/**************************************************************************** * Copyright (c) 1998-2003,2007 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("$Id: setbuf.c,v 1.13 2007/05/12 19:04:02 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). */ NCURSES_EXPORT(void) _nc_set_buffer(FILE *ofp, bool buffered) { /* optional optimization hack -- do before any output to ofp */ #if HAVE_SETVBUF || HAVE_SETBUFFER if (SP->_buffered != buffered) { unsigned buf_len; char *buf_ptr; if (getenv("NCURSES_NO_SETBUF") != 0) return; fflush(ofp); #ifdef __DJGPP__ setmode(ofp, O_BINARY); #endif if (buffered != 0) { buf_len = min(LINES * (COLS + 6), 2800); if ((buf_ptr = SP->_setbuf) == 0) { if ((buf_ptr = typeMalloc(char, 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 SP->_buffered = buffered; } #endif /* HAVE_SETVBUF || HAVE_SETBUFFER */ }