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, 10 insertions, 6 deletions

diff --git a/name-hash.c b/name-hash.c
index 39309efb7f..0e10f3eab8 100644
--- a/name-hash.c
+++ b/name-hash.c
@@ -16,8 +16,10 @@ struct dir_entry {
 	char name[FLEX_ARRAY];
 };
 
-static int dir_entry_cmp(const struct dir_entry *e1,
-		const struct dir_entry *e2, const char *name)
+static int dir_entry_cmp(const void *unused_cmp_data,
+			 const struct dir_entry *e1,
+			 const struct dir_entry *e2,
+			 const char *name)
 {
 	return e1->namelen != e2->namelen || strncasecmp(e1->name,
 			name ? name : e2->name, e1->namelen);
@@ -107,8 +109,10 @@ static void hash_index_entry(struct index_state *istate, struct cache_entry *ce)
 		add_dir_entry(istate, ce);
 }
 
-static int cache_entry_cmp(const struct cache_entry *ce1,
-		const struct cache_entry *ce2, const void *remove)
+static int cache_entry_cmp(const void *unused_cmp_data,
+			   const struct cache_entry *ce1,
+			   const struct cache_entry *ce2,
+			   const void *remove)
 {
 	/*
 	 * For remove_name_hash, find the exact entry (pointer equality); for
@@ -571,9 +575,9 @@ static void lazy_init_name_hash(struct index_state *istate)
 	if (istate->name_hash_initialized)
 		return;
 	hashmap_init(&istate->name_hash, (hashmap_cmp_fn) cache_entry_cmp,
-			istate->cache_nr);
+			NULL, istate->cache_nr);
 	hashmap_init(&istate->dir_hash, (hashmap_cmp_fn) dir_entry_cmp,
-			istate->cache_nr);
+			NULL, istate->cache_nr);
 
 	if (lookup_lazy_params(istate)) {
 		hashmap_disallow_rehash(&istate->dir_hash, 1);