1 /* 2 * RangeDecoderFromBuffer 3 * 4 * Authors: Lasse Collin <lasse.collin@tukaani.org> 5 * Igor Pavlov <http://7-zip.org/> 6 * 7 * This file has been put into the public domain. 8 * You can do whatever you want with this file. 9 */ 10 11 package org.tukaani.xz.rangecoder; 12 13 import java.io.DataInputStream; 14 import java.io.IOException; 15 import org.tukaani.xz.CorruptedInputException; 16 17 public final class RangeDecoderFromBuffer extends RangeDecoder { 18 private static final int INIT_SIZE = 5; 19 20 private final byte[] buf; 21 private int pos = 0; 22 private int end = 0; 23 RangeDecoderFromBuffer(int inputSizeMax)24 public RangeDecoderFromBuffer(int inputSizeMax) { 25 buf = new byte[inputSizeMax - INIT_SIZE]; 26 } 27 prepareInputBuffer(DataInputStream in, int len)28 public void prepareInputBuffer(DataInputStream in, int len) 29 throws IOException { 30 if (len < INIT_SIZE) 31 throw new CorruptedInputException(); 32 33 if (in.readUnsignedByte() != 0x00) 34 throw new CorruptedInputException(); 35 36 code = in.readInt(); 37 range = 0xFFFFFFFF; 38 39 pos = 0; 40 end = len - INIT_SIZE; 41 in.readFully(buf, 0, end); 42 } 43 isInBufferOK()44 public boolean isInBufferOK() { 45 return pos <= end; 46 } 47 isFinished()48 public boolean isFinished() { 49 return pos == end && code == 0; 50 } 51 normalize()52 public void normalize() throws IOException { 53 if ((range & TOP_MASK) == 0) { 54 try { 55 // If the input is corrupt, this might throw 56 // ArrayIndexOutOfBoundsException. 57 code = (code << SHIFT_BITS) | (buf[pos++] & 0xFF); 58 range <<= SHIFT_BITS; 59 } catch (ArrayIndexOutOfBoundsException e) { 60 throw new CorruptedInputException(); 61 } 62 } 63 } 64 } 65