Skip to content

HTTPS clone URL

Subversion checkout URL

You can clone with HTTPS or Subversion.

Download ZIP
Fetching contributors…

Cannot retrieve contributors at this time

242 lines (223 sloc) 6.964 kb
#include "cache.h"
static struct cache_def {
char path[PATH_MAX + 1];
int len;
int flags;
int track_flags;
int prefix_len_stat_func;
} cache;
/*
* Returns the length (on a path component basis) of the longest
* common prefix match of 'name' and the cached path string.
*/
static inline int longest_match_lstat_cache(int len, const char *name,
int *previous_slash)
{
int max_len, match_len = 0, match_len_prev = 0, i = 0;
max_len = len < cache.len ? len : cache.len;
while (i < max_len && name[i] == cache.path[i]) {
if (name[i] == '/') {
match_len_prev = match_len;
match_len = i;
}
i++;
}
/* Is the cached path string a substring of 'name'? */
if (i == cache.len && cache.len < len && name[cache.len] == '/') {
match_len_prev = match_len;
match_len = cache.len;
/* Is 'name' a substring of the cached path string? */
} else if ((i == len && len < cache.len && cache.path[len] == '/') ||
(i == len && len == cache.len)) {
match_len_prev = match_len;
match_len = len;
}
*previous_slash = match_len_prev;
return match_len;
}
static inline void reset_lstat_cache(int track_flags, int prefix_len_stat_func)
{
cache.path[0] = '\0';
cache.len = 0;
cache.flags = 0;
cache.track_flags = track_flags;
cache.prefix_len_stat_func = prefix_len_stat_func;
}
#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(int len, const char *name,
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 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(track_flags, 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_match_lstat_cache(len, name, &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(track_flags, prefix_len_stat_func);
}
return ret_flags;
}
/*
* Invalidate the given 'name' from the cache, if 'name' matches
* completely with the cache.
*/
void invalidate_lstat_cache(int len, const char *name)
{
int match_len, previous_slash;
match_len = longest_match_lstat_cache(len, name, &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(cache.track_flags,
cache.prefix_len_stat_func);
}
}
/*
* Completely clear the contents of the cache
*/
void clear_lstat_cache(void)
{
reset_lstat_cache(0, 0);
}
#define USE_ONLY_LSTAT 0
/*
* Return non-zero if path 'name' has a leading symlink component
*/
int has_symlink_leading_path(int len, const char *name)
{
return lstat_cache(len, name,
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(int len, const char *name)
{
return lstat_cache(len, name,
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(int len, const char *name, int prefix_len)
{
return lstat_cache(len, name,
FL_DIR|FL_FULLPATH, prefix_len) &
FL_DIR;
}
Jump to Line
Something went wrong with that request. Please try again.