convert hashmap comparison functions to oideq()

The comparison functions used for hashmaps don't care about
strict ordering; they only want to compare entries for
equality. Let's use the oideq() function instead, which can
potentially be better optimized. Note that unlike the
previous patches mass-converting calls like "!oidcmp()",
this patch could actually provide an improvement even with
the current implementation. Those comparison functions are
passed around as function pointers, so at compile-time the
compiler cannot realize that the caller (which is in another
file completely) will treat the return value as a boolean.

Note that this does change the return values in quite a
subtle way (it's still an int, but now the sign bit is
irrelevant for ordering). Because of their funny
hashmap-specific signature, it's unlikely that any of these
static functions would be reused for more generic ordering.
But to be double-sure, let's stop using "cmp" in their
names.

Calling them "eq" doesn't quite work either, because the
hashmap convention is actually _inverted_. "0" means "same",
and non-zero means "different". So I've called them "neq" by
convention here.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/describe.c

@@ -62,7 +62,7 @@ static const char *prio_names[] = {
 	N_("head"), N_("lightweight"), N_("annotated"),
 };
 
-static int commit_name_cmp(const void *unused_cmp_data,
+static int commit_name_neq(const void *unused_cmp_data,
 			   const void *entry,
 			   const void *entry_or_key,
 			   const void *peeled)
@@ -70,7 +70,7 @@ static int commit_name_cmp(const void *unused_cmp_data,
 	const struct commit_name *cn1 = entry;
 	const struct commit_name *cn2 = entry_or_key;
 
-	return oidcmp(&cn1->peeled, peeled ? peeled : &cn2->peeled);
+	return !oideq(&cn1->peeled, peeled ? peeled : &cn2->peeled);
 }
 
 static inline struct commit_name *find_commit_name(const struct object_id *peeled)
@@ -596,7 +596,7 @@ int cmd_describe(int argc, const char **argv, const char *prefix)
 		return cmd_name_rev(args.argc, args.argv, prefix);
 	}
 
-	hashmap_init(&names, commit_name_cmp, NULL, 0);
+	hashmap_init(&names, commit_name_neq, NULL, 0);
 	for_each_rawref(get_name, NULL);
 	if (!hashmap_get_size(&names) && !always)
 		die(_("No names found, cannot describe anything."));

oidmap.c

@@ -1,14 +1,14 @@
 #include "cache.h"
 #include "oidmap.h"
 
-static int cmpfn(const void *hashmap_cmp_fn_data,
-		 const void *entry, const void *entry_or_key,
-		 const void *keydata)
+static int oidmap_neq(const void *hashmap_cmp_fn_data,
+		      const void *entry, const void *entry_or_key,
+		      const void *keydata)
 {
 	const struct oidmap_entry *entry_ = entry;
 	if (keydata)
-		return oidcmp(&entry_->oid, (const struct object_id *) keydata);
-	return oidcmp(&entry_->oid,
+		return !oideq(&entry_->oid, (const struct object_id *) keydata);
+	return !oideq(&entry_->oid,
 		      &((const struct oidmap_entry *) entry_or_key)->oid);
 }
 
@@ -21,7 +21,7 @@ static int hash(const struct object_id *oid)
 
 void oidmap_init(struct oidmap *map, size_t initial_size)
 {
-	hashmap_init(&map->map, cmpfn, NULL, initial_size);
+	hashmap_init(&map->map, oidmap_neq, NULL, initial_size);
 }
 
 void oidmap_free(struct oidmap *map, int free_entries)

patch-ids.c

@@ -28,14 +28,14 @@ int commit_patch_id(struct commit *commit, struct diff_options *options,
 /*
  * When we cannot load the full patch-id for both commits for whatever
  * reason, the function returns -1 (i.e. return error(...)). Despite
- * the "cmp" in the name of this function, the caller only cares about
+ * the "neq" in the name of this function, the caller only cares about
  * the return value being zero (a and b are equivalent) or non-zero (a
  * and b are different), and returning non-zero would keep both in the
  * result, even if they actually were equivalent, in order to err on
  * the side of safety.  The actual value being negative does not have
  * any significance; only that it is non-zero matters.
  */
-static int patch_id_cmp(const void *cmpfn_data,
+static int patch_id_neq(const void *cmpfn_data,
 			const void *entry,
 			const void *entry_or_key,
 			const void *unused_keydata)
@@ -53,7 +53,7 @@ static int patch_id_cmp(const void *cmpfn_data,
 	    commit_patch_id(b->commit, opt, &b->patch_id, 0))
 		return error("Could not get patch ID for %s",
 			oid_to_hex(&b->commit->object.oid));
-	return oidcmp(&a->patch_id, &b->patch_id);
+	return !oideq(&a->patch_id, &b->patch_id);
 }
 
 int init_patch_ids(struct patch_ids *ids)
@@ -63,7 +63,7 @@ int init_patch_ids(struct patch_ids *ids)
 	ids->diffopts.detect_rename = 0;
 	ids->diffopts.flags.recursive = 1;
 	diff_setup_done(&ids->diffopts);
-	hashmap_init(&ids->patches, patch_id_cmp, &ids->diffopts, 256);
+	hashmap_init(&ids->patches, patch_id_neq, &ids->diffopts, 256);
 	return 0;
 }