Function sha256

bitvm/src/hash/sha256.rs:30–69

sha256 take indefinite length input on the top of stack and return 256 bit (64 byte)

(num_bytes: usize)

/// sha256 take indefinite length input on the top of stack and return 256 bit (64 byte)
pub fn sha256(num_bytes: usize) -> Script {
    if num_bytes == 32 {
        return sha256_32bytes();
    }
    if num_bytes == 80 {
        return sha256_80bytes();
    }
    let mut chunks_size: usize = num_bytes / 64 + 1;
    if (num_bytes % 64) > 55 {
        chunks_size += 1;
    }

    script! {
        {push_reverse_bytes_to_alt(num_bytes)}

        // top of stack: [ [n bytes input] ]
        {u8_push_xor_table()}
        {sha256_k()}
        // top of stack: [ [64 byte chunks]... ]
        {padding_add_roll(num_bytes)}
        {sha256_init()}
        // top of stack: [ [64 byte chunks]..., state[0-7]]
        for i in 0..chunks_size {
            {sha256_transform(8 + ((chunks_size as u32) - i as u32) *16 + 64 + 1, 8 + ((chunks_size as u32) - i as u32)  *16)}
        }

        {sha256_final()}
        for _ in 0..8 {
            {u32_toaltstack()}
        }
        for _ in 0..64 {
            {u32_drop()}
        }
        {u8_drop_xor_table()}

        for _ in 0..8 {
            {u32_fromaltstack()}
        }
    }
}

pub fn sha256_32bytes() -> Script {
    script! {