Refactor out frame encoding stuff

2 files changed, 54 insertions, 46 deletions

diff --git a/crates/windlass/src/transport/read.rs b/crates/windlass/src/transport/frame.rs
index 1aaf20c..d33a2d8 100644
--- a/crates/windlass/src/transport/read.rs
+++ b/crates/windlass/src/transport/frame.rs
@@ -1,4 +1,4 @@
-use std::{collections::VecDeque, mem};
+use std::{collections::VecDeque, mem, sync::Arc};
 
 use tokio::time::Instant;
 use tracing::trace;
@@ -117,7 +117,7 @@ impl PartialFrameState {
                         continue;
                     }
 
-                    let actual_crc = crc16(&so_far);
+                    let actual_crc = crc16(so_far);
                     let frame_crc = (so_far[len - MESSAGE_TRAILER_CRC] as u16) << 8
                         | (so_far[len - MESSAGE_TRAILER_CRC + 1] as u16);
                     if frame_crc != actual_crc {
@@ -150,3 +150,46 @@ impl PartialFrameState {
         None
     }
 }
+
+/// A frame to be sent to the MCU
+#[derive(Debug, Clone)]
+pub struct SentFrame {
+    /// When the frame was first sent
+    pub sent_at: Instant,
+
+    /// The payload of the message, including frame header
+    pub payload: Arc<Vec<u8>>,
+
+    /// True iff the frame has been retransmitted at least once
+    pub is_retransmit: bool,
+}
+
+impl SentFrame {
+    pub fn new(sequence: u64, data: &[u8]) -> Result<Self, MessageEncodeError> {
+        let len = MESSAGE_LENGTH_MIN + data.len();
+        if len > MESSAGE_LENGTH_MAX {
+            return Err(MessageEncodeError::MessageTooLong);
+        }
+
+        let mut payload = Vec::with_capacity(len);
+        payload.push(len as u8);
+        payload.push(MESSAGE_DEST | ((sequence as u8) & MESSAGE_SEQ_MASK));
+        payload.extend_from_slice(data);
+        let crc = crc16(&payload[0..len - MESSAGE_TRAILER_SIZE]);
+        payload.push(((crc >> 8) & 0xFF) as u8);
+        payload.push((crc & 0xFF) as u8);
+        payload.push(MESSAGE_VALUE_SYNC);
+
+        Ok(Self {
+            sent_at: Instant::now(),
+            payload: Arc::new(payload),
+            is_retransmit: false,
+        })
+    }
+}
+
+#[derive(thiserror::Error, Debug)]
+pub enum MessageEncodeError {
+    #[error("message would exceed the maximum packet length of {MESSAGE_LENGTH_MAX} bytes")]
+    MessageTooLong,
+}
diff --git a/crates/windlass/src/transport/mod.rs b/crates/windlass/src/transport/mod.rs
index 818a594..eecb98d 100644
--- a/crates/windlass/src/transport/mod.rs
+++ b/crates/windlass/src/transport/mod.rs
@@ -1,6 +1,6 @@
-use read::{FrameReader, ReceivedFrame};
+use frame::{FrameReader, MessageEncodeError, ReceivedFrame, SentFrame};
 use rtt::RttState;
-use std::{collections::VecDeque, sync::Arc};
+use std::collections::VecDeque;
 use tokio::io::AsyncReadExt;
 use tokio::{
     io::{AsyncBufRead, AsyncWrite, AsyncWriteExt},
@@ -11,9 +11,7 @@ use tokio::{
 };
 use tokio_util::{bytes::BytesMut, sync::CancellationToken};
 
-use crate::encoding::crc16;
-
-mod read;
+mod frame;
 mod rtt;
 
 pub(crate) const MESSAGE_HEADER_SIZE: usize = 2;
@@ -177,6 +175,7 @@ impl<R: AsyncBufRead + Unpin, W: AsyncWrite + Unpin> TransportState<R, W> {
                 .inflight_messages
                 .front()
                 .map(|msg| msg.sent_at + self.rtt_state.rto());
+
             let retransmit_timeout: futures::future::OptionFuture<_> =
                 retransmit_deadline.map(sleep_until).into();
             pin!(retransmit_timeout);
@@ -306,15 +305,12 @@ impl<R: AsyncBufRead + Unpin, W: AsyncWrite + Unpin> TransportState<R, W> {
             }
         }
 
-        let frame = Arc::new(encode_frame(self.send_sequence, &buf)?);
+        self.inflight_messages
+            .push_back(SentFrame::new(self.send_sequence, &buf)?);
         self.send_sequence += 1;
-        self.inflight_messages.push_back(SentFrame {
-            sent_at: Instant::now(),
-            sequence: self.send_sequence,
-            payload: frame.clone(),
-            is_retransmit: false,
-        });
-        self.wr.write_all(&frame).await?;
+        self.wr
+            .write_all(&self.inflight_messages.back().unwrap().payload)
+            .await?;
 
         Ok(())
     }
@@ -361,34 +357,3 @@ pub enum TransmitterError {
     #[error("connection closed")]
     ConnectionClosed,
 }
-
-#[derive(Debug, Clone)]
-pub(crate) struct SentFrame {
-    pub sent_at: Instant,
-    #[allow(dead_code)]
-    pub sequence: u64,
-    pub payload: Arc<Vec<u8>>,
-    pub is_retransmit: bool,
-}
-
-#[derive(thiserror::Error, Debug)]
-pub enum MessageEncodeError {
-    #[error("message would exceed the maximum packet length of {MESSAGE_LENGTH_MAX} bytes")]
-    MessageTooLong,
-}
-
-fn encode_frame(sequence: u64, payload: &[u8]) -> Result<Vec<u8>, MessageEncodeError> {
-    let len = MESSAGE_LENGTH_MIN + payload.len();
-    if len > MESSAGE_LENGTH_MAX {
-        return Err(MessageEncodeError::MessageTooLong);
-    }
-    let mut buf = Vec::with_capacity(len);
-    buf.push(len as u8);
-    buf.push(MESSAGE_DEST | ((sequence as u8) & MESSAGE_SEQ_MASK));
-    buf.extend_from_slice(payload);
-    let crc = crc16(&buf[0..len - MESSAGE_TRAILER_SIZE]);
-    buf.push(((crc >> 8) & 0xFF) as u8);
-    buf.push((crc & 0xFF) as u8);
-    buf.push(MESSAGE_VALUE_SYNC);
-    Ok(buf)
-}