Java 1.2 How-To/JavaHowTo.iso/3rdParty/jbuilder/unsupported/JDK1.2beta3/SOURCE/SRC.ZIP/java/io/ByteArrayInputStream.java

Java Source | 1998-03-20 | 5.7 KB | 194 lines

/*
 * @(#)ByteArrayInputStream.java    1.24 98/03/18
 *
 * Copyright 1994-1998 by Sun Microsystems, Inc.,
 * 901 San Antonio Road, Palo Alto, California, 94303, U.S.A.
 * All rights reserved.
 *
 * This software is the confidential and proprietary information
 * of Sun Microsystems, Inc. ("Confidential Information").  You
 * shall not disclose such Confidential Information and shall use
 * it only in accordance with the terms of the license agreement
 * you entered into with Sun.
 */

package java.io;

/**
 * This class allows an application to create an input stream in
 * which the bytes read are supplied by the contents of a byte array.
 * Applications can also read bytes from a string by using a
 * <code>StringBufferInputStream</code>.
 *
 * @author  Arthur van Hoff
 * @version 1.24, 03/18/98
 * @see     java.io.StringBufferInputStream
 * @since   JDK1.0
 */
public
class ByteArrayInputStream extends InputStream {
    /**
     * The byte array containing the data.
     */
    protected byte buf[];

    /**
     * The index of the next character to read from the input stream buffer.
     */
    protected int pos;

    /**
     * The currently marked position in the stream.
     * ByteArrayInputStreams are marked at position zero by
     * default when constructed.  They may be marked at another
     * position within the buffer by the <code>mark()</code> method.
     * The current buffer position is set to this point by the
     * <code>reset()</code> method.
     *
     * @since   JDK1.1
     */
    protected int mark = 0;

    /**
     * The index one greater than the last valid character in the input
     * stream buffer.
     */
    protected int count;

    /**
     * Creates a new byte array input stream that reads data from the
     * specified byte array. The byte array is not copied.
     *
     * @param   buf   the input buffer.
     */
    public ByteArrayInputStream(byte buf[]) {
    this.buf = buf;
        this.pos = 0;
    this.count = buf.length;
    }

    /**
     * Creates a new byte array input stream that reads data from the
     * specified byte array. Up to <code>length</code> characters are to
     * be read from the byte array, starting at the indicated offset.
     * <p>
     * The byte array is not copied.
     *
     * @param   buf      the input buffer.
     * @param   offset   the offset in the buffer of the first byte to read.
     * @param   length   the maximum number of bytes to read from the buffer.
     */
    public ByteArrayInputStream(byte buf[], int offset, int length) {
    this.buf = buf;
        this.pos = offset;
    this.count = Math.min(offset + length, buf.length);
        this.mark = offset;
    }

    /**
     * Reads the next byte of data from this 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.
     * <p>
     * The <code>read</code> method of <code>ByteArrayInputStream</code>
     * cannot block.
     *
     * @return  the next byte of data, or <code>-1</code> if the end of the
     *          stream has been reached.
     */
    public synchronized int read() {
    return (pos < count) ? (buf[pos++] & 0xff) : -1;
    }

    /**
     * Reads up to <code>len</code> bytes of data into an array of bytes
     * from this input stream. This <code>read</code> method cannot block.
     *
     * @param   b     the buffer into which the data is read.
     * @param   off   the start offset of the data.
     * @param   len   the maximum number of bytes 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.
     */
    public synchronized int read(byte b[], int off, int len) {
    if (pos >= count) {
        return -1;
    }
    if (pos + len > count) {
        len = count - pos;
    }
    if (len <= 0) {
        return 0;
    }
    System.arraycopy(buf, pos, b, off, len);
    pos += len;
    return len;
    }

    /**
     * Skips <code>n</code> bytes of input from this input stream. Fewer
     * bytes might be skipped if the end of the input stream is reached.
     *
     * @param   n   the number of bytes to be skipped.
     * @return  the actual number of bytes skipped.
     */
    public synchronized long skip(long n) {
    if (pos + n > count) {
        n = count - pos;
    }
    if (n < 0) {
        return 0;
    }
    pos += n;
    return n;
    }

    /**
     * Returns the number of bytes that can be read from this input
     * stream without blocking.
     * <p>
     * The <code>available</code> method of
     * <code>ByteArrayInputStream</code> returns the value of
     * <code>count - pos</code>,
     * which is the number of bytes remaining to be read from the input buffer.
     *
     * @return  the number of bytes that can be read from the input stream
     *          without blocking.
     */
    public synchronized int available() {
    return count - pos;
    }

    /**
     * Tests if ByteArrayInputStream supports mark/reset.
     *
     * @since   JDK1.1
     */
    public boolean markSupported() {
    return true;
    }

    /**
     * Set the current marked position in the stream.
     * ByteArrayInputStreams are marked at position zero by
     * default when constructed.  They may be marked at another
     * position within the buffer by this method.
     *
     * @since   JDK1.1
     */
    public void mark(int readAheadLimit) {
    mark = pos;
    }

    /**
     * Resets the buffer to the marked position.  The marked position
     * is the beginning unless another position was marked.
     */
    public synchronized void reset() {
    pos = mark;
    }
}