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Diffstat (limited to 'gnu/fchdir.c')
| -rw-r--r-- | gnu/fchdir.c | 289 |
1 files changed, 289 insertions, 0 deletions
diff --git a/gnu/fchdir.c b/gnu/fchdir.c new file mode 100644 index 0000000..83d3c33 --- /dev/null +++ b/gnu/fchdir.c @@ -0,0 +1,289 @@ +/* -*- buffer-read-only: t -*- vi: set ro: */ +/* DO NOT EDIT! GENERATED AUTOMATICALLY! */ +/* fchdir replacement. + Copyright (C) 2006-2010 Free Software Foundation, Inc. + + This program is free software: you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation; either version 3 of the License, or + (at your option) any later version. + + This program 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 General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see <http://www.gnu.org/licenses/>. */ + +#include <config.h> + +/* Specification. */ +#include <unistd.h> + +#include <assert.h> +#include <dirent.h> +#include <errno.h> +#include <fcntl.h> +#include <stdbool.h> +#include <stdlib.h> +#include <string.h> +#include <sys/types.h> +#include <sys/stat.h> + +#ifndef REPLACE_OPEN_DIRECTORY +# define REPLACE_OPEN_DIRECTORY 0 +#endif + +#ifndef HAVE_CANONICALIZE_FILE_NAME +# if GNULIB_CANONICALIZE || GNULIB_CANONICALIZE_LGPL +# define HAVE_CANONICALIZE_FILE_NAME 1 +# else +# define HAVE_CANONICALIZE_FILE_NAME 0 +# define canonicalize_file_name(name) NULL +# endif +#endif + +/* This replacement assumes that a directory is not renamed while opened + through a file descriptor. + + FIXME: On mingw, this would be possible to enforce if we were to + also open a HANDLE to each directory currently visited by a file + descriptor, since mingw refuses to rename any in-use file system + object. */ + +/* Array of file descriptors opened. If REPLACE_OPEN_DIRECTORY or if it points + to a directory, it stores info about this directory. */ +typedef struct +{ + char *name; /* Absolute name of the directory, or NULL. */ + /* FIXME - add a DIR* member to make dirfd possible on mingw? */ +} dir_info_t; +static dir_info_t *dirs; +static size_t dirs_allocated; + +/* Try to ensure dirs has enough room for a slot at index fd; free any + contents already in that slot. Return false and set errno to + ENOMEM on allocation failure. */ +static bool +ensure_dirs_slot (size_t fd) +{ + if (fd < dirs_allocated) + free (dirs[fd].name); + else + { + size_t new_allocated; + dir_info_t *new_dirs; + + new_allocated = 2 * dirs_allocated + 1; + if (new_allocated <= fd) + new_allocated = fd + 1; + new_dirs = + (dirs != NULL + ? (dir_info_t *) realloc (dirs, new_allocated * sizeof *dirs) + : (dir_info_t *) malloc (new_allocated * sizeof *dirs)); + if (new_dirs == NULL) + return false; + memset (new_dirs + dirs_allocated, 0, + (new_allocated - dirs_allocated) * sizeof *dirs); + dirs = new_dirs; + dirs_allocated = new_allocated; + } + return true; +} + +/* Return the canonical name of DIR in malloc'd storage. */ +static char * +get_name (char const *dir) +{ + char *result; + if (REPLACE_OPEN_DIRECTORY || !HAVE_CANONICALIZE_FILE_NAME) + { + /* The function canonicalize_file_name has not yet been ported + to mingw, with all its drive letter and backslash quirks. + Fortunately, getcwd is reliable in this case, but we ensure + we can get back to where we started before using it. Treat + "." as a special case, as it is frequently encountered. */ + char *cwd = getcwd (NULL, 0); + int saved_errno; + if (dir[0] == '.' && dir[1] == '\0') + return cwd; + if (chdir (cwd)) + return NULL; + result = chdir (dir) ? NULL : getcwd (NULL, 0); + saved_errno = errno; + if (chdir (cwd)) + abort (); + free (cwd); + errno = saved_errno; + } + else + { + /* Avoid changing the directory. */ + result = canonicalize_file_name (dir); + } + return result; +} + +/* Hook into the