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, 8 insertions, 4 deletions

diff --git a/hashmap.h b/hashmap.h
index de6022a3a9..aaf09e047e 100644
--- a/hashmap.h
+++ b/hashmap.h
@@ -32,12 +32,14 @@ struct hashmap_entry {
 	unsigned int hash;
 };
 
-typedef int (*hashmap_cmp_fn)(const void *entry, const void *entry_or_key,
-		const void *keydata);
+typedef int (*hashmap_cmp_fn)(const void *hashmap_cmp_fn_data,
+			      const void *entry, const void *entry_or_key,
+			      const void *keydata);
 
 struct hashmap {
 	struct hashmap_entry **table;
 	hashmap_cmp_fn cmpfn;
+	const void *cmpfn_data;
 	unsigned int size, tablesize, grow_at, shrink_at;
 	unsigned disallow_rehash : 1;
 };
@@ -50,8 +52,10 @@ struct hashmap_iter {
 
 /* hashmap functions */
 
-extern void hashmap_init(struct hashmap *map, hashmap_cmp_fn equals_function,
-		size_t initial_size);
+extern void hashmap_init(struct hashmap *map,
+			 hashmap_cmp_fn equals_function,
+			 const void *equals_function_data,
+			 size_t initial_size);
 extern void hashmap_free(struct hashmap *map, int free_entries);
 
 /* hashmap_entry functions */