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[PATCH 26/28] is_refname_available(): query only possibly-conflicting references

From
mhagger@alum.mit.edu <mhagger@alum.mit.edu>
Date
Oct 28, 2011, 12:28 UTC
Message-ID
<1319804921-17545-27-git-send-email-mhagger@alum.mit.edu>
In-Reply-To
<1319804921-17545-1-git-send-email-mhagger@alum.mit.edu>
From: Michael Haggerty <mhagger@alum.mit.edu>

Instead of iterating through all of the references, inquire more pointedly about the references that could conflict with the new name. This requires checking for a few individual references, plus iterating through a small subtree of the rest of the references (and usually the subtree iteration ends without having to recurse). A big benefit is that populating the whole loose reference cache (which can be very expensive) can usually be avoided.

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
---
 refs.c |   40 +++++++++++++++++++++++++++++++++-------
 1 files changed, 33 insertions(+), 7 deletions(-)
diff --git a/refs.c b/refs.c
index 88ef9dd..6a7f9c3 100644
--- a/refs.c
+++ b/refs.c
@@ -658,7 +658,7 @@ static int name_conflict_fn(const char *existingrefname, const unsigned char *sh
 			    int flags, void *cb_data)
 {
 	struct name_conflict_cb *data = (struct name_conflict_cb *)cb_data;
-	if (data->oldrefname && !strcmp(data->oldrefname, existingrefname))
+	if (!strcmp(data->oldrefname, existingrefname))
 		return 0;
 	if (names_conflict(data->refname, existingrefname)) {
 		data->conflicting_refname = existingrefname;
@@ -669,22 +669,48 @@ static int name_conflict_fn(const char *existingrefname, const unsigned char *sh
 
 /*
  * Return true iff a reference named refname could be created without
- * conflicting with the name of an existing reference.  If oldrefname
- * is non-NULL, ignore potential conflicts with oldrefname (e.g.,
- * because oldrefname is scheduled for deletion in the same
+ * conflicting with the name of an existing reference in direntry.  If
+ * oldrefname is non-NULL, ignore potential conflicts with oldrefname
+ * (e.g., because oldrefname is scheduled for deletion in the same
  * operation).
  */
 static int is_refname_available(const char *refname, const char *oldrefname,
 				struct ref_entry *direntry)
 {
+	int prefixlen = strlen(refname);
+	char *prefix;
+	char *slash;
 	struct name_conflict_cb data;
+
+	assert(direntry->flag & REF_DIR);
+
+	if (!oldrefname)
+		oldrefname = ""; /* invalid; cannot match any existing refname */
+
+	/* Check whether a prefix of refname is an existing reference: */
+	prefix = xmalloc(prefixlen + 2);
+	memcpy(prefix, refname, prefixlen + 1);
+	for (slash = strchr(prefix, '/'); slash; slash = strchr(slash + 1, '/')) {
+		*slash = '\0';
+		if (strcmp(oldrefname, prefix)) {
+			struct ref_entry *entry = find_ref(direntry, prefix);
+			if (entry) {
+				error("'%s' exists; cannot create '%s'", prefix, refname);
+				free(prefix);
+				return 0;
+			}
+		}
+		*slash = '/';
+	}
+
+	/* Check whether refname is a proper prefix of an existing reference: */
+	prefix[prefixlen++] = '/';
+	prefix[prefixlen] = '\0';
 	data.refname = refname;
 	data.oldrefname = oldrefname;
 	data.conflicting_refname = NULL;
 
-	assert(direntry->flag & REF_DIR);
-
-	if (do_for_each_ref_in_dir(direntry, 0, "", name_conflict_fn,
+	if (do_for_each_ref_in_dir(direntry, 0, prefix, name_conflict_fn,
 				   0, DO_FOR_EACH_INCLUDE_BROKEN,
 				   &data)) {
 		error("'%s' exists; cannot create '%s'",

