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1: /* JPEGImageInputStream.java -- 2: Copyright (C) 2006 Free Software Foundation, Inc. 3: 4: This file is part of GNU Classpath. 5: 6: GNU Classpath is free software; you can redistribute it and/or modify 7: it under the terms of the GNU General Public License as published by 8: the Free Software Foundation; either version 2, or (at your option) 9: any later version. 10: 11: GNU Classpath is distributed in the hope that it will be useful, but 12: WITHOUT ANY WARRANTY; without even the implied warranty of 13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 14: General Public License for more details. 15: 16: You should have received a copy of the GNU General Public License 17: along with GNU Classpath; see the file COPYING. If not, write to the 18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 19: 02110-1301 USA. 20: 21: Linking this library statically or dynamically with other modules is 22: making a combined work based on this library. Thus, the terms and 23: conditions of the GNU General Public License cover the whole 24: combination. 25: 26: As a special exception, the copyright holders of this library give you 27: permission to link this library with independent modules to produce an 28: executable, regardless of the license terms of these independent 29: modules, and to copy and distribute the resulting executable under 30: terms of your choice, provided that you also meet, for each linked 31: independent module, the terms and conditions of the license of that 32: module. An independent module is a module which is not derived from 33: or based on this library. If you modify this library, you may extend 34: this exception to your version of the library, but you are not 35: obligated to do so. If you do not wish to do so, delete this 36: exception statement from your version. */ 37: 38: package gnu.javax.imageio.jpeg; 39: 40: import java.io.IOException; 41: import javax.imageio.stream.ImageInputStream; 42: import javax.imageio.stream.ImageInputStreamImpl; 43: 44: public class JPEGImageInputStream 45: extends ImageInputStreamImpl 46: { 47: private ImageInputStream in; 48: 49: byte marker; 50: 51: public JPEGImageInputStream(ImageInputStream in) 52: { 53: super(); 54: 55: this.in = in; 56: } 57: 58: public int read() 59: throws IOException 60: { 61: setBitOffset(0); 62: return in.read(); 63: } 64: 65: public int read(byte[] data, int offset, int len) 66: throws IOException 67: { 68: setBitOffset(0); 69: return in.read(data, offset, len); 70: } 71: 72: /** 73: * Pull a byte from the stream, this checks to see if the byte is 0xff 74: * and if the next byte isn't 0x00 (stuffed byte) it errors out. If it's 75: * 0x00 then it simply ignores the byte. 76: * 77: * @return the next byte in the buffer 78: * 79: * @throws IOException TODO 80: * @throws BitStreamException TODO 81: */ 82: private byte pullByte() throws IOException, JPEGMarkerFoundException 83: { 84: byte mybyte = readByte(); 85: // FIXME: handle multiple 0xff in a row 86: if(mybyte==(byte)(0xff)) 87: { 88: byte secondbyte = readByte(); 89: if(secondbyte != (byte)(0x00)) 90: { 91: marker = secondbyte; 92: throw new JPEGMarkerFoundException(); 93: } 94: } 95: return mybyte; 96: } 97: 98: /** 99: * This returns the marker that was last encountered. This should only be 100: * used if removeBit() throws a MarkerTagFound exception. 101: * 102: * @return marker as byte 103: */ 104: public byte getMarker() 105: { 106: return marker; 107: } 108: 109: /** 110: * Removes a bit from the buffer. (Removes from the top of a queue). This 111: * also checks for markers and throws MarkerTagFound exception if it does. 112: * If MarkerTagFound is thrown you can use getMarker() method to get the 113: * marker that caused the throw. 114: * 115: * @param l specifies how many bits you want to remove and add to the 116: * integer 117: * @return the amount of bits specified by l as an integer 118: * 119: * @throws IOException TODO 120: * @throws JPEGMarkerFoundException 121: * @throws BitStreamException TODO 122: */ 123: public int readBit() 124: throws IOException, JPEGMarkerFoundException 125: { 126: checkClosed(); 127: 128: // Calc new bit offset here, readByte resets it. 129: int newOffset = (bitOffset + 1) & 0x7; 130: 131: byte data = pullByte(); 132: 133: if (bitOffset != 0) 134: { 135: seek(getStreamPosition() - 1); 136: data = (byte) (data >> (8 - newOffset)); 137: } 138: 139: bitOffset = newOffset; 140: return data & 0x1; 141: } 142: 143: 144: /** 145: * This method skips over the the data and finds the next position 146: * in the bit sequence with a X'FF' X'??' sequence. Multiple X'FF 147: * bytes in sequence are considered padding and interpreted as one 148: * X'FF byte. 149: * 150: * @return the next marker byte in the stream 151: * @throws IOException if the end of the stream is reached 152: * unexpectedly 153: */ 154: public byte findNextMarker() 155: throws IOException 156: { 157: boolean marked0xff = false; 158: byte byteinfo = JPEGMarker.X00; 159: 160: setBitOffset(0); 161: while (true) 162: { 163: byteinfo = readByte(); 164: if (!marked0xff) 165: { 166: if (byteinfo == JPEGMarker.XFF) 167: marked0xff = true; 168: } 169: else 170: { 171: if (byteinfo == JPEGMarker.XFF) 172: // Ignore the value 0xff when it is immediately 173: // followed by another 0xff byte. 174: continue; 175: else if (byteinfo == JPEGMarker.X00) 176: // The sequence 0xff 0x00 is used to encode the 177: // actual value 0xff. So restart our search for a 178: // marker. 179: marked0xff = false; 180: else 181: // One or more 0xff values were follwed by a 182: // non-0x00, non-0xff value so return this as the 183: // marker byte. 184: return byteinfo; 185: } 186: } 187: } 188: }