usr/src/lib/libc/port/stdio/fread.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21
  22 /*
  23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27 /*      Copyright (c) 1988 AT&T */
  28 /*        All Rights Reserved   */
  29
  30 #pragma ident   "%Z%%M% %I%     %E% SMI"
  31
  32 #include "lint.h"
  33 #include "file64.h"
  34 #include "mtlib.h"
  35 #include <stdio.h>
  36 #include <stddef.h>
  37 #include <values.h>
  38 #include <memory.h>
  39 #include <thread.h>
  40 #include <synch.h>
  41 #include <errno.h>
  42 #include <sys/types.h>
  43 #include "stdiom.h"
  44 #include "mse.h"
  45
  46 size_t
  47 fread(void *ptr, size_t size, size_t count, FILE *iop)
  48 {
  49         ssize_t s;
  50         int c;
  51         char *dptr = (char *)ptr;
  52         rmutex_t *lk;
  53
  54         FLOCKFILE(lk, iop);
  55
  56         _SET_ORIENTATION_BYTE(iop);
  57
  58         /* is it a readable stream */
  59         if (!(iop->_flag & (_IOREAD | _IORW))) {
  60                 iop->_flag |= _IOERR;
  61                 errno = EBADF;
  62                 FUNLOCKFILE(lk);
  63                 return (0);
  64         }
  65
  66         if (iop->_flag & _IOEOF) {
  67                 FUNLOCKFILE(lk);
  68                 return (0);
  69         }
  70
  71         /* These checks are here to avoid the multiply */
  72         if (count == 1)
  73                 s = size;
  74         else if (size == 1)
  75                 s = count;
  76         else
  77                 s = size * count;
  78
  79         while (s > 0) {
  80                 if (iop->_cnt < s) {
  81                         if (iop->_cnt > 0) {
  82                                 (void) memcpy((void*)dptr, iop->_ptr,
  83                                     iop->_cnt);
  84                                 dptr += iop->_cnt;
  85                                 s -= iop->_cnt;
  86                         }
  87                         /*
  88                          * filbuf clobbers _cnt & _ptr,
  89                          * so don't waste time setting them.
  90                          */
  91                         if ((c = __filbuf(iop)) == EOF)
  92                                 break;
  93                         *dptr++ = (char)c;
  94                         s--;
  95                 }
  96                 if (iop->_cnt >= s) {
  97                         char *tmp = (char *)iop->_ptr;
  98                         switch (s) {
  99                         case 8:
 100                                 *dptr++ = *tmp++;
 101                                 /*FALLTHRU*/
 102                         case 7:
 103                                 *dptr++ = *tmp++;
 104                                 /*FALLTHRU*/
 105                         case 6:
 106                                 *dptr++ = *tmp++;
 107                                 /*FALLTHRU*/
 108                         case 5:
 109                                 *dptr++ = *tmp++;
 110                                 /*FALLTHRU*/
 111                         case 4:
 112                                 *dptr++ = *tmp++;
 113                                 /*FALLTHRU*/
 114                         case 3:
 115                                 *dptr++ = *tmp++;
 116                                 /*FALLTHRU*/
 117                         case 2:
 118                                 *dptr++ = *tmp++;
 119                                 /*FALLTHRU*/
 120                         case 1:
 121                                 *dptr++ = *tmp++;
 122                                 break;
 123                         default:
 124                                 (void) memcpy((void*)dptr, iop->_ptr,
 125                                     (size_t)s);
 126                         }
 127                         iop->_ptr += s;
 128                         iop->_cnt -= s;
 129                         FUNLOCKFILE(lk);
 130                         return (count);
 131                 }
 132         }
 133         FUNLOCKFILE(lk);
 134         return (size != 0 ? count - ((s + size - 1) / size) : 0);
 135 }