ahsah 2.1.0

Incremental hashing contexts for MD5 and SHA-2 with reader helpers and optional SIMD decode paths
Documentation
use crate::encoding::DigestBytes;

pub(crate) const SHA256_K: [u32; 64] = [
    0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1, 0x923f82a4, 0xab1c5ed5,
    0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3, 0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174,
    0xe49b69c1, 0xefbe4786, 0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
    0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147, 0x06ca6351, 0x14292967,
    0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13, 0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85,
    0xa2bfe8a1, 0xa81a664b, 0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
    0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a, 0x5b9cca4f, 0x682e6ff3,
    0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208, 0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2,
];

pub(crate) const SHA512_K: [u64; 80] = [
    0x428a2f98d728ae22,
    0x7137449123ef65cd,
    0xb5c0fbcfec4d3b2f,
    0xe9b5dba58189dbbc,
    0x3956c25bf348b538,
    0x59f111f1b605d019,
    0x923f82a4af194f9b,
    0xab1c5ed5da6d8118,
    0xd807aa98a3030242,
    0x12835b0145706fbe,
    0x243185be4ee4b28c,
    0x550c7dc3d5ffb4e2,
    0x72be5d74f27b896f,
    0x80deb1fe3b1696b1,
    0x9bdc06a725c71235,
    0xc19bf174cf692694,
    0xe49b69c19ef14ad2,
    0xefbe4786384f25e3,
    0x0fc19dc68b8cd5b5,
    0x240ca1cc77ac9c65,
    0x2de92c6f592b0275,
    0x4a7484aa6ea6e483,
    0x5cb0a9dcbd41fbd4,
    0x76f988da831153b5,
    0x983e5152ee66dfab,
    0xa831c66d2db43210,
    0xb00327c898fb213f,
    0xbf597fc7beef0ee4,
    0xc6e00bf33da88fc2,
    0xd5a79147930aa725,
    0x06ca6351e003826f,
    0x142929670a0e6e70,
    0x27b70a8546d22ffc,
    0x2e1b21385c26c926,
    0x4d2c6dfc5ac42aed,
    0x53380d139d95b3df,
    0x650a73548baf63de,
    0x766a0abb3c77b2a8,
    0x81c2c92e47edaee6,
    0x92722c851482353b,
    0xa2bfe8a14cf10364,
    0xa81a664bbc423001,
    0xc24b8b70d0f89791,
    0xc76c51a30654be30,
    0xd192e819d6ef5218,
    0xd69906245565a910,
    0xf40e35855771202a,
    0x106aa07032bbd1b8,
    0x19a4c116b8d2d0c8,
    0x1e376c085141ab53,
    0x2748774cdf8eeb99,
    0x34b0bcb5e19b48a8,
    0x391c0cb3c5c95a63,
    0x4ed8aa4ae3418acb,
    0x5b9cca4f7763e373,
    0x682e6ff3d6b2b8a3,
    0x748f82ee5defb2fc,
    0x78a5636f43172f60,
    0x84c87814a1f0ab72,
    0x8cc702081a6439ec,
    0x90befffa23631e28,
    0xa4506cebde82bde9,
    0xbef9a3f7b2c67915,
    0xc67178f2e372532b,
    0xca273eceea26619c,
    0xd186b8c721c0c207,
    0xeada7dd6cde0eb1e,
    0xf57d4f7fee6ed178,
    0x06f067aa72176fba,
    0x0a637dc5a2c898a6,
    0x113f9804bef90dae,
    0x1b710b35131c471b,
    0x28db77f523047d84,
    0x32caab7b40c72493,
    0x3c9ebe0a15c9bebc,
    0x431d67c49c100d4c,
    0x4cc5d4becb3e42b6,
    0x597f299cfc657e2a,
    0x5fcb6fab3ad6faec,
    0x6c44198c4a475817,
];

#[inline(always)]
fn ch_u32(x: u32, y: u32, z: u32) -> u32 {
    (x & y) ^ (!x & z)
}

