source: josm/trunk/src/org/tukaani/xz/rangecoder/RangeDecoderFromBuffer.java@ 14039

Last change on this file since 14039 was 13350, checked in by stoecker, 7 years ago

see #15816 - add XZ support

File size: 2.2 KB
Line 
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
11package org.tukaani.xz.rangecoder;
12
13import java.io.DataInputStream;
14import java.io.IOException;
15import org.tukaani.xz.ArrayCache;
16import org.tukaani.xz.CorruptedInputException;
17
18public final class RangeDecoderFromBuffer extends RangeDecoder {
19 private static final int INIT_SIZE = 5;
20
21 private final byte[] buf;
22 private int pos;
23
24 public RangeDecoderFromBuffer(int inputSizeMax, ArrayCache arrayCache) {
25 // We will use the *end* of the array so if the cache gives us
26 // a bigger-than-requested array, we still want to use buf.length.
27 buf = arrayCache.getByteArray(inputSizeMax - INIT_SIZE, false);
28 pos = buf.length;
29 }
30
31 public void putArraysToCache(ArrayCache arrayCache) {
32 arrayCache.putArray(buf);
33 }
34
35 public void prepareInputBuffer(DataInputStream in, int len)
36 throws IOException {
37 if (len < INIT_SIZE)
38 throw new CorruptedInputException();
39
40 if (in.readUnsignedByte() != 0x00)
41 throw new CorruptedInputException();
42
43 code = in.readInt();
44 range = 0xFFFFFFFF;
45
46 // Read the data to the end of the buffer. If the data is corrupt
47 // and the decoder, reading from buf, tries to read past the end of
48 // the data, ArrayIndexOutOfBoundsException will be thrown and
49 // the problem is detected immediately.
50 len -= INIT_SIZE;
51 pos = buf.length - len;
52 in.readFully(buf, pos, len);
53 }
54
55 public boolean isFinished() {
56 return pos == buf.length && code == 0;
57 }
58
59 public void normalize() throws IOException {
60 if ((range & TOP_MASK) == 0) {
61 try {
62 // If the input is corrupt, this might throw
63 // ArrayIndexOutOfBoundsException.
64 code = (code << SHIFT_BITS) | (buf[pos++] & 0xFF);
65 range <<= SHIFT_BITS;
66 } catch (ArrayIndexOutOfBoundsException e) {
67 throw new CorruptedInputException();
68 }
69 }
70 }
71}
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