lz4-block-codec-js.js (9009B) - View raw
/******************************************************************************* lz4-block-codec-js.js A javascript wrapper around a pure javascript implementation of LZ4 block format codec. Copyright (C) 2018 Raymond Hill BSD-2-Clause License (http://www.opensource.org/licenses/bsd-license.php) Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. Home: https://github.com/gorhill/lz4-wasm I used the same license as the one picked by creator of LZ4 out of respect for his creation, see https://lz4.github.io/lz4/ */ 'use strict'; /******************************************************************************/ (function(context) { // >>>> Start of private namespace /******************************************************************************/ const growOutputBuffer = function(instance, size) { if ( instance.outputBuffer === undefined || instance.outputBuffer.byteLength < size ) { instance.outputBuffer = new ArrayBuffer(size + 0xFFFF & 0x7FFF0000); } return instance.outputBuffer; }; const encodeBound = function(size) { return size > 0x7E000000 ? 0 : size + (size / 255 | 0) + 16; }; const encodeBlock = function(instance, iBuf, oOffset) { let iLen = iBuf.byteLength; if ( iLen >= 0x7E000000 ) { throw new RangeError(); } // "The last match must start at least 12 bytes before end of block" let lastMatchPos = iLen - 12; // "The last 5 bytes are always literals" let lastLiteralPos = iLen - 5; if ( instance.hashTable === undefined ) { instance.hashTable = new Int32Array(65536); } instance.hashTable.fill(-65536); if ( iBuf instanceof ArrayBuffer ) { iBuf = new Uint8Array(iBuf); } let oLen = oOffset + encodeBound(iLen); let oBuf = new Uint8Array(growOutputBuffer(instance, oLen), 0, oLen); let iPos = 0; let oPos = oOffset; let anchorPos = 0; // sequence-finding loop for (;;) { let refPos; let mOffset; let sequence = iBuf[iPos] << 8 | iBuf[iPos+1] << 16 | iBuf[iPos+2] << 24; // match-finding loop while ( iPos <= lastMatchPos ) { sequence = sequence >>> 8 | iBuf[iPos+3] << 24; let hash = (sequence * 0x9E37 & 0xFFFF) + (sequence * 0x79B1 >>> 16) & 0xFFFF; refPos = instance.hashTable[hash]; instance.hashTable[hash] = iPos; mOffset = iPos - refPos; if ( mOffset < 65536 && iBuf[refPos+0] === ((sequence ) & 0xFF) && iBuf[refPos+1] === ((sequence >>> 8) & 0xFF) && iBuf[refPos+2] === ((sequence >>> 16) & 0xFF) && iBuf[refPos+3] === ((sequence >>> 24) & 0xFF) ) { break; } iPos += 1; } // no match found if ( iPos > lastMatchPos ) { break; } // match found let lLen = iPos - anchorPos; let mLen = iPos; iPos += 4; refPos += 4; while ( iPos < lastLiteralPos && iBuf[iPos] === iBuf[refPos] ) { iPos += 1; refPos += 1; } mLen = iPos - mLen; let token = mLen < 19 ? mLen - 4 : 15; // write token, length of literals if needed if ( lLen >= 15 ) { oBuf[oPos++] = 0xF0 | token; let l = lLen - 15; while ( l >= 255 ) { oBuf[oPos++] = 255; l -= 255; } oBuf[oPos++] = l; } else { oBuf[oPos++] = (lLen << 4) | token; } // write literals while ( lLen-- ) { oBuf[oPos++] = iBuf[anchorPos++]; } if ( mLen === 0 ) { break; } // write offset of match oBuf[oPos+0] = mOffset; oBuf[oPos+1] = mOffset >>> 8; oPos += 2; // write length of match if needed if ( mLen >= 19 ) { let l = mLen - 19; while ( l >= 255 ) { oBuf[oPos++] = 255; l -= 255; } oBuf[oPos++] = l; } anchorPos = iPos; } // last sequence is literals only let lLen = iLen - anchorPos; if ( lLen >= 15 ) { oBuf[oPos++] = 0xF0; let l = lLen - 15; while ( l >= 255 ) { oBuf[oPos++] = 255; l -= 255; } oBuf[oPos++] = l; } else { oBuf[oPos++] = lLen << 4; } while ( lLen-- ) { oBuf[oPos++] = iBuf[anchorPos++]; } return new Uint8Array(oBuf.buffer, 0, oPos); }; const decodeBlock = function(instance, iBuf, iOffset, oLen) { let iLen = iBuf.byteLength; let oBuf = new Uint8Array(growOutputBuffer(instance, oLen), 0, oLen); let iPos = iOffset, oPos = 0; while ( iPos < iLen ) { let token = iBuf[iPos++]; // literals let clen = token >>> 4; // length of literals if ( clen !== 0 ) { if ( clen === 15 ) { let l; for (;;) { l = iBuf[iPos++]; if ( l !== 255 ) { break; } clen += 255; } clen += l; } // copy literals let end = iPos + clen; while ( iPos < end ) { oBuf[oPos++] = iBuf[iPos++]; } if ( iPos === iLen ) { break; } } // match let mOffset = iBuf[iPos+0] | (iBuf[iPos+1] << 8); if ( mOffset === 0 || mOffset > oPos ) { return; } iPos += 2; // length of match clen = (token & 0x0F) + 4; if ( clen === 19 ) { let l; for (;;) { l = iBuf[iPos++]; if ( l !== 255 ) { break; } clen += 255; } clen += l; } // copy match let mPos = oPos - mOffset; let end = oPos + clen; while ( oPos < end ) { oBuf[oPos++] = oBuf[mPos++]; } } return oBuf; }; /******************************************************************************/ context.LZ4BlockJS = function() { this.hashTable = undefined; this.outputBuffer = undefined; }; context.LZ4BlockJS.prototype = { flavor: 'js', init: function() { return Promise.resolve(true); }, reset: function() { this.hashTable = undefined; this.outputBuffer = undefined; }, bytesInUse: function() { let bytesInUse = 0; if ( this.hashTable !== undefined ) { bytesInUse += this.hashTable.byteLength; } if ( this.outputBuffer !== undefined ) { bytesInUse += this.outputBuffer.byteLength; } return bytesInUse; }, encodeBlock: function(input, outputOffset) { if ( input instanceof ArrayBuffer ) { input = new Uint8Array(input); } else if ( input instanceof Uint8Array === false ) { throw new TypeError(); } return encodeBlock(this, input, outputOffset); }, decodeBlock: function(input, inputOffset, outputSize) { if ( input instanceof ArrayBuffer ) { input = new Uint8Array(input); } else if ( input instanceof Uint8Array === false ) { throw new TypeError(); } return decodeBlock(this, input, inputOffset, outputSize); } }; /******************************************************************************/ })(this || self); // <<<< End of private namespace /******************************************************************************/