diff options
Diffstat (limited to 'vendor/crc32fast/src/baseline.rs')
-rw-r--r-- | vendor/crc32fast/src/baseline.rs | 94 |
1 files changed, 94 insertions, 0 deletions
diff --git a/vendor/crc32fast/src/baseline.rs b/vendor/crc32fast/src/baseline.rs new file mode 100644 index 0000000..fbc4136 --- /dev/null +++ b/vendor/crc32fast/src/baseline.rs @@ -0,0 +1,94 @@ +use table::CRC32_TABLE; + +#[derive(Clone)] +pub struct State { + state: u32, +} + +impl State { + pub fn new(state: u32) -> Self { + State { state } + } + + pub fn update(&mut self, buf: &[u8]) { + self.state = update_fast_16(self.state, buf); + } + + pub fn finalize(self) -> u32 { + self.state + } + + pub fn reset(&mut self) { + self.state = 0; + } + + pub fn combine(&mut self, other: u32, amount: u64) { + self.state = ::combine::combine(self.state, other, amount); + } +} + +pub(crate) fn update_fast_16(prev: u32, mut buf: &[u8]) -> u32 { + const UNROLL: usize = 4; + const BYTES_AT_ONCE: usize = 16 * UNROLL; + + let mut crc = !prev; + + while buf.len() >= BYTES_AT_ONCE { + for _ in 0..UNROLL { + crc = CRC32_TABLE[0x0][buf[0xf] as usize] + ^ CRC32_TABLE[0x1][buf[0xe] as usize] + ^ CRC32_TABLE[0x2][buf[0xd] as usize] + ^ CRC32_TABLE[0x3][buf[0xc] as usize] + ^ CRC32_TABLE[0x4][buf[0xb] as usize] + ^ CRC32_TABLE[0x5][buf[0xa] as usize] + ^ CRC32_TABLE[0x6][buf[0x9] as usize] + ^ CRC32_TABLE[0x7][buf[0x8] as usize] + ^ CRC32_TABLE[0x8][buf[0x7] as usize] + ^ CRC32_TABLE[0x9][buf[0x6] as usize] + ^ CRC32_TABLE[0xa][buf[0x5] as usize] + ^ CRC32_TABLE[0xb][buf[0x4] as usize] + ^ CRC32_TABLE[0xc][buf[0x3] as usize ^ ((crc >> 0x18) & 0xFF) as usize] + ^ CRC32_TABLE[0xd][buf[0x2] as usize ^ ((crc >> 0x10) & 0xFF) as usize] + ^ CRC32_TABLE[0xe][buf[0x1] as usize ^ ((crc >> 0x08) & 0xFF) as usize] + ^ CRC32_TABLE[0xf][buf[0x0] as usize ^ ((crc >> 0x00) & 0xFF) as usize]; + buf = &buf[16..]; + } + } + + update_slow(!crc, buf) +} + +pub(crate) fn update_slow(prev: u32, buf: &[u8]) -> u32 { + let mut crc = !prev; + + for &byte in buf.iter() { + crc = CRC32_TABLE[0][((crc as u8) ^ byte) as usize] ^ (crc >> 8); + } + + !crc +} + +#[cfg(test)] +mod test { + #[test] + fn slow() { + assert_eq!(super::update_slow(0, b""), 0); + + // test vectors from the iPXE project (input and output are bitwise negated) + assert_eq!(super::update_slow(!0x12345678, b""), !0x12345678); + assert_eq!(super::update_slow(!0xffffffff, b"hello world"), !0xf2b5ee7a); + assert_eq!(super::update_slow(!0xffffffff, b"hello"), !0xc9ef5979); + assert_eq!(super::update_slow(!0xc9ef5979, b" world"), !0xf2b5ee7a); + + // Some vectors found on Rosetta code + assert_eq!(super::update_slow(0, b"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"), 0x190A55AD); + assert_eq!(super::update_slow(0, b"\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF"), 0xFF6CAB0B); + assert_eq!(super::update_slow(0, b"\x00\x01\x02\x03\x04\x05\x06\x07\x08\x09\x0A\x0B\x0C\x0D\x0E\x0F\x10\x11\x12\x13\x14\x15\x16\x17\x18\x19\x1A\x1B\x1C\x1D\x1E\x1F"), 0x91267E8A); + } + + quickcheck! { + fn fast_16_is_the_same_as_slow(crc: u32, bytes: Vec<u8>) -> bool { + super::update_fast_16(crc, &bytes) == super::update_slow(crc, &bytes) + } + } +} |