file.c

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/*
 *   This library 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 library 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 library; if not, write to the Free Software
 *   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
 */
 
/** Various miscellaneous functions to manipulate files and paths
 *
 * @file src/lib/util/file.c
 *
 * @copyright 2019 The FreeRADIUS project
 * @copyright 2019 Arran Cudbard-Bell (a.cudbardb@freeradius.org)
 */
RCSID("$Id: ccf8734f8944bbe7524de86f6844f817c78a44ce $")
 
#include <sys/param.h>
#include <fcntl.h>
#include <stdio.h>
#include <sys/stat.h>
 
#include <freeradius-devel/util/file.h>
#include <freeradius-devel/util/syserror.h>
#include <freeradius-devel/util/value.h>
 
/** Callback for the common case of chown() of the directory.
 *
 */
int fr_mkdir_chown(int fd, char const *path, void *uctx)
{
        fr_mkdir_chown_t const *ctx = uctx;
 
        if ((ctx->uid == (uid_t) -1) && (ctx->gid == (gid_t) -1)) return 0;
 
        if (fchown(fd, ctx->uid, ctx->gid) < 0) {
                fr_strerror_printf("Failed changing ownership on directory \"%s\": %s",
                                   path, fr_syserror(errno));
                return -1;
        }
 
        return 0;
}
 
 
static ssize_t _fr_mkdir(int *fd_out, char *start, char *path, mode_t mode, fr_mkdir_func_t func, void *uctx)
{
        int             ret, fd;
        char            *p;
 
        /*
         *      Try to make the path.  If it exists, chmod it.
         *      If a path doesn't exist, that's OK.  Otherwise
         *      return with an error.
         *
         *      Directories permissions are initially set so
         *      that only we should have access. This prevents
         *      an attacker removing them and swapping them
         *      out for a link to somewhere else.
         *      We change them to the correct permissions later.
         */
        ret = mkdir(path, 0700);
        if (ret >= 0) {
                fd = open(path, O_DIRECTORY);
                if (fd < 0) {
                        fr_strerror_printf("Failed opening directory we created: %s",
                                           fr_syserror(errno));
                mkdir_error:
                        p = strrchr(path, FR_DIR_SEP);
                        if (!p) return start - path;
 
                        return start - p;
                }
 
                if (fchmod(fd, mode) < 0) {
                        fr_strerror_printf("Failed setting permissions on directory "
                                           "we created: %s", fr_syserror(errno));
                        close(fd);
                        goto mkdir_error;
                }
                *fd_out = fd;
                return strlen(start);
        }
 
        /*
         *      EEXIST is only OK when we're calling mkdir on the
         *      whole path, and it exists which should have been
         *      caught by fr_mkdir before calling this function.
         *
         *      Unless we're running in an environment with multiple
         *      processes, in which case EEXIST means that another
         *      process created this directory in between our check
         *      and our creation.
         */
        if (errno == EEXIST) {
                fd = open(path, O_DIRECTORY);
                if (fd < 0) {
                        fr_strerror_printf("Failed opening existing directory: %s", fr_syserror(errno));
                        goto mkdir_error;
                }
                *fd_out = fd;
                return strlen(start);
        }
 
        /*
         *      ENOENT means we're trying to create too much path
         *      at once.  Recurse to discover the deepest path
         *      component that already exists.
         */
        if (errno != ENOENT) {
                fr_strerror_printf("Failed creating directory path: %s", fr_syserror(errno));
                goto mkdir_error;
        }
 
        /*
         *      A component in the path doesn't
         *      exist.  Look for the LAST path name.  Try
         *      to create that.  If there's an error, we leave
         *      the path path as the one at which the
         *      error occurred.
         */
        p = strrchr(path, FR_DIR_SEP);
        if (!p || (p == path)) return start - path;     /* last path component and we've previously failed */
 
        *p = '\0';
        if (_fr_mkdir(fd_out, start, path, mode, func, uctx) <= 0) return start - p;
 
        fr_assert_msg((*fd_out) >= 0, "Logic error - Bad FD %i", *fd_out);
 
