c-kzg/lib/kzg.js

NodeJS bindings for C-KZG

/**
 * The public interface of this module exposes the functions as specified by
 * https://github.com/ethereum/consensus-specs/blob/dev/specs/deneb/polynomial-commitments.md#kzg
 */
const fs = require("fs");
const path = require("path");
const bindings = require("bindings")("kzg");

/**
 * NOTE: This path is only exported for testing purposes. It is not announced in
 * the type file.
 *
 * It is critical that this path is kept in sync with where the trusted setup
 * file will be found. The path is dictated by the `build` command in the
 * Makefile in the bindings/node.js folder.
 *
 * This path works for two situations:
 * 1) Production case
 * - this file in BUNDLE_ROOT/dist/lib/kzg.js
 * - trusted_setup in BUNDLE_ROOT/dist/deps/c-kzg/trusted_setup.txt
 *
 *  2) Post `build` state before `bundle` command works
 * - this file in bindings/node.js/lib/kzg.js
 * - trusted_setup in bindings/node.js/deps/c-kzg/trusted_setup.txt
 */
bindings.DEFAULT_TRUSTED_SETUP_PATH = path.resolve(__dirname, "..", "deps", "c-kzg", "trusted_setup.txt");

/**
 * Converts JSON formatted trusted setup into the native format that
 * the native library requires.  Returns the absolute file path to
 * the formatted file.  The path will be the same as the origin
 * file but with a ".txt" extension.
 *
 * @param {string} filePath - The absolute path of JSON formatted trusted setup
 *
 * @return {string} - The absolute path of the re-formatted trusted setup
 *
 * @throws {Error} - For invalid file operations
 */
function transformTrustedSetupJson(filePath) {
  const trustedSetup = JSON.parse(fs.readFileSync(filePath, "utf8"));
  if (trustedSetup.g1_lagrange.length != trustedSetup.g1_monomial.length) {
    throw new TypeError("g1_lagrange & g1_monomial must have the same number of values");
  }
  const setupText =
    trustedSetup.g1_lagrange.length +
    "\n" +
    trustedSetup.g2_monomial.length +
    "\n" +
    trustedSetup.g1_lagrange.map((p) => p.substring(2)).join("\n") +
    "\n" +
    trustedSetup.g2_monomial.map((p) => p.substring(2)).join("\n") +
    "\n" +
    trustedSetup.g1_monomial.map((p) => p.substring(2)).join("\n");
  const outputPath = filePath.replace(".json", ".txt");
  fs.writeFileSync(outputPath, setupText);
  return outputPath;
}

/**
 * Gets location for trusted setup file. Uses user provided location first. If
 * one is not provided then defaults to the official Ethereum mainnet setup from
 * the KZG ceremony.
 *
 * @param {string} filePath - User provided filePath to check for trusted setup
 *
 * @returns {string} - Location of a trusted setup file. Validity is checked by
 *                     the native bindings.loadTrustedSetup
 *
 * @throws {TypeError} - Invalid file type
 * @throws {Error} - Invalid location or no default trusted setup found
 *
 * @remarks - This function is only exported for testing purposes. It should
 *            not be used directly. Not included in the kzg.d.ts types for that
 *            reason.
 */
bindings.getTrustedSetupFilepath = function getTrustedSetupFilepath(filePath) {
  if (filePath) {
    if (typeof filePath !== "string") {
      throw new TypeError("Must initialize kzg with the filePath to a txt/json trusted setup");
    }
    if (!fs.existsSync(filePath)) {
      throw new Error(`No trusted setup found: ${filePath}`);
    }
  } else {
    filePath = bindings.DEFAULT_TRUSTED_SETUP_PATH;
    if (!fs.existsSync(filePath)) {
      throw new Error("Default trusted setup not found. Must pass a valid filepath to load c-kzg library");
    }
  }

  if (path.parse(filePath).ext === ".json") {
    filePath = transformTrustedSetupJson(filePath);
  }

  return filePath;
};

const originalLoadTrustedSetup = bindings.loadTrustedSetup;
// docstring in ./kzg.d.ts with exported definition
bindings.loadTrustedSetup = function loadTrustedSetup(precompute, filePath) {
  originalLoadTrustedSetup(precompute, bindings.getTrustedSetupFilepath(filePath));
};

module.exports = exports = bindings;