feat: CRC-32 implemented

Cargo.lock

@@ -95,6 +95,9 @@ dependencies = [
 [[package]]
 name = "crc"
 version = "0.1.0"
+dependencies = [
+ "num-traits",
+]
 
 [[package]]
 name = "critical-section"

Cargo.toml

@@ -17,7 +17,7 @@ panic-probe = { version = "0.3", features = ["print-defmt"] }
 
 [features]
 default = ["buildscript"]
-buildscript = []
+buildscript = []          # runs build.rs
 
 [profile.release]
 debug = "full" # those are not on the board

crates/crc/Cargo.toml

@@ -4,3 +4,4 @@ version = "0.1.0"
 edition = "2024"
 
 [dependencies]
+num-traits = { version = "0.2.19", default-features = false }

crates/crc/src/crc_32.rs

@@ -0,0 +1,83 @@
+//! See RFC1662 Appendix C.3
+//!
+//! [Link](https://datatracker.ietf.org/doc/html/rfc1662#appendix-C.3)
+
+use crate::Crc;
+
+/// Lookup table from RFC1662 C.3
+pub const CRC32_TABLE: [u32; 256] = [
+    0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f, 0xe963a535, 0x9e6495a3,
+    0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91,
+    0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
+    0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5,
+    0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
+    0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
+    0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f,
+    0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924, 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d,
+    0x76dc4190, 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
+    0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
+    0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457,
+    0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
+    0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb,
+    0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9,
+    0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
+    0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad,
+    0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683,
+    0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
+    0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7,
+    0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
+    0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
+    0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79,
+    0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236, 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f,
+    0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
+    0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
+    0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21,
+    0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
+    0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45,
+    0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db,
+    0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
+    0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693, 0x54de5729, 0x23d967bf,
+    0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d,
+];
+/// Initial Value from RFC1662
+pub const CRC32_INIT: u32 = 0xffffffff;
+
+/// Implements CRC-32/ISO-HDLC with look up table
+pub struct Crc32(<Crc32 as Crc>::Checksum);
+impl Crc32 {}
+impl Crc for Crc32 {
+    type Input = [u8];
+    type Checksum = u32;
+
+    fn new() -> Self {
+        Self(Self::Checksum::default())
+    }
+    fn shift_reg(&mut self) -> &mut Self::Checksum {
+        &mut self.0
+    }
+    fn process(&mut self, data: &Self::Input) {
+        let chksum = self.shift_reg();
+        *chksum = CRC32_INIT;
+        for byte in data {
+            *chksum ^= *byte as u32;
+            *chksum = (*chksum >> 8) ^ CRC32_TABLE[(*chksum & 0xff) as usize];
+        }
+        *chksum ^= CRC32_INIT;
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::CHECK_DATA;
+
+    use super::*;
+
+    #[test]
+    fn test_check() {
+        let mut c = Crc32::new();
+        c.process(&CHECK_DATA);
+        // see https://reveng.sourceforge.io/crc-catalogue/17plus.htm#crc.cat-bits.32 for the check
+        // value
+        assert_eq!(*c.shift_reg(), 0xCBF43926);
+    }
+}

crates/crc/src/crc_dev.rs

@@ -1,23 +0,0 @@
-use crate::Crc;
-
-struct CrcDev;
-impl Crc for CrcDev {
-    type Input = [u8];
-    type Checksum = [u8; Self::CHECKSUM_LEN];
-    const CHECKSUM_LEN: usize = 4;
-
-    fn process(data: &Self::Input) -> Self::Checksum {
-        todo!()
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-
-    #[test]
-    fn it_works() {
-        let data = [0, 1, 2, 3, 4, 5, 6];
-        assert_eq!(CrcDev::process(&data), [1, 2, 3, 4])
-    }
-}

crates/crc/src/lib.rs

@@ -1,16 +1,71 @@
-#![no_std]
+//! # CRC's from scratch, nothing else
+//!
+//! This crate implements some CRC algorithms from scratch in a `no_std` environment.
+//!
+//! ## Acknowledgements
+//!
+//! Many thanks to the [crc-catalogue](https://reveng.sourceforge.io/crc-catalogue/) for providing
+//! some test vectors.
+
+#![cfg_attr(not(test), no_std)]
+
+use num_traits::{AsPrimitive, Num, PrimInt, Unsigned};
 
 mod crc_32;
-pub use crc_32::*;
 
-// for testing purposes
-mod crc_dev;
-pub use crc_dev::*;
+pub const CHECK_DATA: [u8; 9] = *b"123456789";
+
+pub use crc_32::*;
 
 pub trait Crc {
     type Input: ?Sized;
-    type Checksum: Eq;
-    const CHECKSUM_LEN: usize;
+    type Checksum: Eq + Default;
 
-    fn process(data: &Self::Input) -> Self::Checksum;
+    fn new() -> Self;
+    fn process(&mut self, data: &Self::Input);
+    fn shift_reg(&mut self) -> &mut Self::Checksum;
+}
+
+pub fn bit_at<N: PrimInt + Unsigned + AsPrimitive<u8>>(mut n: N, idx: usize) -> u8
+where
+    u8: AsPrimitive<N>,
+{
+    n = n & (1.as_() << idx);
+    (n >> idx).as_()
+}
+
+#[cfg(test)]
+mod test {
+    use crate::bit_at;
+
+    #[test]
+    fn test_bit_at() {
+        let a: u8 = 0b11110000;
+        assert_eq!(bit_at(a, 0), 0);
+        assert_eq!(bit_at(a, 1), 0);
+        assert_eq!(bit_at(a, 2), 0);
+        assert_eq!(bit_at(a, 3), 0);
+        assert_eq!(bit_at(a, 4), 1);
+        assert_eq!(bit_at(a, 5), 1);
+        assert_eq!(bit_at(a, 6), 1);
+        assert_eq!(bit_at(a, 7), 1);
+
+        let a: u16 = 0b1111000011110101;
+        assert_eq!(bit_at(a, 0), 1);
+        assert_eq!(bit_at(a, 1), 0);
+        assert_eq!(bit_at(a, 2), 1);
+        assert_eq!(bit_at(a, 3), 0);
+        assert_eq!(bit_at(a, 4), 1);
+        assert_eq!(bit_at(a, 5), 1);
+        assert_eq!(bit_at(a, 6), 1);
+        assert_eq!(bit_at(a, 7), 1);
+        assert_eq!(bit_at(a, 8), 0);
+        assert_eq!(bit_at(a, 9), 0);
+        assert_eq!(bit_at(a, 10), 0);
+        assert_eq!(bit_at(a, 11), 0);
+        assert_eq!(bit_at(a, 12), 1);
+        assert_eq!(bit_at(a, 13), 1);
+        assert_eq!(bit_at(a, 14), 1);
+        assert_eq!(bit_at(a, 15), 1);
+    }
 }