        /*
         *      At this point *fd_out, should be an FD
         *      for the containing directory.
         *
         *      Dir may already exist if we're racing
         *      other processes as we do in CI.
         */
        if (mkdirat(*fd_out, p + 1, 0700) < 0) {
                /*
                 *      This is usually because of a race with
                 *      other processes trying to create the
                 *      same directory.
                 */
                if (errno == EEXIST) {
                        fd = openat(*fd_out, p + 1, O_DIRECTORY);
                        if (fd < 0) {
                                fr_strerror_printf_push("Failed opening existing directory path component: %s",
                                                        fr_syserror(errno));
                                goto mkdirat_error;
                        }
                        *p = FR_DIR_SEP;
                        goto done;
                }
 
                fr_strerror_printf_push("Failed creating directory path component: %s", fr_syserror(errno));
 
        mkdirat_error:
                close(*fd_out);
                *fd_out = -1;
                return start - p;
        }
 
        fd = openat(*fd_out, p + 1, O_DIRECTORY);
        if (fd < 0) {
                fr_strerror_printf_push("Failed opening directory we "
                                        "created: %s", fr_syserror(errno));
                goto mkdirat_error;
        }
 
        if (fchmod(fd, mode) < 0) {
                fr_strerror_printf_push("Failed setting permissions on "
                                        "directory we created: %s", fr_syserror(errno));
                goto mkdirat_error;
        }
 
        *p = FR_DIR_SEP;
 
        /*
         *      Call the user function
         */
        if (func && (func(fd, path, uctx) < 0)) {
                fr_strerror_printf_push("Callback failed processing directory \"%s\"", path);
                goto mkdirat_error;
        }
 
        /*
         *      Swap active *fd_out to point to the dir
         *      we just created.
         */
done:
        close(*fd_out);
        *fd_out = fd;
 
        return strlen(start);
}
 
/** Create directories that are missing in the specified path
 *
 * @param[out] fd_out   If not NULL, will contain a file descriptor
 *                      for the deepest path component created.
 * @param[in] path      to populate with directories.
 * @param[in] len       Length of the path string.
 * @param[in] mode      for new directories.
 * @param[in] func      to call each time a new directory is created.
 * @param[in] uctx      to pass to func.
 * @return
 *      - >0 on success.
 *      - <= 0 on failure. Negative offset pointing to the
 *        path separator of the path component that caused the error.
 */
ssize_t fr_mkdir(int *fd_out, char const *path, ssize_t len, mode_t mode, fr_mkdir_func_t func, void *uctx)
{
        char    *our_path;
        int     fd = -1;
        ssize_t slen;
 
        if (len < 0) len = strlen(path);
        if (len == 0) return 0;
 
        /*
         *      Fast path (har har)
         *
         *      Avoids duping the input for the
         *      common case.
         */
        fd = open(path, O_DIRECTORY);
        if (fd >= 0) goto done;
 
        /*
         *      Dup the amount of input path
         *      we need.
         */
        our_path = talloc_bstrndup(NULL, path, (size_t)len);
        if (!our_path) {
                fr_strerror_const("Out of memory");
                return -1;
        }
 
        fr_strerror_clear();    /* We make liberal use of push */
 
        /*
         *      Call the recursive function to
         *      create any missing dirs in the
         *      specified path.
         */
        slen = _fr_mkdir(&fd, our_path, our_path, mode, func, uctx);
        talloc_free(our_path);
        if (slen <= 0) return slen;
 
done:
        if (fd_out) {
                *fd_out = fd;
        } else {
                close(fd);
        }
 
        return len;
}
 
/** Convenience wrapper around realpath
 *
 * Wraps realpath, but takes a path with an explicit length, and returns
 * the result in a talloced buffer.
 *
 * On error, errno is set, and the string version of the error is
 * available with fr_strerror().
 *
 * @param[in] ctx       in which to allocate the result.
 * @param[in] path      To convert to an absolute path.
 * @param[in] len       How much of 'path' to read.  If < 0, then
 *                      the entire path will be used.
 * @return
 *      - NULL on error.
 *      - The absolute version of the input path on success.
 */
char *fr_realpath(TALLOC_CTX *ctx, char const *path, ssize_t len)
{
        char            *tmp_path = NULL, *abs_path, *talloc_abs_path;
 
        if (len > 0) path = tmp_path = talloc_bstrndup(NULL, path, (size_t)len);
 
        abs_path = realpath(path, NULL);
        if (!abs_path) {
                fr_strerror_printf("Failed resolving path \"%pV\": %s",
                                   fr_box_strvalue_buffer(path), fr_syserror(errno));
                talloc_free(tmp_path);
                return NULL;
        }
 
        talloc_free(tmp_path);
 
