SegmentedSeekableStream.java
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- /*
- * Copyright (c) 2001 Sun Microsystems, Inc. All Rights Reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions are met:
- *
- * -Redistributions of source code must retain the above copyright notice, this
- * list of conditions and the following disclaimer.
- *
- * -Redistribution in binary form must reproduct the above copyright notice,
- * this list of conditions and the following disclaimer in the documentation
- * and/or other materials provided with the distribution.
- *
- * Neither the name of Sun Microsystems, Inc. or the names of contributors may
- * be used to endorse or promote products derived from this software without
- * specific prior written permission.
- *
- * This software is provided "AS IS," without a warranty of any kind. ALL
- * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING ANY
- * IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR
- * NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN AND ITS LICENSORS SHALL NOT BE
- * LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING
- * OR DISTRIBUTING THE SOFTWARE OR ITS DERIVATIVES. IN NO EVENT WILL SUN OR ITS
- * LICENSORS BE LIABLE FOR ANY LOST REVENUE, PROFIT OR DATA, OR FOR DIRECT,
- * INDIRECT, SPECIAL, CONSEQUENTIAL, INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER
- * CAUSED AND REGARDLESS OF THE THEORY OF LIABILITY, ARISING OUT OF THE USE OF
- * OR INABILITY TO USE SOFTWARE, EVEN IF SUN HAS BEEN ADVISED OF THE
- * POSSIBILITY OF SUCH DAMAGES.
- *
- * You acknowledge that Software is not designed,licensed or intended for use in
- * the design, construction, operation or maintenance of any nuclear facility.
- */
- import java.io.IOException;
- /**
- * An implementation of the <code>StreamSegmentMapper</code> interface
- * that requires an explicit list of the starting locations and
- * lengths of the source segments.
- */
- class StreamSegmentMapperImpl implements StreamSegmentMapper {
- private long[] segmentPositions;
- private int[] segmentLengths;
- public StreamSegmentMapperImpl(long[] segmentPositions,
- int[] segmentLengths) {
- this.segmentPositions = (long[])segmentPositions.clone();
- this.segmentLengths = (int[])segmentLengths.clone();
- }
- public StreamSegment getStreamSegment(long position, int length) {
- int numSegments = segmentLengths.length;
- for (int i = 0; i < numSegments; i++) {
- int len = segmentLengths[i];
- if (position < len) {
- return new StreamSegment(segmentPositions[i] + position,
- Math.min(len - (int)position,
- length));
- }
- position -= len;
- }
- return null;
- }
- public void getStreamSegment(long position, int length,
- StreamSegment seg) {
- int numSegments = segmentLengths.length;
- for (int i = 0; i < numSegments; i++) {
- int len = segmentLengths[i];
- if (position < len) {
- seg.setStartPos(segmentPositions[i] + position);
- seg.setSegmentLength(Math.min(len - (int)position, length));
- return;
- }
- position -= len;
- }
- seg.setStartPos(-1);
- seg.setSegmentLength(-1);
- return;
- }
- }
- /**
- * An implementation of the <code>StreamSegmentMapper</code> interface
- * for segments of equal length.
- */
- class SectorStreamSegmentMapper implements StreamSegmentMapper {
- long[] segmentPositions;
- int segmentLength;
- int totalLength;
- int lastSegmentLength;
- public SectorStreamSegmentMapper(long[] segmentPositions,
- int segmentLength,
- int totalLength) {
- this.segmentPositions = (long[])segmentPositions.clone();
- this.segmentLength = segmentLength;
- this.totalLength = totalLength;
- this.lastSegmentLength = totalLength -
- (segmentPositions.length - 1)*segmentLength;
- }
- public StreamSegment getStreamSegment(long position, int length) {
- int index = (int) (position/segmentLength);
- // Compute segment length
- int len = (index == segmentPositions.length - 1) ?
- lastSegmentLength : segmentLength;
- // Compute position within the segment
- position -= index*segmentLength;
- // Compute maximum legal length
- len -= position;
- if (len > length) {
- len = length;
- }
- return new StreamSegment(segmentPositions[index] + position, len);
- }
- public void getStreamSegment(long position, int length,
- StreamSegment seg) {
- int index = (int) (position/segmentLength);
- // Compute segment length
- int len = (index == segmentPositions.length - 1) ?
- lastSegmentLength : segmentLength;
- // Compute position within the segment
- position -= index*segmentLength;
- // Compute maximum legal length
- len -= position;
- if (len > length) {
- len = length;
- }
- seg.setStartPos(segmentPositions[index] + position);
- seg.setSegmentLength(len);
- }
- }
- /**
- * A <code>SegmentedSeekableStream</code> provides a view of a
- * subset of another <code>SeekableStream</code> consiting of a series
- * of segments with given starting positions in the source stream and
- * lengths. The resulting stream behaves like an ordinary
- * <code>SeekableStream</code>.
