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/* fchdir replacement.
Copyright (C) 2006-2008 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 <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <stdarg.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include "canonicalize.h"
/* This replacement assumes that a directory is not renamed while opened
through a file descriptor. */
/* Array of file descriptors opened. If it points to a directory, it stores
info about this directory; otherwise it stores an errno value of ENOTDIR. */
typedef struct
{
char *name; /* Absolute name of the directory, or NULL. */
int saved_errno; /* If name == NULL: The error code describing the failure
reason. */
} 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. */
static void
ensure_dirs_slot (size_t fd)
{
if (fd >= dirs_allocated)
{
size_t new_allocated;
dir_info_t *new_dirs;
size_t i;
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 (dir_info_t))
: (dir_info_t *) malloc (new_allocated * sizeof (dir_info_t)));
if (new_dirs != NULL)
{
for (i = dirs_allocated; i < new_allocated; i++)
{
new_dirs[i].name = NULL;
new_dirs[i].saved_errno = ENOTDIR;
}
dirs = new_dirs;
dirs_allocated = new_allocated;
}
}
}
/* Hook into the gnulib replacements for open() and close() to keep track
of the open file descriptors. */
void
_gl_unregister_fd (int fd)
{
if (fd >= 0 && fd < dirs_allocated)
{
if (dirs[fd].name != NULL)
free (dirs[fd].name);
dirs[fd].name = NULL;
dirs[fd].saved_errno = ENOTDIR;
}
}
void
_gl_register_fd (int fd, const char *filename)
{
struct stat statbuf;
ensure_dirs_slot (fd);
if (fd < dirs_allocated
&& fstat (fd, &statbuf) >= 0 && S_ISDIR (statbuf.st_mode))
{
dirs[fd].name = canonicalize_file_name (filename);
if (dirs[fd].name == NULL)
dirs[fd].saved_errno = errno;
}
}
/* 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 (fd >= 0)
_gl_register_fd (fd, filename);
}
return dp;
}
/* Override dup() and dup2(), to keep track of open file descriptors. */
int
rpl_dup (int oldfd)
#undef dup
{
int newfd = dup (oldfd);
if (oldfd >= 0 && newfd >= 0)
{
ensure_dirs_slot (newfd);
if (newfd < dirs_allocated)
{
if (oldfd < dirs_allocated)
{
if (dirs[oldfd].name != NULL)
{
dirs[newfd].name = strdup (dirs[oldfd].name);
if (dirs[newfd].name == NULL)
dirs[newfd].saved_errno = ENOMEM;
}
else
{
dirs[newfd].name = NULL;
dirs[newfd].saved_errno = dirs[oldfd].saved_errno;
}
}
else
{
dirs[newfd].name = NULL;
dirs[newfd].saved_errno = ENOMEM;
}
}
}
return newfd;
}
int
rpl_dup2 (int oldfd, int newfd)
#undef dup2
{
int retval = dup2 (oldfd, newfd);
if (retval >= 0 && oldfd >= 0 && newfd >= 0 && newfd != oldfd)
{
ensure_dirs_slot (newfd);
if (newfd < dirs_allocated)
{
if (oldfd < dirs_allocated)
{
if (dirs[oldfd].name != NULL)
{
dirs[newfd].name = strdup (dirs[oldfd].name);
if (dirs[newfd].name == NULL)
dirs[newfd].saved_errno = ENOMEM;
}
else
{
dirs[newfd].name = NULL;
dirs[newfd].saved_errno = dirs[oldfd].saved_errno;
}
}
else
{
dirs[newfd].name = NULL;
dirs[newfd].saved_errno = ENOMEM;
}
}
}
return retval;
}
/* Implement fchdir() in terms of chdir(). */
int
fchdir (int fd)
{
if (fd >= 0)
{
if (fd < dirs_allocated)
{
if (dirs[fd].name != NULL)
return chdir (dirs[fd].name);
else
{
errno = dirs[fd].saved_errno;
return -1;
}
}
else
{
errno = ENOMEM;
return -1;
}
}
else
{
errno = EBADF;
return -1;
}
}
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