lib/libc/stdio/fread.c

   1 /*-
   2  * Copyright (c) 1990, 1993
   3  *      The Regents of the University of California.  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  * 4. Neither the name of the University nor the names of its contributors
  17  *    may be used to endorse or promote products derived from this software
  18  *    without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  *
  32  * @(#)fread.c  8.2 (Berkeley) 12/11/93
  33  * $FreeBSD: src/lib/libc/stdio/fread.c,v 1.15 2008/12/01 14:33:34 ru Exp $
  34  * $DragonFly: src/lib/libc/stdio/fread.c,v 1.8 2005/12/20 00:21:53 davidxu Exp $
  35  */
  36
  37 #include "namespace.h"
  38 #include <stdio.h>
  39 #include <string.h>
  40 #include "un-namespace.h"
  41 #include "local.h"
  42 #include "libc_private.h"
  43 #include "priv_stdio.h"
  44
  45 /*
  46  * MT-safe version
  47  */
  48
  49 size_t
  50 fread(void * __restrict buf, size_t size, size_t count, FILE * __restrict fp)
  51 {
  52         size_t ret;
  53
  54         FLOCKFILE(fp);
  55         ret = __fread(buf, size, count, fp);
  56         FUNLOCKFILE(fp);
  57         return (ret);
  58 }
  59
  60 size_t
  61 __fread(void * __restrict buf, size_t size, size_t count, FILE * __restrict fp)
  62 {
  63         size_t resid;
  64         char *p;
  65         int r;
  66         size_t total;
  67
  68         /*
  69          * The ANSI standard requires a return value of 0 for a count
  70          * or a size of 0.  Peculiarily, it imposes no such requirements
  71          * on fwrite; it only requires fread to be broken.
  72          */
  73         if ((resid = count * size) == 0)
  74                 return (0);
  75         ORIENT(fp, -1);
  76         if (fp->pub._r < 0)
  77                 fp->pub._r = 0;
  78         total = resid;
  79         p = buf;
  80         while (resid > (r = fp->pub._r)) {
  81                 memcpy((void *)p, (void *)fp->pub._p, (size_t)r);
  82                 fp->pub._p += r;
  83                 /* fp->pub._r = 0 ... done in __srefill */
  84                 p += r;
  85                 resid -= r;
  86                 if (__srefill(fp)) {
  87                         /* no more input: return partial result */
  88                         return ((total - resid) / size);
  89                 }
  90         }
  91         memcpy((void *)p, (void *)fp->pub._p, resid);
  92         fp->pub._r -= resid;
  93         fp->pub._p += resid;
  94         return (count);
  95 }