lz-string.js

// Copyright (c) 2013 Pieroxy <pieroxy@pieroxy.net>
// This work is free. You can redistribute it and/or modify it
// under the terms of the WTFPL, Version 2
// For more information see LICENSE.txt or http://www.wtfpl.net/
//
// For more information, the home page:
// http://pieroxy.net/blog/pages/lz-string/testing.html
//
// LZ-based compression algorithm, version 1.4.4
var LZString = (function() {
  
    // private property
    var f = String.fromCharCode;
    var keyStrBase64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
    var keyStrUriSafe = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+-$";
    var baseReverseDic = {};
    
    function getBaseValue(alphabet, character) {
      if (!baseReverseDic[alphabet]) {
        baseReverseDic[alphabet] = {};
        for (var i=0 ; i<alphabet.length ; i++) {
          baseReverseDic[alphabet][alphabet.charAt(i)] = i;
        }
      }
      return baseReverseDic[alphabet][character];
    }
    
    var LZString = {
      compressToBase64 : function (input) {
        if (input == null) return "";
        var res = LZString._compress(input, 6, function(a){return keyStrBase64.charAt(a);});
        switch (res.length % 4) { // To produce valid Base64
        default: // When could this happen ?
        case 0 : return res;
        case 1 : return res+"===";
        case 2 : return res+"==";
        case 3 : return res+"=";
        }
      },
    
      decompressFromBase64 : function (input) {
        if (input == null) return "";
//        if (input == "") return null;
        return LZString._decompress(input.length, 32, function(index) { return getBaseValue(keyStrBase64, input.charAt(index)); });
      },
    
      compressToUTF16 : function (input) {
        if (input == null) return "";
        return LZString._compress(input, 15, function(a){return f(a+32);}) + " ";
      },
    
      decompressFromUTF16: function (compressed) {
        if (compressed == null) return "";
        if (compressed == "") return null;
        return LZString._decompress(compressed.length, 16384, function(index) { return compressed.charCodeAt(index) - 32; });
      },
    
      //compress into uint8array (UCS-2 big endian format)
      compressToUint8Array: function (uncompressed) {
        var compressed = LZString.compress(uncompressed);
        var buf=new Uint8Array(compressed.length*2); // 2 bytes per character
    
        for (var i=0, TotalLen=compressed.length; i<TotalLen; i++) {
          var current_value = compressed.charCodeAt(i);
          buf[i*2] = current_value >>> 8;
          buf[i*2+1] = current_value % 256;
        }
        return buf;
      },
    
      //decompress from uint8array (UCS-2 big endian format)
      decompressFromUint8Array:function (compressed) {
        if (compressed===null || compressed===undefined){
            return LZString.decompress(compressed);
        } else {
            var buf=new Array(compressed.length/2); // 2 bytes per character
            for (var i=0, TotalLen=buf.length; i<TotalLen; i++) {
              buf[i]=compressed[i*2]*256+compressed[i*2+1];
            }
    
            var result = [];
            buf.forEach(function (c) {
              result.push(f(c));
            });
            return LZString.decompress(result.join(''));
    
        }
    
      },
    
    
      //compress into a string that is already URI encoded
      compressToEncodedURIComponent: function (input) {
        if (input == null) return "";
        return LZString._compress(input, 6, function(a){return keyStrUriSafe.charAt(a);});
      },
    
      //decompress from an output of compressToEncodedURIComponent
      decompressFromEncodedURIComponent:function (input) {
        if (input == null) return "";
        if (input == "") return null;
        input = input.replace(/ /g, "+");
        return LZString._decompress(input.length, 32, function(index) { return getBaseValue(keyStrUriSafe, input.charAt(index)); });
      },
    
      compress: function (uncompressed) {
        return LZString._compress(uncompressed, 16, function(a){return f(a);});
      },
      _compress: function (uncompressed, bitsPerChar, getCharFromInt) {
        if (uncompressed == null) return "";
        var i, value,
            context_dictionary= {},
            context_dictionaryToCreate= {},
            context_c="",
            context_wc="",
            context_w="",
            context_enlargeIn= 2, // Compensate for the first entry which should not count
            context_dictSize= 3,
            context_numBits= 2,
            context_data=[],
            context_data_val=0,
            context_data_position=0,
            ii;
    
        for (ii = 0; ii < uncompressed.length; ii += 1) {
          context_c = uncompressed.charAt(ii);
          if (!Object.prototype.hasOwnProperty.call(context_dictionary,context_c)) {
            context_dictionary[context_c] = context_dictSize++;
            context_dictionaryToCreate[context_c] = true;
          }
    
