1/**************************************************************************** 2 * Copyright (c) 1998-2003,2007 Free Software Foundation, Inc. * 3 * * 4 * Permission is hereby granted, free of charge, to any person obtaining a * 5 * copy of this software and associated documentation files (the * 6 * "Software"), to deal in the Software without restriction, including * 7 * without limitation the rights to use, copy, modify, merge, publish, * 8 * distribute, distribute with modifications, sublicense, and/or sell * 9 * copies of the Software, and to permit persons to whom the Software is * 10 * furnished to do so, subject to the following conditions: * 11 * * 12 * The above copyright notice and this permission notice shall be included * 13 * in all copies or substantial portions of the Software. * 14 * * 15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS * 16 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF * 17 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. * 18 * IN NO EVENT SHALL THE ABOVE COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, * 19 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR * 20 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR * 21 * THE USE OR OTHER DEALINGS IN THE SOFTWARE. * 22 * * 23 * Except as contained in this notice, the name(s) of the above copyright * 24 * holders shall not be used in advertising or otherwise to promote the * 25 * sale, use or other dealings in this Software without prior written * 26 * authorization. * 27 ****************************************************************************/ 28 29/**************************************************************************** 30 * Author: Zeyd M. Ben-Halim <zmbenhal@netcom.com> 1992,1995 * 31 * and: Eric S. Raymond <esr@snark.thyrsus.com> * 32 ****************************************************************************/ 33 34/* 35** setbuf.c 36** 37** Support for set_term(), reset_shell_mode(), reset_prog_mode(). 38** 39*/ 40 41#include <curses.priv.h> 42 43MODULE_ID("$Id: setbuf.c,v 1.13 2007/05/12 19:04:02 tom Exp $") 44 45/* 46 * If the output file descriptor is connected to a tty (the typical case) it 47 * will probably be line-buffered. Keith Bostic pointed out that we don't want 48 * this; it hoses people running over networks by forcing out a bunch of small 49 * packets instead of one big one, so screen updates on ptys look jerky. 50 * Restore block buffering to prevent this minor lossage. 51 * 52 * The buffer size is a compromise. Ideally we'd like a buffer that can hold 53 * the maximum possible update size (the whole screen plus cup commands to 54 * change lines as it's painted). On a 66-line xterm this can become 55 * excessive. So we min it with the amount of data we think we can get through 56 * two Ethernet packets (maximum packet size - 100 for TCP/IP overhead). 57 * 58 * Why two ethernet packets? It used to be one, on the theory that said 59 * packets define the maximum size of atomic update. But that's less than the 60 * 2000 chars on a 25 x 80 screen, and we don't want local updates to flicker 61 * either. Two packet lengths will handle up to a 35 x 80 screen. 62 * 63 * The magic '6' is the estimated length of the end-of-line cup sequence to go 64 * to the next line. It's generous. We used to mess with the buffering in 65 * init_mvcur() after cost computation, but that lost the sequences emitted by 66 * init_acs() in setupscreen(). 67 * 68 * "The setvbuf function may be used only after the stream pointed to by stream 69 * has been associated with an open file and before any other operation is 70 * performed on the stream." (ISO 7.9.5.6.) 71 * 72 * Grrrr... 73 * 74 * On a lighter note, many implementations do in fact allow an application to 75 * reset the buffering after it has been written to. We try to do this because 76 * otherwise we leave stdout in buffered mode after endwin() is called. (This 77 * also happens with SVr4 curses). 78 * 79 * There are pros/cons: 80 * 81 * con: 82 * There is no guarantee that we can reestablish buffering once we've 83 * dropped it. 84 * 85 * We _may_ lose data if the implementation does not coordinate this with 86 * fflush. 87 * 88 * pro: 89 * An implementation is more likely to refuse to change the buffering than 90 * to do it in one of the ways mentioned above. 91 * 92 * The alternative is to have the application try to change buffering 93 * itself, which is certainly no improvement. 94 * 95 * Just in case it does not work well on a particular system, the calls to 96 * change buffering are all via the macro NC_BUFFERED. Some implementations 97 * do indeed get confused by changing setbuf on/off, and will overrun the 98 * buffer. So we disable this by default (there may yet be a workaround). 99 */ 100NCURSES_EXPORT(void) 101_nc_set_buffer(FILE *ofp, bool buffered) 102{ 103 /* optional optimization hack -- do before any output to ofp */ 104#if HAVE_SETVBUF || HAVE_SETBUFFER 105 if (SP->_buffered != buffered) { 106 unsigned buf_len; 107 char *buf_ptr; 108 109 if (getenv("NCURSES_NO_SETBUF") != 0) 110 return; 111 112 fflush(ofp); 113#ifdef __DJGPP__ 114 setmode(ofp, O_BINARY); 115#endif 116 if (buffered != 0) { 117 buf_len = min(LINES * (COLS + 6), 2800); 118 if ((buf_ptr = SP->_setbuf) == 0) { 119 if ((buf_ptr = typeMalloc(char, buf_len)) == NULL) 120 return; 121 SP->_setbuf = buf_ptr; 122 /* Don't try to free this! */ 123 } 124#if !USE_SETBUF_0 125 else 126 return; 127#endif 128 } else { 129#if !USE_SETBUF_0 130 return; 131#else 132 buf_len = 0; 133 buf_ptr = 0; 134#endif 135 } 136 137#if HAVE_SETVBUF 138#ifdef SETVBUF_REVERSED /* pre-svr3? */ 139 (void) setvbuf(ofp, buf_ptr, buf_len, buf_len ? _IOFBF : _IOLBF); 140#else 141 (void) setvbuf(ofp, buf_ptr, buf_len ? _IOFBF : _IOLBF, buf_len); 142#endif 143#elif HAVE_SETBUFFER 144 (void) setbuffer(ofp, buf_ptr, (int) buf_len); 145#endif 146 147 SP->_buffered = buffered; 148 } 149#endif /* HAVE_SETVBUF || HAVE_SETBUFFER */ 150} 151