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setvbuf.c revision 1.3 
      1 /*-
      2  * Copyright (c) 1990 The Regents of the University of California.
      3  * All rights reserved.
      4  *
      5  * This code is derived from software contributed to Berkeley by
      6  * Chris Torek.
      7  *
      8  * Redistribution and use in source and binary forms, with or without
      9  * modification, are permitted provided that the following conditions
     10  * are met:
     11  * 1. Redistributions of source code must retain the above copyright
     12  *    notice, this list of conditions and the following disclaimer.
     13  * 2. Redistributions in binary form must reproduce the above copyright
     14  *    notice, this list of conditions and the following disclaimer in the
     15  *    documentation and/or other materials provided with the distribution.
     16  * 3. All advertising materials mentioning features or use of this software
     17  *    must display the following acknowledgement:
     18  *	This product includes software developed by the University of
     19  *	California, Berkeley and its contributors.
     20  * 4. Neither the name of the University nor the names of its contributors
     21  *    may be used to endorse or promote products derived from this software
     22  *    without specific prior written permission.
     23  *
     24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     34  * SUCH DAMAGE.
     35  */
     36 
     37 #if defined(LIBC_SCCS) && !defined(lint)
     38 static char sccsid[] = "@(#)setvbuf.c	5.5 (Berkeley) 5/6/93";
     39 #endif /* LIBC_SCCS and not lint */
     40 
     41 #include <stdio.h>
     42 #include <stdlib.h>
     43 #include "local.h"
     44 
     45 /*
     46  * Set one of the three kinds of buffering, optionally including
     47  * a buffer.
     48  */
     49 setvbuf(fp, buf, mode, size)
     50 	register FILE *fp;
     51 	char *buf;
     52 	register int mode;
     53 	register size_t size;
     54 {
     55 	register int ret, flags;
     56 	size_t iosize;
     57 	int ttyflag;
     58 
     59 	/*
     60 	 * Verify arguments.  The `int' limit on `size' is due to this
     61 	 * particular implementation.  Note, buf and size are ignored
     62 	 * when setting _IONBF.
     63 	 */
     64 	if (mode != _IONBF)
     65 		if ((mode != _IOFBF && mode != _IOLBF) || (int)size < 0)
     66 			return (EOF);
     67 
     68 	/*
     69 	 * Write current buffer, if any.  Discard unread input, cancel
     70 	 * line buffering, and free old buffer if malloc()ed.
     71 	 */
     72 	ret = 0;
     73 	(void)__sflush(fp);
     74 	fp->_r = fp->_lbfsize = 0;
     75 	flags = fp->_flags;
     76 	if (flags & __SMBF)
     77 		free((void *)fp->_bf._base);
     78 	flags &= ~(__SLBF | __SNBF | __SMBF | __SOPT | __SNPT);
     79 
     80 	/* If setting unbuffered mode, skip all the hard work. */
     81 	if (mode == _IONBF)
     82 		goto nbf;
     83 
     84 	/*
     85 	 * Find optimal I/O size for seek optimization.  This also returns
     86 	 * a `tty flag' to suggest that we check isatty(fd), but we do not
     87 	 * care since our caller told us how to buffer.
     88 	 */
     89 	flags |= __swhatbuf(fp, &iosize, &ttyflag);
     90 	if (size == 0) {
     91 		buf = NULL;	/* force local allocation */
     92 		size = iosize;
     93 	}
     94 
     95 	/* Allocate buffer if needed. */
     96 	if (buf == NULL) {
     97 		if ((buf = malloc(size)) == NULL) {
     98 			/*
     99 			 * Unable to honor user's request.  We will return
    100 			 * failure, but try again with file system size.
    101 			 */
    102 			ret = EOF;
    103 			if (size != iosize) {
    104 				size = iosize;
    105 				buf = malloc(size);
    106 			}
    107 		}
    108 		if (buf == NULL) {
    109 			/* No luck; switch to unbuffered I/O. */
    110 nbf:
    111 			fp->_flags = flags | __SNBF;
    112 			fp->_w = 0;
    113 			fp->_bf._base = fp->_p = fp->_nbuf;
    114 			fp->_bf._size = 1;
    115 			return (ret);
    116 		}
    117 		flags |= __SMBF;
    118 	}
    119 
    120 	/*
    121 	 * Kill any seek optimization if the buffer is not the
    122 	 * right size.
    123 	 *
    124 	 * SHOULD WE ALLOW MULTIPLES HERE (i.e., ok iff (size % iosize) == 0)?
    125 	 */
    126 	if (size != iosize)
    127 		flags |= __SNPT;
    128 
    129 	/*
    130 	 * Fix up the FILE fields, and set __cleanup for output flush on
    131 	 * exit (since we are buffered in some way).  If in r/w mode, go
    132 	 * to the intermediate state, so that everyone has to call
    133 	 * __srefill or __swsetup on the first operation -- it is more
    134 	 * trouble than it is worth to set things up correctly here.
    135 	 */
    136 	if (mode == _IOLBF)
    137 		flags |= __SLBF;
    138 	if (flags & __SRW)
    139 		flags &= ~(__SRD | __SWR);
    140 	fp->_w = 0;
    141 	fp->_flags = flags;
    142 	fp->_bf._base = fp->_p = (unsigned char *)buf;
    143 	fp->_bf._size = size;
    144 	fp->_lbfsize = 0;
    145 	__cleanup = _cleanup;
    146 
    147 	return (ret);
    148 }
    149