261 lines
6.8 KiB
JavaScript
261 lines
6.8 KiB
JavaScript
// based on Luigi Auriemma's memory2memory LZARI modification. LZARI was created by Haruhiko Okumura.
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// yellows111 modifications: forced all magic constants to be their actual values,
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// static calculations have been squashed, some functions have been transcluded into others
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/** @copyright MIT license:
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* Based on a work by Haruhiko Okumura dated 1989-07-04.
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* Copyright 2023 yellows111
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
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* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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* DEALINGS IN THE SOFTWARE.
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**/
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//TODO: privatize variables and document the library
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var inputData = null;
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var inputLocation = 0;
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var low = 0;
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var high = 131072;
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var value = 0;
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var text_buffer = new Array(4155);
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var characterToSymbol = new Array(314);
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var symbolToCharacter = new Array(315);
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var symbolFrequency = new Array(315);
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var symbolCumulative = new Array(315);
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var positionCumulative = new Array(4097);
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var bit_Buffer = 0;
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var bit_Mask = 0;
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function GetBit() {
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//partial xgetc modification
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if(inputLocation >= inputData.length) {return -1};
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if((bit_Mask >>= 1) === 0) {
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bit_Buffer = inputData[inputLocation++];
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bit_Mask = 128;
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}
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return +((bit_Buffer & bit_Mask) !== 0);
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}
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function BinarySearchSym(x) {
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let i = 1;
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let j = 314;
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while (i < j) {
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let k = ((i + j) / 2)|0;
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if (symbolCumulative[k] > x) {
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i = k + 1;
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} else {
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j = k;
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}
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}
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return i;
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}
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function BinarySearchPos(x) {
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let i = 1;
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let j = 4096;
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while (i < j) {
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let k = ((i + j) / 2)|0;
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if (positionCumulative[k] > x) {
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i = k + 1;
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} else {
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j = k;
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}
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}
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return i - 1;
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}
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function DecodeChar() {
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var range = high - low;
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var sym = BinarySearchSym((((value - low + 1) * symbolCumulative[0] - 1) / range)|0);
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high = low + ((range * symbolCumulative[sym - 1]) / symbolCumulative[0])|0;
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low += ((range * symbolCumulative[sym ]) / symbolCumulative[0])|0;
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for ( ; ; ) {
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if (low >= 65536) {
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value -= 65536;
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low -= 65536;
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high -= 65536;
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} else if (low >= 32768 && high <= 98304) {
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value -= 32768;
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low -= 32768;
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high -= 32768;
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} else if (high > 65536) { break };
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low += low;
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high += high;
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value = 2 * value + GetBit();
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}
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//transcluded UpdateModel
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let character = symbolToCharacter[sym];
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// do not remove above, will be overwritten otherwise!
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let i;
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if(symbolCumulative[0] >= 32767) {
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let chr = 0;
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for (i = 314; i > 0; i--) {
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symbolCumulative[i] = chr;
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chr += (symbolFrequency[i] = (symbolFrequency[i] + 1) >> 1);
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}
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symbolCumulative[0] = chr;
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}
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for(i = sym; symbolFrequency[i] === symbolFrequency[i - 1]; i--) {};
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if (i < sym) {
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let ch_i = symbolToCharacter[i];
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let ch_sym = symbolToCharacter[sym];
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symbolToCharacter[i] = ch_sym;
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symbolToCharacter[sym] = ch_i;
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characterToSymbol[ch_i] = sym;
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characterToSymbol[ch_sym] = i;
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//i would change these vars...
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//but it looks so darn cool...
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}
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symbolFrequency[i]++;
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while (--i >= 0) {
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symbolCumulative[i]++;
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}
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//end transclusion
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return character;
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}
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function DecodePosition() {
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var range = high - low;
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var position = BinarySearchPos((((value - low + 1) * positionCumulative[0] - 1) / range)|0);
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high = low + ((range * positionCumulative[position ]) / positionCumulative[0])|0;
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low += ((range * positionCumulative[position + 1]) / positionCumulative[0])|0;
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for ( ; ; ) {
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if (low >= 65536) {
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value -= 65536;
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low -= 65536;
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high -= 65536;
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} else if (low >= 32768 && high <= 98304) {
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value -= 32768;
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low -= 32768;
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high -= 32768;
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} else if (high > 65536) { break };
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low += low;
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high += high;
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value = 2 * value + GetBit();
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}
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return position;
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}
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/**
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* Decompresses LZARI-formatted data.
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* @param {Uint8Array} input - source data
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* @returns {Uint8Array} output - uncompressed data
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* @access public
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*/
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function decodeLzari(input) {
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//transcluded reset function.
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inputData = null;
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inputLocation = 0;
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low = 0;
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high = 131072;
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value = 0;
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text_buffer = new Array(4155);
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characterToSymbol = new Array(314);
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symbolToCharacter = new Array(315);
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symbolFrequency = new Array(315);
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symbolCumulative = new Array(315);
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positionCumulative = new Array(4097);
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bit_Buffer = 0;
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bit_Mask = 0;
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//end transclusion
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inputData = input;
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inputLocation = 4;
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let dataSize = new DataView(input.buffer).getInt32(0,1);
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if (dataSize == 0) return(0);
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if (dataSize < 0) return(-1);
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let outputLength = dataSize;
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let outputData = new Uint8Array(dataSize);
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let outputLocation = 0;
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//transcluded StartDecode
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for (let i = 0; i < 17; i++) {
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value = 2 * value + GetBit();
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}
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//transcluded StartModel
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symbolCumulative[314] = 0;
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for (let sym = 314; sym >= 1; sym--) {
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let ch = sym - 1;
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characterToSymbol[ch] = sym;
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symbolToCharacter[sym] = ch;
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symbolFrequency[sym] = 1;
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symbolCumulative[sym - 1] = (symbolCumulative[sym] + symbolFrequency[sym]);
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}
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symbolFrequency[0] = 0;
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positionCumulative[4096] = 0;
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for (let i = 4096; i >= 1; i--) {
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positionCumulative[i - 1] = (positionCumulative[i] + (10000 / (i + 200))|0);
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}
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//end transclusion
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//normal Decode process
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for (let i = 0; i < 4036; i++) {
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text_buffer[i] = 32;
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}
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var r = 4036;
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for (let count = 0; count < dataSize; ) {
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if(inputLocation >= inputData.length) {break};
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let c = DecodeChar();
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if (c < 256) {
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outputData[outputLocation++] = c;
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text_buffer[r++] = c;
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r &= (4095);
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count++;
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} else {
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let i = (r - DecodePosition() - 1) & 4095;
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let j = c - 253;
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for (let k = 0; k < j; k++) {
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c = text_buffer[(i + k) & 4095];
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outputData[outputLocation++] = c;
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text_buffer[r++] = c;
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r &= (4095);
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count++;
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}
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}
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}
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//console.debug("LZARI I/O", {inputData, outputData});
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return(outputData);
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}
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/**
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* Define (module.)exports with all public functions.
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* @exports icondumper2/lzari
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*/ // start c6js
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if(typeof exports !== "object") {
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exports = {
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decodeLzari
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};
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} else {
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exports.decodeLzari = decodeLzari;
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}
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if(typeof module !== "undefined") {
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module.exports = exports;
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}
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//end c6js
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//start esm
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/*export {
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decodeLzari
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};*/
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//end esm
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