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/*

 * 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

ANSI_SYNOPSIS

        #include <stdio.h>

        FILE *fopen(const char *<[file]>, const char *<[mode]>);

        FILE *_fopen_r(struct _reent *<[reent]>,

                       const char *<[file]>, const char *<[mode]>);

TRAD_SYNOPSIS

        #include <stdio.h>

        FILE *fopen(<[file]>, <[mode]>)

        char *<[file]>;

        char *<[mode]>;

        FILE *_fopen_r(<[reent]>, <[file]>, <[mode]>)

        struct _reent *<[reent]>;

        char *<[file]>;

        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 _AND

       _CONST char *file _AND

       _CONST char *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)

    {

      __sfp_lock_acquire ();

      fp->_flags = 0;            /* release */

#ifndef __SINGLE_THREAD__

      __lock_close_recursive (fp->_lock);

#endif

      __sfp_lock_release ();

      return NULL;

    }

  _flockfile (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

  _funlockfile (fp);

  return fp;

}

#ifndef _REENT_ONLY

FILE *

_DEFUN(fopen, (file, mode),

       _CONST char *file _AND

       _CONST char *mode)

{

  return _fopen_r (_REENT, file, mode);

}

#endif