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   * Copyright (c) 1994, 2013, Oracle and/or its affiliates. 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.  Oracle designates this
   * particular file as subject to the "Classpath" exception as provided
   * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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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     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 {
      }
  
  }
  