Re: [PATCH v3 4/5] sha1_name: Parse less while finding common prefix
From: Junio C Hamano <hidden>
Date: 2017-10-04 06:14:59
Derrick Stolee [off-list ref] writes:
quoted hunk
diff --git a/sha1_name.c b/sha1_name.c index f2a1ebe49..5081aeb71 100644 --- a/sha1_name.c +++ b/sha1_name.c@@ -480,13 +480,23 @@ struct min_abbrev_data { char *hex; }; +static inline char get_hex_char_from_oid(const struct object_id *oid, + int pos) +{ + static const char hex[] = "0123456789abcdef"; + + if ((pos & 1) == 0) + return hex[oid->hash[pos >> 1] >> 4]; + else + return hex[oid->hash[pos >> 1] & 0xf]; +} +
static int extend_abbrev_len(const struct object_id *oid, void *cb_data)
{
struct min_abbrev_data *mad = cb_data;
- char *hex = oid_to_hex(oid);
unsigned int i = mad->init_len;
- while (mad->hex[i] && mad->hex[i] == hex[i])
+ while (mad->hex[i] && mad->hex[i] == get_hex_char_from_oid(oid, i))
i++;Assuming that [PATCH 3/5] makes sense, it is an obvious optimization to avoid writing the whole 20-byte out before comparing, and instead to grab hex digits as they become needed. I assume that the "Base Time" in the log message was with whatever version of Git before [PATCH 3/5] and this one were applied (i.e. not comparing to "vanilla Git plus 3/5")? Thanks.