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| 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 javax.imageio.stream.ImageOutputStream; | |
| 30 | + | |
| 31 | +/* | |
| 32 | + * Came from GIFEncoder initially. | |
| 33 | + * Modified - to allow for output compressed data without the block counts | |
| 34 | + * which breakup the compressed data stream for GIF. | |
| 35 | + */ | |
| 36 | +public class BitFile { | |
| 37 | + ImageOutputStream output; | |
| 38 | + byte buffer[]; | |
| 39 | + int index; | |
| 40 | + int bitsLeft; // bits left at current index that are avail. | |
| 41 | + | |
| 42 | + /** note this also indicates gif format BITFile. **/ | |
| 43 | + boolean blocks = false; | |
| 44 | + | |
| 45 | + /* | |
| 46 | + * @param output destination for output data | |
| 47 | + * @param blocks GIF LZW requires block counts for output data | |
| 48 | + */ | |
| 49 | + public BitFile(ImageOutputStream output, boolean blocks) { | |
| 50 | + this.output = output; | |
| 51 | + this.blocks = blocks; | |
| 52 | + buffer = new byte[256]; | |
| 53 | + index = 0; | |
| 54 | + bitsLeft = 8; | |
| 55 | + } | |
| 56 | + | |
| 57 | + public void flush() throws IOException { | |
| 58 | + int numBytes = index + (bitsLeft == 8 ? 0 : 1); | |
| 59 | + if (numBytes > 0) { | |
| 60 | + if (blocks) { | |
| 61 | + output.write(numBytes); | |
| 62 | + } | |
| 63 | + output.write(buffer, 0, numBytes); | |
| 64 | + buffer[0] = 0; | |
| 65 | + index = 0; | |
| 66 | + bitsLeft = 8; | |
| 67 | + } | |
| 68 | + } | |
| 69 | + | |
| 70 | + public void writeBits(int bits, int numbits) throws IOException { | |
| 71 | + int bitsWritten = 0; | |
| 72 | + int numBytes = 255; // gif block count | |
| 73 | + do { | |
| 74 | + // This handles the GIF block count stuff | |
| 75 | + if ((index == 254 && bitsLeft == 0) || index > 254) { | |
| 76 | + if (blocks) { | |
| 77 | + output.write(numBytes); | |
| 78 | + } | |
| 79 | + | |
| 80 | + output.write(buffer, 0, numBytes); | |
| 81 | + | |
| 82 | + buffer[0] = 0; | |
| 83 | + index = 0; | |
| 84 | + bitsLeft = 8; | |
| 85 | + } | |
| 86 | + | |
| 87 | + if (numbits <= bitsLeft) { // bits contents fit in current index byte | |
| 88 | + if (blocks) { // GIF | |
| 89 | + buffer[index] |= (bits & ((1 << numbits) - 1)) << (8 - bitsLeft); | |
| 90 | + bitsWritten += numbits; | |
| 91 | + bitsLeft -= numbits; | |
| 92 | + numbits = 0; | |
| 93 | + } else { | |
| 94 | + buffer[index] |= (bits & ((1 << numbits) - 1)) << (bitsLeft - numbits); | |
| 95 | + bitsWritten += numbits; | |
| 96 | + bitsLeft -= numbits; | |
| 97 | + numbits = 0; | |
| 98 | + } | |
| 99 | + } else { // bits overflow from current byte to next. | |
| 100 | + if (blocks) { // GIF | |
| 101 | + // if bits > space left in current byte then the lowest order bits | |
| 102 | + // of code are taken and put in current byte and rest put in next. | |
| 103 | + buffer[index] |= (bits & ((1 << bitsLeft) - 1)) << (8 - bitsLeft); | |
| 104 | + bitsWritten += bitsLeft; | |
| 105 | + bits >>= bitsLeft; | |
| 106 | + numbits -= bitsLeft; | |
| 107 | + buffer[++index] = 0; | |
| 108 | + bitsLeft = 8; | |
| 109 | + } else { | |
| 110 | + // if bits > space left in current byte then the highest order bits | |
| 111 | + // of code are taken and put in current byte and rest put in next. | |
| 112 | + // at highest order bit location !! | |
| 113 | + int topbits = (bits >>> (numbits - bitsLeft)) & ((1 << bitsLeft) - 1); | |
| 114 | + buffer[index] |= topbits; | |
| 115 | + numbits -= bitsLeft; // ok this many bits gone off the top | |
| 116 | + bitsWritten += bitsLeft; | |
| 117 | + buffer[++index] = 0; // next index | |
| 118 | + bitsLeft = 8; | |
| 119 | + } | |
| 120 | + } | |
| 121 | + } while (numbits != 0); | |
| 122 | + } | |
| 123 | +} | |