Function blake3

bitvm/src/hash/blake3.rs:22–220

Internal BLAKE3 implementation. Set `define_var` to `false` if the message on the stack is already defined as [`StackTracker`] variables. Set `use_full_tables` to `false` to use half tables instead of full tables. ## See [`blake3_compute_script_with_limb`].

(
    stack: &mut StackTracker,
    mut msg_len: u32,
    define_var: bool,
    use_full_tables: bool,
    limb_len: u8,
)

///
/// [`blake3_compute_script_with_limb`].
fn blake3(
    stack: &mut StackTracker,
    mut msg_len: u32,
    define_var: bool,
    use_full_tables: bool,
    limb_len: u8,
) {
    // this assumes that the stack is empty
    if msg_len == 0 {
        // af1349b9f5f9a1a6a0404dea36dcc9499bcb25c9adc112b7cc9a93cae41f3262
        //hardcoded hash of empty msg
        let empty_msg_hash = "af1349b9f5f9a1a6a0404dea36dcc9499bcb25c9adc112b7cc9a93cae41f3262";
        let empty_msg_hash_bytearray = <[u8; 32]>::from_hex(empty_msg_hash).unwrap();

        stack.custom(
            script!(
                // push the hash value
                for byte in empty_msg_hash_bytearray{
                    {byte}
                }
                //convert bytes to nibbles
                {U256::transform_limbsize(8,4)}
            ),
            0,
            false,
            0,
            "push empty string hash in nibble form",
        );
        stack.define(8_u32 * 8, "blake3-hash");
        return;
    }

    // We require message take atmost a chunk. i.e, 1024 bytes.
    assert!(
        msg_len <= 1024,
        "msg length must be less than or equal to 1024 bytes"
    );
    assert!(
        (4..32).contains(&limb_len),
        "limb length must be in the range [4, 32)"
    );

    //number of msg blocks
    let num_blocks = msg_len.div_ceil(64);

    // If the compact form of message is on stack but not associated with variable, convert it to StackVariable
    if define_var {
        let limb_count = 256u32.div_ceil(limb_len as u32);
        for i in (0..num_blocks).rev() {
            stack.define(limb_count, &format!("msg{}p0", i));
            stack.define(limb_count, &format!("msg{}p1", i));
        }
    }

    // Push msg to alt stack to get the table on top
    for _ in 0..num_blocks {
        stack.to_altstack();
        stack.to_altstack();