/* Copyright (c) 2010 Thomas Peri http://www.tumuski.com/ Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */ /*jslint white: true, browser: true, onevar: true, undef: true, nomen: true, eqeqeq: true, plusplus: true, regexp: true, newcap: true, immed: true */ // (good parts minus bitwise and strict, plus white.) /** * Nibbler - Multi-Base Encoder * * version 2010-04-07 * * Options: * dataBits: The number of bits in each character of unencoded data. * codeBits: The number of bits in each character of encoded data. * keyString: The characters that correspond to each value when encoded. * pad (optional): The character to pad the end of encoded output. * arrayData (optional): If truthy, unencoded data is an array instead of a string. * * Example: * * var base64_8bit = new Nibbler({ * dataBits: 8, * codeBits: 6, * keyString: 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/', * pad: '=' * }); * base64_8bit.encode("Hello, World!"); // returns "SGVsbG8sIFdvcmxkIQ==" * base64_8bit.decode("SGVsbG8sIFdvcmxkIQ=="); // returns "Hello, World!" * * var base64_7bit = new Nibbler({ * dataBits: 7, * codeBits: 6, * keyString: 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/', * pad: '=' * }); * base64_7bit.encode("Hello, World!"); // returns "kZdmzesQV9/LZkQg==" * base64_7bit.decode("kZdmzesQV9/LZkQg=="); // returns "Hello, World!" * */ var Nibbler = function (options) { var construct, // options pad, dataBits, codeBits, keyString, arrayData, // private instance variables mask, group, max, // private methods gcd, translate, // public methods encode, decode; // pseudo-constructor construct = function () { var i, mag, prev; // options pad = options.pad || ''; dataBits = options.dataBits; codeBits = options.codeBits; keyString = options.keyString; arrayData = options.arrayData; // bitmasks mag = Math.max(dataBits, codeBits); prev = 0; mask = []; for (i = 0; i < mag; i += 1) { mask.push(prev); prev += prev + 1; } max = prev; // ouput code characters in multiples of this number group = dataBits / gcd(dataBits, codeBits); }; // greatest common divisor gcd = function (a, b) { var t; while (b !== 0) { t = b; b = a % b; a = t; } return a; }; // the re-coder translate = function (input, bitsIn, bitsOut, decoding) { var i, len, chr, byteIn, buffer, size, output, write; // append a byte to the output write = function (n) { if (!decoding) { output.push(keyString.charAt(n)); } else if (arrayData) { output.push(n); } else { output.push(String.fromCharCode(n)); } }; buffer = 0; size = 0; output = []; //if( input.length != null ) { if(input.length && input && input != null) { len = input.length; if(len > 0 ) { for (i = 0; i < len; i += 1) { // the new size the buffer will be after adding these bits size += bitsIn; // read a character if (decoding) { // decode it chr = input.charAt(i); byteIn = keyString.indexOf(chr); if (chr === pad) { break; } else if (byteIn < 0) { throw 'the character "' + chr + '" is not a member of ' + keyString; } } else { if (arrayData) { byteIn = input[i]; } else { byteIn = input.charCodeAt(i); } if ((byteIn | max) !== max) { throw byteIn + " is outside the range 0-" + max; } } // shift the buffer to the left and add the new bits buffer = (buffer << bitsIn) | byteIn; // as long as there's enough in the buffer for another output... while (size >= bitsOut) { // the new size the buffer will be after an output size -= bitsOut; // output the part that lies to the left of that number of bits // by shifting the them to the right write(buffer >> size); // remove the bits we wrote from the buffer // by applying a mask with the new size buffer &= mask[size]; } } } } // If we're encoding and there's input left over, pad the output. // Otherwise, leave the extra bits off, 'cause they themselves are padding if (!decoding && size > 0) { // flush the buffer write(buffer << (bitsOut - size)); // add padding keyString for the remainder of the group len = output.length % group; for (i = 0; i < len; i += 1) { output.push(pad); } } // string! return (arrayData && decoding) ? output : output.join(''); }; /** * Encode. Input and output are strings. */ encode = function (input) { return translate(input, dataBits, codeBits, false); }; /** * Decode. Input and output are strings. */ decode = function (input) { return translate(input, codeBits, dataBits, true); }; this.encode = encode; this.decode = decode; construct(); };