byteoutputbuffer.java

jpeg2000算法实现

/*
 * CVS identifier:
 *
 * $Id: ByteOutputBuffer.java,v 1.9 2000/09/21 16:13:00 dsanta Exp $
 *
 * Class:                   ByteOutputBuffer
 *
 * Description:             Provides buffering for byte based output, similar
 *                          to the standard class ByteArrayOutputStream
 *
 *                          the old jj2000.j2k.io.ByteArrayOutput class by
 *                          Diego SANTA CRUZ, Apr-26-1999
 *
 *
 * COPYRIGHT:
 * 
 * This software module was originally developed by Rapha雔 Grosbois and
 * Diego Santa Cruz (Swiss Federal Institute of Technology-EPFL); Joel
 * Askel鰂 (Ericsson Radio Systems AB); and Bertrand Berthelot, David
 * Bouchard, F閘ix Henry, Gerard Mozelle and Patrice Onno (Canon Research
 * Centre France S.A) in the course of development of the JPEG2000
 * standard as specified by ISO/IEC 15444 (JPEG 2000 Standard). This
 * software module is an implementation of a part of the JPEG 2000
 * Standard. Swiss Federal Institute of Technology-EPFL, Ericsson Radio
 * Systems AB and Canon Research Centre France S.A (collectively JJ2000
 * Partners) agree not to assert against ISO/IEC and users of the JPEG
 * 2000 Standard (Users) any of their rights under the copyright, not
 * including other intellectual property rights, for this software module
 * with respect to the usage by ISO/IEC and Users of this software module
 * or modifications thereof for use in hardware or software products
 * claiming conformance to the JPEG 2000 Standard. Those intending to use
 * this software module in hardware or software products are advised that
 * their use may infringe existing patents. The original developers of
 * this software module, JJ2000 Partners and ISO/IEC assume no liability
 * for use of this software module or modifications thereof. No license
 * or right to this software module is granted for non JPEG 2000 Standard
 * conforming products. JJ2000 Partners have full right to use this
 * software module for his/her own purpose, assign or donate this
 * software module to any third party and to inhibit third parties from
 * using this software module for non JPEG 2000 Standard conforming
 * products. This copyright notice must be included in all copies or
 * derivative works of this software module.
 * 
 * Copyright (c) 1999/2000 JJ2000 Partners.
 * 
 * 
 * 
 */


package jj2000.j2k.entropy.encoder;

import java.io.*;

/**
 * This class provides a buffering output stream similar to
 * ByteArrayOutputStream, with some additional methods.
 *
 * <P>Once an array has been written to an output stream or to a byte
 * array, the object can be reused as a new stream if the reset()
 * method is called.
 *
 * <P>Unlike the ByteArrayOutputStream class, this class is not thread safe.
 *
 * @see #reset
 * */
public class ByteOutputBuffer {

    /** The buffer where the data is stored */
    byte buf[];

    /** The number of valid bytes in the buffer */
    int count;

    /** The buffer increase size */
    public final static int BUF_INC = 512;

    /** The default initial buffer size */
    public final static int BUF_DEF_LEN = 256;

    /**
     * Creates a new byte array output stream. The buffer capacity is
     * initially BUF_DEF_LEN bytes, though its size increases if necessary.
     *
     *
     * */
    public ByteOutputBuffer() {
        buf = new byte[BUF_DEF_LEN];
    }

    /**
     * Creates a new byte array output stream, with a buffer capacity
     * of the specified size, in bytes.
     *
     * @param size the initial size.
     *
     *
     * */
    public ByteOutputBuffer(int size) {
        buf = new byte[size];
    }

    /**
     * Writes the specified byte to this byte array output stream. The
     * functionality provided by this implementation is the same as for the
     * one in the superclass, however this method is not synchronized and
     * therefore not safe thread, but faster.
     *
     * @param b The byte to write
     *
     *
     * */
    public final void write(int b) {
        if (count == buf.length) { // Resize buffer
            byte tmpbuf[] = buf;
            buf = new byte[buf.length+BUF_INC];
            System.arraycopy(tmpbuf,0,buf,0,count);
        }
        buf[count++] = (byte) b;
    }

    /**
     * Copies the specified part of the stream to the 'outbuf' byte
     * array.
     *
     * @param off The index of the first element in the stream to
     * copy.
     *
     * @param len The number of elements of the array to copy
     *
     * @param outbuf The destination array
     *
     * @param outoff The index of the first element in 'outbuf' where
     * to write the data.
     *
     *
     * */
    public void toByteArray(int off, int len, byte outbuf[], int outoff) {
        // Copy the data
        System.arraycopy(buf,off,outbuf,outoff,len);
    }

    /**
     * Returns the number of valid bytes in the output buffer (count class
     * variable).
     *
     * @return The number of bytes written to the buffer
     *
     * */
    public int size() {
        return count;
    }

    /**
     * Discards all the buffered data, by resetting the counter of written
     * bytes to 0.
     *
     * */
    public void reset() {
        count = 0;
    }

    /**
     * Returns the byte buffered at the given position in the buffer. The
     * position in the buffer is the index of the 'write()' method call after
     * the last call to 'reset()'.
     *
     * @param pos The position of the byte to return
     *
     * @return The value (betweeb 0-255) of the byte at position 'pos'.
     *
     * */
    public int getByte(int pos) {
        if (pos >= count) {
            throw new IllegalArgumentException();
        }
        return buf[pos]&0xFF;
    }
}