bitcoinjs-lib/src/util.js

var BigInteger = require('./jsbn/jsbn');
var Crypto = require('./crypto-js/crypto');

module.exports = {
  /**
   * Cross-browser compatibility version of Array.isArray.
   */
  isArray: Array.isArray || function(o)
  {
    return Object.prototype.toString.call(o) === '[object Array]';
  },

  /**
   * Create an array of a certain length filled with a specific value.
   */
  makeFilledArray: function (len, val)
  {
    var array = [];
    var i = 0;
    while (i < len) {
      array[i++] = val;
    }
    return array;
  },
  /**
   * Create a byte array representing a number with the given length
   */
  numToBytes: function(num,bytes) {
    if (bytes === undefined) bytes = 8;
    if (bytes == 0) return [];
    else return [num % 256].concat(module.exports.numToBytes(Math.floor(num / 256),bytes-1));
  },

  /**
   * Create a byte array representing a number with the given length
   */
  bytesToNum: function(bytes) {
    if (bytes.length == 0) return 0;
    else return bytes[0] + 256 * module.exports.bytesToNum(bytes.slice(1));
  },
  /**
   * Turn an integer into a "var_int".
   *
   * "var_int" is a variable length integer used by Bitcoin's binary format.
   *
   * Returns a byte array.
   */
  numToVarInt: function(num) {
    var m = module.exports;
    if (num < 253) return [num];
    else if (num < 65536) return [253].concat(m.numToBytes(num,2));
    else if (num < 4294967296) return [254].concat(m.numToBytes(num,4));
    else return [253].concat(m.numToBytes(num,8));
  },

  /**
   * Parse a Bitcoin value byte array, returning a BigInteger.
   */
  valueToBigInt: function (valueBuffer)
  {
    if (valueBuffer instanceof BigInteger) return valueBuffer;

    // Prepend zero byte to prevent interpretation as negative integer
    return BigInteger.fromByteArrayUnsigned(valueBuffer);
  },

  /**
   * Format a Bitcoin value as a string.
   *
   * Takes a BigInteger or byte-array and returns that amount of Bitcoins in a
   * nice standard formatting.
   *
   * Examples:
   * 12.3555
   * 0.1234
   * 900.99998888
   * 34.00
   */
  formatValue: function (valueBuffer) {
    var value = this.valueToBigInt(valueBuffer).toString();
    var integerPart = value.length > 8 ? value.substr(0, value.length-8) : '0';
    var decimalPart = value.length > 8 ? value.substr(value.length-8) : value;
    while (decimalPart.length < 8) decimalPart = "0"+decimalPart;
    decimalPart = decimalPart.replace(/0*$/, '');
    while (decimalPart.length < 2) decimalPart += "0";
    return integerPart+"."+decimalPart;
  },

  /**
   * Parse a floating point string as a Bitcoin value.
   *
   * Keep in mind that parsing user input is messy. You should always display
   * the parsed value back to the user to make sure we understood his input
   * correctly.
   */
  parseValue: function (valueString) {
    // TODO: Detect other number formats (e.g. comma as decimal separator)
    var valueComp = valueString.split('.');
    var integralPart = valueComp[0];
    var fractionalPart = valueComp[1] || "0";
    while (fractionalPart.length < 8) fractionalPart += "0";
    fractionalPart = fractionalPart.replace(/^0+/g, '');
    var value = BigInteger.valueOf(parseInt(integralPart));
    value = value.multiply(BigInteger.valueOf(100000000));
    value = value.add(BigInteger.valueOf(parseInt(fractionalPart)));
    return value;
  },

  /**
   * Calculate RIPEMD160(SHA256(data)).
   *
   * Takes an arbitrary byte array as inputs and returns the hash as a byte
   * array.
   */
  sha256ripe160: function (data) {
    return Crypto.RIPEMD160(Crypto.SHA256(data, {asBytes: true}), {asBytes: true});
  },
  error: function(msg) {
    throw new Error(msg);
  }
};