lib/libc/stdio/setvbuf.c

   1 /*      $NetBSD: setvbuf.c,v 1.17 2003/08/07 16:43:31 agc 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. Neither the name of the University nor the names of its contributors
  19  *    may be used to endorse or promote products derived from this software
  20  *    without specific prior written permission.
  21  *
  22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  */
  34
  35 #include <sys/cdefs.h>
  36 #if defined(LIBC_SCCS) && !defined(lint)
  37 #if 0
  38 static char sccsid[] = "@(#)setvbuf.c   8.2 (Berkeley) 11/16/93";
  39 #else
  40 __RCSID("$NetBSD: setvbuf.c,v 1.17 2003/08/07 16:43:31 agc Exp $");
  41 #endif
  42 #endif /* LIBC_SCCS and not lint */
  43
  44 #include <assert.h>
  45 #include <errno.h>
  46 #include <stdio.h>
  47 #include <stdlib.h>
  48 #include <wchar.h>
  49 #include "reentrant.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         FILE *fp;
  59         char *buf;
  60         int mode;
  61         size_t size;
  62 {
  63         int ret, flags;
  64         size_t iosize;
  65         int ttyflag;
  66
  67         _DIAGASSERT(fp != NULL);
  68         /* buf may be NULL */
  69
  70         /*
  71          * Verify arguments.  The `int' limit on `size' is due to this
  72          * particular implementation.  Note, buf and size are ignored
  73          * when setting _IONBF.
  74          */
  75         if (mode != _IONBF)
  76                 if ((mode != _IOFBF && mode != _IOLBF) || (int)size < 0)
  77                         return (-1);
  78
  79         FLOCKFILE(fp);
  80         /*
  81          * Write current buffer, if any.  Discard unread input (including
  82          * ungetc data), cancel line buffering, and free old buffer if
  83          * malloc()ed.  We also clear any eof condition, as if this were
  84          * a seek.
  85          */
  86         ret = 0;
  87         (void)__sflush(fp);
  88         if (HASUB(fp))
  89                 FREEUB(fp);
  90         WCIO_FREE(fp);
  91         fp->_r = fp->_lbfsize = 0;
  92         flags = fp->_flags;
  93         if (flags & __SMBF)
  94                 free((void *)fp->_bf._base);
  95         flags &= ~(__SLBF | __SNBF | __SMBF | __SOPT | __SNPT | __SEOF);
  96
  97         /* If setting unbuffered mode, skip all the hard work. */
  98         if (mode == _IONBF)
  99                 goto nbf;
 100
 101         /*
 102          * Find optimal I/O size for seek optimization.  This also returns
 103          * a `tty flag' to suggest that we check isatty(fd), but we do not
 104          * care since our caller told us how to buffer.
 105          */
 106         flags |= __swhatbuf(fp, &iosize, &ttyflag);
 107         if (size == 0) {
 108                 buf = NULL;     /* force local allocation */
 109                 size = iosize;
 110         }
 111
 112         /* Allocate buffer if needed. */
 113         if (buf == NULL) {
 114                 if ((buf = malloc(size)) == NULL) {
 115                         /*
 116                          * Unable to honor user's request.  We will return
 117                          * failure, but try again with file system size.
 118                          */
 119                         ret = -1;
 120                         if (size != iosize) {
 121                                 size = iosize;
 122                                 buf = malloc(size);
 123                         }
 124                 }
 125                 if (buf == NULL) {
 126                         /* No luck; switch to unbuffered I/O. */
 127 nbf:
 128                         fp->_flags = flags | __SNBF;
 129                         fp->_w = 0;
 130                         fp->_bf._base = fp->_p = fp->_nbuf;
 131                         fp->_bf._size = 1;
 132                         FUNLOCKFILE(fp);
 133                         return (ret);
 134                 }
 135                 flags |= __SMBF;
 136         }
 137
 138         /*
 139          * Kill any seek optimization if the buffer is not the
 140          * right size.
 141          *
 142          * SHOULD WE ALLOW MULTIPLES HERE (i.e., ok iff (size % iosize) == 0)?
 143          */
 144         if (size != iosize)
 145                 flags |= __SNPT;
 146
 147         /*
 148          * Fix up the FILE fields, and set __cleanup for output flush on
 149          * exit (since we are buffered in some way).
 150          */
 151         if (mode == _IOLBF)
 152                 flags |= __SLBF;
 153         fp->_flags = flags;
 154         fp->_bf._base = fp->_p = (unsigned char *)buf;
 155         fp->_bf._size = size;
 156         /* fp->_lbfsize is still 0 */
 157         if (flags & __SWR) {
 158                 /*
 159                  * Begin or continue writing: see __swsetup().  Note
 160                  * that __SNBF is impossible (it was handled earlier).
 161                  */
 162                 if (flags & __SLBF) {
 163                         fp->_w = 0;
 164                         fp->_lbfsize = -fp->_bf._size;
 165                 } else
 166                         fp->_w = size;
 167         } else {
 168                 /* begin/continue reading, or stay in intermediate state */
 169                 fp->_w = 0;
 170         }
 171         __cleanup = _cleanup;
 172
 173         FUNLOCKFILE(fp);
 174         return (ret);
 175 }