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#include "cache.h"

/*
* Returns the length (on a path component basis) of the longest
* common prefix match of 'name_a' and 'name_b'.
*/
static int longest_path_match(const char *name_a, int len_a,
const char *name_b, int len_b,
int *previous_slash)
{
int max_len, match_len = 0, match_len_prev = 0, i = 0;

max_len = len_a < len_b ? len_a : len_b;
while (i < max_len && name_a[i] == name_b[i]) {
if (name_a[i] == '/') {
match_len_prev = match_len;
match_len = i;
}
i++;
}
/*
* Is 'name_b' a substring of 'name_a', the other way around,
* or is 'name_a' and 'name_b' the exact same string?
*/
if (i >= max_len && ((len_a > len_b && name_a[len_b] == '/') ||
(len_a < len_b && name_b[len_a] == '/') ||
(len_a == len_b))) {
match_len_prev = match_len;
match_len = i;
}
*previous_slash = match_len_prev;
return match_len;
}

static struct cache_def {
char path[PATH_MAX + 1];
int len;
int flags;
int track_flags;
int prefix_len_stat_func;
} cache;

static inline void reset_lstat_cache(void)
{
cache.path[0] = '\0';
cache.len = 0;
cache.flags = 0;
/*
* The track_flags and prefix_len_stat_func members is only
* set by the safeguard rule inside lstat_cache()
*/
}

#define FL_DIR (1 << 0)
#define FL_NOENT (1 << 1)
#define FL_SYMLINK (1 << 2)
#define FL_LSTATERR (1 << 3)
#define FL_ERR (1 << 4)
#define FL_FULLPATH (1 << 5)

/*
* Check if name 'name' of length 'len' has a symlink leading
* component, or if the directory exists and is real, or not.
*
* To speed up the check, some information is allowed to be cached.
* This can be indicated by the 'track_flags' argument, which also can
* be used to indicate that we should check the full path.
*
* The 'prefix_len_stat_func' parameter can be used to set the length
* of the prefix, where the cache should use the stat() function
* instead of the lstat() function to test each path component.
*/
static int lstat_cache(const char *name, int len,
int track_flags, int prefix_len_stat_func)
{
int match_len, last_slash, last_slash_dir, previous_slash;
int match_flags, ret_flags, save_flags, max_len, ret;
struct stat st;

if (cache.track_flags != track_flags ||
cache.prefix_len_stat_func != prefix_len_stat_func) {
/*
* As a safeguard rule we clear the cache if the
* values of track_flags and/or prefix_len_stat_func
* does not match with the last supplied values.
*/
reset_lstat_cache();
cache.track_flags = track_flags;
cache.prefix_len_stat_func = prefix_len_stat_func;
match_len = last_slash = 0;
} else {
/*
* Check to see if we have a match from the cache for
* the 2 "excluding" path types.
*/
match_len = last_slash =
longest_path_match(name, len, cache.path, cache.len,
&previous_slash);
match_flags = cache.flags & track_flags & (FL_NOENT|FL_SYMLINK);
if (match_flags && match_len == cache.len)
return match_flags;
/*
* If we now have match_len > 0, we would know that
* the matched part will always be a directory.
*
* Also, if we are tracking directories and 'name' is
* a substring of the cache on a path component basis,
* we can return immediately.
*/
match_flags = track_flags & FL_DIR;
if (match_flags && len == match_len)
return match_flags;
}

/*
* Okay, no match from the cache so far, so now we have to
* check the rest of the path components.
*/
ret_flags = FL_DIR;
last_slash_dir = last_slash;
max_len = len < PATH_MAX ? len : PATH_MAX;
while (match_len < max_len) {
do {
cache.path[match_len] = name[match_len];
match_len++;
} while (match_len < max_len && name[match_len] != '/');
if (match_len >= max_len && !(track_flags & FL_FULLPATH))
break;
last_slash = match_len;
cache.path[last_slash] = '\0';

if (last_slash <= prefix_len_stat_func)
ret = stat(cache.path, &st);
else
ret = lstat(cache.path, &st);

if (ret) {
ret_flags = FL_LSTATERR;
if (errno == ENOENT)
ret_flags |= FL_NOENT;
} else if (S_ISDIR(st.st_mode)) {
last_slash_dir = last_slash;
continue;
} else if (S_ISLNK(st.st_mode)) {
ret_flags = FL_SYMLINK;
} else {
ret_flags = FL_ERR;
}
break;
}