          context_wc = context_w + context_c;
          if (Object.prototype.hasOwnProperty.call(context_dictionary,context_wc)) {
            context_w = context_wc;
          } else {
            if (Object.prototype.hasOwnProperty.call(context_dictionaryToCreate,context_w)) {
              if (context_w.charCodeAt(0)<256) {
                for (i=0 ; i<context_numBits ; i++) {
                  context_data_val = (context_data_val << 1);
                  if (context_data_position == bitsPerChar-1) {
                    context_data_position = 0;
                    context_data.push(getCharFromInt(context_data_val));
                    context_data_val = 0;
                  } else {
                    context_data_position++;
                  }
                }
                value = context_w.charCodeAt(0);
                for (i=0 ; i<8 ; i++) {
                  context_data_val = (context_data_val << 1) | (value&1);
                  if (context_data_position == bitsPerChar-1) {
                    context_data_position = 0;
                    context_data.push(getCharFromInt(context_data_val));
                    context_data_val = 0;
                  } else {
                    context_data_position++;
                  }
                  value = value >> 1;
                }
              } else {
                value = 1;
                for (i=0 ; i<context_numBits ; i++) {
                  context_data_val = (context_data_val << 1) | value;
                  if (context_data_position ==bitsPerChar-1) {
                    context_data_position = 0;
                    context_data.push(getCharFromInt(context_data_val));
                    context_data_val = 0;
                  } else {
                    context_data_position++;
                  }
                  value = 0;
                }
                value = context_w.charCodeAt(0);
                for (i=0 ; i<16 ; i++) {
                  context_data_val = (context_data_val << 1) | (value&1);
                  if (context_data_position == bitsPerChar-1) {
                    context_data_position = 0;
                    context_data.push(getCharFromInt(context_data_val));
                    context_data_val = 0;
                  } else {
                    context_data_position++;
                  }
                  value = value >> 1;
                }
              }
              context_enlargeIn--;
              if (context_enlargeIn == 0) {
                context_enlargeIn = Math.pow(2, context_numBits);
                context_numBits++;
              }
              delete context_dictionaryToCreate[context_w];
            } else {
              value = context_dictionary[context_w];
              for (i=0 ; i<context_numBits ; i++) {
                context_data_val = (context_data_val << 1) | (value&1);
                if (context_data_position == bitsPerChar-1) {
                  context_data_position = 0;
                  context_data.push(getCharFromInt(context_data_val));
                  context_data_val = 0;
                } else {
                  context_data_position++;
                }
                value = value >> 1;
              }
    
    
            }
            context_enlargeIn--;
            if (context_enlargeIn == 0) {
              context_enlargeIn = Math.pow(2, context_numBits);
              context_numBits++;
            }
            // Add wc to the dictionary.
            context_dictionary[context_wc] = context_dictSize++;
            context_w = String(context_c);
          }
        }
    
        // Output the code for w.
        if (context_w !== "") {
          if (Object.prototype.hasOwnProperty.call(context_dictionaryToCreate,context_w)) {
            if (context_w.charCodeAt(0)<256) {
              for (i=0 ; i<context_numBits ; i++) {
                context_data_val = (context_data_val << 1);
                if (context_data_position == bitsPerChar-1) {
                  context_data_position = 0;
                  context_data.push(getCharFromInt(context_data_val));
                  context_data_val = 0;
                } else {
                  context_data_position++;
                }
              }
              value = context_w.charCodeAt(0);
              for (i=0 ; i<8 ; i++) {
                context_data_val = (context_data_val << 1) | (value&1);
                if (context_data_position == bitsPerChar-1) {
                  context_data_position = 0;
                  context_data.push(getCharFromInt(context_data_val));
                  context_data_val = 0;
                } else {
                  context_data_position++;
                }
                value = value >> 1;
              }
            } else {
              value = 1;
              for (i=0 ; i<context_numBits ; i++) {
                context_data_val = (context_data_val << 1) | value;
                if (context_data_position == bitsPerChar-1) {
                  context_data_position = 0;
                  context_data.push(getCharFromInt(context_data_val));
                  context_data_val = 0;
                } else {
                  context_data_position++;
                }
                value = 0;
              }
              value = context_w.charCodeAt(0);
              for (i=0 ; i<16 ; i++) {
                context_data_val = (context_data_val << 1) | (value&1);
                if (context_data_position == bitsPerChar-1) {
                  context_data_position = 0;
                  context_data.push(getCharFromInt(context_data_val));
                  context_data_val = 0;
                } else {
                  context_data_position++;
                }
                value = value >> 1;
              }
            }
            context_enlargeIn--;
            if (context_enlargeIn == 0) {
              context_enlargeIn = Math.pow(2, context_numBits);
              context_numBits++;
            }
            delete context_dictionaryToCreate[context_w];
          } else {
            value = context_dictionary[context_w];
            for (i=0 ; i<context_numBits ; i++) {
              context_data_val = (context_data_val << 1) | (value&1);
              if (context_data_position == bitsPerChar-1) {
                context_data_position = 0;
                context_data.push(getCharFromInt(context_data_val));
                context_data_val = 0;
              } else {
                context_data_position++;
              }
              value = value >> 1;
            }
    
    
          }
          context_enlargeIn--;
          if (context_enlargeIn == 0) {
            context_enlargeIn = Math.pow(2, context_numBits);
            context_numBits++;
          }
        }
    
