/* Open a stream to a file.

   Copyright (C) 2007-2025 Free Software Foundation, Inc.

   This file is free software: you can redistribute it and/or modify

   it under the terms of the GNU Lesser General Public License as

   published by the Free Software Foundation; either version 2.1 of the

   License, or (at your option) any later version.

   This file is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

   GNU Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public License

   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */

/* Written by Bruno Haible <bruno@clisp.org>, 2007.  */

/* If the user's config.h happens to include <stdio.h>, let it include only

   the system's <stdio.h> here, so that orig_fopen doesn't recurse to

   rpl_fopen.  */

#define _GL_SKIP_GNULIB_STDIO_H

#include <config.h>

/* Get the original definition of fopen.  It might be defined as a macro.  */

#include <stdio.h>

#undef _GL_SKIP_GNULIB_STDIO_H

static FILE *

orig_fopen (const char *filename, const char *mode)

{

  return fopen (filename, mode);

}

/* Specification.  */

#ifdef __osf__

/* Write "stdio.h" here, not <stdio.h>, otherwise OSF/1 5.1 DTK cc eliminates

   this include because of the preliminary #include <stdio.h> above.  */

# include "stdio.h"

#else

# include <stdio.h>

#endif

#include <errno.h>

#include <fcntl.h>

#include <string.h>

#include <unistd.h>

#include <sys/types.h>

#include <sys/stat.h>

FILE *

rpl_fopen (const char *filename, const char *mode)

{

  int open_direction;

  int open_flags;

#if GNULIB_FOPEN_GNU

  bool open_flags_gnu;

# define BUF_SIZE 80

  char fdopen_mode_buf[BUF_SIZE + 1];

#endif

#if defined _WIN32 && ! defined __CYGWIN__

  if (strcmp (filename, "/dev/null") == 0)

    filename = "NUL";

#endif

  /* Parse the mode.  */

  open_direction = 0;

  open_flags = 0;

#if GNULIB_FOPEN_GNU

  open_flags_gnu = false;

#endif

  {

    const char *p = mode;

#if GNULIB_FOPEN_GNU

    char *q = fdopen_mode_buf;

#endif

    for (; *p != '\0'; p++)

      {

        switch (*p)

          {

          case 'r':

            open_direction = O_RDONLY;

#if GNULIB_FOPEN_GNU

            if (q < fdopen_mode_buf + BUF_SIZE)

              *q++ = *p;

#endif

            continue;

          case 'w':

            open_direction = O_WRONLY;

            open_flags |= O_CREAT | O_TRUNC;

#if GNULIB_FOPEN_GNU

            if (q < fdopen_mode_buf + BUF_SIZE)

              *q++ = *p;

#endif

            continue;

          case 'a':

            open_direction = O_WRONLY;

            open_flags |= O_CREAT | O_APPEND;

#if GNULIB_FOPEN_GNU

            if (q < fdopen_mode_buf + BUF_SIZE)

              *q++ = *p;

#endif

            continue;

          case 'b':

            /* While it is non-standard, O_BINARY is guaranteed by

               gnulib <fcntl.h>.  We can also assume that orig_fopen

               supports the 'b' flag.  */

            open_flags |= O_BINARY;

#if GNULIB_FOPEN_GNU

            if (q < fdopen_mode_buf + BUF_SIZE)

              *q++ = *p;

#endif

            continue;

          case '+':

            open_direction = O_RDWR;

#if GNULIB_FOPEN_GNU

            if (q < fdopen_mode_buf + BUF_SIZE)

              *q++ = *p;

#endif

            continue;

#if GNULIB_FOPEN_GNU

          case 'x':

            open_flags |= O_EXCL;

            open_flags_gnu = true;

            continue;

          case 'e':

            open_flags |= O_CLOEXEC;

            open_flags_gnu = true;

            continue;

#endif

          default:

            break;

          }

#if GNULIB_FOPEN_GNU

        /* The rest of the mode string can be a platform-dependent extension.

           Copy it unmodified.  */

        {

          size_t len = strlen (p);

          if (len > fdopen_mode_buf + BUF_SIZE - q)

            len = fdopen_mode_buf + BUF_SIZE - q;

          memcpy (q, p, len);

          q += len;

        }

#endif

        break;

      }

#if GNULIB_FOPEN_GNU

    *q = '\0';

#endif

  }

#if FOPEN_TRAILING_SLASH_BUG

  /* Fail if the mode requires write access and the filename ends in a slash,

     as POSIX says such a filename must name a directory

     <https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap04.html#tag_04_13>:

       "A pathname that contains at least one non-<slash> character and that

        ends with one or more trailing <slash> characters shall not be resolved

        successfully unless the last pathname component before the trailing

        <slash> characters names an existing directory"

     If the named file already exists as a directory, then if a mode that

     requires write access is specified, fopen() must fail because POSIX

     <https://pubs.opengroup.org/onlinepubs/9699919799/functions/fopen.html>

     says that it fails with errno = EISDIR in this case.

     If the named file does not exist or does not name a directory, then

     fopen() must fail since the file does not contain a '.' directory.  */

  {

    size_t len = strlen (filename);

    if (len > 0 && filename[len - 1] == '/')

      {

        int fd;

        struct stat statbuf;

        FILE *fp;

        if (open_direction != O_RDONLY)

          {

            errno = EISDIR;

            return NULL;

          }

        fd = open (filename, open_direction | open_flags,

                   S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH);

        if (fd < 0)

          return NULL;

        if (fstat (fd, &statbuf) >= 0 && !S_ISDIR (statbuf.st_mode))

          {

            close (fd);

            errno = ENOTDIR;

            return NULL;

          }

# if GNULIB_FOPEN_GNU

        fp = fdopen (fd, fdopen_mode_buf);

# else

        fp = fdopen (fd, mode);

# endif

        if (fp == NULL)

          {

            int saved_errno = errno;

            close (fd);

            errno = saved_errno;

          }

        return fp;

      }

  }

#endif

#if GNULIB_FOPEN_GNU

  if (open_flags_gnu)

    {

      int fd;

      FILE *fp;

      fd = open (filename, open_direction | open_flags,

                 S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH);

      if (fd < 0)

        return NULL;

      fp = fdopen (fd, fdopen_mode_buf);

      if (fp == NULL)

        {

          int saved_errno = errno;

          close (fd);

          errno = saved_errno;

        }

      return fp;

    }

#endif

  /* open_direction is sometimes used, sometimes unused.

     Silence gcc's warning about this situation.  */

  (void) open_direction;

  return orig_fopen (filename, mode);

}