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>

3 files changed, 24 insertions, 15 deletions

diff --git a/builtin/describe.c b/builtin/describe.c
index 70eb144608..8868f00ed0 100644
--- a/builtin/describe.c
+++ b/builtin/describe.c
@@ -54,8 +54,10 @@ static const char *prio_names[] = {
 	N_("head"), N_("lightweight"), N_("annotated"),
 };
 
-static int commit_name_cmp(const struct commit_name *cn1,
-		const struct commit_name *cn2, const void *peeled)
+static int commit_name_cmp(const void *unused_cmp_data,
+			   const struct commit_name *cn1,
+			   const struct commit_name *cn2,
+			   const void *peeled)
 {
 	return oidcmp(&cn1->peeled, peeled ? peeled : &cn2->peeled);
 }
@@ -501,7 +503,7 @@ int cmd_describe(int argc, const char **argv, const char *prefix)
 		return cmd_name_rev(args.argc, args.argv, prefix);
 	}
 
-	hashmap_init(&names, (hashmap_cmp_fn) commit_name_cmp, 0);
+	hashmap_init(&names, (hashmap_cmp_fn) commit_name_cmp, NULL, 0);
 	for_each_rawref(get_name, NULL);
 	if (!names.size && !always)
 		die(_("No names found, cannot describe anything."));
diff --git a/builtin/difftool.c b/builtin/difftool.c
index 9199227f6e..a1a26ba891 100644
--- a/builtin/difftool.c
+++ b/builtin/difftool.c
@@ -130,8 +130,10 @@ struct working_tree_entry {
 	char path[FLEX_ARRAY];
 };
 
-static int working_tree_entry_cmp(struct working_tree_entry *a,
-				  struct working_tree_entry *b, void *keydata)
+static int working_tree_entry_cmp(const void *unused_cmp_data,
+				  struct working_tree_entry *a,
+				  struct working_tree_entry *b,
+				  void *unused_keydata)
 {
 	return strcmp(a->path, b->path);
 }
@@ -146,7 +148,9 @@ struct pair_entry {
 	const char path[FLEX_ARRAY];
 };
 
-static int pair_cmp(struct pair_entry *a, struct pair_entry *b, void *keydata)
+static int pair_cmp(const void *unused_cmp_data,
+		    struct pair_entry *a, struct pair_entry *b,
+		    void *unused_keydata)
 {
 	return strcmp(a->path, b->path);
 }
@@ -174,7 +178,9 @@ struct path_entry {
 	char path[FLEX_ARRAY];
 };
 
-static int path_entry_cmp(struct path_entry *a, struct path_entry *b, void *key)
+static int path_entry_cmp(const void *unused_cmp_data,
+			  struct path_entry *a, struct path_entry *b,
+			  void *key)
 {
 	return strcmp(a->path, key ? key : b->path);
 }
@@ -367,9 +373,9 @@ static int run_dir_diff(const char *extcmd, int symlinks, const char *prefix,
 	wtdir_len = wtdir.len;
 
 	hashmap_init(&working_tree_dups,
-		     (hashmap_cmp_fn)working_tree_entry_cmp, 0);
-	hashmap_init(&submodules, (hashmap_cmp_fn)pair_cmp, 0);
-	hashmap_init(&symlinks2, (hashmap_cmp_fn)pair_cmp, 0);
+		     (hashmap_cmp_fn)working_tree_entry_cmp, NULL, 0);
+	hashmap_init(&submodules, (hashmap_cmp_fn)pair_cmp, NULL, 0);
+	hashmap_init(&symlinks2, (hashmap_cmp_fn)pair_cmp, NULL, 0);
 
 	child.no_stdin = 1;
 	child.git_cmd = 1;
@@ -580,9 +586,9 @@ static int run_dir_diff(const char *extcmd, int symlinks, const char *prefix,
 	 * files through the symlink.
 	 */
 	hashmap_init(&wt_modified, (hashmap_cmp_fn)path_entry_cmp,
-		     wtindex.cache_nr);
+		     NULL, wtindex.cache_nr);
 	hashmap_init(&tmp_modified, (hashmap_cmp_fn)path_entry_cmp,
-		     wtindex.cache_nr);
+		     NULL, wtindex.cache_nr);
 
 	for (i = 0; i < wtindex.cache_nr; i++) {
 		struct hashmap_entry dummy;
diff --git a/builtin/fast-export.c b/builtin/fast-export.c
index 12d501bfde..d412c0a8f3 100644
--- a/builtin/fast-export.c
+++ b/builtin/fast-export.c
@@ -93,8 +93,9 @@ struct anonymized_entry {
 	size_t anon_len;
 };
 
-static int anonymized_entry_cmp(const void *va, const void *vb,
-				const void *data)
+static int anonymized_entry_cmp(const void *unused_cmp_data,
+				const void *va, const void *vb,
+				const void *unused_keydata)
 {
 	const struct anonymized_entry *a = va, *b = vb;
 	return a->orig_len != b->orig_len ||
@@ -113,7 +114,7 @@ static const void *anonymize_mem(struct hashmap *map,
 	struct anonymized_entry key, *ret;
 
 	if (!map->cmpfn)
-		hashmap_init(map, anonymized_entry_cmp, 0);
+		hashmap_init(map, anonymized_entry_cmp, NULL, 0);
 
 	hashmap_entry_init(&key, memhash(orig, *len));
 	key.orig = orig;