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+/* ByteArrayInputStream.java -- Read an array as a stream
+   Copyright (C) 1998, 1999, 2001, 2005  Free Software Foundation, Inc.
+
+This file is part of GNU Classpath.
+
+GNU Classpath is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2, or (at your option)
+any later version.
+ 
+GNU Classpath 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 for more details.
+
+You should have received a copy of the GNU General Public License
+along with GNU Classpath; see the file COPYING.  If not, write to the
+Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+02110-1301 USA.
+
+Linking this library statically or dynamically with other modules is
+making a combined work based on this library.  Thus, the terms and
+conditions of the GNU General Public License cover the whole
+combination.
+
+As a special exception, the copyright holders of this library give you
+permission to link this library with independent modules to produce an
+executable, regardless of the license terms of these independent
+modules, and to copy and distribute the resulting executable under
+terms of your choice, provided that you also meet, for each linked
+independent module, the terms and conditions of the license of that
+module.  An independent module is a module which is not derived from
+or based on this library.  If you modify this library, you may extend
+this exception to your version of the library, but you are not
+obligated to do so.  If you do not wish to do so, delete this
+exception statement from your version. */
+
+
+package java.io;
+
+/**
+  * This class permits an array of bytes to be read as an input stream.
+  *
+  * @author Warren Levy (warrenl@cygnus.com)
+  * @author Aaron M. Renn (arenn@urbanophile.com)
+  */ 
+public class ByteArrayInputStream extends InputStream
+{
+  /**
+   * The array that contains the data supplied during read operations
+   */
+  protected byte[] buf;
+
+  /**
+   * The array index of the next byte to be read from the buffer
+   * <code>buf</code>
+   */
+  protected int pos;
+
+  /**
+   * The currently marked position in the stream.  This defaults to 0, so a
+   * reset operation on the stream resets it to read from array index 0 in
+   * the buffer - even if the stream was initially created with an offset
+   * greater than 0
+   */
+  protected int mark;
+
+  /**
+   * This indicates the maximum number of bytes that can be read from this
+   * stream.  It is the array index of the position after the last valid
+   * byte in the buffer <code>buf</code>
+   */
+  protected int count;
+
+  /**
+   * Create a new ByteArrayInputStream that will read bytes from the passed
+   * in byte array.  This stream will read from the beginning to the end
+   * of the array.  It is identical to calling an overloaded constructor
+   * as <code>ByteArrayInputStream(buf, 0, buf.length)</code>.
+   * <p>
+   * Note that this array is not copied.  If its contents are changed 
+   * while this stream is being read, those changes will be reflected in the
+   * bytes supplied to the reader.  Please use caution in changing the 
+   * contents of the buffer while this stream is open.
+   *
+   * @param buffer The byte array buffer this stream will read from.
+   */
+  public ByteArrayInputStream(byte[] buffer)
+  {
+    this(buffer, 0, buffer.length);
+  }
+
+  /**
+   * Create a new ByteArrayInputStream that will read bytes from the
+   * passed in byte array.  This stream will read from position
+   * <code>offset</code> in the array for a length of
+   * <code>length</code> bytes past <code>offset</code>.  If the
+   * stream is reset to a position before <code>offset</code> then
+   * more than <code>length</code> bytes can be read from the stream.
+   * The <code>length</code> value should be viewed as the array index
+   * one greater than the last position in the buffer to read.
+   * <p>
+   * Note that this array is not copied.  If its contents are changed 
+   * while this stream is being read, those changes will be reflected in the
+   * bytes supplied to the reader.  Please use caution in changing the 
+   * contents of the buffer while this stream is open.
+   *
+   * @param buffer The byte array buffer this stream will read from.
+   * @param offset The index into the buffer to start reading bytes from
+   * @param length The number of bytes to read from the buffer
+   */
+  public ByteArrayInputStream(byte[] buffer, int offset, int length)
+  {
+    if (offset < 0  || length < 0 || offset > buffer.length)
+      throw new IllegalArgumentException();
+
+    buf = buffer;
+
+    count = offset + length;
+    if (count > buf.length)
+      count = buf.length;
+
+    pos = offset;
+    mark = pos;
+  }
+
+  /**
+   * This method returns the number of bytes available to be read from this
+   * stream.  The value returned will be equal to <code>count - pos</code>.
