/*

 * Copyright 1994-2005 Sun Microsystems, Inc.  All Rights Reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Sun designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Sun in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 */

package java.io;

/**

 * A <code>ByteArrayInputStream</code> contains

 * an internal buffer that contains bytes that

 * may be read from the stream. An internal

 * counter keeps track of the next byte to

 * be supplied by the <code>read</code> method.

 * <p>

 * Closing a <tt>ByteArrayInputStream</tt> has no effect. The methods in

 * this class can be called after the stream has been closed without

 * generating an <tt>IOException</tt>.

 *

 * @author  Arthur van Hoff

 * @see     java.io.StringBufferInputStream

 * @since   JDK1.0

 */

public

class ByteArrayInputStream extends InputStream {

    /**

     * An array of bytes that was provided

     * by the creator of the stream. Elements <code>buf[0]</code>

     * through <code>buf[count-1]</code> are the

     * only bytes that can ever be read from the

     * stream;  element <code>buf[pos]</code> is

     * the next byte to be read.

     */

    protected byte buf[];

    /**

     * The index of the next character to read from the input stream buffer.

     * This value should always be nonnegative

     * and not larger than the value of <code>count</code>.

     * The next byte to be read from the input stream buffer

     * will be <code>buf[pos]</code>.

     */

    protected int pos;

    /**

     * The currently marked position in the stream.

     * ByteArrayInputStream objects 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.

     * <p>

     * If no mark has been set, then the value of mark is the offset

     * passed to the constructor (or 0 if the offset was not supplied).

     *

     * @since   JDK1.1

     */

    protected int mark = 0;

    /**

     * The index one greater than the last valid character in the input

     * stream buffer.

     * This value should always be nonnegative

     * and not larger than the length of <code>buf</code>.

     * It  is one greater than the position of

     * the last byte within <code>buf</code> that

     * can ever be read  from the input stream buffer.

     */

    protected int count;

    /**

     * Creates a <code>ByteArrayInputStream</code>

     * so that it  uses <code>buf</code> as its

     * buffer array.

     * The buffer array is not copied.

     * The initial value of <code>pos</code>

     * is <code>0</code> and the initial value

     * of  <code>count</code> is the length of

     * <code>buf</code>.

     *

     * @param   buf   the input buffer.

     */

    public ByteArrayInputStream(byte buf[]) {

        this.buf = buf;

        this.pos = 0;

        this.count = buf.length;

    }

    /**

     * Creates <code>ByteArrayInputStream</code>

     * that uses <code>buf</code> as its

     * buffer array. The initial value of <code>pos</code>

     * is <code>offset</code> and the initial value

     * of <code>count</code> is the minimum of <code>offset+length</code>

     * and <code>buf.length</code>.

     * The buffer array is not copied. The buffer's mark is

     * set to the specified offset.

     *

     * @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>

     * This <code>read</code> method

     * 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.

     * If <code>pos</code> equals <code>count</code>,

     * then <code>-1</code> is returned to indicate

     * end of file. Otherwise, the  number <code>k</code>

     * of bytes read is equal to the smaller of

     * <code>len</code> and <code>count-pos</code>.

     * If <code>k</code> is positive, then bytes

     * <code>buf[pos]</code> through <code>buf[pos+k-1]</code>

     * are copied into <code>b[off]</code>  through

     * <code>b[off+k-1]</code> in the manner performed

     * by <code>System.arraycopy</code>. The

     * value <code>k</code> is added into <code>pos</code>

     * and <code>k</code> is returned.

     * <p>

     * This <code>read</code> method cannot block.

     *

     * @param   b     the buffer into which the data is read.

     * @param   off   the start offset in the destination array <code>b</code>

     * @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.

     * @exception  NullPointerException If <code>b</code> is <code>null</code>.

     * @exception  IndexOutOfBoundsException If <code>off</code> is negative,

     * <code>len</code> is negative, or <code>len</code> is greater than

     * <code>b.length - off</code>

     */

    public synchronized int read(byte b[], int off, int len) {

        if (b == null) {

            throw new NullPointerException();

        } else if (off < 0 || len < 0 || len > b.length - off) {

            throw new IndexOutOfBoundsException();

        }

        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.

     * The actual number <code>k</code>

     * of bytes to be skipped is equal to the smaller

     * of <code>n</code> and  <code>count-pos</code>.

     * The value <code>k</code> is added into <code>pos</code>

     * and <code>k</code> is returned.

     *

     * @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 remaining bytes that can be read (or skipped over)

     * from this input stream.

     * <p>

     * The value returned is <code>count&nbsp;- pos</code>,

     * which is the number of bytes remaining to be read from the input buffer.

     *

     * @return  the number of remaining bytes that can be read (or skipped

     *          over) from this input stream without blocking.

     */

    public synchronized int available() {

        return count - pos;

    }

    /**

     * Tests if this <code>InputStream</code> supports mark/reset. The

     * <code>markSupported</code> method of <code>ByteArrayInputStream</code>

     * always returns <code>true</code>.

     *

     * @since   JDK1.1

     */

    public boolean markSupported() {

        return true;

    }

    /**

     * Set the current marked position in the stream.

     * ByteArrayInputStream objects are marked at position zero by

     * default when constructed.  They may be marked at another

     * position within the buffer by this method.

     * <p>

     * If no mark has been set, then the value of the mark is the

     * offset passed to the constructor (or 0 if the offset was not

     * supplied).

     *

     * <p> Note: The <code>readAheadLimit</code> for this class

     *  has no meaning.

     *

     * @since   JDK1.1

     */

    public void mark(int readAheadLimit) {

        mark = pos;

    }

    /**

     * Resets the buffer to the marked position.  The marked position

     * is 0 unless another position was marked or an offset was specified

     * in the constructor.

     */

    public synchronized void reset() {

        pos = mark;

    }

    /**

     * Closing a <tt>ByteArrayInputStream</tt> has no effect. The methods in

     * this class can be called after the stream has been closed without

     * generating an <tt>IOException</tt>.

     * <p>

     */

    public void close() throws IOException {

    }

}