1 files changed, 49 insertions, 0 deletions
diff --git a/net/src/codec/length_codec.rs b/net/src/codec/length_codec.rs
new file mode 100644
index 0000000..76a1679
--- /dev/null
+++ b/net/src/codec/length_codec.rs
@@ -0,0 +1,49 @@
+use karyon_core::util::{decode, encode_into_slice};
+
+use crate::{
+    codec::{Codec, Decoder, Encoder},
+    Result,
+};
+
+/// The size of the message length.
+const MSG_LENGTH_SIZE: usize = std::mem::size_of::<u32>();
+
+#[derive(Clone)]
+pub struct LengthCodec {}
+impl Codec for LengthCodec {
+    type Item = Vec<u8>;
+}
+
+impl Encoder for LengthCodec {
+    type EnItem = Vec<u8>;
+    fn encode(&self, src: &Self::EnItem, dst: &mut [u8]) -> Result<usize> {
+        let length_buf = &mut [0; MSG_LENGTH_SIZE];
+        encode_into_slice(&(src.len() as u32), length_buf)?;
+        dst[..MSG_LENGTH_SIZE].copy_from_slice(length_buf);
+        dst[MSG_LENGTH_SIZE..src.len() + MSG_LENGTH_SIZE].copy_from_slice(src);
+        Ok(src.len() + MSG_LENGTH_SIZE)
+    }
+}
+
+impl Decoder for LengthCodec {
+    type DeItem = Vec<u8>;
+    fn decode(&self, src: &mut [u8]) -> Result<Option<(usize, Self::DeItem)>> {
+        if src.len() < MSG_LENGTH_SIZE {
+            return Ok(None);
+        }
+
+        let mut length = [0; MSG_LENGTH_SIZE];
+        length.copy_from_slice(&src[..MSG_LENGTH_SIZE]);
+        let (length, _) = decode::<u32>(&length)?;
+        let length = length as usize;
+
+        if src.len() - MSG_LENGTH_SIZE >= length {
+            Ok(Some((
+                length + MSG_LENGTH_SIZE,
+                src[MSG_LENGTH_SIZE..length + MSG_LENGTH_SIZE].to_vec(),
+            )))
+        } else {
+            Ok(None)
+        }
+    }
+}