jingle_drls_srtp: Add a new parser and serialiser.

src/util/helpers.rs

@@ -65,3 +65,28 @@ impl WhitespaceAwareBase64 {
         Some(base64::encode(b))
     }
 }
+
+/// Codec for colon-separated bytes of uppercase hexadecimal.
+pub struct ColonSeparatedHex;
+
+impl ColonSeparatedHex {
+    pub fn decode(s: &str) -> Result<Vec<u8>, Error> {
+        let mut bytes = vec![];
+        for i in 0..(1 + s.len()) / 3 {
+            let byte = u8::from_str_radix(&s[3 * i..3 * i + 2], 16)?;
+            if 3 * i + 2 < s.len() {
+                assert_eq!(&s[3 * i + 2..3 * i + 3], ":");
+            }
+            bytes.push(byte);
+        }
+        Ok(bytes)
+    }
+
+    pub fn encode(b: &[u8]) -> Option<String> {
+        let mut bytes = vec![];
+        for byte in b {
+            bytes.push(format!("{:02X}", byte));
+        }
+        Some(bytes.join(":"))
+    }
+}