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setvbuf.c revision 1.10 
      1 /*	$NetBSD: setvbuf.c,v 1.10 1997/12/19 14:08:43 kleink Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1990, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * This code is derived from software contributed to Berkeley by
      8  * Chris Torek.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. All advertising materials mentioning features or use of this software
     19  *    must display the following acknowledgement:
     20  *	This product includes software developed by the University of
     21  *	California, Berkeley and its contributors.
     22  * 4. Neither the name of the University nor the names of its contributors
     23  *    may be used to endorse or promote products derived from this software
     24  *    without specific prior written permission.
     25  *
     26  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     27  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     28  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     29  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     30  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     31  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     32  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     33  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     34  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     35  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     36  * SUCH DAMAGE.
     37  */
     38 
     39 #include <sys/cdefs.h>
     40 #if defined(LIBC_SCCS) && !defined(lint)
     41 #if 0
     42 static char sccsid[] = "@(#)setvbuf.c	8.2 (Berkeley) 11/16/93";
     43 #else
     44 __RCSID("$NetBSD: setvbuf.c,v 1.10 1997/12/19 14:08:43 kleink Exp $");
     45 #endif
     46 #endif /* LIBC_SCCS and not lint */
     47 
     48 #include <stdio.h>
     49 #include <stdlib.h>
     50 #include "local.h"
     51 
     52 /*
     53  * Set one of the three kinds of buffering, optionally including
     54  * a buffer.
     55  */
     56 int
     57 setvbuf(fp, buf, mode, size)
     58 	register FILE *fp;
     59 	char *buf;
     60 	register int mode;
     61 	register size_t size;
     62 {
     63 	register int ret, flags;
     64 	size_t iosize;
     65 	int ttyflag;
     66 
     67 	/*
     68 	 * Verify arguments.  The `int' limit on `size' is due to this
     69 	 * particular implementation.  Note, buf and size are ignored
     70 	 * when setting _IONBF.
     71 	 */
     72 	if (mode != _IONBF)
     73 		if ((mode != _IOFBF && mode != _IOLBF) || (int)size < 0)
     74 			return (-1);
     75 
     76 	/*
     77 	 * Write current buffer, if any.  Discard unread input (including
     78 	 * ungetc data), cancel line buffering, and free old buffer if
     79 	 * malloc()ed.  We also clear any eof condition, as if this were
     80 	 * a seek.
     81 	 */
     82 	ret = 0;
     83 	(void)__sflush(fp);
     84 	if (HASUB(fp))
     85 		FREEUB(fp);
     86 	fp->_r = fp->_lbfsize = 0;
     87 	flags = fp->_flags;
     88 	if (flags & __SMBF)
     89 		free((void *)fp->_bf._base);
     90 	flags &= ~(__SLBF | __SNBF | __SMBF | __SOPT | __SNPT | __SEOF);
     91 
     92 	/* If setting unbuffered mode, skip all the hard work. */
     93 	if (mode == _IONBF)
     94 		goto nbf;
     95 
     96 	/*
     97 	 * Find optimal I/O size for seek optimization.  This also returns
     98 	 * a `tty flag' to suggest that we check isatty(fd), but we do not
     99 	 * care since our caller told us how to buffer.
    100 	 */
    101 	flags |= __swhatbuf(fp, &iosize, &ttyflag);
    102 	if (size == 0) {
    103 		buf = NULL;	/* force local allocation */
    104 		size = iosize;
    105 	}
    106 
    107 	/* Allocate buffer if needed. */
    108 	if (buf == NULL) {
    109 		if ((buf = malloc(size)) == NULL) {
    110 			/*
    111 			 * Unable to honor user's request.  We will return
    112 			 * failure, but try again with file system size.
    113 			 */
    114 			ret = -1;
    115 			if (size != iosize) {
    116 				size = iosize;
    117 				buf = malloc(size);
    118 			}
    119 		}
    120 		if (buf == NULL) {
    121 			/* No luck; switch to unbuffered I/O. */
    122 nbf:
    123 			fp->_flags = flags | __SNBF;
    124 			fp->_w = 0;
    125 			fp->_bf._base = fp->_p = fp->_nbuf;
    126 			fp->_bf._size = 1;
    127 			return (ret);
    128 		}
    129 		flags |= __SMBF;
    130 	}
    131 
    132 	/*
    133 	 * Kill any seek optimization if the buffer is not the
    134 	 * right size.
    135 	 *
    136 	 * SHOULD WE ALLOW MULTIPLES HERE (i.e., ok iff (size % iosize) == 0)?
    137 	 */
    138 	if (size != iosize)
    139 		flags |= __SNPT;
    140 
    141 	/*
    142 	 * Fix up the FILE fields, and set __cleanup for output flush on
    143 	 * exit (since we are buffered in some way).
    144 	 */
    145 	if (mode == _IOLBF)
    146 		flags |= __SLBF;
    147 	fp->_flags = flags;
    148 	fp->_bf._base = fp->_p = (unsigned char *)buf;
    149 	fp->_bf._size = size;
    150 	/* fp->_lbfsize is still 0 */
    151 	if (flags & __SWR) {
    152 		/*
    153 		 * Begin or continue writing: see __swsetup().  Note
    154 		 * that __SNBF is impossible (it was handled earlier).
    155 		 */
    156 		if (flags & __SLBF) {
    157 			fp->_w = 0;
    158 			fp->_lbfsize = -fp->_bf._size;
    159 		} else
    160 			fp->_w = size;
    161 	} else {
    162 		/* begin/continue reading, or stay in intermediate state */
    163 		fp->_w = 0;
    164 	}
    165 	__cleanup = _cleanup;
    166 
    167 	return (ret);
    168 }
    169