lib/libc/stdio/fread.c

   1 /*      $NetBSD: fread.c,v 1.22 2012/03/15 18:22:30 christos 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[] = "@(#)fread.c     8.2 (Berkeley) 12/11/93";
  39 #else
  40 __RCSID("$NetBSD: fread.c,v 1.22 2012/03/15 18:22:30 christos 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 <string.h>
  48 #include "reentrant.h"
  49 #include "local.h"
  50
  51 size_t
  52 fread(void *buf, size_t size, size_t count, FILE *fp)
  53 {
  54         size_t resid;
  55         char *p;
  56         int r;
  57         size_t total;
  58
  59         _DIAGASSERT(fp != NULL);
  60         /*
  61          * The ANSI standard requires a return value of 0 for a count
  62          * or a size of 0.  Whilst ANSI imposes no such requirements on
  63          * fwrite, the SUSv2 does.
  64          */
  65         if ((resid = count * size) == 0)
  66                 return 0;
  67
  68         _DIAGASSERT(buf != NULL);
  69
  70         FLOCKFILE(fp);
  71         if (fp->_r < 0)
  72                 fp->_r = 0;
  73         total = resid;
  74         p = buf;
  75         while (resid > (size_t)(r = fp->_r)) {
  76                 (void)memcpy(p, fp->_p, (size_t)r);
  77                 fp->_p += r;
  78                 /* fp->_r = 0 ... done in __srefill */
  79                 p += r;
  80                 resid -= r;
  81                 if (__srefill(fp)) {
  82                         /* no more input: return partial result */
  83                         FUNLOCKFILE(fp);
  84                         return (total - resid) / size;
  85                 }
  86         }
  87         (void)memcpy(p, fp->_p, resid);
  88
  89         _DIAGASSERT(__type_fit(int, fp->_r - resid));
  90         fp->_r -= (int)resid;
  91         fp->_p += resid;
  92         FUNLOCKFILE(fp);
  93         return count;
  94 }