Showing the changes to java/pkg/com/sun/imageio/plugins/common/LZWCompressor.java (1 of 18352 files). Show all
Unified · Split
| @@ -0,0 +1,146 @@ | ||
| 1 | +/* | |
| 2 | + * Copyright (c) 2005, Oracle and/or its affiliates. All rights reserved. | |
| 3 | + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | |
| 4 | + * | |
| 5 | + * This code is free software; you can redistribute it and/or modify it | |
| 6 | + * under the terms of the GNU General Public License version 2 only, as | |
| 7 | + * published by the Free Software Foundation. Oracle designates this | |
| 8 | + * particular file as subject to the "Classpath" exception as provided | |
| 9 | + * by Oracle in the LICENSE file that accompanied this code. | |
| 10 | + * | |
| 11 | + * This code is distributed in the hope that it will be useful, but WITHOUT | |
| 12 | + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
| 13 | + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
| 14 | + * version 2 for more details (a copy is included in the LICENSE file that | |
| 15 | + * accompanied this code). | |
| 16 | + * | |
| 17 | + * You should have received a copy of the GNU General Public License version | |
| 18 | + * 2 along with this work; if not, write to the Free Software Foundation, | |
| 19 | + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | |
| 20 | + * | |
| 21 | + * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | |
| 22 | + * or visit www.oracle.com if you need additional information or have any | |
| 23 | + * questions. | |
| 24 | + */ | |
| 25 | + | |
| 26 | +package com.sun.imageio.plugins.common; | |
| 27 | + | |
| 28 | +import java.io.IOException; | |
| 29 | +import java.io.PrintStream; | |
| 30 | +import javax.imageio.stream.ImageOutputStream; | |
| 31 | + | |
| 32 | +/* | |
| 33 | + * Modified from original LZWCompressor to change interface to passing a | |
| 34 | + * buffer of data to be compressed. | |
| 35 | + */ | |
| 36 | +public class LZWCompressor { | |
| 37 | + /** base underlying code size of data being compressed 8 for TIFF, 1 to 8 for GIF **/ | |
| 38 | + int codeSize; | |
| 39 | + | |
| 40 | + /** reserved clear code based on code size **/ | |
| 41 | + int clearCode; | |
| 42 | + | |
| 43 | + /** reserved end of data code based on code size **/ | |
| 44 | + int endOfInfo; | |
| 45 | + | |
| 46 | + /** current number bits output for each code **/ | |
| 47 | + int numBits; | |
| 48 | + | |
| 49 | + /** limit at which current number of bits code size has to be increased **/ | |
| 50 | + int limit; | |
| 51 | + | |
| 52 | + /** the prefix code which represents the predecessor string to current input point **/ | |
| 53 | + short prefix; | |
| 54 | + | |
| 55 | + /** output destination for bit codes **/ | |
| 56 | + BitFile bf; | |
| 57 | + | |
| 58 | + /** general purpose LZW string table **/ | |
| 59 | + LZWStringTable lzss; | |
| 60 | + | |
| 61 | + /** modify the limits of the code values in LZW encoding due to TIFF bug / feature **/ | |
| 62 | + boolean tiffFudge; | |
| 63 | + | |
| 64 | + /** | |
| 65 | + * @param out destination for compressed data | |
| 66 | + * @param codeSize the initial code size for the LZW compressor | |
| 67 | + * @param TIFF flag indicating that TIFF lzw fudge needs to be applied | |
| 68 | + * @exception IOException if underlying output stream error | |
| 69 | + **/ | |
| 70 | + public LZWCompressor(ImageOutputStream out, int codeSize, boolean TIFF) | |
| 71 | + throws IOException | |
| 72 | + { | |
| 73 | + bf = new BitFile(out, !TIFF); // set flag for GIF as NOT tiff | |
| 74 | + this.codeSize = codeSize; | |
| 75 | + tiffFudge = TIFF; | |
| 76 | + clearCode = 1 << codeSize; | |
| 77 | + endOfInfo = clearCode + 1; | |
| 78 | + numBits = codeSize + 1; | |
| 79 | + | |
| 80 | + limit = (1 << numBits) - 1; | |
| 81 | + if (tiffFudge) { | |
| 82 | + --limit; | |
| 83 | + } | |
| 84 | + | |
| 85 | + prefix = (short)0xFFFF; | |
| 86 | + lzss = new LZWStringTable(); | |
| 87 | + lzss.clearTable(codeSize); | |
| 88 | + bf.writeBits(clearCode, numBits); | |
| 89 | + } | |
| 90 | + | |
| 91 | + /** | |
| 92 | + * @param buf data to be compressed to output stream | |
| 93 | + * @exception IOException if underlying output stream error | |
| 94 | + **/ | |
| 95 | + public void compress(byte[] buf, int offset, int length) | |
| 96 | + throws IOException | |
| 97 | + { | |
| 98 | + int idx; | |
| 99 | + byte c; | |
| 100 | + short index; | |
| 101 | + | |
| 102 | + int maxOffset = offset + length; | |
| 103 | + for (idx = offset; idx < maxOffset; ++idx) { | |
| 104 | + c = buf[idx]; | |
| 105 | + if ((index = lzss.findCharString(prefix, c)) != -1) { | |
| 106 | + prefix = index; | |
| 107 | + } else { | |
| 108 | + bf.writeBits(prefix, numBits); | |
| 109 | + if (lzss.addCharString(prefix, c) > limit) { | |
| 110 | + if (numBits == 12) { | |
| 111 | + bf.writeBits(clearCode, numBits); | |
| 112 | + lzss.clearTable(codeSize); | |
| 113 | + numBits = codeSize + 1; | |
| 114 | + } else { | |
| 115 | + ++numBits; | |
| 116 | + } | |
| 117 | + | |
| 118 | + limit = (1 << numBits) - 1; | |
| 119 | + if (tiffFudge) { | |
| 120 | + --limit; | |
| 121 | + } | |
| 122 | + } | |
| 123 | + prefix = (short)((short)c & 0xFF); | |
| 124 | + } | |
| 125 | + } | |
| 126 | + } | |
| 127 | + | |
| 128 | + /* | |
| 129 | + * Indicate to compressor that no more data to go so write out | |
| 130 | + * any remaining buffered data. | |
| 131 | + * | |
| 132 | + * @exception IOException if underlying output stream error | |
| 133 | + */ | |
| 134 | + public void flush() throws IOException { | |
| 135 | + if (prefix != -1) { | |
| 136 | + bf.writeBits(prefix, numBits); | |
| 137 | + } | |
| 138 | + | |
| 139 | + bf.writeBits(endOfInfo, numBits); | |
| 140 | + bf.flush(); | |
| 141 | + } | |
| 142 | + | |
| 143 | + public void dump(PrintStream out) { | |
| 144 | + lzss.dump(out); | |
| 145 | + } | |
| 146 | +} | |