/*
* @(#)TelnetInputStream.java 1.12 95/08/22 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 sun.net;
import java.io.*;
/**
* This class provides input and output streams for telnet clients.
* This class overrides read to do CRLF processing as specified in
* RFC 854. The class assumes it is running on a system where lines
* are terminated with a single newline <LF> character.
*
* This is the relevant section of RFC 824 regarding CRLF processing:
*
* <pre>
* The sequence "CR LF", as defined, will cause the NVT to be
* positioned at the left margin of the next print line (as would,
* for example, the sequence "LF CR"). However, many systems and
* terminals do not treat CR and LF independently, and will have to
* go to some effort to simulate their effect. (For example, some
* terminals do not have a CR independent of the LF, but on such
* terminals it may be possible to simulate a CR by backspacing.)
* Therefore, the sequence "CR LF" must be treated as a single "new
* line" character and used whenever their combined action is
* intended; the sequence "CR NUL" must be used where a carriage
* return alone is actually desired; and the CR character must be
* avoided in other contexts. This rule gives assurance to systems
* which must decide whether to perform a "new line" function or a
* multiple-backspace that the TELNET stream contains a character
* following a CR that will allow a rational decision.
*
* Note that "CR LF" or "CR NUL" is required in both directions
* (in the default ASCII mode), to preserve the symmetry of the
* NVT model. Even though it may be known in some situations
* (e.g., with remote echo and suppress go ahead options in
* effect) that characters are not being sent to an actual
* printer, nonetheless, for the sake of consistency, the protocol
* requires that a NUL be inserted following a CR not followed by
* a LF in the data stream. The converse of this is that a NUL
* received in the data stream after a CR (in the absence of
* options negotiations which explicitly specify otherwise) should
* be stripped out prior to applying the NVT to local character
* set mapping.
* </pre>
*
* @version 1.12, 22 Aug 1995
* @author Jonathan Payne
*/
public class TelnetInputStream extends FilterInputStream {
/** If stickyCRLF is true, then we're a machine, like an IBM PC,
where a Newline is a CR followed by LF. On UNIX, this is false
because Newline is represented with just a LF character. */
boolean stickyCRLF = false;
boolean seenCR = false;
public boolean binaryMode = false;
public TelnetInputStream(InputStream fd, boolean binary) {
super(fd);
binaryMode = binary;
}
public void setStickyCRLF(boolean on) {
stickyCRLF = on;
}
public int read() throws IOException {
if (binaryMode)
return super.read();
int c;
/* If last time we determined we saw a CRLF pair, and we're
not turning that into just a Newline (that is, we're
stickyCRLF), then return the LF part of that sticky
pair now. */
if (seenCR) {
seenCR = false;
return '\n';
}
if ((c = super.read()) == '\r') { /* CR */
switch (c = super.read()) {
default:
case -1: /* this is an error */
throw new TelnetProtocolException("misplaced CR in input");
case 0: /* NUL - treat CR as CR */
return '\r';
case '\n': /* CRLF - treat as NL */
if (stickyCRLF) {
seenCR = true;
return '\r';
} else {
return '\n';
}
}
}
return c;
}
/** read into a byte array */
public int read(byte bytes[]) throws IOException {
return read(bytes, 0, bytes.length);
}
/**
* Read into a byte array at offset <i>off</i> for length <i>length</i>
* bytes.
*/
public int read(byte bytes[], int off, int length) throws IOException {
if (binaryMode)
return super.read(bytes, off, length);
int c;
int offStart = off;
while (--length >= 0) {
c = read();
if (c == -1)
break;
bytes[off++] = (byte)c;
}
return (off > offStart) ? off - offStart : -1;
}
}