sm_utils.js

/*
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

const BN = require('bn.js');
const crypto = require('crypto');


function strToBytes(s) {
	let ch, st, re = [];
	for (let i = 0; i < s.length; i++) {
		ch = s.charCodeAt(i);  // get char
		st = [];                 // set up "stack"
		do {
			st.push(ch & 0xFF);  // push byte to stack
			ch = ch >> 8;          // shift value down by 1 byte
		}
		while (ch);
		// add stack contents to result
		// done because chars have "wrong" endianness
		re = re.concat(st.reverse());
	}
	return re;
}

function hashToBN(hash) {
	if (typeof hash === 'string') {
		return new BN(hash, 16);
	} else {
		let hex = '';
		for (let i = 0; i < hash.length; i++) {
			const b = hash[i].toString(16);
			if (b.length === 1) {
				hex += '0';
			}
			hex += b;
		}
		return new BN(hex, 16);
	}
}

/**
 * Generate cryptographic random value.
 *
 * @param {Number} n: byte length of the generated value
 */
function random(n) {
	return crypto.randomBytes(n).toString('hex');
}

module.exports = {
	strToBytes,
	hashToBN,
	random,
};