@holochain/client/lib/utils/hash-parts.js

A JavaScript client for the Holochain Conductor API

import blake2b from "@bitgo/blake2b";
const HASH_TYPE_START = 0;
const HASH_TYPE_BYTE_LENGTH = 3;
const CORE_HASH_BYTE_LENGTH = 32;
const DHT_LOCATION_BYTE_LENGTH = 4;
/**
 * Hash type labels and their 3 byte values (forming the first 3 bytes of hash).
 *
 * From https://github.com/holochain/holochain/blob/develop/crates/holo_hash/src/hash_type/primitive.rs
 *
 * @public
 */
export const HASH_TYPE_PREFIX = {
    Agent: Uint8Array.from([132, 32, 36]),
    Entry: Uint8Array.from([132, 33, 36]),
    Dna: Uint8Array.from([132, 45, 36]),
    Action: Uint8Array.from([132, 41, 36]),
    External: Uint8Array.from([132, 47, 36]),
};
/**
 * Get hash type (initial 3 bytes) from a hash.
 *
 * From https://github.com/holochain/holochain/blob/develop/crates/holo_hash/src/hash_type/primitive.rs
 *
 * @param hash - The full 39 byte hash.
 * @returns The initial 3 bytes of the hash.
 *
 * @public
 */
export function sliceHashType(hash) {
    return Uint8Array.from(hash.slice(0, 3));
}
/**
 * Get core hash from a Holochain hash (32 bytes).
 *
 * From https://github.com/holochain/holochain/blob/develop/crates/holo_hash/src/hash_type/primitive.rs
 *
 * @param hash - The full 39 byte hash.
 * @returns The core 32 bytes of the hash.
 *
 * @public
 */
export function sliceCore32(hash) {
    const start = HASH_TYPE_START + HASH_TYPE_BYTE_LENGTH;
    const end = start + CORE_HASH_BYTE_LENGTH;
    return Uint8Array.from(hash.slice(start, end));
}
/**
 * Get DHT location (last 4 bytes) from a hash.
 *
 * From https://github.com/holochain/holochain/blob/develop/crates/holo_hash/src/hash_type/primitive.rs
 *
 * @param hash - The full 39 byte hash.
 * @returns The last 4 bytes of the hash.
 *
 * @public
 */
export function sliceDhtLocation(hash) {
    const start = HASH_TYPE_START + HASH_TYPE_BYTE_LENGTH + CORE_HASH_BYTE_LENGTH;
    const end = start + DHT_LOCATION_BYTE_LENGTH;
    return Uint8Array.from(hash.slice(start, end));
}
/**
 * Generate DHT location (last 4 bytes) from a core hash (middle 32 bytes).
 *
 * From https://github.com/holochain/holochain/blob/develop/crates/holo_hash/src/hash_type/primitive.rs
 *
 * @param hashCore - The core 32 bytes of the hash.
 * @returns The last 4 bytes of the hash.
 *
 * @public
 */
export function dhtLocationFrom32(hashCore) {
    const hash = new Uint8Array(16);
    blake2b(hash.length).update(hashCore).digest(hash);
    const out = hash.slice(0, 4);
    [4, 8, 12].forEach((i) => {
        out[0] ^= hash[i];
        out[1] ^= hash[i + 1];
        out[2] ^= hash[i + 2];
        out[3] ^= hash[i + 3];
    });
    return out;
}
/**
 * Generate full hash from a core hash (middle 32 bytes) and hash type label.
 *
 * From https://github.com/holochain/holochain/blob/develop/crates/holo_hash/src/hash_type/primitive.rs
 *
 * @param hashCore - The core 32 bytes of the hash.
 * @param hashType - The type of the hash.
 * @returns The full 39 byte hash.
 *
 * @public
 */
export function hashFrom32AndType(hashCore, hashType) {
    return Uint8Array.from([
        ...HASH_TYPE_PREFIX[hashType],
        ...hashCore,
        ...dhtLocationFrom32(hashCore),
    ]);
}