diff options
Diffstat (limited to 'lib/fopen.c')
| -rw-r--r-- | lib/fopen.c | 230 |
1 files changed, 230 insertions, 0 deletions
diff --git a/lib/fopen.c b/lib/fopen.c new file mode 100644 index 0000000..a5b3ae3 --- /dev/null +++ b/lib/fopen.c @@ -0,0 +1,230 @@ +/* Open a stream to a file. + Copyright (C) 2007-2022 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_ALREADY_INCLUDING_STDIO_H +#include <config.h> + +/* Get the original definition of fopen. It might be defined as a macro. */ +#include <stdio.h> +#undef _GL_ALREADY_INCLUDING_STDIO_H + +static FILE * +orig_fopen (const char *filename, const char *mode) +{ + return fopen (filename, mode); +} + +/* Specification. */ +/* 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" + +#include <errno.h> +#include <fcntl.h> +#include <stdbool.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 + + return orig_fopen (filename, mode); +} |