84 lines
2.3 KiB
Rust
84 lines
2.3 KiB
Rust
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use hashing::hash;
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const SSZ_CHUNK_SIZE: usize = 128;
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const HASHSIZE: usize = 32;
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pub trait TreeHash {
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fn hash_tree_root(&self) -> Vec<u8>;
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}
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/// Returns a 32 byte hash of 'list' - a vector of byte vectors.
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/// Note that this will consume 'list'.
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pub fn merkle_hash(list: &mut Vec<Vec<u8>>) -> Vec<u8> {
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// flatten list
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let (mut chunk_size, mut chunkz) = list_to_blob(list);
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// get data_len as bytes. It will hashed will the merkle root
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let datalen = list.len().to_le_bytes();
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// Tree-hash
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while chunkz.len() > HASHSIZE {
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let mut new_chunkz: Vec<u8> = Vec::new();
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for two_chunks in chunkz.chunks(chunk_size * 2) {
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if two_chunks.len() == chunk_size {
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// Odd number of chunks
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let mut c = two_chunks.to_vec();
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c.append(&mut vec![0; SSZ_CHUNK_SIZE]);
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new_chunkz.append(&mut hash(&c));
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} else {
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// Hash two chuncks together
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new_chunkz.append(&mut hash(two_chunks));
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}
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}
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chunk_size = HASHSIZE;
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chunkz = new_chunkz;
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}
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chunkz.append(&mut datalen.to_vec());
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hash(&chunkz)
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}
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fn list_to_blob(list: &mut Vec<Vec<u8>>) -> (usize, Vec<u8>) {
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let chunk_size = if list.is_empty() {
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SSZ_CHUNK_SIZE
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} else if list[0].len() < SSZ_CHUNK_SIZE {
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let items_per_chunk = SSZ_CHUNK_SIZE / list[0].len();
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items_per_chunk * list[0].len()
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} else {
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list[0].len()
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};
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let mut data = Vec::new();
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if list.is_empty() {
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// handle and empty list
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data.append(&mut vec![0; SSZ_CHUNK_SIZE]);
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} else {
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// just create a blob here; we'll divide into
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// chunked slices when we merklize
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data.reserve(list[0].len() * list.len());
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for item in list.iter_mut() {
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data.append(item);
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}
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}
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(chunk_size, data)
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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#[test]
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fn test_merkle_hash() {
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let data1 = vec![1; 100];
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let data2 = vec![2; 100];
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let data3 = vec![3; 100];
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let mut list = vec![data1, data2, data3];
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let result = merkle_hash(&mut list);
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//note: should test againt a known test hash value
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assert_eq!(HASHSIZE, result.len());
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}
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}
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