/* Copyright (C) 1998, 1999  Cygnus Solutions

   This file is part of libgcj.

This software is copyrighted work licensed under the terms of the
Libgcj License.  Please consult the file "LIBGCJ_LICENSE" for
details.  */
 
package java.io;

/**
 * @author Warren Levy <warrenl@cygnus.com>
 * @date October 7, 1998.  
 */ 

/* Written using "Java Class Libraries", 2nd edition, ISBN 0-201-31002-3
 * "The Java Language Specification", ISBN 0-201-63451-1
 * plus online API docs for JDK 1.2 beta from http://www.javasoft.com.
 * Status:  Believed complete and correct
 */
 
public class ByteArrayInputStream extends InputStream
{
  /* An array of bytes provided by the creator of the stream. */
  protected byte[] buf;

  /* Position of the next byte in buf to be read. */
  protected int pos;

  /* The currently marked position in the stream. */
  protected int mark;

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

  public ByteArrayInputStream(byte[] buffer)
  {
    this(buffer, 0, buffer.length);
  }

  public ByteArrayInputStream(byte[] buffer, int offset, int length)
  {
    buf = buffer;

    count = offset + length;
    if (count > buf.length)
      count = buf.length;

    pos = offset;
    // TBD: What should we do if pos is neg. or > count?  E.g. throw exc. or:
    // if (pos < 0 || pos > count)
    //   pos = 0;

    mark = pos;
  }

  public synchronized int available()
  {
    return count - pos;
  }

  public synchronized void mark(int readAheadLimit)
  {
    // readAheadLimit is ignored per Java Class Lib. book, p.220.
    mark = pos;
  }

  public boolean markSupported()
  {
    return true;
  }

  public synchronized int read()
  {
    if (pos < 0)
      throw new ArrayIndexOutOfBoundsException(pos);

    if (pos < count)
      return ((int) buf[pos++]) & 0xFF;
    return -1;
  }

  public synchronized int read(byte[] b, int off, int len)
  {
    /* Don't need to check pos value, arraycopy will check it. */
    if (off < 0 || len < 0 || off + len > b.length)
      throw new ArrayIndexOutOfBoundsException();

    if (pos >= count)
      return -1;

    int numBytes = Math.min(count - pos, len);
    System.arraycopy(buf, pos, b, off, numBytes);
    pos += numBytes;
    return numBytes;
  }

  public synchronized void reset()
  {
    pos = mark;
  }

  public synchronized long skip(long n)
  {
    // 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), n < 0 ? 0L : n);
    pos += numBytes;
    return numBytes;
  }
}