path: root/Documentation/technical/api-hash.txt
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authorStephen Boyd <>2009-12-18 00:05:29 (GMT)
committerJunio C Hamano <>2009-12-18 05:54:50 (GMT)
commitafab0fe052b8a6b36c3860f7673ee1e9731c1679 (patch)
tree59cdb07b48373b89628382c99f34563e9f8a6692 /Documentation/technical/api-hash.txt
parent63b76948e1d211ad4a95c3a9c7a0087fe6a1e371 (diff)
technical-docs: document hash API
Signed-off-by: Stephen Boyd <> Signed-off-by: Junio C Hamano <>
Diffstat (limited to 'Documentation/technical/api-hash.txt')
1 files changed, 48 insertions, 2 deletions
diff --git a/Documentation/technical/api-hash.txt b/Documentation/technical/api-hash.txt
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--- a/Documentation/technical/api-hash.txt
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@@ -1,6 +1,52 @@
hash API
-Talk about <hash.h>
+The hash API is a collection of simple hash table functions. Users are expected
+to implement their own hashing.
+Data Structures
+`struct hash_table`::
+ The hash table structure. The `array` member points to the hash table
+ entries. The `size` member counts the total number of valid and invalid
+ entries in the table. The `nr` member keeps track of the number of
+ valid entries.
+`struct hash_table_entry`::
+ An opaque structure representing an entry in the hash table. The `hash`
+ member is the entry's hash key and the `ptr` member is the entry's
+ value.
+ Initialize the hash table.
+ Release memory associated with the hash table.
+ Insert a pointer into the hash table. If an entry with that hash
+ already exists, a pointer to the existing entry's value is returned.
+ Otherwise NULL is returned. This allows callers to implement
+ chaining, etc.
+ Lookup an entry in the hash table. If an entry with that hash exists
+ the entry's value is returned. Otherwise NULL is returned.
+ Call a function for each entry in the hash table. The function is
+ expected to take the entry's value as its only argument and return an
+ int. If the function returns a negative int the loop is aborted
+ immediately. Otherwise, the return value is accumulated and the sum
+ returned upon completion of the loop.