channels_sv2 1.0.2

Sv2 Channel Primitives
Documentation 
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extern crate alloc;

use alloc::vec::Vec;
use bitcoin::{
    consensus,
    hashes::{sha256d::Hash as DHash, Hash},
    Transaction,
};
use tracing::error;

/// Computes the Merkle root from coinbase transaction components and a path of transaction hashes.
///
/// Validates and deserializes a coinbase transaction before building the 32-byte Merkle root.
/// Returns [`None`] is the arguments are invalid.
///
/// ## Components
/// * `coinbase_tx_prefix`: First part of the coinbase transaction (the part before the extranonce).
///   Should be converted from [`binary_sv2::B064K`].
/// * `coinbase_tx_suffix`: Coinbase transaction suffix (the part after the extranonce). Should be
///   converted from [`binary_sv2::B064K`].
/// * `extranonce`: Extra nonce space. Should be converted from [`binary_sv2::B032`] and padded with
///   zeros if not `32` bytes long.
/// * `path`: List of transaction hashes. Should be converted from [`binary_sv2::U256`].
pub fn merkle_root_from_path<T: AsRef<[u8]>>(
    coinbase_tx_prefix: &[u8],
    coinbase_tx_suffix: &[u8],
    extranonce: &[u8],
    path: &[T],
) -> Option<Vec<u8>> {
    let mut coinbase =
        Vec::with_capacity(coinbase_tx_prefix.len() + coinbase_tx_suffix.len() + extranonce.len());
    coinbase.extend_from_slice(coinbase_tx_prefix);
    coinbase.extend_from_slice(extranonce);
    coinbase.extend_from_slice(coinbase_tx_suffix);
    let coinbase: Transaction = match consensus::deserialize(&coinbase[..]) {
        Ok(trans) => trans,
        Err(e) => {
            error!("ERROR: {}", e);
            return None;
        }
    };

    let coinbase_id: [u8; 32] = *coinbase.compute_txid().as_ref();

    Some(merkle_root_from_path_(coinbase_id, path).to_vec())
}

/// Computes the Merkle root from a validated coinbase transaction and a path of transaction
/// hashes.
///
/// If the `path` is empty, the coinbase transaction hash (`coinbase_id`) is returned as the root.
///
/// ## Components
/// * `coinbase_id`: Coinbase transaction hash.
/// * `path`: List of transaction hashes. Should be converted from [`binary_sv2::U256`].
pub fn merkle_root_from_path_<T: AsRef<[u8]>>(coinbase_id: [u8; 32], path: &[T]) -> [u8; 32] {
    match path.len() {
        0 => coinbase_id,
        _ => reduce_path(coinbase_id, path),
    }
}

// Computes the Merkle root by iteratively combining the coinbase transaction hash with each
// transaction hash in the `path`.
//
// Handles the core logic of combining hashes using the Bitcoin double-SHA256 hashing algorithm.
fn reduce_path<T: AsRef<[u8]>>(coinbase_id: [u8; 32], path: &[T]) -> [u8; 32] {
    let mut root = coinbase_id;
    for node in path {
        let to_hash = [&root[..], node.as_ref()].concat();
        let hash = DHash::hash(&to_hash);
        root = *hash.as_ref();
    }
    root
}