1 /* 2 * Copyright (c) 2005, 2018, 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 }