libjava/java/io/InputStream.java

/* Copyright (C) 1998, 1999  Free Software Foundation

   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 2, 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 abstract class InputStream
{
  public InputStream()
  {
  }

  public int available() throws IOException
  {
    return 0;
  }

  public void close() throws IOException
  {
    // Do nothing
  }

  public void mark(int readlimit)
  {
    // Do nothing
  }

  public boolean markSupported()
  {
    return false;
  }

  public abstract int read() throws IOException;

  public int read(byte[] b) throws IOException
  {
    return read(b, 0, b.length);
  }

  public int read(byte[] b, int off, int len) throws IOException
  {
    if (off < 0 || len < 0 || off + len > b.length)
      throw new IndexOutOfBoundsException();
    if (b.length == 0)
      return 0;

    int i, ch;

    for (i = 0; i < len; ++i)
      try
      {
        if ((ch = read()) < 0)
	  return i == 0 ? -1 : i;		// EOF
        b[off + i] = (byte) ch;
      }
      catch (IOException ex)
      {
        // Only reading the first byte should cause an IOException.
	if (i == 0)
	  throw ex;
	return i;
      }

    return i;
  }

  public void reset() throws IOException
  {
    throw new IOException("mark/reset not supported");
  }

  public long skip(long n) throws IOException
  {
    // Throw away n bytes by reading them into a temp byte[].
    // Limit the temp array to 2Kb so we don't grab too much memory.
    final int buflen = n > 2048 ? 2048 : (int) n;
    byte[] tmpbuf = new byte[buflen];
    final long origN = n;

    while (n > 0L)
      {
	int numread = read(tmpbuf, 0, n > buflen ? buflen : (int) n);
	if (numread <= 0)
	  break;
	n -= numread;
      }

    return origN - n;
  }
}