api documentation for lz-string (v1.4.4)

LZ-based compression algorithm

module lz-string

module lz-string

function lz-string._compress (uncompressed, bitsPerChar, getCharFromInt)

description and source-code

_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 ...

example usage
```
n/a
```

function lz-string._decompress (length, resetValue, getNextValue)

description and source-code

_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++;
    }

  }
}

example usage
```
n/a
```

function lz-string.compress (uncompressed)

description and source-code

compress = function (uncompressed) {
  return LZString._compress(uncompressed, 16, function(a){return f(a);});
}

example usage

...
var fs = require('fs');

if (process.argv.length < 3) {
  console.error('Usage: lz-string <input_file>');
  process.exit(1);
}

console.log(lzString.compress(fs.readFileSync(process.argv[2], {
  encoding: 'utf8',
})));
...

function lz-string.compressToBase64 (input)

description and source-code

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+"=";
  }
}

example usage
```
n/a
```

function lz-string.compressToEncodedURIComponent (input)

description and source-code

compressToEncodedURIComponent = function (input) {
  if (input == null) return "";
  return LZString._compress(input, 6, function(a){return keyStrUriSafe.charAt(a);});
}

example usage
```
n/a
```

function lz-string.compressToUTF16 (input)

description and source-code

compressToUTF16 = function (input) {
  if (input == null) return "";
  return LZString._compress(input, 15, function(a){return f(a+32);}) + " ";
}

example usage
```
n/a
```

function lz-string.compressToUint8Array (uncompressed)

description and source-code

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;
}

example usage
```
n/a
```

function lz-string.decompress (compressed)

description and source-code

decompress = function (compressed) {
  if (compressed == null) return "";
  if (compressed == "") return null;
  return LZString._decompress(compressed.length, 32768, function(index) { return compressed.charCodeAt(index); });
}

example usage

...
        break;
    }


    i++;
  }

  return this.decompress(output.join(''));
  //return output;

},


// private property
_keyStr : "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=",
...

function lz-string.decompressFromBase64 (input)

description and source-code

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)); });
}

example usage
```
n/a
```

function lz-string.decompressFromEncodedURIComponent (input)

description and source-code

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)); });
}

example usage
```
n/a
```

function lz-string.decompressFromUTF16 (compressed)

description and source-code

decompressFromUTF16 = function (compressed) {
  if (compressed == null) return "";
  if (compressed == "") return null;
  return LZString._decompress(compressed.length, 16384, function(index) { return compressed.charCodeAt(index) - 32; });
}

example usage
```
n/a
```

function lz-string.decompressFromUint8Array (compressed)

description and source-code

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(''));

  }

}

example usage
```
n/a
```

[ this document was created with utility2 ]

api documentation for lz-string (v1.4.4)

LZ-based compression algorithm

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