        talloc_abs_path = talloc_strdup(ctx, abs_path);
        free(abs_path);
        if (!talloc_abs_path) {
                fr_strerror_const("Out of Memory");
                return NULL;
        }
 
        return talloc_abs_path;
}
 
/** Create an empty file
 *
 * @param[out] fd_out   If not NULL, will contain a file descriptor
 *                      for the file we just opened.
 * @param[in] filename  path to file.
 * @param[in] mode      Specifies the file mode bits be applied.
 * @param[in] mkdir     Whether we should create directories
 *                      for any missing path components.
 * @param[in] dir_mode  Mode of any directories created.
 * @return
 *      - >0 on success.
 *      - <= 0 on failure. Error available in error stack (use fr_strerror())
 */
ssize_t fr_touch(int *fd_out, char const *filename, mode_t mode, bool mkdir, mode_t dir_mode) {
        int fd;
 
        fd = open(filename, O_WRONLY | O_CREAT, mode);
        if (fd < 0) {
                ssize_t slen = 0;
                char    *q;
 
                if (mkdir && (errno == ENOENT) && (q = strrchr(filename, FR_DIR_SEP))) {
                        int dir_fd = -1;
 
                        slen = fr_mkdir(&dir_fd, filename, q - filename, dir_mode, NULL, NULL);
                        if((slen <= 0) || (dir_fd < 0)) return slen;
 
                        fd = openat(dir_fd, q + 1, O_WRONLY | O_CREAT, mode);
                        if (fd >= 0) {
                                close(dir_fd);
                                close(fd);
                                return strlen(filename);
                        }
                        close(dir_fd);
                        slen = -(q - filename);
                }
                fr_strerror_printf("Failed creating file: %s", fr_syserror(errno));
                return slen;
        }
 
        if (fd_out) {
                *fd_out = fd;
        } else {
                close(fd);
        }
 
        return strlen(filename);
}
 
/** Remove a regular file from the filesystem
 *
 * @param[in] filename path to file.
 * @return
 *      - -1 On error.
 *      - 0 if the file was removed.
 *      - 1 if the file didn't exist.
 */
int fr_unlink(char const *filename) {
        if (unlink(filename) == 0) return 0;
 
        if (errno == ENOENT) return 1;
 
        fr_strerror_printf("Failed removing regular file \"%s\": %s", filename, fr_syserror(errno));
 
        return -1;
}
 
/** Intended to be used in logging functions to make output more readable
 *
 * This function is not performant and should probably not be used at runtime.
 *
 * @param[in] filename  to strip working directory from.
 * @return Position in filename after our working directory.
 */
char const *fr_cwd_strip(char const *filename)
{
        static char our_wd[MAXPATHLEN];
        char *found;
 
        if (!getcwd(our_wd, sizeof(our_wd))) return filename;
 
        found = strstr(filename, our_wd);
        if (found && (found == our_wd)) {
                filename += strlen(our_wd);
                while (*filename == '/') filename++;
                return filename;
        }
 
        return filename;
}
 
/** From a pathname, return fd and filename needed for *at() functions
 *
 * @param[in] dirfd     points to place to store the dirfd
 * @param[in] filename  points to placd to store a pointer into pathname
 *                      that points to the filename
 * @param[in] pathname  the full pathname of the file
 *
 * @return
 *      - -1 on error
 *      -  0 on success
 */
int fr_dirfd(int *dirfd, char const **filename, char const *pathname)
{
        char const *last_slash = strrchr(pathname, '/');
 
        if (last_slash == NULL) {
                *filename = pathname;
                *dirfd = AT_FDCWD;
                return 0;
        }
        {
                char dirpath[(last_slash - pathname) + 1];
 
                memcpy(dirpath, pathname, last_slash - pathname);
                dirpath[last_slash - pathname] = '\0';
                *filename = last_slash + 1;
                *dirfd = open(dirpath, O_DIRECTORY);
                return (*dirfd < 0) ? -1 : 0;
        }
}
 
static bool fr_globdir_file_ok(char const *try, fr_globdir_iter_t *iter)
{
        size_t len, room;
        char const *p;
        char *filename;
        struct stat stat_buf;
 
        /*
         *      Filter the filenames.
         */
        if (try[0] == '.') return false;
 
        /*
         *      Check for valid characters
         */
        p = try;
        while (*p) {
                /*
                 *      Control characters are invalid UTF-8, too.
                 */
                len = fr_utf8_char((uint8_t const *) p, -1);
                if (!len) return false;
 
