3 files changed, 22 insertions, 4 deletions
diff --git a/src/codec/decode.rs b/src/codec/decode.rs
index 31ed725..fa4ae95 100644
--- a/src/codec/decode.rs
+++ b/src/codec/decode.rs
@@ -1,3 +1,4 @@
+//! Decoding: reading protocol values from a byte stream.
 use std::{io::Read, sync::Arc};
 
 use crate::{DEFAULT_BUFFER_LEN, codec::error::Result};
@@ -5,6 +6,7 @@ use crate::{DEFAULT_BUFFER_LEN, codec::error::Result};
 macro_rules! impl_decode {
     ($type: ty) => {
         impl<Ctx> Decode<Ctx> for $type {
+            // decode number using big endian
             fn decode(reader: &mut dyn Read, _: &mut Ctx) -> Result<Self>
             where
                 Self: Sized,
@@ -18,6 +20,7 @@ macro_rules! impl_decode {
     };
 }
 
+/// Read a value from a byte stream
 pub trait Decode<Ctx> {
     fn decode(reader: &mut dyn Read, ctx: &mut Ctx) -> Result<Self>
     where
diff --git a/src/codec/encode.rs b/src/codec/encode.rs
index bd76605..c8d1c7b 100644
--- a/src/codec/encode.rs
+++ b/src/codec/encode.rs
@@ -1,9 +1,11 @@
+//! Encoding: writing protocol values into a byte stream.
 use crate::codec::error::Error;
 use std::{io::Write, sync::Arc};
 
 macro_rules! impl_encode {
     ($t: ty) => {
         impl<Ctx> Encode<Ctx> for $t {
+            /// write number using big endian
             fn encode(&self, buffer: &mut dyn Write, _: &mut Ctx) -> Result<usize, Error> {
                 let size = buffer.write(&self.to_be_bytes())?;
                 Ok(size)
@@ -12,6 +14,7 @@ macro_rules! impl_encode {
     };
 }
 
+/// Write a value into a byte stream
 pub trait Encode<Ctx> {
     fn encode(&self, buffer: &mut dyn Write, ctx: &mut Ctx) -> Result<usize, Error>;
 }
@@ -24,21 +27,24 @@ impl<Ctx> Encode<Ctx> for bool {
 }
 
 impl<Ctx, T: Encode<Ctx>> Encode<Ctx> for Option<T> {
+    /// Encode `T` if Some(T) or do nothing if None
     fn encode(&self, buffer: &mut dyn Write, ctx: &mut Ctx) -> Result<usize, Error> {
         match self {
             Some(val) => {
-                let mut size = 1u8.encode(buffer, ctx)?;
-                size += val.encode(buffer, ctx)?;
+                let size = val.encode(buffer, ctx)?;
                 Ok(size)
             }
-            None => 0u8.encode(buffer, ctx),
+            None => Ok(0),
         }
     }
 }
 
 impl<Ctx, T: Encode<Ctx>> Encode<Ctx> for Vec<T> {
+    /// Encode each element of vector
+    /// use `CountPrefix` to prefix the vector with number of elements
+    /// use `LenPrefix` to prefix the vector with encoded byte size
     fn encode(&self, buffer: &mut dyn Write, ctx: &mut Ctx) -> Result<usize, Error> {
-        let mut size = self.len().encode(buffer, ctx)?;
+        let mut size = 0;
         for item in self {
             size += item.encode(buffer, ctx)?;
         }
@@ -47,6 +53,9 @@ impl<Ctx, T: Encode<Ctx>> Encode<Ctx> for Vec<T> {
 }
 
 impl<Ctx> Encode<Ctx> for String {
+    /// Encode the string using utf8
+    /// use `CountPrefix` to prefix the string with char length
+    /// use `LenPrefix` to prefix the string with utf8 bytes length
     fn encode(&self, buffer: &mut dyn Write, _: &mut Ctx) -> Result<usize, Error> {
         let utf8 = self.as_bytes();
         buffer.write_all(utf8)?;
@@ -55,6 +64,8 @@ impl<Ctx> Encode<Ctx> for String {
 }
 
 impl<Ctx> Encode<Ctx> for Arc<[u8]> {
+    /// write raw slice into the buffer
+    /// use `LenPrefix` to prefix with byte length
     fn encode(&self, buffer: &mut dyn Write, _: &mut Ctx) -> Result<usize, Error> {
         let len = buffer.write(self)?;
         Ok(len)
@@ -62,6 +73,8 @@ impl<Ctx> Encode<Ctx> for Arc<[u8]> {
 }
 
 impl<Ctx, const S: usize> Encode<Ctx> for [u8; S] {
+    /// write raw slice into the buffer
+    /// use `LenPrefix` to prefix with byte length
     fn encode(&self, buffer: &mut dyn Write, _ctx: &mut Ctx) -> Result<usize, Error> {
         let len = buffer.write(self)?;
         Ok(len)
diff --git a/src/codec/error.rs b/src/codec/error.rs
index 6037a9a..c1bd4f7 100644
--- a/src/codec/error.rs
+++ b/src/codec/error.rs
@@ -1,5 +1,7 @@
 use std::fmt::Display;
 
+// TODO : better error (using thiserror)
+
 #[derive(Debug)]
 pub enum Error {
     IoError(std::io::Error),