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  * 3. All advertising materials mentioning features or use of this software
  17  *    must display the following acknowledgement:
  18  *      This product includes software developed by the University of
  19  *      California, Berkeley and its contributors.
  20  * 4. Neither the name of the University nor the names of its contributors
  21  *    may be used to endorse or promote products derived from this software
  22  *    without specific prior written permission.
  23  *
  24  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  25  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  26  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  27  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  28  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  29  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  30  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  31  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  32  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  33  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  34  * SUCH DAMAGE.
  35  *
  36  * @(#)fread.c  8.2 (Berkeley) 12/11/93
  37  * $FreeBSD: src/lib/libc/stdio/fread.c,v 1.7 1999/08/28 00:01:04 peter Exp $
  38  * $DragonFly: src/lib/libc/stdio/fread.c,v 1.8 2005/12/20 00:21:53 davidxu Exp $
  39  */
  40
  41 #include "namespace.h"
  42 #include <stdio.h>
  43 #include <string.h>
  44 #include "un-namespace.h"
  45
  46 #include "local.h"
  47 #include "libc_private.h"
  48 #include "priv_stdio.h"
  49
  50 size_t
  51 fread(void *buf, size_t size, size_t count, FILE *fp)
  52 {
  53         size_t ret;
  54
  55         FLOCKFILE(fp);
  56         ret = __fread(buf, size, count, fp);
  57         FUNLOCKFILE(fp);
  58         return (ret);
  59 }
  60
  61 size_t
  62 __fread(void *buf, size_t size, size_t count, FILE *fp)
  63 {
  64         size_t resid;
  65         char *p;
  66         int r;
  67         size_t total;
  68
  69         /*
  70          * The ANSI standard requires a return value of 0 for a count
  71          * or a size of 0.  Peculiarily, it imposes no such requirements
  72          * on fwrite; it only requires fread to be broken.
  73          */
  74         if ((resid = count * size) == 0)
  75                 return (0);
  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->_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 }