bitcoinjs-lib/base58.js

(function () {
	var B58 = Bitcoin.Base58 = {
		alphabet: "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz",
		base: BigInteger.valueOf(58),

		/**
		 * Convert a byte array to a base58-encoded string.
		 *
		 * Written by Mike Hearn for BitcoinJ.
		 *   Copyright (c) 2011 Google Inc.
		 *
		 * Ported to JavaScript by Stefan Thomas.
		 */
		encode: function (input) {
			var bi = BigInteger.fromByteArrayUnsigned(input);
			var chars = [];

			while (bi.compareTo(B58.base) >= 0) {
				var mod = bi.mod(B58.base);
				chars.unshift(B58.alphabet[mod.intValue()]);
				bi = bi.subtract(mod).divide(B58.base);
			}
			chars.unshift(B58.alphabet[bi.intValue()]);

			// Convert leading zeros too.
			for (var i = 0; i < input.length; i++) {
				if (input[i] == 0x00) {
					chars.unshift(B58.alphabet[0]);
				} else break;
			}

			s = chars.join('');
			return s;
		},

		/**
		 * Convert a base58-encoded string to a byte array.
		 *
		 * Written by Mike Hearn for BitcoinJ.
		 *   Copyright (c) 2011 Google Inc.
		 *
		 * Ported to JavaScript by Stefan Thomas.
		 */
		decode: function (input) {
			bi = BigInteger.valueOf(0);
			var leadingZerosNum = 0;
			for (var i = input.length - 1; i >= 0; i--) {
				var alphaIndex = B58.alphabet.indexOf(input[i]);
				bi = bi.add(BigInteger.valueOf(alphaIndex)
							.multiply(B58.base.pow(input.length - 1 -i)));

				// This counts leading zero bytes
				if (input[i] == "1") leadingZerosNum++;
				else leadingZerosNum = 0;
			}
			var bytes = bi.toByteArrayUnsigned();

			// Add leading zeros
			while (leadingZerosNum-- > 0) bytes.unshift(0);

			return bytes;
		}
	};
})();