1 files changed, 74 insertions, 0 deletions
diff --git a/src/tag.rs b/src/tag.rs
new file mode 100644
index 0000000..c7130c1
--- /dev/null
+++ b/src/tag.rs
@@ -0,0 +1,74 @@
+use crate::{Error, Result};
+use alloc::string::ToString;
+use rusticata_macros::newtype_enum;
+
+/// BER/DER Tag as defined in X.680 section 8.4
+///
+/// X.690 doesn't specify the maximum tag size so we're assuming that people
+/// aren't going to need anything more than a u32.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct Tag(pub u32);
+
+newtype_enum! {
+impl display Tag {
+    EndOfContent = 0,
+    Boolean = 1,
+    Integer = 2,
+    BitString = 3,
+    OctetString = 4,
+    Null = 5,
+    Oid = 6,
+    ObjectDescriptor = 7,
+    External = 8,
+    RealType = 9,
+    Enumerated = 10,
+    EmbeddedPdv = 11,
+    Utf8String = 12,
+    RelativeOid = 13,
+
+    Sequence = 16,
+    Set = 17,
+    NumericString = 18,
+    PrintableString = 19,
+    T61String = 20,
+    TeletexString = 20,
+    VideotexString = 21,
+
+    Ia5String = 22,
+    UtcTime = 23,
+    GeneralizedTime = 24,
+
+    GraphicString = 25,
+    VisibleString = 26,
+    GeneralString = 27,
+
+    UniversalString = 28,
+    BmpString = 30,
+}
+}
+
+impl Tag {
+    pub const fn assert_eq(&self, tag: Tag) -> Result<()> {
+        if self.0 == tag.0 {
+            Ok(())
+        } else {
+            Err(Error::UnexpectedTag {
+                expected: Some(tag),
+                actual: *self,
+            })
+        }
+    }
+
+    pub fn invalid_value(&self, msg: &str) -> Error {
+        Error::InvalidValue {
+            tag: *self,
+            msg: msg.to_string(),
+        }
+    }
+}
+
+impl From<u32> for Tag {
+    fn from(v: u32) -> Self {
+        Tag(v)
+    }
+}