gnulib replacements for open() and close() to keep track + of the open file descriptors. */ + +/* Close FD, cleaning up any fd to name mapping if fd was visiting a + directory. */ +void +_gl_unregister_fd (int fd) +{ + if (fd >= 0 && fd < dirs_allocated) + { + free (dirs[fd].name); + dirs[fd].name = NULL; + } +} + +/* Mark FD as visiting FILENAME. FD must be non-negative, and refer + to an open file descriptor. If REPLACE_OPEN_DIRECTORY is non-zero, + this should only be called if FD is visiting a directory. Close FD + and return -1 if there is insufficient memory to track the + directory name; otherwise return FD. */ +int +_gl_register_fd (int fd, const char *filename) +{ + struct stat statbuf; + + assert (0 <= fd); + if (REPLACE_OPEN_DIRECTORY + || (fstat (fd, &statbuf) == 0 && S_ISDIR (statbuf.st_mode))) + { + if (!ensure_dirs_slot (fd) + || (dirs[fd].name = get_name (filename)) == NULL) + { + int saved_errno = errno; + close (fd); + errno = saved_errno; + return -1; + } + } + return fd; +} + +/* Mark NEWFD as a duplicate of OLDFD; useful from dup, dup2, dup3, + and fcntl. Both arguments must be valid and distinct file + descriptors. Close NEWFD and return -1 if OLDFD is tracking a + directory, but there is insufficient memory to track the same + directory in NEWFD; otherwise return NEWFD. */ +int +_gl_register_dup (int oldfd, int newfd) +{ + assert (0 <= oldfd && 0 <= newfd && oldfd != newfd); + if (oldfd < dirs_allocated && dirs[oldfd].name) + { + /* Duplicated a directory; must ensure newfd is allocated. */ + if (!ensure_dirs_slot (newfd) + || (dirs[newfd].name = strdup (dirs[oldfd].name)) == NULL) + { + int saved_errno = errno; + close (newfd); + errno = saved_errno; + newfd = -1; + } + } + else if (newfd < dirs_allocated) + { + /* Duplicated a non-directory; ensure newfd is cleared. */ + free (dirs[newfd].name); + dirs[newfd].name = NULL; + } + return newfd; +} + +/* If FD is currently visiting a directory, then return the name of + that directory. Otherwise, return NULL and set errno. */ +const char * +_gl_directory_name (int fd) +{ + if (0 <= fd && fd < dirs_allocated && dirs[fd].name != NULL) + return dirs[fd].name; + /* At this point, fd is either invalid, or open but not a directory. + If dup2 fails, errno is correctly EBADF. */ + if (0 <= fd) + { + if (dup2 (fd, fd) == fd) + errno = ENOTDIR; + } + else + errno = EBADF; + return NULL; +} + +#if REPLACE_OPEN_DIRECTORY +/* Return stat information about FD in STATBUF. Needed when + rpl_open() used a dummy file to work around an open() that can't + normally visit directories. */ +# undef fstat +int +rpl_fstat (int fd, struct stat *statbuf) +{ + if (0 <= fd && fd < dirs_allocated && dirs[fd].name != NULL) + return stat (dirs[fd].name, statbuf); + return fstat (fd, statbuf); +} +#endif + +/* Override opendir() and closedir(), to keep track of the open file + descriptors. Needed because there is a function dirfd(). */ + +int +rpl_closedir (DIR *dp) +#undef closedir +{ + int fd = dirfd (dp); + int retval = closedir (dp); + + if (retval >= 0) + _gl_unregister_fd (fd); + return retval; +} + +DIR * +rpl_opendir (const char *filename) +#undef opendir +{ + DIR *dp; + + dp = opendir (filename); + if (dp != NULL) + { + int fd = dirfd (dp); + if (0 <= fd && _gl_register_fd (fd, filename) != fd) + { + int saved_errno = errno; + closedir (dp); + errno = saved_errno; + return NULL; + } + } + return dp; +} + +/* Override dup(), to keep track of open file descriptors. */ + +int +rpl_dup (int oldfd) +#undef dup +{ + int newfd = dup (oldfd); + + if (0 <= newfd) + newfd = _gl_register_dup (oldfd, newfd); + return newfd; +} + + +/* Implement fchdir() in terms of chdir(). */ + +int +fchdir (int fd) +{ + const char *name = _gl_directory_name (fd); + return name ? chdir (name) : -1; +} |