hashmap.h: compare function has access to a data field

When using the hashmap a common need is to have access to caller provided
data in the compare function. A couple of times we abuse the keydata field
to pass in the data needed. This happens for example in patch-ids.c.

This patch changes the function signature of the compare function
to have one more void pointer available. The pointer given for each
invocation of the compare function must be defined in the init function
of the hashmap and is just passed through.

Documentation of this new feature is deferred to a later patch.
This is a rather mechanical conversion, just adding the new pass-through
parameter.  However while at it improve the naming of the fields of all
compare functions used by hashmaps by ensuring unused parameters are
prefixed with 'unused_' and naming the parameters what they are (instead
of 'unused' make it 'unused_keydata').

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 6 insertions, 3 deletions

diff --git a/config.c b/config.c
index 1cd40a5fe6..4a31e31ac3 100644
--- a/config.c
+++ b/config.c
@@ -1753,15 +1753,18 @@ static int configset_add_value(struct config_set *cs, const char *key, const cha
 	return 0;
 }
 
-static int config_set_element_cmp(const struct config_set_element *e1,
-				 const struct config_set_element *e2, const void *unused)
+static int config_set_element_cmp(const void *unused_cmp_data,
+				  const struct config_set_element *e1,
+				  const struct config_set_element *e2,
+				  const void *unused_keydata)
 {
 	return strcmp(e1->key, e2->key);
 }
 
 void git_configset_init(struct config_set *cs)
 {
-	hashmap_init(&cs->config_hash, (hashmap_cmp_fn)config_set_element_cmp, 0);
+	hashmap_init(&cs->config_hash, (hashmap_cmp_fn)config_set_element_cmp,
+		     NULL, 0);
 	cs->hash_initialized = 1;
 	cs->list.nr = 0;
 	cs->list.alloc = 0;