@ethersphere/bee-js/dist/mjs/chunk/bmt.js

Javascript client for Bee

import { Binary } from 'cafe-utility';
import { BeeArgumentError } from "../utils/error.js";
import { Reference, Span } from "../utils/typed-bytes.js";
const MAX_CHUNK_PAYLOAD_SIZE = 4096;
const SEGMENT_SIZE = 32;
/**
 * Calculate a Binary Merkle Tree hash for a chunk
 *
 * The BMT chunk address is the hash of the 8 byte span and the root
 * hash of a binary Merkle tree (BMT) built on the 32-byte segments
 * of the underlying data.
 *
 * If the chunk content is less than 4k, the hash is calculated as
 * if the chunk was padded with all zeros up to 4096 bytes.
 *
 * @param chunkContent Chunk data including span and payload as well
 *
 * @returns the keccak256 hash in a byte array
 */
export function calculateChunkAddress(chunkContent) {
  const span = chunkContent.slice(0, Span.LENGTH);
  const payload = chunkContent.slice(Span.LENGTH);
  const rootHash = calculateBmtRootHash(payload);
  const chunkHash = Binary.keccak256(Binary.concatBytes(span, rootHash));
  return new Reference(chunkHash);
}
function calculateBmtRootHash(payload) {
  if (payload.length > MAX_CHUNK_PAYLOAD_SIZE) {
    throw new BeeArgumentError(`payload size ${payload.length} exceeds maximum chunk payload size ${MAX_CHUNK_PAYLOAD_SIZE}`, payload);
  }
  const input = new Uint8Array(MAX_CHUNK_PAYLOAD_SIZE);
  input.set(payload);
  return Binary.log2Reduce(Binary.partition(input, SEGMENT_SIZE), (a, b) => Binary.keccak256(Binary.concatBytes(a, b)));
}