Hashmap entries are typically looked up by just a key. The hashmap_get()
API expects an initialized entry structure instead, to support compound
keys. This flexibility is currently only needed by find_dir_entry() in
name-hash.c (and compat/win32/fscache.c in the msysgit fork). All other
(currently five) call sites of hashmap_get() have to set up a near emtpy
entry structure, resulting in duplicate code like this:

  struct hashmap_entry keyentry;
  hashmap_entry_init(&keyentry, hash(key));
  return hashmap_get(map, &keyentry, key);

Add a hashmap_get_from_hash() API that allows hashmap lookups by just
specifying the key and its hash code, i.e.:

  return hashmap_get_from_hash(map, hash(key), key);

Signed-off-by: Karsten Blees <bl...@dcon.de>
---
 Documentation/technical/api-hashmap.txt | 14 ++++++++++++++
 builtin/describe.c                      |  4 +---
 diffcore-rename.c                       |  7 +++----
 hashmap.h                               |  8 ++++++++
 name-hash.c                             |  5 ++---
 test-hashmap.c                          | 11 +++--------
 6 files changed, 31 insertions(+), 18 deletions(-)

diff --git a/Documentation/technical/api-hashmap.txt 
b/Documentation/technical/api-hashmap.txt
index dc21a7c..f9215d6 100644
--- a/Documentation/technical/api-hashmap.txt
+++ b/Documentation/technical/api-hashmap.txt
@@ -118,6 +118,20 @@ hashmap_entry) that has at least been initialized with the 
proper hash code
 If an entry with matching hash code is found, `key` and `keydata` are passed
 to `hashmap_cmp_fn` to decide whether the entry matches the key.
 
+`void *hashmap_get_from_hash(const struct hashmap *map, unsigned int hash, 
const void *keydata)`::
+
+       Returns the hashmap entry for the specified hash code and key data,
+       or NULL if not found.
++
+`map` is the hashmap structure.
++
+`hash` is the hash code of the entry to look up.
++
+If an entry with matching hash code is found, `keydata` is passed to
+`hashmap_cmp_fn` to decide whether the entry matches the key. The
+`entry_or_key` parameter points to a bogus hashmap_entry structure that
+should not be used in the comparison.
+
 `void *hashmap_get_next(const struct hashmap *map, const void *entry)`::
 
        Returns the next equal hashmap entry, or NULL if not found. This can be
diff --git a/builtin/describe.c b/builtin/describe.c
index 57e84c8..ee6a3b9 100644
--- a/builtin/describe.c
+++ b/builtin/describe.c
@@ -58,9 +58,7 @@ static int commit_name_cmp(const struct commit_name *cn1,
 
 static inline struct commit_name *find_commit_name(const unsigned char *peeled)
 {
-       struct commit_name key;
-       hashmap_entry_init(&key, sha1hash(peeled));
-       return hashmap_get(&names, &key, peeled);
+       return hashmap_get_from_hash(&names, sha1hash(peeled), peeled);
 }
 
 static int replace_name(struct commit_name *e,
diff --git a/diffcore-rename.c b/diffcore-rename.c
index 6fa97d4..2e44a37 100644
--- a/diffcore-rename.c
+++ b/diffcore-rename.c
@@ -257,15 +257,14 @@ static int find_identical_files(struct hashmap *srcs,
        int renames = 0;
 
        struct diff_filespec *target = rename_dst[dst_index].two;
-       struct file_similarity *p, *best, dst;
+       struct file_similarity *p, *best = NULL;
        int i = 100, best_score = -1;
 
        /*
         * Find the best source match for specified destination.
         */
-       best = NULL;
-       hashmap_entry_init(&dst, hash_filespec(target));
-       for (p = hashmap_get(srcs, &dst, NULL); p; p = hashmap_get_next(srcs, 
p)) {
+       p = hashmap_get_from_hash(srcs, hash_filespec(target), NULL);
+       for (; p; p = hashmap_get_next(srcs, p)) {
                int score;
                struct diff_filespec *source = p->filespec;
 
diff --git a/hashmap.h b/hashmap.h
index ed5425a..12f0668 100644
--- a/hashmap.h
+++ b/hashmap.h
@@ -68,6 +68,14 @@ extern void *hashmap_put(struct hashmap *map, void *entry);
 extern void *hashmap_remove(struct hashmap *map, const void *key,
                const void *keydata);
 
+static inline void *hashmap_get_from_hash(const struct hashmap *map,
+               unsigned int hash, const void *keydata)
+{
+       struct hashmap_entry key;
+       hashmap_entry_init(&key, hash);
+       return hashmap_get(map, &key, keydata);
+}
+
 /* hashmap_iter functions */
 
 extern void hashmap_iter_init(struct hashmap *map, struct hashmap_iter *iter);
diff --git a/name-hash.c b/name-hash.c
index 49fd508..702cd05 100644
--- a/name-hash.c
+++ b/name-hash.c
@@ -213,12 +213,11 @@ struct cache_entry *index_dir_exists(struct index_state 
*istate, const char *nam
 struct cache_entry *index_file_exists(struct index_state *istate, const char 
*name, int namelen, int icase)
 {
        struct cache_entry *ce;
-       struct hashmap_entry key;
 
        lazy_init_name_hash(istate);
 
-       hashmap_entry_init(&key, memihash(name, namelen));
-       ce = hashmap_get(&istate->name_hash, &key, NULL);
+       ce = hashmap_get_from_hash(&istate->name_hash,
+                                  memihash(name, namelen), NULL);
        while (ce) {
                if (same_name(ce, name, namelen, icase))
                        return ce;
diff --git a/test-hashmap.c b/test-hashmap.c
index f5183fb..3c9f67b 100644
--- a/test-hashmap.c
+++ b/test-hashmap.c
@@ -115,9 +115,8 @@ static void perf_hashmap(unsigned int method, unsigned int 
rounds)
 
                for (j = 0; j < rounds; j++) {
                        for (i = 0; i < TEST_SIZE; i++) {
-                               struct hashmap_entry key;
-                               hashmap_entry_init(&key, hashes[i]);
-                               hashmap_get(&map, &key, entries[i]->key);
+                               hashmap_get_from_hash(&map, hashes[i],
+                                                     entries[i]->key);
                        }
                }
 
@@ -199,12 +198,8 @@ int main(int argc, char *argv[])
 
                } else if (!strcmp("get", cmd) && l1) {
 
-                       /* setup static key */
-                       struct hashmap_entry key;
-                       hashmap_entry_init(&key, hash);
-
                        /* lookup entry in hashmap */
-                       entry = hashmap_get(&map, &key, p1);
+                       entry = hashmap_get_from_hash(&map, hash, p1);
 
                        /* print result */
                        if (!entry)
-- 
1.9.4.msysgit.0.dirty

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