feat: scaffold relay client auth workspace

common/src/codec.rs

@@ -0,0 +1,42 @@
+use std::io;
+
+use serde::{Serialize, de::DeserializeOwned};
+use tokio::io::{AsyncRead, AsyncReadExt, AsyncWrite, AsyncWriteExt};
+
+const MAX_FRAME_SIZE: usize = 1024 * 1024;
+
+pub async fn write_frame<W, T>(writer: &mut W, value: &T) -> io::Result<()>
+where
+    W: AsyncWrite + Unpin,
+    T: Serialize,
+{
+    let payload = serde_json::to_vec(value)
+        .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e.to_string()))?;
+    if payload.len() > MAX_FRAME_SIZE {
+        return Err(io::Error::new(
+            io::ErrorKind::InvalidInput,
+            "frame exceeds max size",
+        ));
+    }
+    writer.write_u32(payload.len() as u32).await?;
+    writer.write_all(&payload).await?;
+    writer.flush().await
+}
+
+pub async fn read_frame<R, T>(reader: &mut R) -> io::Result<T>
+where
+    R: AsyncRead + Unpin,
+    T: DeserializeOwned,
+{
+    let len = reader.read_u32().await? as usize;
+    if len > MAX_FRAME_SIZE {
+        return Err(io::Error::new(
+            io::ErrorKind::InvalidData,
+            "frame too large",
+        ));
+    }
+    let mut payload = vec![0u8; len];
+    reader.read_exact(&mut payload).await?;
+    serde_json::from_slice(&payload)
+        .map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e.to_string()))
+}