stdio/FreeBSD/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
  33 #if defined(LIBC_SCCS) && !defined(lint)
  34 static char sccsid[] = "@(#)fread.c     8.2 (Berkeley) 12/11/93";
  35 #endif /* LIBC_SCCS and not lint */
  36 #include <sys/cdefs.h>
  37 __FBSDID("$FreeBSD: src/lib/libc/stdio/fread.c,v 1.16 2009/07/12 13:09:43 ed Exp $");
  38
  39 #include "namespace.h"
  40 #include <stdio.h>
  41 #include <string.h>
  42 #include "un-namespace.h"
  43 #include "local.h"
  44 #include "libc_private.h"
  45
  46 /*
  47  * MT-safe version
  48  */
  49
  50 size_t
  51 fread(void * __restrict buf, size_t size, size_t count, FILE * __restrict 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 /*
  62  * The maximum amount to read to avoid integer overflow.  INT_MAX is odd,
  63  * so it make sense to make it even.  We subtract (BUFSIZ - 1) to get a
  64  * whole number of BUFSIZ chunks.
  65  */
  66 #define MAXREAD (INT_MAX - (BUFSIZ - 1))
  67
  68 /* __fread0: int sized, with size = 1 */
  69 static inline int
  70 __fread0(void * __restrict buf, int count, FILE * __restrict fp)
  71 {
  72         int resid;
  73         char *p;
  74         int r, ret;
  75
  76         resid = count;
  77         p = buf;
  78         /* first deal with anything left in buffer, plus any ungetc buffers */
  79         while (resid > (r = fp->_r)) {
  80                 (void)memcpy((void *)p, (void *)fp->_p, (size_t)r);
  81                 fp->_p += r;
  82                 /* fp->_r = 0 ... done in __srefill */
  83                 p += r;
  84                 resid -= r;
  85                 if ((ret = __srefill0(fp)) > 0)
  86                         break;
  87                 else if (ret) {
  88                         /* no more input: return partial result */
  89                         return (count - resid);
  90                 }
  91         }
  92         /*
  93          * 5980080: don't use optimization if __SMBF not set (meaning setvbuf
  94          * was called, and the buffer belongs to the user).
  95          * 6180417: but for unbuffered (__SMBF is not set), so specifically
  96          * test for it.
  97          */
  98         if ((fp->_flags & (__SMBF | __SNBF)) && resid > fp->_bf._size) {
  99                 struct __sbuf save;
 100                 size_t n;
 101
 102                 save = fp->_bf;
 103                 fp->_bf._base = (unsigned char *)p;
 104                 fp->_bf._size = resid;
 105                 while (fp->_bf._size > 0) {
 106                         if ((ret = __srefill1(fp)) != 0) {
 107                                 /* no more input: return partial result */
 108                                 resid = fp->_bf._size;
 109                                 fp->_bf = save;
 110                                 fp->_p = fp->_bf._base;
 111                                 /* fp->_r = 0;  already set in __srefill1 */
 112                                 return (count - resid);
 113                         }
 114                         fp->_bf._base += fp->_r;
 115                         fp->_bf._size -= fp->_r;
 116                 }
 117                 fp->_bf = save;
 118                 n = fp->_bf._size * ((resid - 1) / fp->_bf._size);
 119                 r = resid - n;
 120                 (void)memcpy((void *)fp->_bf._base, (void *)(p + n), (size_t)r);
 121                 fp->_p = fp->_bf._base + r;
 122                 fp->_r = 0;
 123         } else {
 124                 while (resid > (r = fp->_r)) {
 125                         (void)memcpy((void *)p, (void *)fp->_p, (size_t)r);
 126                         fp->_p += r;
 127                         /* fp->_r = 0 ... done in __srefill */
 128                         p += r;
 129                         resid -= r;
 130                         if (__srefill1(fp)) {
 131                                 /* no more input: return partial result */
 132                                 return (count - resid);
 133                         }
 134                 }
 135                 (void)memcpy((void *)p, (void *)fp->_p, resid);
 136                 fp->_r -= resid;
 137                 fp->_p += resid;
 138         }
 139         return (count);
 140 }
 141
 142 size_t
 143 __fread(void * __restrict buf, size_t size, size_t count, FILE * __restrict fp)
 144 {
 145         size_t resid;
 146         int r, ret;
 147         size_t total;
 148
 149         /*
 150          * ANSI and SUSv2 require a return value of 0 if size or count are 0.
 151          */
 152         if ((resid = count * size) == 0)
 153                 return (0);
 154         ORIENT(fp, -1);
 155         if (fp->_r < 0)
 156                 fp->_r = 0;
 157
 158         for (total = resid; resid > 0; buf += r, resid -= r) {
 159                 r = resid > INT_MAX ? MAXREAD : (int)resid;
 160                 if ((ret = __fread0(buf, r, fp)) != r) {
 161                         count = (total - resid + ret) / size;
 162                         break;
 163                 }
 164         }
 165         return (count);
 166 }