sha1_name.c: refactor find_short_packed_object()

Extract the logic to find object(s) that match a given prefix inside
a single pack into a separate helper function, and give it a bit more
comment.

Signed-off-by: Junio C Hamano <[email protected]>

Author: gitster

sha1_name.c

@@ -78,60 +78,69 @@ static int match_sha(unsigned len, const unsigned char *a, const unsigned char *
 	return 1;
 }
 
+static int unique_in_pack(int len,
+			  const unsigned char *match,
+			  struct packed_git *p,
+			  const unsigned char **found_sha1,
+			  int seen_so_far)
+{
+	uint32_t num, last, i, first = 0;
+	const unsigned char *current = NULL;
+
+	open_pack_index(p);
+	num = p->num_objects;
+	last = num;
+	while (first < last) {
+		uint32_t mid = (first + last) / 2;
+		const unsigned char *current;
+		int cmp;
+
+		current = nth_packed_object_sha1(p, mid);
+		cmp = hashcmp(match, current);
+		if (!cmp) {
+			first = mid;
+			break;
+		}
+		if (cmp > 0) {
+			first = mid+1;
+			continue;
+		}
+		last = mid;
+	}
+
+	/*
+	 * At this point, "first" is the location of the lowest object
+	 * with an object name that could match "match".  See if we have
+	 * 0, 1 or more objects that actually match(es).
+	 */
+	for (i = first; i < num; i++) {
+		current = nth_packed_object_sha1(p, first);
+		if (!match_sha(len, match, current))
+			break;
+
+		/* current matches */
+		if (!seen_so_far) {
+			*found_sha1 = current;
+			seen_so_far++;
+		} else if (seen_so_far) {
+			/* is it the same as the one previously found elsewhere? */
+			if (hashcmp(*found_sha1, current))
+				return 2; /* definitely not unique */
+		}
+	}
+	return seen_so_far;
+}
+
 static int find_short_packed_object(int len, const unsigned char *match, unsigned char *sha1)
 {
 	struct packed_git *p;
 	const unsigned char *found_sha1 = NULL;
 	int found = 0;
 
 	prepare_packed_git();
-	for (p = packed_git; p && found < 2; p = p->next) {
-		uint32_t num, last;
-		uint32_t first = 0;
-		open_pack_index(p);
-		num = p->num_objects;
-		last = num;
-		while (first < last) {
-			uint32_t mid = (first + last) / 2;
-			const unsigned char *current;
-			int cmp;
-
-			current = nth_packed_object_sha1(p, mid);
-			cmp = hashcmp(match, current);
-			if (!cmp) {
-				first = mid;
-				break;
-			}
-			if (cmp > 0) {
-				first = mid+1;
-				continue;
-			}
-			last = mid;
-		}
-		if (first < num) {
-			const unsigned char *current, *next;
-			current = nth_packed_object_sha1(p, first);
-			if (match_sha(len, match, current)) {
-				next = nth_packed_object_sha1(p, first+1);
-				if (!next|| !match_sha(len, match, next)) {
-					/* unique within this pack */
-					if (!found) {
-						found_sha1 = current;
-						found++;
-					}
-					else if (hashcmp(found_sha1, current)) {
-						found = 2;
-						break;
-					}
-				}
-				else {
-					/* not even unique within this pack */
-					found = 2;
-					break;
-				}
-			}
-		}
-	}
+	for (p = packed_git; p && found < 2; p = p->next)
+		found = unique_in_pack(len, match, p, &found_sha1, found);
+
 	if (found == 1)
 		hashcpy(sha1, found_sha1);
 	return found;