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/* 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 15, 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 PushbackInputStream extends FilterInputStream
{
/* Internal buffer array for data. */
protected byte[] buf;
/* The current position in the buffer. */
protected int pos;
public PushbackInputStream(InputStream in)
{
this(in, 1);
}
public PushbackInputStream(InputStream in, int size)
{
super(in);
if (size < 0)
throw new IllegalArgumentException();
buf = new byte[size];
pos = buf.length;
}
public int available() throws IOException
{
return pos + super.available();
}
public void close() throws IOException
{
buf = null;
super.close();
}
public boolean markSupported()
{
return false;
}
public int read() throws IOException
{
if (pos < buf.length)
return ((int) buf[pos++]) & 0xFF;
return super.read();
}
public int read(byte[] b, int off, int len) throws IOException
{
if (off < 0 || len < 0 || off + len > b.length)
throw new ArrayIndexOutOfBoundsException();
int numBytes = Math.min(buf.length - pos, len);
for (int i = 0; i < numBytes; i++)
b[off++] = buf[pos++];
// `off' was just incremented to include `numBytes', so we can
// just pass ithere.
return numBytes + super.read(b, off, len - numBytes);
}
public void unread(int b) throws IOException
{
if (pos <= 0)
throw new IOException();
buf[--pos] = (byte) b;
}
public void unread(byte[] b) throws IOException
{
unread(b, 0, b.length);
}
public void unread(byte[] b, int off, int len) throws IOException
{
if (pos < len)
throw new IOException();
// Note the order that these bytes are being added is the opposite
// of what would be done if they were added to the buffer one at a time.
// See the Java Class Libraries book p. 1390.
System.arraycopy(b, off, buf, pos - len, len);
// Don't put this into the arraycopy above, an exception might be thrown
// and in that case we don't want to modify pos.
pos -= len;
}
// JDK1.2
public long skip(long n) throws IOException
{
final long origN = n;
if (n > 0L)
{
int numread = (int) Math.min((long) (buf.length - pos), n);
pos += numread;
n -= numread;
n -= super.skip(n);
}
return origN - n;
}
}
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