                /*
                 *      The string is valid UTF-8, but is NOT an ASCII
                 *      character.  We allow it.
                 */
                if (len > 1) {
                        p += len;
                        continue;
                }
 
                /*
                 *      Limit the ASCII characters we allow.
                 */
                if (isalpha((uint8_t)*p) ||
                    isdigit((uint8_t)*p) ||
                    (*p == '-') ||
                    (*p == '_') ||
                    (*p == '.')) {
                        p++;
                        continue;
                }
 
                /*
                 *      Invalid character in filename, it's not a match.
                 */
                return false;
        }
 
        len = p - try;
        if (!len) return false;
 
        /*
         *      Ignore files generated by deb / rpm packaging updates.
         */
        if ((len > 10) && (strncmp(&try[len - 10], ".dpkg-dist", 10) == 0)) return false;
        if ((len > 9) && (strncmp(&try[len - 9], ".dpkg-old", 9) == 0)) return false;
        if ((len > 7) && (strncmp(&try[len - 7], ".rpmnew", 7) == 0)) return false;
        if ((len > 8) && (strncmp(&try[len - 8], ".rpmsave", 8) == 0)) return false;
 
        /*
         *      When reading all files in a directory, iter->filename points to the directory
         *      name which is being read.  The file being tested needs to be added after that.
         */
        filename = iter->filename + (iter->type == FR_GLOBDIR_DIR ? strlen(iter->filename) : 0);
 
        /*
         *      strlcpy() returns the length of the input, which can be larger than the available space.
         */
        room = (iter->path + PATH_MAX) - filename;
 
        if (strlcpy(filename, try, room) >= room) return false;
 
        /*
         *      We only read normal files which are NOT executable, and symlinks.
         */
        if (stat(iter->path, &stat_buf) != 0) {
                return false;
        }
 
        if (S_ISREG(stat_buf.st_mode)) {
                if ((stat_buf.st_mode & (S_IXUSR | S_IXGRP | S_IXOTH)) != 0) {
                        return false;
                }
        } else if (!S_ISLNK(stat_buf.st_mode)) { /* soft links are executable */
                return false;
        }
 
        return true;
}
 
#ifdef HAVE_DIRENT_H
/*
 *      Filter filenames when reading a directory.
 */
static int fr_globdir_dir_next(char const **filename, fr_globdir_iter_t *iter)
{
        struct dirent *dp;
 
        fr_assert(iter->dir != NULL);
 
        /*
         *      Reading all of the directory entries will result in
         *      reading ones we don't want, so we filter them.
         */
        while (true) {
                errno = 0;
                dp = readdir(iter->dir);
                if (!dp) {
                        if (errno != 0) return -1;
 
                        *filename = NULL;
                        return 0;
                }
 
                if (!fr_globdir_file_ok(dp->d_name, iter)) continue;
 
                /*
                 *      It's mostly ASCII, and not a leftover file name, stop.
                 */
                break;
        }
 
        *filename = iter->filename;
        return 0;
}
#endif
 
/** Create a full path from dir + pattern.
 *
 */
static int fr_globdir_get_path(char const *dir, char const *pattern, fr_globdir_iter_t *iter)
{
        char const *p;
        char *q;
        bool slash;
 
        /*
         *      Bootstrap the full path.
         */
        iter->path = malloc(PATH_MAX);
        if (!iter->path) {
                errno = ENOMEM;
                return -1;
        }
 
        /*
         *      Sanity check the directory name.
         *
         *      We assume that the directory name is otherwise safe.
         */
        p = dir;
        q = iter->path;
        while (*p) {
                /*
                 *      Suppress duplicate '/', and trailing '/'.
                 */
                if (*p == '/') {
                        *(q++) = *(p++);
 
                        while (*p == '/') p++;
 
                        if (!p[1]) break;
                        continue;
                }
 
                if ((size_t) (q - iter->path) >= PATH_MAX) {
                        free(iter->path);
                        errno = ENOMEM;
                        return -1;
                }
 
                *(q++) = *(p++);
        }
 
        /*
         *      Add in a trailing '/' to the directory.
         */
        *(q++) = '/';
        slash = true;
        iter->filename = q;
 
