On Tue, Jan 15, 2013 at 09:35:21PM -0800, Junio C Hamano wrote:
> >> Also the original only
> >> scanned the string from the beginning once (instead of letting
> >> strlen() to scan once and go back).
> >
> > But we do need to strlen() anyway in collect_all_attrs().
> 
> That is exactly my point, isn't it?

OK I get your point now. Something like this?

-- 8< --
Subject: [PATCH] attr: avoid calling find_basename() twice per path

find_basename() is only used inside collect_all_attrs(), called once
in prepare_attr_stack, then again after prepare_attr_stack()
returns. Both calls return exact same value. Reorder the code to do
the same task once. Also avoid strlen() because we knows the length
after finding basename.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclo...@gmail.com>
---
 attr.c | 45 ++++++++++++++++++---------------------------
 1 file changed, 18 insertions(+), 27 deletions(-)

diff --git a/attr.c b/attr.c
index cfc6748..880f862 100644
--- a/attr.c
+++ b/attr.c
@@ -564,32 +564,12 @@ static void bootstrap_attr_stack(void)
        attr_stack = elem;
 }
 
-static const char *find_basename(const char *path)
-{
-       const char *cp, *last_slash = NULL;
-
-       for (cp = path; *cp; cp++) {
-               if (*cp == '/' && cp[1])
-                       last_slash = cp;
-       }
-       return last_slash ? last_slash + 1 : path;
-}
-
-static void prepare_attr_stack(const char *path)
+static void prepare_attr_stack(const char *path, int dirlen)
 {
        struct attr_stack *elem, *info;
-       int dirlen, len;
+       int len;
        const char *cp;
 
-       dirlen = find_basename(path) - path;
-
-       /*
-        * find_basename() includes the trailing slash, but we do
-        * _not_ want it.
-        */
-       if (dirlen)
-               dirlen--;
-
        /*
         * At the bottom of the attribute stack is the built-in
         * set of attribute definitions, followed by the contents
@@ -769,15 +749,26 @@ static int macroexpand_one(int attr_nr, int rem)
 static void collect_all_attrs(const char *path)
 {
        struct attr_stack *stk;
-       int i, pathlen, rem;
-       const char *basename;
+       int i, pathlen, rem, dirlen;
+       const char *basename, *cp, *last_slash = NULL;
+
+       for (cp = path; *cp; cp++) {
+               if (*cp == '/' && cp[1])
+                       last_slash = cp;
+       }
+       pathlen = cp - path;
+       if (last_slash) {
+               basename = last_slash + 1;
+               dirlen = last_slash - path;
+       } else {
+               basename = path;
+               dirlen = 0;
+       }
 
-       prepare_attr_stack(path);
+       prepare_attr_stack(path, dirlen);
        for (i = 0; i < attr_nr; i++)
                check_all_attr[i].value = ATTR__UNKNOWN;
 
-       basename = find_basename(path);
-       pathlen = strlen(path);
        rem = attr_nr;
        for (stk = attr_stack; 0 < rem && stk; stk = stk->prev)
                rem = fill(path, pathlen, basename, stk, rem);
-- 
1.8.0.rc3.18.g0d9b108

-- 8< --
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