Merge branch 'nd/worktree-add-lock'

diff --git a/Documentation/technical/api-hashmap.txt b/Documentation/technical/api-hashmap.txt
index ad7a5bddd24d91ceda78d430fd86a204b21fd005..ccc634bbd754f6e0bab80fb3ccf1cc42afc5b829 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.
++
+When `disallow_rehash` is set, automatic rehashes are prevented during inserts
+and deletes.
 
 `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 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).
@@ -65,6 +69,9 @@ Functions
 `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)`::
 
@@ -104,6 +111,11 @@ If `free_entries` is true, each hashmap_entry in the map is freed as well
 `entry` points to the entry to initialize.
 +
 `hash` is the hash code of the entry.
++
+The hashmap_entry structure does not hold references to external resources,
+and it is safe to just discard it once you are done with it (i.e. if
+your structure was allocated with xmalloc(), you can just free(3) it,
+and if it is on stack, you can just let it go out of scope).
 
 `void *hashmap_get(const struct hashmap *map, const void *key, const void *keydata)`::
 
@@ -179,11 +191,28 @@ passed to `hashmap_cmp_fn` to decide whether the entry matches the key.
 +
 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)`::
 
-       Used to iterate over all entries of a hashmap.
+       Used to iterate over all entries of a hashmap. Note that it is
+       not safe to add or remove entries to the hashmap while
+       iterating.
 +
 `hashmap_iter_init` initializes a `hashmap_iter` structure.
 +