- *
- * <p> For example, given a <code>SeekableStream</code> containing
- * data in a format consisting of a number of sub-streams stored in
- * non-contiguous sectors indexed by a directory, it is possible to
- * construct a set of <code>SegmentedSeekableStream</code>s, one for
- * each sub-stream, that each provide a view of the sectors comprising
- * a particular stream by providing the positions and lengths of the
- * stream's sectors as indicated by the directory. The complex
- * multi-stream structure of the original stream may be ignored by
- * users of the <code>SegmentedSeekableStream</code>, who see a
- * separate <code>SeekableStream</code> for each sub-stream and do not
- * need to understand the directory structure at all.
- *
- * <p> For further efficiency, a directory structure such as in the
- * example described above need not be fully parsed in order to build
- * a <code>SegmentedSeekableStream</code>. Instead, the
- * <code>StreamSegmentMapper</code> interface allows the association
- * between a desired region of the output and an input segment to be
- * provided dynamically. This mapping might be computed by reading
- * from a directory in piecemeal fashion in order to avoid consuming
- * memory resources.
- *
- * <p> It is the responsibility of the user of this class to determine
- * whether backwards seeking should be enabled. If the source stream
- * supports only forward seeking, backwards seeking must be disabled
- * and the <code>StreamSegmentMapper</code> must be monotone; that is,
- * forward motion in the destination must always result in forward
- * motion within the source. If the source stream supports backwards
- * seeking, there are no restrictions on the
- * <code>StreamSegmentMapper</code> and backwards seeking may always
- * be enabled for the <code>SegmentedSeekableStream</code>.
- *
- * <p><b> This class is not a committed part of the JAI API. It may
- * be removed or changed in future releases of JAI.</b>
- */
- public class SegmentedSeekableStream extends SeekableStream {
- private SeekableStream stream;
- private StreamSegmentMapper mapper;
- private long pointer = 0;
- private boolean canSeekBackwards;
-
- /**
- * Constructs a <code>SegmentedSeekableStream</code>
- * given a <code>SeekableStream</code> as input,
- * an instance of <code>StreamSegmentMapper</code>,
- * and a <code>boolean</code> indicating whether the
- * output <code>SegmentedSeekableStream</code> should
- * support seeking backwards. If <code>canSeekBackwards</code>
- * is <code>true</code>, the source stream must itself
- * support seeking backwards.
- *
- * @param stream A source <code>SeekableStream</code>
- * @param mapper An instance of the <code>StreamSegmentMapper</code>
- * interface.
- * @param canSeekBackwards <code>true</code> if the ability to
- * seek backwards is desired.
- */
- public SegmentedSeekableStream(SeekableStream stream,
- StreamSegmentMapper mapper,
- boolean canSeekBackwards) {
- this.stream = stream;
- this.mapper = mapper;
- this.canSeekBackwards = canSeekBackwards;
-
- if (canSeekBackwards && !stream.canSeekBackwards()) {
- throw new IllegalArgumentException(JaiI18N.getString("SegmentedSeekableStream0"));
- }
- }
- /**
- * Constructs a <code>SegmentedSeekableStream</code> given a
- * <code>SeekableStream</code> as input, a list of the starting
- * positions and lengths of the segments of the source stream, and
- * a <code>boolean</code> indicating whether the output
- * <code>SegmentedSeekableStream</code> should support seeking
- * backwards. If <code>canSeekBakckwards</code> is
- * <code>true</code>, the source stream must itself support
- * seeking backwards.
- *
- * @param stream A source <code>SeekableStream</code>
- * @param segmentPositions An array of <code>long</code>s
- * giving the starting positions of the segments in the
- * source stream.
- * @param segmentLengths An array of <code>int</code>s
- * giving the lengths of segments in the source stream.
- * @param canSeekBackwards <code>true</code> if the ability to
- * seek backwards is desired.
- */
- public SegmentedSeekableStream(SeekableStream stream,
- long[] segmentPositions,
- int[] segmentLengths,
- boolean canSeekBackwards) {
- this(stream,
- new StreamSegmentMapperImpl(segmentPositions, segmentLengths),
- canSeekBackwards);
- }
- /**
- * Constructs a <code>SegmentedSeekableStream</code> given a
- * <code>SeekableStream</code> as input, a list of the starting
- * positions of the segments of the source stream, the common
- * length of each segment, the total length of the segments and
- * a <code>boolean</code> indicating whether the output
- * <code>SegmentedSeekableStream</code> should support seeking
- * backwards. If <code>canSeekBakckwards</code> is
- * <code>true</code>, the source stream must itself support
- * seeking backwards.
- *
- * <p> This constructor is useful for selecting substreams
- * of sector-oriented file formats in which each segment
- * of the substream (except possibly the final segment)
- * occupies a fixed-length sector.
- *
- * @param stream A source <code>SeekableStream</code>
- * @param segmentPositions An array of <code>long</code>s
- * giving the starting positions of the segments in the
- * source stream.
- * @param segmentLength The common length of each segment.
- * @param totalLength The total length of the source segments.
- * @param canSeekBackwards <code>true</code> if the ability to
- * seek backwards is desired.
