aboutsummaryrefslogtreecommitdiff
path: root/newlib/libc/stdio/fopen.c
blob: e6b044557f7aed9c82f781002c476ce1414239c9 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
/*
 * Copyright (c) 1990 The Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted
 * provided that the above copyright notice and this paragraph are
 * duplicated in all such forms and that any documentation,
 * advertising materials, and other materials related to such
 * distribution and use acknowledge that the software was developed
 * by the University of California, Berkeley.  The name of the
 * University may not be used to endorse or promote products derived
 * from this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

/*
FUNCTION
<<fopen>>---open a file

INDEX
	fopen
INDEX
	_fopen_r

SYNOPSIS
	#include <stdio.h>
	FILE *fopen(const char *<[file]>, const char *<[mode]>);

	FILE *_fopen_r(struct _reent *<[reent]>, 
                       const char *<[file]>, const char *<[mode]>);

DESCRIPTION
<<fopen>> initializes the data structures needed to read or write a
file.  Specify the file's name as the string at <[file]>, and the kind
of access you need to the file with the string at <[mode]>.

The alternate function <<_fopen_r>> is a reentrant version.
The extra argument <[reent]> is a pointer to a reentrancy structure.

Three fundamental kinds of access are available: read, write, and append.
<<*<[mode]>>> must begin with one of the three characters `<<r>>',
`<<w>>', or `<<a>>', to select one of these:

o+
o r
Open the file for reading; the operation will fail if the file does
not exist, or if the host system does not permit you to read it.

o w
Open the file for writing @emph{from the beginning} of the file:
effectively, this always creates a new file.  If the file whose name you
specified already existed, its old contents are discarded.

o a
Open the file for appending data, that is writing from the end of
file.  When you open a file this way, all data always goes to the
current end of file; you cannot change this using <<fseek>>.
o-

Some host systems distinguish between ``binary'' and ``text'' files.
Such systems may perform data transformations on data written to, or
read from, files opened as ``text''.
If your system is one of these, then you can append a `<<b>>' to any
of the three modes above, to specify that you are opening the file as
a binary file (the default is to open the file as a text file).

`<<rb>>', then, means ``read binary''; `<<wb>>', ``write binary''; and
`<<ab>>', ``append binary''.

To make C programs more portable, the `<<b>>' is accepted on all
systems, whether or not it makes a difference.

Finally, you might need to both read and write from the same file.
You can also append a `<<+>>' to any of the three modes, to permit
this.  (If you want to append both `<<b>>' and `<<+>>', you can do it
in either order: for example, <<"rb+">> means the same thing as
<<"r+b">> when used as a mode string.)

Use <<"r+">> (or <<"rb+">>) to permit reading and writing anywhere in
an existing file, without discarding any data; <<"w+">> (or <<"wb+">>)
to create a new file (or begin by discarding all data from an old one)
that permits reading and writing anywhere in it; and <<"a+">> (or
<<"ab+">>) to permit reading anywhere in an existing file, but writing
only at the end.

RETURNS
<<fopen>> returns a file pointer which you can use for other file
operations, unless the file you requested could not be opened; in that
situation, the result is <<NULL>>.  If the reason for failure was an
invalid string at <[mode]>, <<errno>> is set to <<EINVAL>>.

PORTABILITY
<<fopen>> is required by ANSI C.

Supporting OS subroutines required: <<close>>, <<fstat>>, <<isatty>>,
<<lseek>>, <<open>>, <<read>>, <<sbrk>>, <<write>>.
*/

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "%W% (Berkeley) %G%";
#endif /* LIBC_SCCS and not lint */

#include <_ansi.h>
#include <reent.h>
#include <stdio.h>
#include <errno.h>
#include <sys/lock.h>
#ifdef __CYGWIN__
#include <fcntl.h>
#endif
#include "local.h"

FILE *
_DEFUN(_fopen_r, (ptr, file, mode),
       struct _reent *ptr,
       const char *__restrict file,
       const char *__restrict mode)
{
  register FILE *fp;
  register int f;
  int flags, oflags;

  if ((flags = __sflags (ptr, mode, &oflags)) == 0)
    return NULL;
  if ((fp = __sfp (ptr)) == NULL)
    return NULL;

  if ((f = _open_r (ptr, file, oflags, 0666)) < 0)
    {
      _newlib_sfp_lock_start (); 
      fp->_flags = 0;		/* release */
#ifndef __SINGLE_THREAD__
      __lock_close_recursive (fp->_lock);
#endif
      _newlib_sfp_lock_end (); 
      return NULL;
    }

  _newlib_flockfile_start (fp);

  fp->_file = f;
  fp->_flags = flags;
  fp->_cookie = (_PTR) fp;
  fp->_read = __sread;
  fp->_write = __swrite;
  fp->_seek = __sseek;
  fp->_close = __sclose;

  if (fp->_flags & __SAPP)
    _fseek_r (ptr, fp, 0, SEEK_END);

#ifdef __SCLE
  if (__stextmode (fp->_file))
    fp->_flags |= __SCLE;
#endif

  _newlib_flockfile_end (fp);
  return fp;
}

#ifndef _REENT_ONLY

FILE *
_DEFUN(fopen, (file, mode),
       const char *file,
       const char *mode)
{
  return _fopen_r (_REENT, file, mode);
}

#endif