1 files changed, 120 insertions, 0 deletions
diff --git a/p2p/src/codec.rs b/p2p/src/codec.rs
new file mode 100644
index 0000000..e521824
--- /dev/null
+++ b/p2p/src/codec.rs
@@ -0,0 +1,120 @@
+use std::time::Duration;
+
+use bincode::{Decode, Encode};
+
+use karyons_core::{
+    async_util::timeout,
+    util::{decode, encode, encode_into_slice},
+};
+
+use karyons_net::{Connection, NetError};
+
+use crate::{
+    message::{NetMsg, NetMsgCmd, NetMsgHeader, MAX_ALLOWED_MSG_SIZE, MSG_HEADER_SIZE},
+    Error, Result,
+};
+
+pub trait CodecMsg: Decode + Encode + std::fmt::Debug {}
+impl<T: Encode + Decode + std::fmt::Debug> CodecMsg for T {}
+
+/// A Codec working with generic network connections.
+///
+/// It is responsible for both decoding data received from the network and
+/// encoding data before sending it.
+pub struct Codec {
+    conn: Box<dyn Connection>,
+}
+
+impl Codec {
+    /// Creates a new Codec.
+    pub fn new(conn: Box<dyn Connection>) -> Self {
+        Self { conn }
+    }
+
+    /// Reads a message of type `NetMsg` from the connection.
+    ///
+    /// It reads the first 6 bytes as the header of the message, then reads
+    /// and decodes the remaining message data based on the determined header.
+    pub async fn read(&self) -> Result<NetMsg> {
+        // Read 6 bytes to get the header of the incoming message
+        let mut buf = [0; MSG_HEADER_SIZE];
+        self.read_exact(&mut buf).await?;
+
+        // Decode the header from bytes to NetMsgHeader
+        let (header, _) = decode::<NetMsgHeader>(&buf)?;
+
+        if header.payload_size > MAX_ALLOWED_MSG_SIZE {
+            return Err(Error::InvalidMsg(
+                "Message exceeds the maximum allowed size".to_string(),
+            ));
+        }
+
+        // Create a buffer to hold the message based on its length
+        let mut payload = vec![0; header.payload_size as usize];
+        self.read_exact(&mut payload).await?;
+
+        Ok(NetMsg { header, payload })
+    }
+
+    /// Writes a message of type `T` to the connection.
+    ///
+    /// Before appending the actual message payload, it calculates the length of
+    /// the encoded message in bytes and appends this length to the message header.
+    pub async fn write<T: CodecMsg>(&self, command: NetMsgCmd, msg: &T) -> Result<()> {
+        let payload = encode(msg)?;
+
+        // Create a buffer to hold the message header (6 bytes)
+        let header_buf = &mut [0; MSG_HEADER_SIZE];
+        let header = NetMsgHeader {
+            command,
+            payload_size: payload.len() as u32,
+        };
+        encode_into_slice(&header, header_buf)?;
+
+        let mut buffer = vec![];
+        // Append the header bytes to the buffer
+        buffer.extend_from_slice(header_buf);
+        // Append the message payload to the buffer
+        buffer.extend_from_slice(&payload);
+
+        self.write_all(&buffer).await?;
+        Ok(())
+    }
+
+    /// Reads a message of type `NetMsg` with the given timeout.
+    pub async fn read_timeout(&self, duration: Duration) -> Result<NetMsg> {
+        timeout(duration, self.read())
+            .await
+            .map_err(|_| NetError::Timeout)?
+    }
+
+    /// Reads the exact number of bytes required to fill `buf`.
+    async fn read_exact(&self, mut buf: &mut [u8]) -> Result<()> {
+        while !buf.is_empty() {
+            let n = self.conn.read(buf).await?;
+            let (_, rest) = std::mem::take(&mut buf).split_at_mut(n);
+            buf = rest;
+
+            if n == 0 {
+                return Err(Error::IO(std::io::ErrorKind::UnexpectedEof.into()));
+            }
+        }
+
+        Ok(())
+    }
+
+    /// Writes an entire buffer into the connection.
+    async fn write_all(&self, mut buf: &[u8]) -> Result<()> {
+        while !buf.is_empty() {
+            let n = self.conn.write(buf).await?;
+            let (_, rest) = std::mem::take(&mut buf).split_at(n);
+            buf = rest;
+
+            if n == 0 {
+                return Err(Error::IO(std::io::ErrorKind::UnexpectedEof.into()));
+            }
+        }
+
+        Ok(())
+    }
+}