From 3ec9788eb1199ca9da7cc52703fc3911aad036ca Mon Sep 17 00:00:00 2001
From: Sebastien Bourdeauducq <sb@m-labs.hk>
Date: Sun, 19 Jul 2020 16:07:55 +0800
Subject: [PATCH] proto_async: always consume one byte in recv

---
 src/runtime/src/proto_async.rs | 106 ++++++++++++++++++++++-----------
 1 file changed, 70 insertions(+), 36 deletions(-)

diff --git a/src/runtime/src/proto_async.rs b/src/runtime/src/proto_async.rs
index 953c6f2..f02e8c1 100644
--- a/src/runtime/src/proto_async.rs
+++ b/src/runtime/src/proto_async.rs
@@ -5,23 +5,39 @@ use core::cell::RefCell;
 use libboard_zynq::smoltcp;
 use libasync::smoltcp::TcpStream;
 
-// TODO: use byteorder, make it more like libio
-
 type Result<T> = core::result::Result<T, smoltcp::Error>;
 
+enum RecvState<T> {
+    NeedsMore(usize, T), // bytes consumed so far, partial result
+    Completed(T),        // final result
+}
+
 pub async fn expect(stream: &TcpStream, pattern: &[u8]) -> Result<bool> {
-    stream.recv(|buf| {
-        for (i, b) in buf.iter().enumerate() {
-            if *b == pattern[i] {
-                if i + 1 == pattern.len() {
-                    return Poll::Ready((i + 1, Ok(true)));
+    let mut state = RecvState::NeedsMore(0, true);
+    loop {
+        state = stream.recv(|buf| {
+            let mut consumed = 0;
+            if let RecvState::NeedsMore(mut cur_index, _) = state {
+                for b in buf.iter() {
+                    consumed += 1;
+                    if *b == pattern[cur_index] {
+                        if cur_index + 1 == pattern.len() {
+                            return Poll::Ready((consumed, RecvState::Completed(true)));
+                        }
+                    } else {
+                        return Poll::Ready((consumed, RecvState::Completed(false)));
+                    }
+                    cur_index += 1;
                 }
+                Poll::Ready((consumed, RecvState::NeedsMore(cur_index, true)))
             } else {
-                return Poll::Ready((i + 1, Ok(false)));
+                unreachable!();
             }
+        }).await?;
+        if let RecvState::Completed(result) = state {
+            return Ok(result);
         }
-        Poll::Pending
-    }).await?
+    }
 }
 
 pub async fn read_bool(stream: &TcpStream) -> Result<bool> {
@@ -37,37 +53,55 @@ pub async fn read_i8(stream: &TcpStream) -> Result<i8> {
 }
 
 pub async fn read_i32(stream: &TcpStream) -> Result<i32> {
-    Ok(stream.recv(|buf| {
-        if buf.len() >= 4 {
-            let value =
-                  ((buf[0] as i32) << 24)
-                | ((buf[1] as i32) << 16)
-                | ((buf[2] as i32) << 8)
-                |  (buf[3] as i32);
-            Poll::Ready((4, value))
-        } else {
-            Poll::Pending
+    let mut state = RecvState::NeedsMore(0, 0);
+    loop {
+        state = stream.recv(|buf| {
+            let mut consumed = 0;
+            if let RecvState::NeedsMore(mut cur_index, mut cur_value) = state {
+                for b in buf.iter() {
+                    consumed += 1;
+                    cur_index += 1;
+                    cur_value <<= 8;
+                    cur_value |= *b as i32;
+                    if cur_index == 4 {
+                        return Poll::Ready((consumed, RecvState::Completed(cur_value)));
+                    }
+                }
+                Poll::Ready((consumed, RecvState::NeedsMore(cur_index, cur_value)))
+            } else {
+                unreachable!();
+            }
+        }).await?;
+        if let RecvState::Completed(result) = state {
+            return Ok(result);
         }
-    }).await?)
+    }
 }
 
 pub async fn read_i64(stream: &TcpStream) -> Result<i64> {
-    Ok(stream.recv(|buf| {
-        if buf.len() >= 8 {
-            let value =
-                  ((buf[0] as i64) << 56)
-                | ((buf[1] as i64) << 48)
-                | ((buf[2] as i64) << 40)
-                | ((buf[3] as i64) << 32)
-                | ((buf[4] as i64) << 24)
-                | ((buf[5] as i64) << 16)
-                | ((buf[6] as i64) << 8)
-                |  (buf[7] as i64);
-            Poll::Ready((8, value))
-        } else {
-            Poll::Pending
+    let mut state = RecvState::NeedsMore(0, 0);
+    loop {
+        state = stream.recv(|buf| {
+            let mut consumed = 0;
+            if let RecvState::NeedsMore(mut cur_index, mut cur_value) = state {
+                for b in buf.iter() {
+                    consumed += 1;
+                    cur_index += 1;
+                    cur_value <<= 8;
+                    cur_value |= *b as i64;
+                    if cur_index == 8 {
+                        return Poll::Ready((consumed, RecvState::Completed(cur_value)));
+                    }
+                }
+                Poll::Ready((consumed, RecvState::NeedsMore(cur_index, cur_value)))
+            } else {
+                unreachable!();
+            }
+        }).await?;
+        if let RecvState::Completed(result) = state {
+            return Ok(result);
         }
-    }).await?)
+    }
 }
 
 pub async fn read_chunk(stream: &TcpStream, destination: &mut [u8]) -> Result<()> {