/*
* Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package sun.net;
import java.io.*;
/**
* This class provides input and output streams for telnet clients.
* This class overrides write 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 {@literal <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>
*
* @author Jonathan Payne
*/
public class TelnetOutputStream extends BufferedOutputStream {
boolean stickyCRLF = false;
boolean seenCR = false;
public boolean binaryMode = false;
public TelnetOutputStream(OutputStream fd, boolean binary) {
super(fd);
binaryMode = binary;
}
/**
* set the stickyCRLF flag. Tells whether the terminal considers CRLF as a single
* char.
*
* @param on the <code>boolean</code> to set the flag to.
*/
public void setStickyCRLF(boolean on) {
stickyCRLF = on;
}
/**
* Writes the int to the stream and does CR LF processing if necessary.
*/
public void write(int c) throws IOException {
if (binaryMode) {
super.write(c);
return;
}
if (seenCR) {
if (c != '\n')
super.write(0);
super.write(c);
if (c != '\r')
seenCR = false;
} else { // !seenCR
if (c == '\n') {
super.write('\r');
super.write('\n');
return;
}
if (c == '\r') {
if (stickyCRLF)
seenCR = true;
else {
super.write('\r');
c = 0;
}
}
super.write(c);
}
}
/**
* Write the bytes at offset <i>off</i> in buffer <i>bytes</i> for
* <i>length</i> bytes.
*/
public void write(byte bytes[], int off, int length) throws IOException {
if (binaryMode) {
super.write(bytes, off, length);
return;
}
while (--length >= 0) {
write(bytes[off++]);
}
}
}