sha2 0.11.1

Pure Rust implementation of the SHA-2 hash function family including SHA-224, SHA-256, SHA-384, and SHA-512.
Documentation 
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use super::{sha256sig0, sha256sig1, sha256sum0, sha256sum1};
use crate::consts::K32;

#[inline]
#[target_feature(enable = "zknh")]
pub(super) fn compress_block(state: &mut [u32; 8], mut block: [u32; 16]) {
    let s = &mut state.clone();
    let b = &mut block;

    for i in 0..3 {
        let k = &K32[16 * i..];
        round_schedule::<0>(s, b, k);
        round_schedule::<1>(s, b, k);
        round_schedule::<2>(s, b, k);
        round_schedule::<3>(s, b, k);
        round_schedule::<4>(s, b, k);
        round_schedule::<5>(s, b, k);
        round_schedule::<6>(s, b, k);
        round_schedule::<7>(s, b, k);
        round_schedule::<8>(s, b, k);
        round_schedule::<9>(s, b, k);
        round_schedule::<10>(s, b, k);
        round_schedule::<11>(s, b, k);
        round_schedule::<12>(s, b, k);
        round_schedule::<13>(s, b, k);
        round_schedule::<14>(s, b, k);
        round_schedule::<15>(s, b, k);
    }

    let k = &K32[48..];
    round::<0>(s, b, k);
    round::<1>(s, b, k);
    round::<2>(s, b, k);
    round::<3>(s, b, k);
    round::<4>(s, b, k);
    round::<5>(s, b, k);
    round::<6>(s, b, k);
    round::<7>(s, b, k);
    round::<8>(s, b, k);
    round::<9>(s, b, k);
    round::<10>(s, b, k);
    round::<11>(s, b, k);
    round::<12>(s, b, k);
    round::<13>(s, b, k);
    round::<14>(s, b, k);
    round::<15>(s, b, k);

    for i in 0..8 {
        state[i] = state[i].wrapping_add(s[i]);
    }
}

#[inline]
#[target_feature(enable = "zknh")]
fn round_schedule<const R: usize>(state: &mut [u32; 8], block: &mut [u32; 16], k: &[u32]) {
    round::<R>(state, block, k);

    block[R] = block[R]
        .wrapping_add(sha256sig1(block[(R + 14) % 16]))
        .wrapping_add(block[(R + 9) % 16])
        .wrapping_add(sha256sig0(block[(R + 1) % 16]));
}

#[inline]
#[target_feature(enable = "zknh")]
fn round<const R: usize>(state: &mut [u32; 8], block: &[u32; 16], k: &[u32]) {
    let n = K32.len() - R;
    let [a, b, c, d, e, f, g, h] = core::array::from_fn(|i| (n + i) % 8);

    state[h] = state[h]
        .wrapping_add(sha256sum1(state[e]))
        .wrapping_add(ch(state[e], state[f], state[g]))
        .wrapping_add(opaque_load::<R>(k))
        .wrapping_add(block[R]);
    state[d] = state[d].wrapping_add(state[h]);
    state[h] = state[h]
        .wrapping_add(sha256sum0(state[a]))
        .wrapping_add(maj(state[a], state[b], state[c]))
}

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

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

/// This function returns `k[R]`, but prevents the compiler from inlining the indexed value
#[inline(always)]
fn opaque_load<const R: usize>(k: &[u32]) -> u32 {
    assert!(R < k.len());
    let dst;

    #[cfg(target_arch = "riscv64")]
    unsafe {
        core::arch::asm!(
            "lwu {dst}, 4*{R}({k})",
            R = const R,
            k = in(reg) k.as_ptr(),
            dst = out(reg) dst,
            options(pure, readonly, nostack, preserves_flags),
        );
    }

    #[cfg(target_arch = "riscv32")]
    unsafe {
        core::arch::asm!(
            "lw {dst}, 4*{R}({k})",
            R = const R,
            k = in(reg) k.as_ptr(),
            dst = out(reg) dst,
            options(pure, readonly, nostack, preserves_flags),
        );
    }

    dst
}