- */
- public SegmentedSeekableStream(SeekableStream stream,
- long[] segmentPositions,
- int segmentLength,
- int totalLength,
- boolean canSeekBackwards) {
- this(stream,
- new SectorStreamSegmentMapper(segmentPositions,
- segmentLength,
- totalLength),
- canSeekBackwards);
- }
- /**
- * Returns the current offset in this stream.
- *
- * @return the offset from the beginning of the stream, in bytes,
- * at which the next read occurs.
- */
- public long getFilePointer() {
- return (long)pointer;
- }
- /**
- * Returns <code>true</code> if seeking backwards is supported.
- * Support is determined by the value of the
- * <code>canSeekBackwards</code> parameter at construction time.
- */
- public boolean canSeekBackwards() {
- return canSeekBackwards;
- }
- /**
- * Sets the offset, measured from the beginning of this
- * stream, at which the next read occurs.
- *
- * <p> If <code>canSeekBackwards()</code> returns <code>false</code>,
- * then setting <code>pos</code> to an offset smaller than
- * the current value of <code>getFilePointer()</code> will have
- * no effect.
- *
- * @param pos the offset position, measured in bytes from the
- * beginning of the stream, at which to set the stream
- * pointer.
- * @exception IOException if <code>pos</code> is less than
- * <code>0</code> or if an I/O error occurs.
- */
- public void seek(long pos) throws IOException {
- if (pos < 0) {
- throw new IOException();
- }
- pointer = pos;
- }
- private StreamSegment streamSegment = new StreamSegment();
-
- /**
- * Reads the next byte of data from the input stream. The value byte is
- * returned as an <code>int</code> in the range <code>0</code> to
- * <code>255</code>. If no byte is available because the end of the stream
- * has been reached, the value <code>-1</code> is returned. This method
- * blocks until input data is available, the end of the stream is detected,
- * or an exception is thrown.
- *
- * @return the next byte of data, or <code>-1</code> if the end of the
- * stream is reached.
- * @exception IOException if an I/O error occurs.
- */
- public int read() throws IOException {
- mapper.getStreamSegment(pointer, 1, streamSegment);
- stream.seek(streamSegment.getStartPos());
- int val = stream.read();
- ++pointer;
- return val;
- }
- /**
- * Reads up to <code>len</code> bytes of data from the input stream into
- * an array of bytes. An attempt is made to read as many as
- * <code>len</code> bytes, but a smaller number may be read, possibly
- * zero. The number of bytes actually read is returned as an integer.
- *
- * <p> This method blocks until input data is available, end of stream is
- * detected, or an exception is thrown.
- *
- * <p> If <code>b</code> is <code>null</code>, a
- * <code>NullPointerException</code> is thrown.
- *
- * <p> If <code>off</code> is negative, or <code>len</code> is negative, or
- * <code>off+len</code> is greater than the length of the array
- * <code>b</code>, then an <code>IndexOutOfBoundsException</code> is
- * thrown.
- *
- * <p> If <code>len</code> is zero, then no bytes are read and
- * <code>0</code> is returned; otherwise, there is an attempt to read at
- * least one byte. If no byte is available because the stream is at end of
- * stream, the value <code>-1</code> is returned; otherwise, at least one
- * byte is read and stored into <code>b</code>.
- *
- * <p> The first byte read is stored into element <code>b[off]</code>, the
- * next one into <code>b[off+1]</code>, and so on. The number of bytes read
- * is, at most, equal to <code>len</code>. Let <i>k</i> be the number of
- * bytes actually read; these bytes will be stored in elements
- * <code>b[off]</code> through <code>b[off+</code><i>k</i><code>-1]</code>,
- * leaving elements <code>b[off+</code><i>k</i><code>]</code> through
- * <code>b[off+len-1]</code> unaffected.
- *
- * <p> In every case, elements <code>b[0]</code> through
- * <code>b[off]</code> and elements <code>b[off+len]</code> through
- * <code>b[b.length-1]</code> are unaffected.
- *
- * <p> If the first byte cannot be read for any reason other than end of
- * stream, then an <code>IOException</code> is thrown. In particular, an
- * <code>IOException</code> is thrown if the input stream has been closed.
- *
- * @param b the buffer into which the data is read.
- * @param off the start offset in array <code>b</code>
- * at which the data is written.
- * @param len the maximum number of bytes to read.
- * @return the total number of bytes read into the buffer, or
- * <code>-1</code> if there is no more data because the end of
- * the stream has been reached.
- * @exception IOException if an I/O error occurs.
- */
- public int read(byte[] b, int off, int len) throws IOException {
- if (b == null) {
- throw new NullPointerException();
- }
- if ((off < 0) || (len < 0) || (off + len > b.length)) {
- throw new IndexOutOfBoundsException();
- }
- if (len == 0) {
- return 0;
- }
- mapper.getStreamSegment(pointer, len, streamSegment);
- stream.seek(streamSegment.getStartPos());
- int nbytes = stream.read(b, off, streamSegment.getSegmentLength());
- pointer += nbytes;
- return nbytes;
- }
- }