stdio/fopen.c

   1 /* Copyright (C) 1991, 1992, 1993, 1996 Free Software Foundation, Inc.
   2 This file is part of the GNU C Library.
   3
   4 The GNU C Library is free software; you can redistribute it and/or
   5 modify it under the terms of the GNU Library General Public License as
   6 published by the Free Software Foundation; either version 2 of the
   7 License, or (at your option) any later version.
   8
   9 The GNU C Library is distributed in the hope that it will be useful,
  10 but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12 Library General Public License for more details.
  13
  14 You should have received a copy of the GNU Library General Public
  15 License along with the GNU C Library; see the file COPYING.LIB.  If
  16 not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  17 Cambridge, MA 02139, USA.  */
  18
  19 #include <ctype.h>
  20 #include <errno.h>
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24
  25
  26 #define badmode()       return ((__set_errno (EINVAL)), 0)
  27
  28 /* Dissect the given mode string into an __io_mode.  */
  29 int
  30 __getmode (const char *mode, __io_mode *mptr)
  31 {
  32   register unsigned char i;
  33
  34   if (mode == NULL)
  35     badmode ();
  36
  37   memset ((void *) mptr, 0, sizeof (*mptr));
  38
  39   switch (*mode)
  40     {
  41     case 'a':
  42       mptr->__write = mptr->__create = mptr->__append = 1;
  43       break;
  44     case 'w':
  45       mptr->__write = mptr->__create = mptr->__truncate = 1;
  46       break;
  47     case 'r':
  48       mptr->__read = 1;
  49       break;
  50     default:
  51       badmode ();
  52     }
  53
  54   for (i = 1; i < 3; ++i)
  55     {
  56       ++mode;
  57       if (*mode == '\0')
  58         break;
  59       switch (*mode)
  60         {
  61         case '+':
  62           mptr->__read = mptr->__write = 1;
  63           break;
  64         case 'b':
  65           mptr->__binary = 1;
  66           break;
  67         }
  68     }
  69
  70   if (!mptr->__read && !mptr->__write)
  71     badmode ();
  72
  73   mptr->__exclusive = *mode == 'x';
  74
  75   return 1;
  76 }
  77 \f
  78 /* Open a new stream on the given file.  */
  79 FILE *
  80 fopen (filename, mode)
  81      const char *filename;
  82      const char *mode;
  83 {
  84   FILE *stream;
  85   __io_mode m;
  86
  87   if (filename == NULL)
  88     {
  89       __set_errno (EINVAL);
  90       return NULL;
  91     }
  92
  93   if (!__getmode (mode, &m))
  94     return NULL;
  95
  96   stream = __newstream ();
  97   if (stream == NULL)
  98     return NULL;
  99
 100   if (__stdio_open (filename, m, &stream->__cookie))
 101     {
 102       int save = errno;
 103       (void) fclose (stream);
 104       __set_errno (save);
 105       return NULL;
 106     }
 107
 108   stream->__mode = m;
 109
 110   return stream;
 111 }