1 files changed, 40 insertions, 0 deletions
diff --git a/src/rand.rs b/src/rand.rs
new file mode 100644
index 0000000..15d88f7
--- /dev/null
+++ b/src/rand.rs
@@ -0,0 +1,40 @@
+#![allow(unsafe_code)]
+#![allow(unused)]
+
+#[derive(Debug)]
+pub(crate) struct Rand {
+    state: u64,
+}
+
+impl Rand {
+    pub(crate) const fn new(seed: u64) -> Self {
+        Self { state: seed }
+    }
+
+    pub(crate) fn rand_u32(&mut self) -> u32 {
+        // sPCG32 from https://www.pcg-random.org/paper.html
+        // see also https://nullprogram.com/blog/2017/09/21/
+        const M: u64 = 0xbb2efcec3c39611d;
+        const A: u64 = 0x7590ef39;
+
+        let s = self.state.wrapping_mul(M).wrapping_add(A);
+        self.state = s;
+
+        let shift = 29 - (s >> 61);
+        (s >> shift) as u32
+    }
+
+    pub(crate) fn rand_u16(&mut self) -> u16 {
+        let n = self.rand_u32();
+        (n ^ (n >> 16)) as u16
+    }
+
+    pub(crate) fn rand_source_port(&mut self) -> u16 {
+        loop {
+            let res = self.rand_u16();
+            if res > 1024 {
+                return res;
+            }
+        }
+    }
+}