        // Mark the end of the stream
        value = 2;
        for (i=0 ; i<context_numBits ; i++) {
          context_data_val = (context_data_val << 1) | (value&1);
          if (context_data_position == bitsPerChar-1) {
            context_data_position = 0;
            context_data.push(getCharFromInt(context_data_val));
            context_data_val = 0;
          } else {
            context_data_position++;
          }
          value = value >> 1;
        }
    
        // Flush the last char
        while (true) {
          context_data_val = (context_data_val << 1);
          if (context_data_position == bitsPerChar-1) {
            context_data.push(getCharFromInt(context_data_val));
            break;
          }
          else context_data_position++;
        }
        return context_data.join('');
      },
    
      decompress: function (compressed) {
        if (compressed == null) return "";
        if (compressed == "") return null;
        return LZString._decompress(compressed.length, 32768, function(index) { return compressed.charCodeAt(index); });
      },
    
      _decompress: function (length, resetValue, getNextValue) {
        var dictionary = [],
            next,
            enlargeIn = 4,
            dictSize = 4,
            numBits = 3,
            entry = "",
            result = [],
            i,
            w,
            bits, resb, maxpower, power,
            c,
            data = {val:getNextValue(0), position:resetValue, index:1};
    
        for (i = 0; i < 3; i += 1) {
          dictionary[i] = i;
        }
    
        bits = 0;
        maxpower = Math.pow(2,2);
        power=1;
        while (power!=maxpower) {
          resb = data.val & data.position;
          data.position >>= 1;
          if (data.position == 0) {
            data.position = resetValue;
            data.val = getNextValue(data.index++);
          }
          bits |= (resb>0 ? 1 : 0) * power;
          power <<= 1;
        }
    
        switch (next = bits) {
          case 0:
              bits = 0;
              maxpower = Math.pow(2,8);
              power=1;
              while (power!=maxpower) {
                resb = data.val & data.position;
                data.position >>= 1;
                if (data.position == 0) {
                  data.position = resetValue;
                  data.val = getNextValue(data.index++);
                }
                bits |= (resb>0 ? 1 : 0) * power;
                power <<= 1;
              }
            c = f(bits);
            break;
          case 1:
              bits = 0;
              maxpower = Math.pow(2,16);
              power=1;
              while (power!=maxpower) {
                resb = data.val & data.position;
                data.position >>= 1;
                if (data.position == 0) {
                  data.position = resetValue;
                  data.val = getNextValue(data.index++);
                }
                bits |= (resb>0 ? 1 : 0) * power;
                power <<= 1;
              }
            c = f(bits);
            break;
          case 2:
            return "";
        }
        dictionary[3] = c;
        w = c;
        result.push(c);
        while (true) {
          if (data.index > length) {
            return "";
          }
    
          bits = 0;
          maxpower = Math.pow(2,numBits);
          power=1;
          while (power!=maxpower) {
            resb = data.val & data.position;
            data.position >>= 1;
            if (data.position == 0) {
              data.position = resetValue;
              data.val = getNextValue(data.index++);
            }
            bits |= (resb>0 ? 1 : 0) * power;
            power <<= 1;
          }
    
          switch (c = bits) {
            case 0:
              bits = 0;
              maxpower = Math.pow(2,8);
              power=1;
              while (power!=maxpower) {
                resb = data.val & data.position;
                data.position >>= 1;
                if (data.position == 0) {
                  data.position = resetValue;
                  data.val = getNextValue(data.index++);
                }
                bits |= (resb>0 ? 1 : 0) * power;
                power <<= 1;
              }
    
              dictionary[dictSize++] = f(bits);
              c = dictSize-1;
              enlargeIn--;
              break;
            case 1:
              bits = 0;
              maxpower = Math.pow(2,16);
              power=1;
              while (power!=maxpower) {
                resb = data.val & data.position;
                data.position >>= 1;
                if (data.position == 0) {
                  data.position = resetValue;
                  data.val = getNextValue(data.index++);
                }
                bits |= (resb>0 ? 1 : 0) * power;
                power <<= 1;
              }
              dictionary[dictSize++] = f(bits);
              c = dictSize-1;
              enlargeIn--;
              break;
            case 2:
              return result.join('');
          }
    
          if (enlargeIn == 0) {
            enlargeIn = Math.pow(2, numBits);
            numBits++;
          }
    
          if (dictionary[c]) {
            entry = dictionary[c];
          } else {
            if (c === dictSize) {
              entry = w + w.charAt(0);
            } else {
              return null;
            }
          }
          result.push(entry);
    
          // Add w+entry[0] to the dictionary.
          dictionary[dictSize++] = w + entry.charAt(0);
          enlargeIn--;
    
          w = entry;
    
          if (enlargeIn == 0) {
            enlargeIn = Math.pow(2, numBits);
            numBits++;
          }
    
        }
      }
    };
      return LZString;
    })();
    
    if (typeof define === 'function' && define.amd) {
      define(function () { return LZString; });
    } else if( typeof module !== 'undefined' && module != null ) {
      module.exports = LZString
    } else if( typeof angular !== 'undefined' && angular != null ) {
      angular.module('LZString', [])
      .factory('LZString', function () {
        return LZString;
      });
    }