        /*
         *      Copy over the pattern name, but sanity check it.
         */
        p = pattern;
        while (*p) {
                if ((size_t) (q - iter->path) >= PATH_MAX) {
                        free(iter->path);
                        errno = ENOMEM;
                        return -1;
                }
 
                /*
                 *      @todo - if it's a pattern, then handle [./] as a special case.
                 */
 
                /*
                 *      Handle the case of bad things after the directory name, too.
                 *
                 *      But otherwise copy over any '/' which we see in the pattern.
                 */
                if (!slash) {
                        slash = (*p == '/');
                        *(q++) = *(p++);
 
                        if (!slash) continue;
                }
 
        more_slash:
                /*
                 *      ///// --> /
                 */
                while (*p == '/') p++;
 
                /*
                 *      foo/. may be special
                 */
                if (*p != '.') {
                        slash = false;
                        continue;
                }
 
                /*
                 *      foo/./ --> foo/
                 */
                if (p[1] == '/') {
                        p += 2;
                        goto more_slash;
                }
 
                /*
                 *      foo/../ --> error
                 */
                if ((p[1] == '.') && (p[2] == '/')) {
                        free(iter->path);
                        errno = ENOENT;
                        return -1;
                }
 
                /*
                 *      foo/.bar is OK
                 */
                slash = false;
        }
        *q = '\0';
 
        return 0;
}
 
/** Initialize an iterator over filenames.
 *
 * @param[out] filename the _relative_ filename which should be opened
 * @param[in] dir       the directory to read
 * @param[in] pattern   the filename or pattern to read.  Cannot be an absolute path.
 * @param[in,out] iter  the iteration structure.
 * @return
 *      - <0 on error
 *      - 0 on success, but no filename
 *      - 1 for "have file".
 */
int fr_globdir_iter_init(char const **filename, char const *dir, char const *pattern, fr_globdir_iter_t *iter)
{
        char const *p;
        char const *to_open;
 
        /*
         *      Default to files, which is the most common case.
         */
        *iter = (fr_globdir_iter_t) {
                .type= FR_GLOBDIR_FILE,
        };
 
        /*
         *      Figure out what kind of thing we're opening.
         */
        for (p = pattern; *p != '\0'; p++) {
                /*
                 *      foo/ - read the entire directory.
                 */
                if (*p == '/') {
                        if (p[1]) continue;
 
#ifdef HAVE_DIRENT_H
                        iter->type = FR_GLOBDIR_DIR;
                        break;
#else
                        errno = ENOENT;
                        return -1;
#endif
                }
 
                /*
                 *      foo*.txt
                 *      foo?.txt
                 *      foo.[ch]
                 *
                 *      - file globbing.
                 *
                 *      File globbing is either full path, or a path relative to CWD.  It is most notably NOT
                 *      relative to the input "dir".  So if there are globs, we need a full path.
                 */
                if ((*p == '*') || (*p == '?') || (*p == '[')) {
#ifdef HAVE_GLOB_H
                        /*
                         *      @todo - call realpath() to get the canonical filename?
                         */
                        if ((pattern[0] != '/') && (dir[0] != '/')) {
                                errno = ENOENT;
                                return -1;
                        }
 
                        iter->type = FR_GLOBDIR_GLOB;
                        break;
#else
                        errno = ENOENT;
                        return -1;
#endif
                }
        }
 
        /*
         *      The pattern is an absolute path, we just use that as-is.
         */
        if (pattern[0] == '/') {
                to_open = pattern;
 
        } else if (iter->type == FR_GLOBDIR_FILE) {
                /*
                 *      Short-circuit the common case for files.  We're just opening a file, and the file is
                 *      relative to the directory which was passed in.
                 */
                *filename = pattern;
                return 1;
 
        } else {
                /*
                 *      Either dir is absolute and pattern is relative, or they're both relative.  Merge dir +
                 *      pattern into a path.
                 *
                 *      Note that globs are relative to CWD, so relative globs must be passed in correctly
                 *      (that's an @todo), otherwise they won't work.
                 */
                if (fr_globdir_get_path(dir, pattern, iter) < 0) {
                        return -1;
                }
 
                to_open = iter->path;
        }
 
        /*
         *      Now that we know what type of thing it is, go do the
         *      right thing.
         */
        switch (iter->type) {
        case FR_GLOBDIR_INVALID:
                (void) fr_globdir_iter_free(iter);
                errno = ENOENT;
                return -1;
 
        case FR_GLOBDIR_FILE:
                *filename = iter->path;
                break;
 
