usr/src/lib/libbc/libc/stdio/common/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, Version 1.0 only
   6  * (the "License").  You may not use this file except in compliance
   7  * with the License.
   8  *
   9  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
  10  * or http://www.opensolaris.org/os/licensing.
  11  * See the License for the specific language governing permissions
  12  * and limitations under the License.
  13  *
  14  * When distributing Covered Code, include this CDDL HEADER in each
  15  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  16  * If applicable, add the following below this CDDL HEADER, with the
  17  * fields enclosed by brackets "[]" replaced with your own identifying
  18  * information: Portions Copyright [yyyy] [name of copyright owner]
  19  *
  20  * CDDL HEADER END
  21  */
  22 /*
  23  * Copyright 1986 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27 /*      Copyright (c) 1984 AT&T */
  28 /*        All Rights Reserved   */
  29
  30 #pragma ident   "%Z%%M% %I%     %E% SMI"
  31
  32 /*LINTLIBRARY*/
  33 /*
  34  * This version reads directly from the buffer rather than looping on getc.
  35  * Ptr args aren't checked for NULL because the program would be a
  36  * catastrophic mess anyway.  Better to abort than just to return NULL.
  37  */
  38 #include <stdio.h>
  39 #include "stdiom.h"
  40 #include <memory.h>
  41
  42 #define MIN(x, y)       (x < y ? x : y)
  43
  44 extern int _filbuf();
  45
  46 int
  47 fread(char *ptr, int size, int count, FILE *iop)
  48 {
  49         unsigned int nleft;
  50         int n;
  51
  52         if (size <= 0 || count <= 0) return 0;
  53         nleft = count * size;
  54
  55         /* Put characters in the buffer */
  56         /* note that the meaning of n when just starting this loop is
  57            irrelevant.  It is defined in the loop */
  58         for ( ; ; ) {
  59                 if (iop->_cnt <= 0) { /* empty buffer */
  60                         if (_filbuf(iop) == EOF)
  61                                 return (count - (nleft + size - 1)/size);
  62                         iop->_ptr--;
  63                         iop->_cnt++;
  64                 }
  65                 n = MIN(nleft, iop->_cnt);
  66                 ptr = memcpy(ptr, (char *) iop->_ptr, n) + n;
  67                 iop->_cnt -= n;
  68                 iop->_ptr += n;
  69                 _BUFSYNC(iop);
  70                 if ((nleft -= n) == 0)
  71                         return (count);
  72         }
  73 }