#[inline(always)]
fn maj_u32(x: u32, y: u32, z: u32) -> u32 {
    (x & y) ^ (x & z) ^ (y & z)
}

#[inline(always)]
fn ch_u64(x: u64, y: u64, z: u64) -> u64 {
    (x & y) ^ (!x & z)
}

#[inline(always)]
fn maj_u64(x: u64, y: u64, z: u64) -> u64 {
    (x & y) ^ (x & z) ^ (y & z)
}

#[inline(always)]
fn bsig0_u32(x: u32) -> u32 {
    x.rotate_right(2) ^ x.rotate_right(13) ^ x.rotate_right(22)
}

#[inline(always)]
fn bsig1_u32(x: u32) -> u32 {
    x.rotate_right(6) ^ x.rotate_right(11) ^ x.rotate_right(25)
}

#[inline(always)]
fn ssig0_u32(x: u32) -> u32 {
    x.rotate_right(7) ^ x.rotate_right(18) ^ (x >> 3)
}

#[inline(always)]
fn ssig1_u32(x: u32) -> u32 {
    x.rotate_right(17) ^ x.rotate_right(19) ^ (x >> 10)
}

#[inline(always)]
fn bsig0_u64(x: u64) -> u64 {
    x.rotate_right(28) ^ x.rotate_right(34) ^ x.rotate_right(39)
}

#[inline(always)]
fn bsig1_u64(x: u64) -> u64 {
    x.rotate_right(14) ^ x.rotate_right(18) ^ x.rotate_right(41)
}

#[inline(always)]
fn ssig0_u64(x: u64) -> u64 {
    x.rotate_right(1) ^ x.rotate_right(8) ^ (x >> 7)
}

#[inline(always)]
fn ssig1_u64(x: u64) -> u64 {
    x.rotate_right(19) ^ x.rotate_right(61) ^ (x >> 6)
}

pub(crate) fn compress_sha256(state: &mut [u32; 8], block: &[u8; 64]) {
    let mut w = [0u32; 64];
    w[..16].copy_from_slice(&decode_be_u32_words(block));
    for index in 16..64 {
        w[index] = ssig1_u32(w[index - 2])
            .wrapping_add(w[index - 7])
            .wrapping_add(ssig0_u32(w[index - 15]))
            .wrapping_add(w[index - 16]);
    }

    let [mut a, mut b, mut c, mut d, mut e, mut f, mut g, mut h] = *state;
    for index in 0..64 {
        let temp1 = h
            .wrapping_add(bsig1_u32(e))
            .wrapping_add(ch_u32(e, f, g))
            .wrapping_add(SHA256_K[index])
            .wrapping_add(w[index]);
        let temp2 = bsig0_u32(a).wrapping_add(maj_u32(a, b, c));
        h = g;
        g = f;
        f = e;
        e = d.wrapping_add(temp1);
        d = c;
        c = b;
        b = a;
        a = temp1.wrapping_add(temp2);
    }

    state[0] = state[0].wrapping_add(a);
    state[1] = state[1].wrapping_add(b);
    state[2] = state[2].wrapping_add(c);
    state[3] = state[3].wrapping_add(d);
    state[4] = state[4].wrapping_add(e);
    state[5] = state[5].wrapping_add(f);
    state[6] = state[6].wrapping_add(g);
    state[7] = state[7].wrapping_add(h);
}

pub(crate) fn compress_sha512(state: &mut [u64; 8], block: &[u8; 128]) {
    let mut w = [0u64; 80];
    w[..16].copy_from_slice(&decode_be_u64_words(block));
    for index in 16..80 {
        w[index] = ssig1_u64(w[index - 2])
            .wrapping_add(w[index - 7])
            .wrapping_add(ssig0_u64(w[index - 15]))
            .wrapping_add(w[index - 16]);
    }

    let [mut a, mut b, mut c, mut d, mut e, mut f, mut g, mut h] = *state;
    for index in 0..80 {
        let temp1 = h
            .wrapping_add(bsig1_u64(e))
            .wrapping_add(ch_u64(e, f, g))
            .wrapping_add(SHA512_K[index])
            .wrapping_add(w[index]);
        let temp2 = bsig0_u64(a).wrapping_add(maj_u64(a, b, c));
        h = g;
        g = f;
        f = e;
        e = d.wrapping_add(temp1);
        d = c;
        c = b;
        b = a;
        a = temp1.wrapping_add(temp2);
    }

