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-rw-r--r--symlinks.c165
1 files changed, 125 insertions, 40 deletions
diff --git a/symlinks.c b/symlinks.c
index 5a5e781..49fb4d8 100644
--- a/symlinks.c
+++ b/symlinks.c
@@ -1,64 +1,149 @@
#include "cache.h"
-struct pathname {
- int len;
+static struct cache_def {
char path[PATH_MAX];
-};
+ int len;
+ int flags;
+} cache;
-/* Return matching pathname prefix length, or zero if not matching */
-static inline int match_pathname(int len, const char *name, struct pathname *match)
+/*
+ * 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 match_len = match->len;
- return (len > match_len &&
- name[match_len] == '/' &&
- !memcmp(name, match->path, match_len)) ? match_len : 0;
+ int max_len, match_len = 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 = i;
+ i++;
+ }
+ /* Is the cached path string a substring of 'name'? */
+ if (i == cache.len && cache.len < len && name[cache.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 = len;
+ return match_len;
}
-static inline void set_pathname(int len, const char *name, struct pathname *match)
+static inline void reset_lstat_cache(void)
{
- if (len < PATH_MAX) {
- match->len = len;
- memcpy(match->path, name, len);
- match->path[len] = 0;
- }
+ cache.path[0] = '\0';
+ cache.len = 0;
+ cache.flags = 0;
}
-int has_symlink_leading_path(int len, const char *name)
+#define FL_DIR (1 << 0)
+#define FL_SYMLINK (1 << 1)
+#define FL_LSTATERR (1 << 2)
+#define FL_ERR (1 << 3)
+
+/*
+ * Check if name 'name' of length 'len' has a symlink leading
+ * component, or if the directory exists and is real.
+ *
+ * To speed up the check, some information is allowed to be cached.
+ * This can be indicated by the 'track_flags' argument.
+ */
+static int lstat_cache(int len, const char *name,
+ int track_flags)
{
- static struct pathname link, nonlink;
- char path[PATH_MAX];
+ int match_len, last_slash, last_slash_dir;
+ int match_flags, ret_flags, save_flags, max_len;
struct stat st;
- char *sp;
- int known_dir;
/*
- * See if the last known symlink cache matches.
+ * Check to see if we have a match from the cache for the
+ * symlink path type.
*/
- if (match_pathname(len, name, &link))
- return 1;
-
+ match_len = last_slash = longest_match_lstat_cache(len, name);
+ match_flags = cache.flags & track_flags & FL_SYMLINK;
+ if (match_flags && match_len == cache.len)
+ return match_flags;
/*
- * Get rid of the last known directory part
+ * 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.
*/
- known_dir = match_pathname(len, name, &nonlink);
+ match_flags = track_flags & FL_DIR;
+ if (match_flags && len == match_len)
+ return match_flags;
- while ((sp = strchr(name + known_dir + 1, '/')) != NULL) {
- int thislen = sp - name ;
- memcpy(path, name, thislen);
- path[thislen] = 0;
+ /*
+ * 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)
+ break;
+ last_slash = match_len;
+ cache.path[last_slash] = '\0';
- if (lstat(path, &st))
- return 0;
- if (S_ISDIR(st.st_mode)) {
- set_pathname(thislen, path, &nonlink);
- known_dir = thislen;
+ if (lstat(cache.path, &st)) {
+ ret_flags = FL_LSTATERR;
+ } else if (S_ISDIR(st.st_mode)) {
+ last_slash_dir = last_slash;
continue;
- }
- if (S_ISLNK(st.st_mode)) {
- set_pathname(thislen, path, &link);
- return 1;
+ } else if (S_ISLNK(st.st_mode)) {
+ ret_flags = FL_SYMLINK;
+ } else {
+ ret_flags = FL_ERR;
}
break;
}
- return 0;
+
+ /*
+ * At the end update the cache. Note that max 2 different
+ * path types, FL_SYMLINK and FL_DIR, can be cached for the
+ * moment!
+ */
+ save_flags = ret_flags & track_flags & 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 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 component).
+ */
+ cache.path[last_slash_dir] = '\0';
+ cache.len = last_slash_dir;
+ cache.flags = FL_DIR;
+ } else {
+ reset_lstat_cache();
+ }
+ return ret_flags;
+}
+
+/*
+ * 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) &
+ FL_SYMLINK;
}