Jeff King <peff@xxxxxxxx> writes:
> When commit fe8e3b7 refactored type_from_string to allow
> input that was not NUL-terminated, it switched to using
> strncmp instead of strcmp. But this means we check only the
> first "len" bytes of the strings, and ignore any remaining
> bytes in the object_type_string. We should make sure that it
> is also "len" bytes, or else we would accept "comm" as
> "commit", and so forth.
>
> Signed-off-by: Jeff King <peff@xxxxxxxx>
> ---
> Since the strings we are matching are literals, we could also record
> their sizes in the object_type_strings array and check the length first
> before even calling strncmp. I doubt this is a performance hot-spot,
> though.
>
> You could also potentially just use strlen(object_type_strings[i]), but
> I'm not sure if compilers will optimize out the strlen in this case,
> since it is in a loop.
That thought crossed my mind while reading your patch. It could
even make it go faster if we made object_type_strings into an array
of counted strings (i.e. "struct { const char *str; int len; }")
and then took advantage of the fact that we have lengths of both.
object.c | 24 ++++++++++++++----------
1 file changed, 14 insertions(+), 10 deletions(-)
diff --git a/object.c b/object.c
index aedac24..51584ea 100644
--- a/object.c
+++ b/object.c
@@ -18,19 +18,22 @@ struct object *get_indexed_object(unsigned int idx)
return obj_hash[idx];
}
-static const char *object_type_strings[] = {
- NULL, /* OBJ_NONE = 0 */
- "commit", /* OBJ_COMMIT = 1 */
- "tree", /* OBJ_TREE = 2 */
- "blob", /* OBJ_BLOB = 3 */
- "tag", /* OBJ_TAG = 4 */
+static struct {
+ const char *str;
+ int len;
+} object_type_name[] = {
+ { NULL, 0 }, /* OBJ_NONE = 0 */
+ { "commit", 6 }, /* OBJ_COMMIT = 1 */
+ { "tree", 4 }, /* OBJ_TREE = 2 */
+ { "blob", 4 }, /* OBJ_BLOB = 3 */
+ { "tag", 3 }, /* OBJ_TAG = 4 */
};
const char *typename(unsigned int type)
{
- if (type >= ARRAY_SIZE(object_type_strings))
+ if (type >= ARRAY_SIZE(object_type_name))
return NULL;
- return object_type_strings[type];
+ return object_type_name[type].str;
}
int type_from_string_gently(const char *str, ssize_t len, int gentle)
@@ -40,8 +43,9 @@ int type_from_string_gently(const char *str, ssize_t len, int gentle)
if (len < 0)
len = strlen(str);
- for (i = 1; i < ARRAY_SIZE(object_type_strings); i++)
- if (!strncmp(str, object_type_strings[i], len))
+ for (i = 1; i < ARRAY_SIZE(object_type_name); i++)
+ if (object_type_name[i].len == len &&
+ !strncmp(str, object_type_name[i].str, len))
return i;
if (gentle)
--
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