lstat_cache(): small cleanup and optimisation

Simplify the if-else test in longest_match_lstat_cache() such that we
only have one simple if test.  Instead of testing for 'i == cache.len'
or 'i == len', we transform this to a common test for 'i == max_len'.

And to further optimise we use 'i >= max_len' instead of 'i ==
max_len', the reason is that it is now the exact opposite of one part
inside the while-loop termination expression 'i < max_len && name[i]
== cache.path[i]', and then the compiler can probably reuse a test
instruction from it.

We also throw away the arguments to reset_lstat_cache(), such that all
the safeguard logic inside lstat_cache() is handled at one place.

Signed-off-by: Kjetil Barvik <barvik@broadpark.no>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/symlinks.c b/symlinks.c
index f262b7c44b387f4c60901124c30585b3c059fa73..ae57e5603bb3e07f3d4c28204850913a9ba2b0ba 100644 (file)
--- a/symlinks.c
+++ b/symlinks.c
@@ -25,27 +25,30 @@ static inline int longest_match_lstat_cache(int len, const char *name,
                }
                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)) {
+       /*
+        * Is the cached path string a substring of 'name', is 'name'
+        * a substring of the cached path string, or is 'name' and the
+        * cached path string the exact same string?
+        */
+       if (i >= max_len && ((len > cache.len && name[cache.len] == '/') ||
+                            (len < cache.len && cache.path[len] == '/') ||
+                            (len == cache.len))) {
                match_len_prev = match_len;
-               match_len = len;
+               match_len = i;
        }
        *previous_slash = match_len_prev;
        return match_len;
 }
 
-static inline void reset_lstat_cache(int track_flags, int prefix_len_stat_func)
+static inline void reset_lstat_cache(void)
 {
        cache.path[0] = '\0';
        cache.len = 0;
        cache.flags = 0;
-       cache.track_flags = track_flags;
-       cache.prefix_len_stat_func = prefix_len_stat_func;
+       /*
+        * The track_flags and prefix_len_stat_func members is only
+        * set by the safeguard rule inside lstat_cache()
+        */
 }
 
 #define FL_DIR      (1 << 0)
@@ -77,11 +80,13 @@ static int lstat_cache(int len, const char *name,
        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.
+                * 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(track_flags, prefix_len_stat_func);
+               reset_lstat_cache();
+               cache.track_flags = track_flags;
+               cache.prefix_len_stat_func = prefix_len_stat_func;
                match_len = last_slash = 0;
        } else {
                /*
@@ -153,7 +158,7 @@ static int lstat_cache(int len, const char *name,
                cache.path[last_slash] = '\0';
                cache.len = last_slash;
                cache.flags = save_flags;
-       } else if (track_flags & FL_DIR &&
+       } else if ((track_flags & FL_DIR) &&
                   last_slash_dir > 0 && last_slash_dir <= PATH_MAX) {
                /*
                 * We have a separate test for the directory case,
@@ -170,7 +175,7 @@ static int lstat_cache(int len, const char *name,
                cache.len = last_slash_dir;
                cache.flags = FL_DIR;
        } else {
-               reset_lstat_cache(track_flags, prefix_len_stat_func);
+               reset_lstat_cache();
        }
        return ret_flags;
 }
@@ -190,8 +195,7 @@ void invalidate_lstat_cache(int len, const char *name)
                        cache.len = previous_slash;
                        cache.flags = FL_DIR;
                } else
-                       reset_lstat_cache(cache.track_flags,
-                                         cache.prefix_len_stat_func);
+                       reset_lstat_cache();
        }
 }
 
@@ -200,7 +204,7 @@ void invalidate_lstat_cache(int len, const char *name)
  */
 void clear_lstat_cache(void)
 {
-       reset_lstat_cache(0, 0);
+       reset_lstat_cache();
 }
 
 #define USE_ONLY_LSTAT  0