/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
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* 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).
*
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* 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
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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 <LF> character. This is the relevant section of RFC 824 regarding CRLF processing: 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.
Author: Jonathan Payne
/**
* 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.
Params: - on – the
boolean to set the flag to.
/**
* 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.
/**
* 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 off in buffer bytes for
length bytes.
/**
* 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++]);
}
}
}