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setvbuf.c revision 1.8 
      1 /*	$NetBSD: setvbuf.c,v 1.8 1996/03/29 23:29:22 jtc 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 #if defined(LIBC_SCCS) && !defined(lint)
     40 #if 0
     41 static char sccsid[] = "@(#)setvbuf.c	8.2 (Berkeley) 11/16/93";
     42 #endif
     43 static char rcsid[] = "$NetBSD: setvbuf.c,v 1.8 1996/03/29 23:29:22 jtc Exp $";
     44 #endif /* LIBC_SCCS and not lint */
     45 
     46 #include <stdio.h>
     47 #include <stdlib.h>
     48 #include "local.h"
     49 
     50 /*
     51  * Set one of the three kinds of buffering, optionally including
     52  * a buffer.
     53  */
     54 int
     55 setvbuf(fp, buf, mode, size)
     56 	register FILE *fp;
     57 	char *buf;
     58 	register int mode;
     59 	register size_t size;
     60 {
     61 	register int ret, flags;
     62 	size_t iosize;
     63 	int ttyflag;
     64 
     65 	/*
     66 	 * Verify arguments.  The `int' limit on `size' is due to this
     67 	 * particular implementation.  Note, buf and size are ignored
     68 	 * when setting _IONBF.
     69 	 */
     70 	if (mode != _IONBF)
     71 		if ((mode != _IOFBF && mode != _IOLBF) || (int)size < 0)
     72 			return (EOF);
     73 
     74 	/*
     75 	 * Write current buffer, if any.  Discard unread input (including
     76 	 * ungetc data), cancel line buffering, and free old buffer if
     77 	 * malloc()ed.  We also clear any eof condition, as if this were
     78 	 * a seek.
     79 	 */
     80 	ret = 0;
     81 	(void)__sflush(fp);
     82 	if (HASUB(fp))
     83 		FREEUB(fp);
     84 	fp->_r = fp->_lbfsize = 0;
     85 	flags = fp->_flags;
     86 	if (flags & __SMBF)
     87 		free((void *)fp->_bf._base);
     88 	flags &= ~(__SLBF | __SNBF | __SMBF | __SOPT | __SNPT | __SEOF);
     89 
     90 	/* If setting unbuffered mode, skip all the hard work. */
     91 	if (mode == _IONBF)
     92 		goto nbf;
     93 
     94 	/*
     95 	 * Find optimal I/O size for seek optimization.  This also returns
     96 	 * a `tty flag' to suggest that we check isatty(fd), but we do not
     97 	 * care since our caller told us how to buffer.
     98 	 */
     99 	flags |= __swhatbuf(fp, &iosize, &ttyflag);
    100 	if (size == 0) {
    101 		buf = NULL;	/* force local allocation */
    102 		size = iosize;
    103 	}
    104 
    105 	/* Allocate buffer if needed. */
    106 	if (buf == NULL) {
    107 		if ((buf = malloc(size)) == NULL) {
    108 			/*
    109 			 * Unable to honor user's request.  We will return
    110 			 * failure, but try again with file system size.
    111 			 */
    112 			ret = EOF;
    113 			if (size != iosize) {
    114 				size = iosize;
    115 				buf = malloc(size);
    116 			}
    117 		}
    118 		if (buf == NULL) {
    119 			/* No luck; switch to unbuffered I/O. */
    120 nbf:
    121 			fp->_flags = flags | __SNBF;
    122 			fp->_w = 0;
    123 			fp->_bf._base = fp->_p = fp->_nbuf;
    124 			fp->_bf._size = 1;
    125 			return (ret);
    126 		}
    127 		flags |= __SMBF;
    128 	}
    129 
    130 	/*
    131 	 * Kill any seek optimization if the buffer is not the
    132 	 * right size.
    133 	 *
    134 	 * SHOULD WE ALLOW MULTIPLES HERE (i.e., ok iff (size % iosize) == 0)?
    135 	 */
    136 	if (size != iosize)
    137 		flags |= __SNPT;
    138 
    139 	/*
    140 	 * Fix up the FILE fields, and set __cleanup for output flush on
    141 	 * exit (since we are buffered in some way).
    142 	 */
    143 	if (mode == _IOLBF)
    144 		flags |= __SLBF;
    145 	fp->_flags = flags;
    146 	fp->_bf._base = fp->_p = (unsigned char *)buf;
    147 	fp->_bf._size = size;
    148 	/* fp->_lbfsize is still 0 */
    149 	if (flags & __SWR) {
    150 		/*
    151 		 * Begin or continue writing: see __swsetup().  Note
    152 		 * that __SNBF is impossible (it was handled earlier).
    153 		 */
    154 		if (flags & __SLBF) {
    155 			fp->_w = 0;
    156 			fp->_lbfsize = -fp->_bf._size;
    157 		} else
    158 			fp->_w = size;
    159 	} else {
    160 		/* begin/continue reading, or stay in intermediate state */
    161 		fp->_w = 0;
    162 	}
    163 	__cleanup = _cleanup;
    164 
    165 	return (ret);
    166 }
    167