    state[0] = state[0].wrapping_add(a);
    state[1] = state[1].wrapping_add(b);
    state[2] = state[2].wrapping_add(c);
    state[3] = state[3].wrapping_add(d);
    state[4] = state[4].wrapping_add(e);
    state[5] = state[5].wrapping_add(f);
    state[6] = state[6].wrapping_add(g);
    state[7] = state[7].wrapping_add(h);
}

pub(crate) fn digest_from_u32_state(state: &[u32], output_bytes: usize) -> DigestBytes {
    let mut bytes = Vec::with_capacity(output_bytes);
    for word in state {
        bytes.extend_from_slice(&word.to_be_bytes());
    }
    bytes.truncate(output_bytes);
    DigestBytes::new(bytes)
}

pub(crate) fn digest_from_u64_state(state: &[u64], output_bytes: usize) -> DigestBytes {
    let mut bytes = Vec::with_capacity(output_bytes);
    for word in state {
        bytes.extend_from_slice(&word.to_be_bytes());
    }
    bytes.truncate(output_bytes);
    DigestBytes::new(bytes)
}

pub(crate) fn decode_be_u32_words(block: &[u8; 64]) -> [u32; 16] {
    #[cfg(feature = "simd")]
    {
        if let Some(words) = super::simd::decode_be_u32x16(block) {
            return words;
        }
    }

    let mut words = [0u32; 16];
    for (word, chunk) in words.iter_mut().zip(block.chunks_exact(4)) {
        *word = u32::from_be_bytes(chunk.try_into().expect("chunk has 4 bytes"));
    }
    words
}

pub(crate) fn decode_be_u64_words(block: &[u8; 128]) -> [u64; 16] {
    #[cfg(feature = "simd")]
    {
        if let Some(words) = super::simd::decode_be_u64x16(block) {
            return words;
        }
    }

    let mut words = [0u64; 16];
    for (word, chunk) in words.iter_mut().zip(block.chunks_exact(8)) {
        *word = u64::from_be_bytes(chunk.try_into().expect("chunk has 8 bytes"));
    }
    words
}

#[cfg(all(test, feature = "simd"))]
pub(crate) fn decode_be_u32_words_scalar(block: &[u8; 64]) -> [u32; 16] {
    let mut words = [0u32; 16];
    for (word, chunk) in words.iter_mut().zip(block.chunks_exact(4)) {
        *word = u32::from_be_bytes(chunk.try_into().expect("chunk has 4 bytes"));
    }
    words
}

#[cfg(all(test, feature = "simd"))]
pub(crate) fn decode_be_u64_words_scalar(block: &[u8; 128]) -> [u64; 16] {
    let mut words = [0u64; 16];
    for (word, chunk) in words.iter_mut().zip(block.chunks_exact(8)) {
        *word = u64::from_be_bytes(chunk.try_into().expect("chunk has 8 bytes"));
    }
    words
}

#[cfg(all(test, feature = "simd"))]
mod tests {
    use super::{
        decode_be_u32_words, decode_be_u32_words_scalar, decode_be_u64_words,
        decode_be_u64_words_scalar,
    };

    #[test]
    fn sha256_word_decode_matches_scalar() {
        let mut block = [0u8; 64];
        for (index, byte) in block.iter_mut().enumerate() {
            *byte = index as u8;
        }
        assert_eq!(
            decode_be_u32_words_scalar(&block),
            decode_be_u32_words(&block)
        );
    }

    #[test]
    fn sha512_word_decode_matches_scalar() {
        let mut block = [0u8; 128];
        for (index, byte) in block.iter_mut().enumerate() {
            *byte = index as u8;
        }
        assert_eq!(
            decode_be_u64_words_scalar(&block),
            decode_be_u64_words(&block)
        );
    }
}