+    /// people.insert("Jones");
+    /// people.insert("Charlie");
+    /// assert_eq!(people.len(), 3);
+    /// ```
+    pub fn len(&self) -> usize {
+        self.inner.len()
+    }
+
+    /// Checks if the set is empty or not.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashSet;
+    ///
+    /// let map = DashSet::<()>::new();
+    /// assert!(map.is_empty());
+    /// ```
+    pub fn is_empty(&self) -> bool {
+        self.inner.is_empty()
+    }
+
+    /// Removes all keys in the set.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashSet;
+    ///
+    /// let people = DashSet::new();
+    /// people.insert("Albin");
+    /// assert!(!people.is_empty());
+    /// people.clear();
+    /// assert!(people.is_empty());
+    /// ```
+    pub fn clear(&self) {
+        self.inner.clear()
+    }
+
+    /// Returns how many keys the set can store without reallocating.
+    pub fn capacity(&self) -> usize {
+        self.inner.capacity()
+    }
+
+    /// Checks if the set contains a specific key.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use dashmap::DashSet;
+    ///
+    /// let people = DashSet::new();
+    /// people.insert("Dakota Cherries");
+    /// assert!(people.contains("Dakota Cherries"));
+    /// ```
+    pub fn contains<Q>(&self, key: &Q) -> bool
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized,
+    {
+        self.inner.contains_key(key)
+    }
+}
+
+impl<K: Eq + Hash, S: BuildHasher + Clone> IntoIterator for DashSet<K, S> {
+    type Item = K;
+
+    type IntoIter = OwningIter<K, S>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        OwningIter::new(self.inner.into_iter())
+    }
+}
+
+impl<K: Eq + Hash, S: BuildHasher + Clone> Extend<K> for DashSet<K, S> {
+    fn extend<T: IntoIterator<Item = K>>(&mut self, iter: T) {
+        let iter = iter.into_iter().map(|k| (k, ()));
+
+        self.inner.extend(iter)
+    }
+}
+
+impl<K: Eq + Hash, S: BuildHasher + Clone + Default> FromIterator<K> for DashSet<K, S> {
+    fn from_iter<I: IntoIterator<Item = K>>(iter: I) -> Self {
+        let mut set = DashSet::default();
+
+        set.extend(iter);
+
+        set
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::DashSet;
+
+    #[test]
+    fn test_basic() {
+        let set = DashSet::new();
+
+        set.insert(0);
+
+        assert_eq!(set.get(&0).as_deref(), Some(&0));
+    }
+
+    #[test]
+    fn test_default() {
+        let set: DashSet<u32> = DashSet::default();
+
+        set.insert(0);
+
+        assert_eq!(set.get(&0).as_deref(), Some(&0));
+    }
+
+    #[test]
+    fn test_multiple_hashes() {
+        let set = DashSet::<u32>::default();
+
+        for i in 0..100 {
+            assert!(set.insert(i));
+        }
+
+        for i in 0..100 {
+            assert!(!set.insert(i));
+        }
+
+        for i in 0..100 {
+            assert_eq!(Some(i), set.remove(&i));
+        }
+
+        for i in 0..100 {
+            assert_eq!(None, set.remove(&i));
+        }
+    }
+}
diff --git a/src/setref/mod.rs b/src/setref/mod.rs
new file mode 100644
index 0000000..95ae8f4