/*
* At the end update the cache. Note that max 3 different
* path types, FL_NOENT, FL_SYMLINK and FL_DIR, can be cached
* for the moment!
*/
save_flags = ret_flags & track_flags & (FL_NOENT|FL_SYMLINK);
if (save_flags && last_slash > 0 && last_slash <= PATH_MAX) {
cache.path[last_slash] = '\0';
cache.len = last_slash;
cache.flags = save_flags;
} else if ((track_flags & FL_DIR) &&
last_slash_dir > 0 && last_slash_dir <= PATH_MAX) {
/*
* We have a separate test for the directory case,
* since it could be that we have found a symlink or a
* non-existing directory and the track_flags says
* that we cannot cache this fact, so the cache would
* then have been left empty in this case.
*
* But if we are allowed to track real directories, we
* can still cache the path components before the last
* one (the found symlink or non-existing component).
*/
cache.path[last_slash_dir] = '\0';
cache.len = last_slash_dir;
cache.flags = FL_DIR;
} else {
reset_lstat_cache();
}
return ret_flags;
}

/*
* Invalidate the given 'name' from the cache, if 'name' matches
* completely with the cache.
*/
void invalidate_lstat_cache(const char *name, int len)
{
int match_len, previous_slash;

match_len = longest_path_match(name, len, cache.path, cache.len,
&previous_slash);
if (len == match_len) {
if ((cache.track_flags & FL_DIR) && previous_slash > 0) {
cache.path[previous_slash] = '\0';
cache.len = previous_slash;
cache.flags = FL_DIR;
} else
reset_lstat_cache();
}
}

/*
* Completely clear the contents of the cache
*/
void clear_lstat_cache(void)
{
reset_lstat_cache();
}

#define USE_ONLY_LSTAT 0

/*
* Return non-zero if path 'name' has a leading symlink component
*/
int has_symlink_leading_path(const char *name, int len)
{
return lstat_cache(name, len,
FL_SYMLINK|FL_DIR, USE_ONLY_LSTAT) &
FL_SYMLINK;
}

/*
* Return non-zero if path 'name' has a leading symlink component or
* if some leading path component does not exists.
*/
int has_symlink_or_noent_leading_path(const char *name, int len)
{
return lstat_cache(name, len,
FL_SYMLINK|FL_NOENT|FL_DIR, USE_ONLY_LSTAT) &
(FL_SYMLINK|FL_NOENT);
}

/*
* Return non-zero if all path components of 'name' exists as a
* directory. If prefix_len > 0, we will test with the stat()
* function instead of the lstat() function for a prefix length of
* 'prefix_len', thus we then allow for symlinks in the prefix part as
* long as those points to real existing directories.
*/
int has_dirs_only_path(const char *name, int len, int prefix_len)
{
return lstat_cache(name, len,
FL_DIR|FL_FULLPATH, prefix_len) &
FL_DIR;
}

static struct removal_def {
char path[PATH_MAX];
int len;
} removal;

static void do_remove_scheduled_dirs(int new_len)
{
while (removal.len > new_len) {
removal.path[removal.len] = '\0';
if (rmdir(removal.path))
break;
do {
removal.len--;
} while (removal.len > new_len &&
removal.path[removal.len] != '/');
}
removal.len = new_len;
return;
}

void schedule_dir_for_removal(const char *name, int len)
{
int match_len, last_slash, i, previous_slash;

match_len = last_slash = i =
longest_path_match(name, len, removal.path, removal.len,
&previous_slash);
/* Find last slash inside 'name' */
while (i < len) {
if (name[i] == '/')
last_slash = i;
i++;
}

/*
* If we are about to go down the directory tree, we check if
* we must first go upwards the tree, such that we then can
* remove possible empty directories as we go upwards.
*/
if (match_len < last_slash && match_len < removal.len)
do_remove_scheduled_dirs(match_len);
/*
* If we go deeper down the directory tree, we only need to
* save the new path components as we go down.
*/
if (match_len < last_slash) {
memcpy(&removal.path[match_len], &name[match_len],
last_slash - match_len);
removal.len = last_slash;
}
return;
}

void remove_scheduled_dirs(void)
{
do_remove_scheduled_dirs(0);
return;
}
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