fine-third/fine-jai/src/main/java/com/fr/third/JAI/ByteArraySeekableStream.java

package com.fr.third.JAI;
/*
 * 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.InputStream;
import java.io.IOException;

/**
 * A subclass of <code>SeekableStream</code> that takes input from an
 * array of bytes.  Seeking backwards is supported.  The
 * <code>mark()</code> and <code>resest()</code> methods are
 * supported.
 *
 * <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 ByteArraySeekableStream extends SeekableStream {

    /** Array holding the source data. */
    private byte[] src;

    /** The starting offset within the array. */
    private int offset;

    /** The length of the valid segment of the array. */
    private int length;
    
    /** The current output position. */
    private int pointer;

    /**
     * Constructs a <code>ByteArraySeekableStream</code> taking
     * input from a given segment of an input <code>byte</code> array.
     */
    public ByteArraySeekableStream(byte[] src, int offset, int length)
        throws IOException {
        this.src = src;
        this.offset = offset;
        this.length = length;
    }

    /**
     * Constructs a <code>ByteArraySeekableStream</code> taking
     * input from an entire input <code>byte</code> array.
     */
    public ByteArraySeekableStream(byte[] src) throws IOException {
        this(src, 0, src.length);
    }

    /**
     * Returns <code>true</code> since this object supports seeking
     * backwards.
     */
    public boolean canSeekBackwards() {
        return true;
    }

    /**
     * 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;
    }

    /**
     * Sets the offset, measured from the beginning of this 
     * stream, at which the next read occurs.  Seeking backwards is
     * allowed.
     *
     * @param      pos   the offset position, measured in bytes from the 
     *                   beginning of the stream, at which to set the stream 
     *                   pointer.
     */
    public void seek(long pos) {
        pointer = (int)pos;
    }

    /**
     * Reads the next byte of data from the input array. 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.
     */
    public int read() {
        if (pointer < length + offset) {
            return (int)(src[pointer++ + offset] & 0xff);
        } else {
            return -1;
        }
    }

    /**
     * Copies up to <code>len</code> bytes of data from the input array into
     * an array of bytes.  An attempt is made to copy as many as
     * <code>len</code> bytes, but a smaller number may be copied, possibly
     * zero. The number of bytes actually copied is returned as an integer.
     *
     * <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 copied and
     * <code>0</code> is returned; otherwise, there is an attempt to copy 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 copied into <code>b</code>.
     *
     * <p> The first byte copied is stored into element
     * <code>b[off]</code>, the next one into <code>b[off+1]</code>,
     * and so on. The number of bytes copied is, at most, equal to
     * <code>len</code>. Let <i>k</i> be the number of bytes actually
     * copied; 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.
     *
     * @param      b     the buffer into which the data is copied.
     * @param      off   the start offset in array <code>b</code>
     *                   at which the data is written.
     * @param      len   the maximum number of bytes to copy.
     * @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.
     */
    public int read(byte[] b, int off, int len) {
        if (b == null) {
            throw new NullPointerException();
        }
        if ((off < 0) || (len < 0) || (off + len > b.length)) {
            throw new IndexOutOfBoundsException();
        }
        if (len == 0) {
            return 0;
        }

        int oldPointer = pointer;
        pointer = Math.min(pointer + len, length + offset);

        if (pointer == oldPointer) {
            return -1;
        } else {
            System.arraycopy(src, oldPointer, b, off, pointer - oldPointer);
            return pointer - oldPointer;
        }
    }

    /**
     * Attempts to skip over <code>n</code> bytes of input discarding the 
     * skipped bytes. 
     * <p>
     * 
     * This method may skip over some smaller number of bytes, possibly zero. 
     * This may result from any of a number of conditions; reaching end of 
     * stream before <code>n</code> bytes have been skipped is only one 
     * possibility. This method never throws an <code>EOFException</code>. 
     * The actual number of bytes skipped is returned.  If <code>n</code> 
     * is negative, no bytes are skipped.
     *
     * @param      n   the number of bytes to be skipped.
     * @return     the actual number of bytes skipped.
     */
    public int skipBytes(int n) {
        int oldPointer = pointer;
        pointer = Math.min(pointer + n, length + offset);
        return pointer - oldPointer;
    }

    /** Does nothing. */
    public void close() {
    }

    /** Returns the number of valid bytes in the input array. */
    public long length() {
        return length;
    }
}