--- /dev/null
+++ b/src/setref/mod.rs
@@ -0,0 +1,2 @@
+pub mod multiple;
+pub mod one;
diff --git a/src/setref/multiple.rs b/src/setref/multiple.rs
new file mode 100644
index 0000000..21e7ed4
--- /dev/null
+++ b/src/setref/multiple.rs
@@ -0,0 +1,25 @@
+use crate::mapref;
+use core::hash::{BuildHasher, Hash};
+use core::ops::Deref;
+use std::collections::hash_map::RandomState;
+pub struct RefMulti<'a, K, S = RandomState> {
+    inner: mapref::multiple::RefMulti<'a, K, (), S>,
+}
+
+impl<'a, K: Eq + Hash, S: BuildHasher> RefMulti<'a, K, S> {
+    pub(crate) fn new(inner: mapref::multiple::RefMulti<'a, K, (), S>) -> Self {
+        Self { inner }
+    }
+
+    pub fn key(&self) -> &K {
+        self.inner.key()
+    }
+}
+
+impl<'a, K: Eq + Hash, S: BuildHasher> Deref for RefMulti<'a, K, S> {
+    type Target = K;
+
+    fn deref(&self) -> &K {
+        self.key()
+    }
+}
diff --git a/src/setref/one.rs b/src/setref/one.rs
new file mode 100644
index 0000000..0787187
--- /dev/null
+++ b/src/setref/one.rs
@@ -0,0 +1,25 @@
+use crate::mapref;
+use core::hash::{BuildHasher, Hash};
+use core::ops::Deref;
+use std::collections::hash_map::RandomState;
+pub struct Ref<'a, K, S = RandomState> {
+    inner: mapref::one::Ref<'a, K, (), S>,
+}
+
+impl<'a, K: Eq + Hash, S: BuildHasher> Ref<'a, K, S> {
+    pub(crate) fn new(inner: mapref::one::Ref<'a, K, (), S>) -> Self {
+        Self { inner }
+    }
+
+    pub fn key(&self) -> &K {
+        self.inner.key()
+    }
+}
+
+impl<'a, K: Eq + Hash, S: BuildHasher> Deref for Ref<'a, K, S> {
+    type Target = K;
+
+    fn deref(&self) -> &K {
+        self.key()
+    }
+}
diff --git a/src/t.rs b/src/t.rs
new file mode 100644
index 0000000..5e1fedc
--- /dev/null
+++ b/src/t.rs
@@ -0,0 +1,134 @@
+//! Central map trait to ease modifications and extensions down the road.
+
+use crate::iter::{Iter, IterMut};
+use crate::lock::{RwLockReadGuard, RwLockWriteGuard};
+use crate::mapref::entry::Entry;
+use crate::mapref::one::{Ref, RefMut};
+use crate::try_result::TryResult;
+use crate::HashMap;
+use core::borrow::Borrow;
+use core::hash::{BuildHasher, Hash};
+
+/// Implementation detail that is exposed due to generic constraints in public types.
+pub trait Map<'a, K: 'a + Eq + Hash, V: 'a, S: 'a + Clone + BuildHasher> {
+    fn _shard_count(&self) -> usize;
+
+    /// # Safety
+    ///
+    /// The index must not be out of bounds.
+    unsafe fn _get_read_shard(&'a self, i: usize) -> &'a HashMap<K, V, S>;
+
+    /// # Safety
+    ///
+    /// The index must not be out of bounds.
+    unsafe fn _yield_read_shard(&'a self, i: usize) -> RwLockReadGuard<'a, HashMap<K, V, S>>;
+
+    /// # Safety
+    ///
+    /// The index must not be out of bounds.
+    unsafe fn _yield_write_shard(&'a self, i: usize) -> RwLockWriteGuard<'a, HashMap<K, V, S>>;
+
+    /// # Safety
+    ///
+    /// The index must not be out of bounds.
+    unsafe fn _try_yield_read_shard(
+        &'a self,
+        i: usize,
+    ) -> Option<RwLockReadGuard<'a, HashMap<K, V, S>>>;
+
+    /// # Safety
+    ///
+    /// The index must not be out of bounds.
