/*
 * Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */

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;
 }

 int avail = count - pos;
 if (len > avail) {
 len = avail;
 }
 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) {
 long k = count - pos;
 if (n < k) {
 k = n < 0 ? 0 : n;
 }

 pos += k;
 return k;
 }

 /**
 * 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>.
 */
 public void close() throws IOException {
 }

}