-- 
1.7.7
Previous: mhagger@alum.mit.eduNext: mhagger@alum.mit.edu
Message 27 of 36 in “Store references hierarchically in cache”
  1. 00/28 Store references hierarchically in cachemhagger@alum.mit.edu, Oct 28, 2011
  2. 01/28 refs.c: reorder definitions more logicallymhagger@alum.mit.edu, Oct 28, 2011
  3. 02/28 free_ref_entry(): new functionmhagger@alum.mit.edu, Oct 28, 2011
  4. 03/28 check_refname_component(): return 0 for zero-length componentsmhagger@alum.mit.edu, Oct 28, 2011
  5. 04/28 struct ref_entry: nest the value part in a unionmhagger@alum.mit.edu, Oct 28, 2011
  6. 05/28 refs.c: rename ref_array -> ref_dirmhagger@alum.mit.edu, Oct 28, 2011
  7. 06/28 refs: store references hierarchicallymhagger@alum.mit.edu, Oct 28, 2011
  8. 07/28 sort_ref_dir(): do not sort if already sortedmhagger@alum.mit.edu, Oct 28, 2011
  9. 08/28 refs: sort ref_dirs lazilymhagger@alum.mit.edu, Oct 28, 2011
  10. 09/28 do_for_each_ref(): only iterate over the subtree that was requestedmhagger@alum.mit.edu, Oct 28, 2011
  11. 10/28 get_ref_dir(): keep track of the current ref_dirmhagger@alum.mit.edu, Oct 28, 2011
  12. 11/28 refs: wrap top-level ref_dirs in ref_entriesmhagger@alum.mit.edu, Oct 28, 2011
  13. 12/28 get_packed_refs(): return (ref_entry *) instead of (ref_dir *)mhagger@alum.mit.edu, Oct 28, 2011
  14. 13/28 get_loose_refs(): return (ref_entry *) instead of (ref_dir *)mhagger@alum.mit.edu, Oct 28, 2011
  15. 14/28 is_refname_available(): take (ref_entry *) instead of (ref_dir *)mhagger@alum.mit.edu, Oct 28, 2011
  16. 15/28 find_ref(): take (ref_entry *) instead of (ref_dir *)mhagger@alum.mit.edu, Oct 28, 2011
  17. 16/28 read_packed_refs(): take (ref_entry *) instead of (ref_dir *)mhagger@alum.mit.edu, Oct 28, 2011
  18. 17/28 add_ref(): take (ref_entry *) instead of (ref_dir *)mhagger@alum.mit.edu, Oct 28, 2011
  19. 18/28 find_containing_direntry(): use (ref_entry *) instead of (ref_dir *)mhagger@alum.mit.edu, Oct 28, 2011
  20. 19/28 search_ref_dir(): take (ref_entry *) instead of (ref_dir *)mhagger@alum.mit.edu, Oct 28, 2011
  21. 20/28 add_entry(): take (ref_entry *) instead of (ref_dir *)mhagger@alum.mit.edu, Oct 28, 2011
  22. 21/28 do_for_each_ref_in_dir*(): take (ref_entry *) instead of (ref_dir *)mhagger@alum.mit.edu, Oct 28, 2011
  23. 22/28 sort_ref_dir(): take (ref_entry *) instead of (ref_dir *)mhagger@alum.mit.edu, Oct 28, 2011
  24. 23/28 struct ref_dir: store a reference to the enclosing ref_cachemhagger@alum.mit.edu, Oct 28, 2011
  25. 24/28 read_loose_refs(): take a (ref_entry *) as argumentmhagger@alum.mit.edu, Oct 28, 2011
  26. 25/28 refs: read loose references lazilymhagger@alum.mit.edu, Oct 28, 2011
  27. 26/28 is_refname_available(): query only possibly-conflicting referencesmhagger@alum.mit.edu, Oct 28, 2011
  28. Fix "is_refname_available(): query only possibly-conflicting references"mhagger@alum.mit.edu, Nov 15, 2011
  29. Junio C HamanoNov 15, 2011
  30. Michael HaggertyNov 15, 2011
  31. Junio C HamanoNov 15, 2011
  32. 27/28 read_packed_refs(): keep track of the directory being worked inmhagger@alum.mit.edu, Oct 28, 2011
  33. 28/28 repack_without_ref(): call clear_packed_ref_cache()mhagger@alum.mit.edu, Oct 28, 2011
  34. Ramkumar RamachandraOct 28, 2011
  35. Michael HaggertyOct 28, 2011
  36. Michael HaggertyNov 16, 2011

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