| /* |
| * Copyright (c) 2005, Oracle and/or its affiliates. All rights reserved. |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| package com.sun.imageio.plugins.common; |
| |
| import java.io.IOException; |
| import java.io.PrintStream; |
| import javax.imageio.stream.ImageOutputStream; |
| |
| /* |
| * Modified from original LZWCompressor to change interface to passing a |
| * buffer of data to be compressed. |
| */ |
| public class LZWCompressor { |
| /** base underlying code size of data being compressed 8 for TIFF, 1 to 8 for GIF **/ |
| int codeSize; |
| |
| /** reserved clear code based on code size **/ |
| int clearCode; |
| |
| /** reserved end of data code based on code size **/ |
| int endOfInfo; |
| |
| /** current number bits output for each code **/ |
| int numBits; |
| |
| /** limit at which current number of bits code size has to be increased **/ |
| int limit; |
| |
| /** the prefix code which represents the predecessor string to current input point **/ |
| short prefix; |
| |
| /** output destination for bit codes **/ |
| BitFile bf; |
| |
| /** general purpose LZW string table **/ |
| LZWStringTable lzss; |
| |
| /** modify the limits of the code values in LZW encoding due to TIFF bug / feature **/ |
| boolean tiffFudge; |
| |
| /** |
| * @param out destination for compressed data |
| * @param codeSize the initial code size for the LZW compressor |
| * @param TIFF flag indicating that TIFF lzw fudge needs to be applied |
| * @exception IOException if underlying output stream error |
| **/ |
| public LZWCompressor(ImageOutputStream out, int codeSize, boolean TIFF) |
| throws IOException |
| { |
| bf = new BitFile(out, !TIFF); // set flag for GIF as NOT tiff |
| this.codeSize = codeSize; |
| tiffFudge = TIFF; |
| clearCode = 1 << codeSize; |
| endOfInfo = clearCode + 1; |
| numBits = codeSize + 1; |
| |
| limit = (1 << numBits) - 1; |
| if (tiffFudge) { |
| --limit; |
| } |
| |
| prefix = (short)0xFFFF; |
| lzss = new LZWStringTable(); |
| lzss.clearTable(codeSize); |
| bf.writeBits(clearCode, numBits); |
| } |
| |
| /** |
| * @param buf data to be compressed to output stream |
| * @exception IOException if underlying output stream error |
| **/ |
| public void compress(byte[] buf, int offset, int length) |
| throws IOException |
| { |
| int idx; |
| byte c; |
| short index; |
| |
| int maxOffset = offset + length; |
| for (idx = offset; idx < maxOffset; ++idx) { |
| c = buf[idx]; |
| if ((index = lzss.findCharString(prefix, c)) != -1) { |
| prefix = index; |
| } else { |
| bf.writeBits(prefix, numBits); |
| if (lzss.addCharString(prefix, c) > limit) { |
| if (numBits == 12) { |
| bf.writeBits(clearCode, numBits); |
| lzss.clearTable(codeSize); |
| numBits = codeSize + 1; |
| } else { |
| ++numBits; |
| } |
| |
| limit = (1 << numBits) - 1; |
| if (tiffFudge) { |
| --limit; |
| } |
| } |
| prefix = (short)((short)c & 0xFF); |
| } |
| } |
| } |
| |
| /* |
| * Indicate to compressor that no more data to go so write out |
| * any remaining buffered data. |
| * |
| * @exception IOException if underlying output stream error |
| */ |
| public void flush() throws IOException { |
| if (prefix != -1) { |
| bf.writeBits(prefix, numBits); |
| } |
| |
| bf.writeBits(endOfInfo, numBits); |
| bf.flush(); |
| } |
| |
| public void dump(PrintStream out) { |
| lzss.dump(out); |
| } |
| } |