Re: [PATCH] attr: fix off-by-one directory component length calculation
From: Junio C Hamano <hidden>
Date: 2016-06-15 22:55:47
Duy Nguyen [off-list ref] writes:
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 <redacted>
Yeah, I think this is a nice code reduction, readability improvement and micro optimization rolled into one.
quoted hunk
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);