Build production from a2ddb23

multihash.js

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+import bs58 from 'bs58';
+
+/**
+ * @typedef {Object} Multihash
+ * @property {string} digest The digest output of hash function in hex with prepended '0x'
+ * @property {number} hashFunction The hash function code for the function used
+ * @property {number} size The length of digest
+ */
+
+/**
+ * Partition multihash string into object representing multihash
+ *
+ * @param {string} multihash A base58 encoded multihash string
+ * @returns {Multihash}
+ */
+export function getBytes32FromMultiash(multihash) {
+  const decoded = bs58.decode(multihash);
+
+  return {
+    digest: `0x${decoded.slice(2).toString('hex')}`,
+    hashFunction: decoded[0],
+    size: decoded[1],
+  };
+}
+
+/**
+ * Encode a multihash structure into base58 encoded multihash string
+ *
+ * @param {Multihash} multihash
+ * @returns {(string|null)} base58 encoded multihash string
+ */
+export function getMultihashFromBytes32(multihash) {
+  const { digest, hashFunction, size } = multihash;
+  if (size === 0) return null;
+
+  // cut off leading "0x"
+  const hashBytes = Buffer.from(digest.slice(2), 'hex');
+
+  // prepend hashFunction and digest size
+  const multihashBytes = new (hashBytes.constructor)(2 + hashBytes.length);
+  multihashBytes[0] = hashFunction;
+  multihashBytes[1] = size;
+  multihashBytes.set(hashBytes, 2);
+
+  return bs58.encode(multihashBytes);
+}
+
+/**
+ * Parse Solidity response in array to a Multihash object
+ *
+ * @param {array} response Response array from Solidity
+ * @returns {Multihash} multihash object
+ */
+export function parseContractResponse(response) {
+  const [digest, hashFunction, size] = response;
+  return {
+    digest,
+    hashFunction: hashFunction.toNumber(),
+    size: size.toNumber(),
+  };
+}
+
+/**
+ * Parse Solidity response in array to a base58 encoded multihash string
+ *
+ * @param {array} response Response array from Solidity
+ * @returns {string} base58 encoded multihash string
+ */
+export function getMultihashFromContractResponse(response) {
+  return getMultihashFromBytes32(parseContractResponse(response));
+}