1 | /*
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2 | * RangeDecoderFromBuffer
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3 | *
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4 | * Authors: Lasse Collin <lasse.collin@tukaani.org>
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5 | * Igor Pavlov <http://7-zip.org/>
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6 | *
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7 | * This file has been put into the public domain.
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8 | * You can do whatever you want with this file.
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9 | */
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10 |
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11 | package org.tukaani.xz.rangecoder;
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12 |
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13 | import java.io.DataInputStream;
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14 | import java.io.IOException;
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15 | import org.tukaani.xz.ArrayCache;
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16 | import org.tukaani.xz.CorruptedInputException;
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17 |
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18 | public final class RangeDecoderFromBuffer extends RangeDecoder {
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19 | private static final int INIT_SIZE = 5;
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20 |
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21 | private final byte[] buf;
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22 | private int pos;
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23 |
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24 | public RangeDecoderFromBuffer(int inputSizeMax, ArrayCache arrayCache) {
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25 | // We will use the *end* of the array so if the cache gives us
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26 | // a bigger-than-requested array, we still want to use buf.length.
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27 | buf = arrayCache.getByteArray(inputSizeMax - INIT_SIZE, false);
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28 | pos = buf.length;
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29 | }
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30 |
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31 | public void putArraysToCache(ArrayCache arrayCache) {
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32 | arrayCache.putArray(buf);
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33 | }
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34 |
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35 | public void prepareInputBuffer(DataInputStream in, int len)
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36 | throws IOException {
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37 | if (len < INIT_SIZE)
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38 | throw new CorruptedInputException();
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39 |
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40 | if (in.readUnsignedByte() != 0x00)
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41 | throw new CorruptedInputException();
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42 |
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43 | code = in.readInt();
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44 | range = 0xFFFFFFFF;
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45 |
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46 | // Read the data to the end of the buffer. If the data is corrupt
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47 | // and the decoder, reading from buf, tries to read past the end of
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48 | // the data, ArrayIndexOutOfBoundsException will be thrown and
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49 | // the problem is detected immediately.
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50 | len -= INIT_SIZE;
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51 | pos = buf.length - len;
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52 | in.readFully(buf, pos, len);
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53 | }
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54 |
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55 | public boolean isFinished() {
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56 | return pos == buf.length && code == 0;
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57 | }
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58 |
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59 | public void normalize() throws IOException {
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60 | if ((range & TOP_MASK) == 0) {
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61 | try {
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62 | // If the input is corrupt, this might throw
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63 | // ArrayIndexOutOfBoundsException.
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64 | code = (code << SHIFT_BITS) | (buf[pos++] & 0xFF);
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65 | range <<= SHIFT_BITS;
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66 | } catch (ArrayIndexOutOfBoundsException e) {
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67 | throw new CorruptedInputException();
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68 | }
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69 | }
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70 | }
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71 | }
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