git/Documentation/technical/api-hash.txt

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hash API
========
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.
Functions
---------
`init_hash`::
Initialize the hash table.
`free_hash`::
Release memory associated with the hash table.
`insert_hash`::
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_hash`::
Lookup an entry in the hash table. If an entry with that hash exists
the entry's value is returned. Otherwise NULL is returned.
`for_each_hash`::
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.