[PATCH 2/3] sha1_name: Unroll len loop in find_unique_abbrev_r

From

Derrick Stolee <dstolee@microsoft.com>

Date

Sep 15, 2017, 16:57 UTC

Message-ID

<20170915165750.198201-3-dstolee@microsoft.com>

In-Reply-To

<20170915165750.198201-1-dstolee@microsoft.com>

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
---
 sha1_name.c | 57 ++++++++++++++++++++++++++++++++++++++++++---------------
 1 file changed, 42 insertions(+), 15 deletions(-)

diff --git a/sha1_name.c b/sha1_name.c
index 134ac9742..f2a1ebe49 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -474,10 +474,32 @@ static unsigned msb(unsigned long val)
 	return r;
 }
 
-int find_unique_abbrev_r(char *hex, const unsigned char *sha1, int len)
+struct min_abbrev_data {
+	unsigned int init_len;
+	unsigned int cur_len;
+	char *hex;
+};
+
+static int extend_abbrev_len(const struct object_id *oid, void *cb_data)
 {
-	int status, exists;
+	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])
+		i++;
+
+	if (i < GIT_MAX_RAWSZ && i >= mad->cur_len)
+		mad->cur_len = i + 1;
+
+	return 0;
+}
 
+int find_unique_abbrev_r(char *hex, const unsigned char *sha1, int len)
+{
+	struct disambiguate_state ds;
+	struct min_abbrev_data mad;
+	struct object_id oid_ret;
 	if (len < 0) {
 		unsigned long count = approximate_object_count();
 		/*
@@ -503,19 +525,24 @@ int find_unique_abbrev_r(char *hex, const unsigned char *sha1, int len)
 	sha1_to_hex_r(hex, sha1);
 	if (len == GIT_SHA1_HEXSZ || !len)
 		return GIT_SHA1_HEXSZ;
-	exists = has_sha1_file(sha1);
-	while (len < GIT_SHA1_HEXSZ) {
-		struct object_id oid_ret;
-		status = get_short_oid(hex, len, &oid_ret, GET_OID_QUIETLY);
-		if (exists
-		    ? !status
-		    : status == SHORT_NAME_NOT_FOUND) {
-			hex[len] = 0;
-			return len;
-		}
-		len++;
-	}
-	return len;
+
+	if (init_object_disambiguation(hex, len, &ds) < 0)
+		return -1;
+
+	mad.init_len = len;
+	mad.cur_len = len;
+	mad.hex = hex;
+
+	ds.fn = extend_abbrev_len;
+	ds.always_call_fn = 1;
+	ds.cb_data = (void*)&mad;
+
+	find_short_object_filename(&ds);
+	find_short_packed_object(&ds);
+	(void)finish_object_disambiguation(&ds, &oid_ret);
+
+	hex[mad.cur_len] = 0;
+	return mad.cur_len;
 }
 
 const char *find_unique_abbrev(const unsigned char *sha1, int len)

-- 
2.14.1.538.g56ec8fc98.dirty