/*
* @(#)PushbackInputStream.java 1.11 95/08/10 Jonathan Payne
*
* Copyright (c) 1994 Sun Microsystems, Inc. All Rights Reserved.
*
* Permission to use, copy, modify, and distribute this software
* and its documentation for NON-COMMERCIAL purposes and without
* fee is hereby granted provided that this copyright notice
* appears in all copies. Please refer to the file "copyright.html"
* for further important copyright and licensing information.
*
* SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF
* THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
* TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
* PARTICULAR PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR
* ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR
* DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES.
*/
package java.io;
/**
* An input stream that has a 1 byte push back buffer.
*
* @version 1.11, 10 Aug 1995
* @author Jonathan Payne
*/
public
class PushbackInputStream extends FilterInputStream {
/**
* Push back character.
*/
protected int pushBack = -1;
/**
* Creates a PushbackInputStream.
* @param in the input stream
*/
public PushbackInputStream(InputStream in) {
super(in);
}
/**
* Reads a byte of data. This method will block if no input is
* available.
* @return the byte read, or -1 if the end of the
* stream is reached.
* @exception IOException If an I/O error has occurred.
*/
public int read() throws IOException {
int c = pushBack;
if (c != -1) {
pushBack = -1;
} else {
c = in.read();
}
return c;
}
/**
* Reads into an array of bytes. This method
* blocks until some input is available.
* @param b the buffer into which the data is read
* @param off the start offset of the data
* @param len the maximum number of bytes read
* @return the actual number of bytes read, -1 is
* returned when the end of the stream is reached.
* @exception IOException If an I/O error has occurred.
*/
public int read(byte bytes[], int offset, int length) throws IOException {
if (pushBack != -1) {
if (length == 0) {
return 0;
}
bytes[offset] = (byte)pushBack;
pushBack = -1;
return 1;
}
return in.read(bytes, offset, length);
}
/**
* Pushes back a character.
* @param ch the character to push back.
* @exception IOException If an attempt to push back more than one
* character is made.
*/
public void unread(int ch) throws IOException {
if (pushBack != -1) {
throw new IOException("Attempt to unread more than one character!");
}
pushBack = ch;
}
/**
* Returns the number of bytes that can be read.
* without blocking.
*/
public int available() throws IOException {
return (pushBack == -1) ? super.available() : super.available() + 1;
}
/**
* Returns true if this stream type supports mark/reset.
*/
public boolean markSupported() {
return false;
}
}