+   *
+   * @return The number of bytes that can be read from this stream
+   * before blocking, which is all of them 
+   */
+  public synchronized int available()
+  {
+    return count - pos;
+  }
+
+  /**
+   * This method sets the mark position in this stream to the current
+   * position.  Note that the <code>readlimit</code> parameter in this
+   * method does nothing as this stream is always capable of
+   * remembering all the bytes int it.
+   * <p>
+   * Note that in this class the mark position is set by default to
+   * position 0 in the stream.  This is in constrast to some other
+   * stream types where there is no default mark position.
+   *
+   * @param readLimit The number of bytes this stream must remember.
+   * This parameter is ignored.
+   */
+  public synchronized void mark(int readLimit)
+  {
+    // readLimit is ignored per Java Class Lib. book, p.220.
+    mark = pos;
+  }
+
+  /**
+   * This method overrides the <code>markSupported</code> method in
+   * <code>InputStream</code> in order to return <code>true</code> -
+   * indicating that this stream class supports mark/reset
+   * functionality.
+   *
+   * @return <code>true</code> to indicate that this class supports
+   * mark/reset.
+   */
+  public boolean markSupported()
+  {
+    return true;
+  }
+
+  /**
+   * This method reads one byte from the stream.  The <code>pos</code>
+   * counter is advanced to the next byte to be read.  The byte read is
+   * returned as an int in the range of 0-255.  If the stream position
+   * is already at the end of the buffer, no byte is read and a -1 is
+   * returned in order to indicate the end of the stream.
+   *
+   * @return The byte read, or -1 if end of stream
+   */
+  public synchronized int read()
+  {
+    if (pos < count)
+      return ((int) buf[pos++]) & 0xFF;
+    return -1;
+  }
+
+  /**
+   * This method reads bytes from the stream and stores them into a
+   * caller supplied buffer.  It starts storing the data at index
+   * <code>offset</code> into the buffer and attempts to read
+   * <code>len</code> bytes.  This method can return before reading
+   * the number of bytes requested if the end of the stream is
+   * encountered first.  The actual number of bytes read is returned.
+   * If no bytes can be read because the stream is already at the end
+   * of stream position, a -1 is returned.
+   * <p>
+   * This method does not block.
+   *
+   * @param buffer The array into which the bytes read should be stored.
+   * @param offset The offset into the array to start storing bytes
+   * @param length The requested number of bytes to read
+   *
+   * @return The actual number of bytes read, or -1 if end of stream.
+   */
+  public synchronized int read(byte[] buffer, int offset, int length)
+  {
+    if (pos >= count)
+      return -1;
+
+    int numBytes = Math.min(count - pos, length);
+    System.arraycopy(buf, pos, buffer, offset, numBytes);
+    pos += numBytes;
+    return numBytes;
+  }
+
+  /**
+   * This method sets the read position in the stream to the mark
+   * point by setting the <code>pos</code> variable equal to the
+   * <code>mark</code> variable.  Since a mark can be set anywhere in
+   * the array, the mark/reset methods int this class can be used to
+   * provide random search capabilities for this type of stream.
+   */
+  public synchronized void reset()
+  {
+    pos = mark;
+  }
+
+  /**
+   * This method attempts to skip the requested number of bytes in the
+   * input stream.  It does this by advancing the <code>pos</code>
+   * value by the specified number of bytes.  It this would exceed the
+   * length of the buffer, then only enough bytes are skipped to
+   * position the stream at the end of the buffer.  The actual number
+   * of bytes skipped is returned.
+   *
+   * @param num The requested number of bytes to skip
+   *
+   * @return The actual number of bytes skipped.
+   */
+  public synchronized long skip(long num)
+  {
+    // Even though the var numBytes is a long, in reality it can never
+    // be larger than an int since the result of subtracting 2 positive
+    // ints will always fit in an int.  Since we have to return a long
+    // anyway, numBytes might as well just be a long.
+    long numBytes = Math.min((long) (count - pos), num < 0 ? 0L : num);
+    pos += numBytes;
+    return numBytes;
+  }
+}