# 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.