56 lines
1.8 KiB
JavaScript
56 lines
1.8 KiB
JavaScript
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// For ESM compatibility
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import pkg from 'js-sha3';
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const {
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keccak256
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} = pkg;
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import { BeeArgumentError } from "../utils/error.js";
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import { keccak256Hash } from "../utils/hash.js";
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const MAX_CHUNK_PAYLOAD_SIZE = 4096;
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const SEGMENT_SIZE = 32;
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const SEGMENT_PAIR_SIZE = 2 * SEGMENT_SIZE;
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const HASH_SIZE = 32;
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/**
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* Calculate a Binary Merkle Tree hash for a chunk
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*
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* The BMT chunk address is the hash of the 8 byte span and the root
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* hash of a binary Merkle tree (BMT) built on the 32-byte segments
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* of the underlying data.
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*
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* If the chunk content is less than 4k, the hash is calculated as
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* if the chunk was padded with all zeros up to 4096 bytes.
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*
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* @param chunkContent Chunk data including span and payload as well
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*
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* @returns the keccak256 hash in a byte array
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*/
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export function bmtHash(chunkContent) {
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const span = chunkContent.slice(0, 8);
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const payload = chunkContent.slice(8);
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const rootHash = bmtRootHash(payload);
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const chunkHashInput = new Uint8Array([...span, ...rootHash]);
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const chunkHash = keccak256Hash(chunkHashInput);
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return chunkHash;
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}
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function bmtRootHash(payload) {
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if (payload.length > MAX_CHUNK_PAYLOAD_SIZE) {
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throw new BeeArgumentError('invalid data length', payload);
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} // create an input buffer padded with zeros
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let input = new Uint8Array([...payload, ...new Uint8Array(MAX_CHUNK_PAYLOAD_SIZE - payload.length)]);
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while (input.length !== HASH_SIZE) {
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const output = new Uint8Array(input.length / 2); // in each round we hash the segment pairs together
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for (let offset = 0; offset < input.length; offset += SEGMENT_PAIR_SIZE) {
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const hashNumbers = keccak256.array(input.slice(offset, offset + SEGMENT_PAIR_SIZE));
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output.set(hashNumbers, offset / 2);
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}
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input = output;
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}
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return input;
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}
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