proto fw: refactor cxp crc into helper function

src/libboard_artiq/src/cxp_proto.rs

@@ -1,7 +1,7 @@
 use core::slice;
 
 use core_io::{Error as IoError, Read, Write};
-use crc::crc32;
+use crc::crc32::checksum_ieee;
 use io::Cursor;
 use libboard_zynq::println;
 
@@ -58,7 +58,14 @@ pub enum DownConnPacket {
     },
 }
 
-pub fn capture_ctrl_packet(reader: &mut Cursor<&mut [u8]>, with_tag: bool) -> Result<DownConnPacket, Error> {
+// Section 9.2.2.2 (CXP-001-2021)
+// Only Control packet need CRC32 appended in the end of the packet
+// CoaXpress use the polynomial of IEEE-802.3 (Ethernet) CRC but the checksum calculation is different
+fn get_cxp_crc(bytes: &[u8]) -> u32 {
+    (!checksum_ieee(bytes)).swap_bytes()
+}
+
+fn capture_ctrl_packet(reader: &mut Cursor<&mut [u8]>, with_tag: bool) -> Result<DownConnPacket, Error> {
     let mut tag: Option<u8> = None;
     if with_tag {
         tag = Some((read_word(reader)? & 0xFF) as u8);
@@ -71,6 +78,14 @@ pub fn capture_ctrl_packet(reader: &mut Cursor<&mut [u8]>, with_tag: bool) -> Re
             let length = read_word(reader)?;
             let mut data: [u8; DATA_MAXSIZE] = [0; DATA_MAXSIZE];
             reader.read(&mut data[0..length as usize])?;
+
+            let checksum = get_cxp_crc(&reader.get_ref()[0..reader.position()]);
+            let recv_checksum = read_word(reader)?;
+            println!("calculated checksum = {:#010X}", checksum);
+            println!("read checksum = {:#010X}", recv_checksum);
+            if recv_checksum != checksum {
+                return Err(Error::CorruptedPacket);
+            }
             return Ok(DownConnPacket::CtrlReply { tag, length, data });
         }
         0x01 => return Ok(DownConnPacket::CtrlAck { tag }),
@@ -78,6 +93,14 @@ pub fn capture_ctrl_packet(reader: &mut Cursor<&mut [u8]>, with_tag: bool) -> Re
             let length = read_word(reader)?;
             let mut time: [u8; DATA_MAXSIZE] = [0; DATA_MAXSIZE];
             reader.read(&mut time[0..length as usize])?;
+
+            let checksum = get_cxp_crc(&reader.get_ref()[0..reader.position()]);
+            let recv_checksum = read_word(reader)?;
+            println!("calculated checksum = {:#010X}", checksum);
+            println!("read checksum = {:#010X}", recv_checksum);
+            if recv_checksum != checksum {
+                return Err(Error::CorruptedPacket);
+            }
             return Ok(DownConnPacket::CtrlDelay { tag, length, time });
         }
         _ => return Err(Error::CtrlAckError(ackcode)),
@@ -172,22 +195,18 @@ impl Packet {
                     writer.write(&data[0..length as usize])?;
                 }
 
-                let checksum = (!crc::crc32::checksum_ieee(&writer.get_ref()[4..writer.position()])).swap_bytes();
+                writer.write(&get_cxp_crc(&writer.get_ref()[4..writer.position()]).to_be_bytes())?;
-                writer.write(&checksum.to_be_bytes())?;
             }
             _ => {}
         }
         // Section 9.2.2.2 (CXP-001-2021)
-        // Only Control packet need CRC32 appended in the end of the packet
+        // The crc calculation does not include the first 4 bytes of packet_type
-        // CoaXpress use the polynomial of IEEE-802.3 (Ethernet) CRC but the checksum calculation is different
-        // Also, the calculation does not include the first 4 bytes of packet_type
         match *self {
             Packet::CtrlRead { .. }
             | Packet::CtrlWrite { .. }
             | Packet::CtrlReadWithTag { .. }
             | Packet::CtrlWriteWithTag { .. } => {
-                let checksum = (!crc::crc32::checksum_ieee(&writer.get_ref()[4..writer.position()])).swap_bytes();
+                writer.write(&get_cxp_crc(&writer.get_ref()[4..writer.position()]).to_be_bytes())?;
-                writer.write(&checksum.to_be_bytes())?;
             }
             _ => {}
         }
@@ -204,27 +223,11 @@ pub fn receive(channel: usize) -> Result<(), Error> {
 
         let packet = match packet_type {
             0x03 => capture_ctrl_packet(&mut reader, false),
-            0x06 => capture_ctrl_packet(&mut reader, false),
+            0x06 => capture_ctrl_packet(&mut reader, true),
             _ => return Err(Error::UnknownPacket(packet_type)),
         };
         println!("{:?}", packet);
 
-        // Section 9.2.2.2 (CXP-001-2021)
-        // Only Control packet need CRC32 appended in the end of the packet
-        // CoaXpress use the polynomial of IEEE-802.3 (Ethernet) CRC but the checksum calculation is different
-        // Also, the calculation does not include the first 4 bytes of packet_type
-        if packet_type == 0x03 || packet_type == 0x06 {
-            let checksum_at = reader.position();
-            let checksum = (!crc::crc32::checksum_ieee(&reader.get_ref()[0..checksum_at])).swap_bytes();
-            println!("checksum location = {:#010X}", checksum_at);
-            println!("calculated checksum = {:#010X}", checksum);
-            println!("read checksum = {:#010X}", read_word(&mut reader)?);
-            reader.set_position(checksum_at);
-            if read_word(&mut reader)? != checksum {
-                return Err(Error::CorruptedPacket);
-            }
-        }
-
         print_packet(slice::from_raw_parts_mut(ptr as *mut u8, MEM_LEN));
     }
     Ok(())