+    unsafe fn _try_yield_write_shard(
+        &'a self,
+        i: usize,
+    ) -> Option<RwLockWriteGuard<'a, HashMap<K, V, S>>>;
+
+    fn _insert(&self, key: K, value: V) -> Option<V>;
+
+    fn _remove<Q>(&self, key: &Q) -> Option<(K, V)>
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized;
+
+    fn _remove_if<Q>(&self, key: &Q, f: impl FnOnce(&K, &V) -> bool) -> Option<(K, V)>
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized;
+
+    fn _remove_if_mut<Q>(&self, key: &Q, f: impl FnOnce(&K, &mut V) -> bool) -> Option<(K, V)>
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized;
+
+    fn _iter(&'a self) -> Iter<'a, K, V, S, Self>
+    where
+        Self: Sized;
+
+    fn _iter_mut(&'a self) -> IterMut<'a, K, V, S, Self>
+    where
+        Self: Sized;
+
+    fn _get<Q>(&'a self, key: &Q) -> Option<Ref<'a, K, V, S>>
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized;
+
+    fn _get_mut<Q>(&'a self, key: &Q) -> Option<RefMut<'a, K, V, S>>
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized;
+
+    fn _try_get<Q>(&'a self, key: &Q) -> TryResult<Ref<'a, K, V, S>>
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized;
+
+    fn _try_get_mut<Q>(&'a self, key: &Q) -> TryResult<RefMut<'a, K, V, S>>
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized;
+
+    fn _shrink_to_fit(&self);
+
+    fn _retain(&self, f: impl FnMut(&K, &mut V) -> bool);
+
+    fn _len(&self) -> usize;
+
+    fn _capacity(&self) -> usize;
+
+    fn _alter<Q>(&self, key: &Q, f: impl FnOnce(&K, V) -> V)
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized;
+
+    fn _alter_all(&self, f: impl FnMut(&K, V) -> V);
+
+    fn _view<Q, R>(&self, key: &Q, f: impl FnOnce(&K, &V) -> R) -> Option<R>
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized;
+
+    fn _entry(&'a self, key: K) -> Entry<'a, K, V, S>;
+
+    fn _try_entry(&'a self, key: K) -> Option<Entry<'a, K, V, S>>;
+
+    fn _hasher(&self) -> S;
+
+    // provided
+    fn _clear(&self) {
+        self._retain(|_, _| false)
+    }
+
+    fn _contains_key<Q>(&'a self, key: &Q) -> bool
+    where
+        K: Borrow<Q>,
+        Q: Hash + Eq + ?Sized,
+    {
+        self._get(key).is_some()
+    }
+
+    fn _is_empty(&self) -> bool {
+        self._len() == 0
+    }
+}
diff --git a/src/try_result.rs b/src/try_result.rs
new file mode 100644
index 0000000..aa93d3b
--- /dev/null
+++ b/src/try_result.rs
@@ -0,0 +1,46 @@
+/// Represents the result of a non-blocking read from a [DashMap](crate::DashMap).
+#[derive(Debug)]
+pub enum TryResult<R> {
+    /// The value was present in the map, and the lock for the shard was successfully obtained.
+    Present(R),
+    /// The shard wasn't locked, and the value wasn't present in the map.
+    Absent,
+    /// The shard was locked.
+    Locked,
+}
+
+impl<R> TryResult<R> {
+    /// Returns `true` if the value was present in the map, and the lock for the shard was successfully obtained.
+    pub fn is_present(&self) -> bool {
+        matches!(self, TryResult::Present(_))
+    }
+
+    /// Returns `true` if the shard wasn't locked, and the value wasn't present in the map.
+    pub fn is_absent(&self) -> bool {
+        matches!(self, TryResult::Absent)
+    }
+
+    /// Returns `true` if the shard was locked.
+    pub fn is_locked(&self) -> bool {
+        matches!(self, TryResult::Locked)
+    }
+
+    /// If `self` is [Present](TryResult::Present), returns the reference to the value in the map.
+    /// Panics if `self` is not [Present](TryResult::Present).
