Read from serial device with timeouts

src/serial.rs

@@ -18,7 +18,7 @@ use crate::utils::{
     to_ascii_debug,
 };
 
-pub fn find_begin_of_improv_packet(buffer: &Vec<u8>) -> Result<usize> {
+pub fn find_begin_of_improv_packet(buffer: &[u8]) -> Result<usize> {
     let mut improv_header_char: usize = 0;
 
     for (i, b) in buffer.iter().enumerate() {
@@ -40,6 +40,31 @@ pub fn find_begin_of_improv_packet(buffer: &Vec<u8>) -> Result<usize> {
     bail!("Improv header not found");
 }
 
+pub struct PacketBounds {
+    begin: usize,
+    end: usize,
+}
+
+pub fn find_packet(buffer: &[u8]) -> Result<PacketBounds> {
+        let improv_packet_offset = find_begin_of_improv_packet(buffer)
+            .context("Failed to find improv header in received bytes from serial device")?;
+
+        let improv_packet_len_position = improv_packet_offset + 8;
+        if buffer.len() <= improv_packet_len_position {
+            bail!("Byte that contains length of improv packet not available in buffer");
+        }
+
+        let improv_packet_end = improv_packet_offset + 10 + <u8 as Into<usize>>::into(buffer[improv_packet_len_position]);
+        if buffer.len() <= improv_packet_end {
+            bail!("Buffer stops before improv packet ends");
+        }
+
+        Ok(PacketBounds {
+            begin: improv_packet_offset,
+            end: improv_packet_end,
+        })
+}
+
 pub struct SerialInterface {
     interface: Box<dyn tokio_serial::SerialPort>,
     buffer: Vec<u8>,
@@ -77,7 +102,7 @@ impl SerialInterface {
         Ok(())
     }
 
-    pub fn recv_bytes(&mut self) -> Result<Vec<u8>> {
+    pub fn fill_buffer(&mut self) -> Result<()> {
         let available_bytes = self.interface.bytes_to_read()
             .context("Failed to figure out how many bytes are available to read")?
             .try_into()?;
@@ -85,10 +110,13 @@ impl SerialInterface {
         debug!("Available bytes to read: {}", available_bytes);
         let mut buffer: Vec<u8> = vec![0; available_bytes];
 
-        if buffer.len() > 0 {
+        if buffer.len() <= 0 {
+            debug!("No bytes available to read");
+            return Ok(());
+        }
+
         self.interface.read(&mut buffer)
             .context("Failed to read bytes from serial device")?;
-        }
 
         if log_enabled!(Level::Debug) {
             debug!("Received bytes: \n{}\n{}", hex::encode(&buffer), to_ascii_debug(&buffer));
@@ -96,23 +124,36 @@ impl SerialInterface {
 
         self.buffer.append(&mut buffer);
 
+        Ok(())
+    }
+
+    pub fn recv_bytes(&mut self) -> Result<Vec<u8>> {
+        let retry_counter = 0;
+
+        let packet_bounds: PacketBounds;
+        let mut buffer: Vec<u8>;
+
+        loop {
+            if retry_counter > 300 {
+                bail!("Failed to fetch more data, timed out");
+            }
+
+            self.fill_buffer()
+                .context("Failed to fill read buffer")?;
+
             buffer = self.buffer.clone();
 
-        if log_enabled!(Level::Debug) {
-            debug!("Buffer: \n{}\n{}", hex::encode(&buffer), to_ascii_debug(&buffer));
+            if let Ok(pb) = find_packet(&buffer) {
+                packet_bounds = pb;
+                break;
             }
 
-        let improv_packet_offset = find_begin_of_improv_packet(&buffer).context("Failed to find improv header in received bytes from serial device")?;
-
-        let improv_packet_end = improv_packet_offset + 10 + <u8 as Into<usize>>::into(buffer[improv_packet_offset+8]);
-
-        if buffer.len() <= improv_packet_end {
-            bail!("Incomplete packet, packet longer than available in buffer");
+            std::thread::sleep(std::time::Duration::from_millis(10));
         }
 
-        let packet_bytes = buffer[improv_packet_offset..improv_packet_end].to_vec();
+        let packet_bytes = buffer[packet_bounds.begin..packet_bounds.end].to_vec();
 
-        self.buffer = buffer[improv_packet_end..].to_vec();
+        self.buffer = buffer[packet_bounds.end..].to_vec();
 
         if log_enabled!(Level::Debug) {
             debug!("Received packet: \n{}\n{}", hex::encode(&packet_bytes), to_ascii_debug(&packet_bytes));