hashmap: document memihash_cont, hashmap_disallow_rehash api

Document memihash_cont() and hashmap_disallow_rehash()
in Documentation/technical/api-hashmap.txt.

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Documentation/technical/api-hashmap.txt b/Documentation/technical/api-hashmap.txt
index 28f5a8b71574916820cdb1f1a023e27cb45ed6e6..4e4ae6f249c3eea5a1e7913b7a08312298cfeabf 100644 (file)
--- a/Documentation/technical/api-hashmap.txt
+++ b/Documentation/technical/api-hashmap.txt
@@ -21,6 +21,9 @@ that the hashmap is initialized. It may also be useful for statistical purposes
 `cmpfn` stores the comparison function specified in `hashmap_init()`. In
 advanced scenarios, it may be useful to change this, e.g. to switch between
 case-sensitive and case-insensitive lookup.
 `cmpfn` stores the comparison function specified in `hashmap_init()`. In
 advanced scenarios, it may be useful to change this, e.g. to switch between
 case-sensitive and case-insensitive lookup.

++
+When `disallow_rehash` is set, automatic rehashes are prevented during inserts
+and deletes.

 
 `struct hashmap_entry`::
 
 
 `struct hashmap_entry`::
 


@@ -57,6 +60,7 @@ Functions
 `unsigned int strihash(const char *buf)`::
 `unsigned int memhash(const void *buf, size_t len)`::
 `unsigned int memihash(const void *buf, size_t len)`::
 `unsigned int strihash(const char *buf)`::
 `unsigned int memhash(const void *buf, size_t len)`::
 `unsigned int memihash(const void *buf, size_t len)`::

+`unsigned int memihash_cont(unsigned int hash_seed, const void *buf, size_t len)`::

 
        Ready-to-use hash functions for strings, using the FNV-1 algorithm (see
        http://www.isthe.com/chongo/tech/comp/fnv).
 
        Ready-to-use hash functions for strings, using the FNV-1 algorithm (see
        http://www.isthe.com/chongo/tech/comp/fnv).


@@ -65,6 +69,9 @@ Functions
 `memihash` operate on arbitrary-length memory.
 +
 `strihash` and `memihash` are case insensitive versions.
 `memihash` operate on arbitrary-length memory.
 +
 `strihash` and `memihash` are case insensitive versions.

++
+`memihash_cont` is a variant of `memihash` that allows a computation to be
+continued with another chunk of data.

 
 `unsigned int sha1hash(const unsigned char *sha1)`::
 
 
 `unsigned int sha1hash(const unsigned char *sha1)`::
 


@@ -184,6 +191,21 @@ passed to `hashmap_cmp_fn` to decide whether the entry matches the key.
 +
 Returns the removed entry, or NULL if not found.
 
 +
 Returns the removed entry, or NULL if not found.
 

+`void hashmap_disallow_rehash(struct hashmap *map, unsigned value)`::
+
+       Disallow/allow automatic rehashing of the hashmap during inserts
+       and deletes.
++
+This is useful if the caller knows that the hashmap will be accessed
+by multiple threads.
++
+The caller is still responsible for any necessary locking; this simply
+prevents unexpected rehashing.  The caller is also responsible for properly
+sizing the initial hashmap to ensure good performance.
++
+A call to allow rehashing does not force a rehash; that might happen
+with the next insert or delete.
+

 `void hashmap_iter_init(struct hashmap *map, struct hashmap_iter *iter)`::
 `void *hashmap_iter_next(struct hashmap_iter *iter)`::
 `void *hashmap_iter_first(struct hashmap *map, struct hashmap_iter *iter)`::
 `void hashmap_iter_init(struct hashmap *map, struct hashmap_iter *iter)`::
 `void *hashmap_iter_next(struct hashmap_iter *iter)`::
 `void *hashmap_iter_first(struct hashmap *map, struct hashmap_iter *iter)`::