+    pub fn unwrap(self) -> R {
+        match self {
+            TryResult::Present(r) => r,
+            TryResult::Locked => panic!("Called unwrap() on TryResult::Locked"),
+            TryResult::Absent => panic!("Called unwrap() on TryResult::Absent"),
+        }
+    }
+
+    /// If `self` is [Present](TryResult::Present), returns the reference to the value in the map.
+    /// If `self` is not [Present](TryResult::Present), returns `None`.
+    pub fn try_unwrap(self) -> Option<R> {
+        match self {
+            TryResult::Present(r) => Some(r),
+            _ => None,
+        }
+    }
+}
diff --git a/src/util.rs b/src/util.rs
new file mode 100644
index 0000000..d84e37d
--- /dev/null
+++ b/src/util.rs
@@ -0,0 +1,102 @@
+//! This module is full of hackery and dark magic.
+//! Either spend a day fixing it and quietly submit a PR or don't mention it to anybody.
+use core::cell::UnsafeCell;
+use core::{mem, ptr};
+
+pub const fn ptr_size_bits() -> usize {
+    mem::size_of::<usize>() * 8
+}
+
+pub fn map_in_place_2<T, U, F: FnOnce(U, T) -> T>((k, v): (U, &mut T), f: F) {
+    unsafe {
+        // # Safety
+        //
+        // If the closure panics, we must abort otherwise we could double drop `T`
+        let _promote_panic_to_abort = AbortOnPanic;
+
+        ptr::write(v, f(k, ptr::read(v)));
+    }
+}
+
+/// # Safety
+///
+/// Requires that you ensure the reference does not become invalid.
+/// The object has to outlive the reference.
+pub unsafe fn change_lifetime_const<'a, 'b, T>(x: &'a T) -> &'b T {
+    &*(x as *const T)
+}
+
+/// # Safety
+///
+/// Requires that you ensure the reference does not become invalid.
+/// The object has to outlive the reference.
+pub unsafe fn change_lifetime_mut<'a, 'b, T>(x: &'a mut T) -> &'b mut T {
+    &mut *(x as *mut T)
+}
+
+/// A simple wrapper around `T`
+///
+/// This is to prevent UB when using `HashMap::get_key_value`, because
+/// `HashMap` doesn't expose an api to get the key and value, where
+/// the value is a `&mut T`.
+///
+/// See [#10](https://github.com/xacrimon/dashmap/issues/10) for details
+///
+/// This type is meant to be an implementation detail, but must be exposed due to the `Dashmap::shards`
+#[repr(transparent)]
+pub struct SharedValue<T> {
+    value: UnsafeCell<T>,
+}
+
+impl<T: Clone> Clone for SharedValue<T> {
+    fn clone(&self) -> Self {
+        let inner = self.get().clone();
+
+        Self {
+            value: UnsafeCell::new(inner),
+        }
+    }
+}
+
+unsafe impl<T: Send> Send for SharedValue<T> {}
+
+unsafe impl<T: Sync> Sync for SharedValue<T> {}
+
+impl<T> SharedValue<T> {
+    /// Create a new `SharedValue<T>`
+    pub const fn new(value: T) -> Self {
+        Self {
+            value: UnsafeCell::new(value),
+        }
+    }
+
+    /// Get a shared reference to `T`
+    pub fn get(&self) -> &T {
+        unsafe { &*self.value.get() }
+    }
+
+    /// Get an unique reference to `T`
+    pub fn get_mut(&mut self) -> &mut T {
+        unsafe { &mut *self.value.get() }
+    }
+
+    /// Unwraps the value
+    pub fn into_inner(self) -> T {
+        self.value.into_inner()
+    }
+
+    /// Get a mutable raw pointer to the underlying value
+    pub(crate) fn as_ptr(&self) -> *mut T {
+        self.value.get()
+    }
+}
+
+struct AbortOnPanic;
+
+impl Drop for AbortOnPanic {
+    fn drop(&mut self) {
+        if std::thread::panicking() {
+            std::process::abort()
+        }
+    }
+}