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/* $OpenBSD: setbuf.c,v 1.2 1999/02/24 05:36:11 millert Exp $ */
/****************************************************************************
* Copyright (c) 1998 Free Software Foundation, Inc. *
* *
* Permission is hereby granted, free of charge, to any person obtaining a *
* copy of this software and associated documentation files (the *
* "Software"), to deal in the Software without restriction, including *
* without limitation the rights to use, copy, modify, merge, publish, *
* distribute, distribute with modifications, sublicense, and/or sell *
* copies of the Software, and to permit persons to whom the Software is *
* furnished to do so, subject to the following conditions: *
* *
* The above copyright notice and this permission notice shall be included *
* in all copies or substantial portions of the Software. *
* *
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS *
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF *
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. *
* IN NO EVENT SHALL THE ABOVE COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, *
* DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR *
* OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR *
* THE USE OR OTHER DEALINGS IN THE SOFTWARE. *
* *
* Except as contained in this notice, the name(s) of the above copyright *
* holders shall not be used in advertising or otherwise to promote the *
* sale, use or other dealings in this Software without prior written *
* authorization. *
****************************************************************************/
/****************************************************************************
* Author: Zeyd M. Ben-Halim <zmbenhal@netcom.com> 1992,1995 *
* and: Eric S. Raymond <esr@snark.thyrsus.com> *
****************************************************************************/
/*
** setbuf.c
**
** Support for set_term(), reset_shell_mode(), reset_prog_mode().
**
*/
#include <curses.priv.h>
MODULE_ID("$From: setbuf.c,v 1.4 1999/02/10 03:15:09 tom Exp $")
/*
* If the output file descriptor is connected to a tty (the typical case) it
* will probably be line-buffered. Keith Bostic pointed out that we don't want
* this; it hoses people running over networks by forcing out a bunch of small
* packets instead of one big one, so screen updates on ptys look jerky.
* Restore block buffering to prevent this minor lossage.
*
* The buffer size is a compromise. Ideally we'd like a buffer that can hold
* the maximum possible update size (the whole screen plus cup commands to
* change lines as it's painted). On a 66-line xterm this can become
* excessive. So we min it with the amount of data we think we can get through
* two Ethernet packets (maximum packet size - 100 for TCP/IP overhead).
*
* Why two ethernet packets? It used to be one, on the theory that said
* packets define the maximum size of atomic update. But that's less than the
* 2000 chars on a 25 x 80 screen, and we don't want local updates to flicker
* either. Two packet lengths will handle up to a 35 x 80 screen.
*
* The magic '6' is the estimated length of the end-of-line cup sequence to go
* to the next line. It's generous. We used to mess with the buffering in
* init_mvcur() after cost computation, but that lost the sequences emitted by
* init_acs() in setupscreen().
*
* "The setvbuf function may be used only after the stream pointed to by stream
* has been associated with an open file and before any other operation is
* performed on the stream." (ISO 7.9.5.6.)
*
* Grrrr...
*
* On a lighter note, many implementations do in fact allow an application to
* reset the buffering after it has been written to. We try to do this because
* otherwise we leave stdout in buffered mode after endwin() is called. (This
* also happens with SVr4 curses).
*
* There are pros/cons:
*
* con:
* There is no guarantee that we can reestablish buffering once we've
* dropped it.
*
* We _may_ lose data if the implementation does not coordinate this with
* fflush.
*
* pro:
* An implementation is more likely to refuse to change the buffering than
* to do it in one of the ways mentioned above.
*
* The alternative is to have the application try to change buffering
* itself, which is certainly no improvement.
*
* Just in case it does not work well on a particular system, the calls to
* change buffering are all via the macro NC_BUFFERED. Some implementations
* do indeed get confused by changing setbuf on/off, and will overrun the
* buffer. So we disable this by default (there may yet be a workaround).
*/
void _nc_set_buffer(FILE *ofp, bool buffered)
{
/* optional optimization hack -- do before any output to ofp */
#if HAVE_SETVBUF || HAVE_SETBUFFER
unsigned buf_len;
char *buf_ptr;
if (getenv("NCURSES_NO_SETBUF") != 0)
return;
fflush(ofp);
if ((SP->_buffered = buffered) != 0) {
buf_len = min(LINES * (COLS + 6), 2800);
if ((buf_ptr = SP->_setbuf) == 0) {
if ((buf_ptr = malloc(buf_len)) == NULL)
return;
SP->_setbuf = buf_ptr;
/* Don't try to free this! */
}
#if !USE_SETBUF_0
else return;
#endif
} else {
#if !USE_SETBUF_0
return;
#else
buf_len = 0;
buf_ptr = 0;
#endif
}
#if HAVE_SETVBUF
#ifdef SETVBUF_REVERSED /* pre-svr3? */
(void) setvbuf(ofp, buf_ptr, buf_len, buf_len ? _IOFBF : _IOLBF);
#else
(void) setvbuf(ofp, buf_ptr, buf_len ? _IOFBF : _IOLBF, buf_len);
#endif
#elif HAVE_SETBUFFER
(void) setbuffer(ofp, buf_ptr, (int)buf_len);
#endif
#endif /* HAVE_SETVBUF || HAVE_SETBUFFER */
}
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