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1 /*******************************************************************************
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2 * Copyright (c) 2000, 2003 IBM Corporation and others.
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3 * All rights reserved. This program and the accompanying materials
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4 * are made available under the terms of the Eclipse Public License v1.0
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5 * which accompanies this distribution, and is available at
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6 * http://www.eclipse.org/legal/epl-v10.html
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7 *
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8 * Contributors:
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9 * IBM Corporation - initial API and implementation
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10 *******************************************************************************/
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11 module dwt.internal.image.TIFFRandomFileAccess;
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12
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13 import dwt.internal.image.LEDataInputStream;
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14 import Math = tango.math.Math;
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15 import tango.core.Exception;
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16
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17 final class TIFFRandomFileAccess {
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18
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19 LEDataInputStream inputStream;
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20 int start, current, next;
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21 byte[][] buffers;
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22
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23 static final int CHUNK_SIZE = 8192;
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24 static final int LIST_SIZE = 128;
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25
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26 public this(LEDataInputStream stream) {
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27 inputStream = stream;
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28 start = current = next = inputStream.getPosition();
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29 buffers = new byte[][](LIST_SIZE);
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30 }
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31
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32 void seek(int pos) {
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33 if (pos == current) return;
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34 if (pos < start) throw new IOException( "pos < start" );
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35 current = pos;
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36 if (current > next) {
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37 int n = current - next;
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38 /* store required bytes */
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39 int index = next / CHUNK_SIZE;
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40 int offset = next % CHUNK_SIZE;
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41 while (n > 0) {
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42 if (index >= buffers.length) {
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43 byte[][] oldBuffers = buffers;
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44 buffers = new byte[][]( Math.max(index + 1, oldBuffers.length + LIST_SIZE) );
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45 buffers[ 0 .. oldBuffers.length ] = oldBuffers[];
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46 }
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47 if (buffers[index] == null) buffers[index] = new byte[CHUNK_SIZE];
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48 int cnt = inputStream.read(buffers[index], offset, Math.min(n, CHUNK_SIZE - offset));
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49 n -= cnt;
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50 next += cnt;
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51 index++;
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52 offset = 0;
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53 }
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54 }
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55 }
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56
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57 void read(byte b[]) {
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58 int size = b.length;
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59 int nCached = Math.min(size, next - current);
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60 int nMissing = size - next + current;
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61 int destNext = 0;
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62 if (nCached > 0) {
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63 /* Get cached bytes */
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64 int index = current / CHUNK_SIZE;
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65 int offset = current % CHUNK_SIZE;
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66 while (nCached > 0) {
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67 int cnt = Math.min(nCached, CHUNK_SIZE - offset);
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68 b[ destNext .. destNext+cnt ] = buffers[index][ offset .. offset+cnt ];
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69 nCached -= cnt;
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70 destNext += cnt;
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71 index++;
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72 offset = 0;
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73 }
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74 }
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75 if (nMissing > 0) {
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76 /* Read required bytes */
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77 int index = next / CHUNK_SIZE;
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78 int offset = next % CHUNK_SIZE;
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79 while (nMissing > 0) {
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80 if (index >= buffers.length) {
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81 byte[][] oldBuffers = buffers;
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82 buffers = new byte[][](Math.max(index, oldBuffers.length + LIST_SIZE));
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83 buffers[ 0 .. oldBuffers.length ] = oldBuffers[];
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84 }
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85 if (buffers[index] == null) buffers[index] = new byte[CHUNK_SIZE];
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86 int cnt = inputStream.read(buffers[index], offset, Math.min(nMissing, CHUNK_SIZE - offset));
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87 b[ destNext .. destNext+cnt ] = buffers[index][ offset .. offset+cnt ];
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88 nMissing -= cnt;
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89 next += cnt;
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90 destNext += cnt;
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91 index++;
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92 offset = 0;
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93 }
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94 }
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95 current += size;
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96 }
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97
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98 }
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