#ifdef HAVE_DIRENT_H
        case FR_GLOBDIR_DIR:
                /*
                 *      No directory means no file.  The caller then decides if the file is required.
                 */
                iter->dir = opendir(to_open);
                if (!iter->dir) {
                        (void) fr_globdir_iter_free(iter);
                        return 0;
                }
 
                if (fr_globdir_dir_next(filename, iter) < 0) {
                        (void) fr_globdir_iter_free(iter);
                        return -1;
                }
                break;
#endif
 
#ifdef HAVE_GLOB_H
        case FR_GLOBDIR_GLOB:
                if (glob(to_open, GLOB_NOESCAPE | GLOB_ERR, NULL, &iter->glob) < 0) {
                        (void) fr_globdir_iter_free(iter);
                        return -1;
                }
 
                if (iter->glob.gl_pathc == 0) {
                        *filename = NULL;
                } else {
                        iter->gl_current = 0;
 
                        /*
                         *      @todo - check the filenames using fr_globdir_file_ok()
                         */
                        *filename = iter->glob.gl_pathv[iter->gl_current];
                }
                break;
#endif
        }
 
        return 0 + (*filename != NULL);
}
 
/** Get the next filename.
 *
 *  fr_globdir_iter_init()
 *  do {
 *      ... use filename
 *  } while (fr_globdir_iter_next() == 1);
 *  fr_globdir_iter_free()
 *
 * @return
 *      - <0 for error
 *      - 0 for done
 *      - 1 for "have filename"
 */
int fr_globdir_iter_next(char const **filename, fr_globdir_iter_t *iter)
{
        switch (iter->type) {
        case FR_GLOBDIR_INVALID:
                break;
 
        case FR_GLOBDIR_FILE:
                *filename = NULL;
                return 0;
 
#ifdef HAVE_DIRENT_H
        case FR_GLOBDIR_DIR:
                if (fr_globdir_dir_next(filename, iter) < 0) return -1;
 
                return 0 + (*filename != NULL);
#endif
 
#ifdef HAVE_GLOB_H
        case FR_GLOBDIR_GLOB:
                iter->gl_current++;
                if (iter->gl_current >= iter->glob.gl_pathc) {
                        return 0;
                }
 
                *filename = iter->glob.gl_pathv[iter->gl_current];
                fr_assert(*filename != NULL);
 
                return 1;
#endif
        }
 
        return -1;
}
 
int fr_globdir_iter_free(fr_globdir_iter_t *iter)
{
        if (iter->path) {
                free(iter->path);
                iter->path = NULL;
        }
 
        switch (iter->type) {
        case FR_GLOBDIR_INVALID:
                return -1;
 
        case FR_GLOBDIR_FILE:
                break;
 
#ifdef HAVE_DIRENT_H
        case FR_GLOBDIR_DIR:
                if (!iter->dir) return 0;
 
                return closedir(iter->dir);
#endif
 
#ifdef HAVE_GLOB_H
        case FR_GLOBDIR_GLOB:
                globfree(&iter->glob);
                break;
#endif
        }
 
        return 0;
}
 
const fr_sbuff_escape_rules_t fr_filename_escape = {
        .name = "filename",
        .chr = '_',
        .do_utf8 = true,
        .do_hex = true,
 
        .esc = {
                [ 0x00 ... 0x2d ] = true,               // special characters, but not '.'
                [ 0x2f ] = true,                        // /
                [ 0x3A ... 0x3f ] = true,               // :;<=>?, but not "@"
                [ 0x5b ... 0x5e ] = true,               // [\]^
                [ 0x60 ] = true,                        // back-tick
                [ 0x7b ... 0xff ] = true,               // {|}, and all chars which have high bit set, but aren't UTF-8
        },
};
 
const fr_sbuff_escape_rules_t fr_filename_escape_dots = {
        .name = "filename",
        .chr = '_',
        .do_utf8 = true,
        .do_hex = true,
 
        .esc = {
                [ 0x00 ... 0x2f ] = true,               // special characters, '.', '/', etc.
                [ 0x3A ... 0x3f ] = true,               // :;<=>?, but not "@"
                [ 0x5b ... 0x5e ] = true,               // [\]^
                [ 0x60 ] = true,                        // back-tick
                [ 0x7b ... 0xff ] = true,               // {|}, and all chars which have high bit set, but aren't UTF-8
        },
};