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1#ifndef HASH_FUNCTION
2#define HASH_FUNCTION
3
4/** This represents the shell of a hash function. It must be aggregated in
5 * order to be used. Please read about it's two functions for specificatins
6 * relating to what values will be passed to them and what they should return
7 * for creating your own hash functions.
8 *@author Mike Buland.
9 */
10class HashFunction
11{
12public:
13 /**
14 * Standard Constructor.
15 */
16 HashFunction();
17
18 /**
19 * Standard Deconstructor.
20 */
21 virtual ~HashFunction();
22
23 /** Hashes the value represnted by id. This must return a fairly unique
24 * number in the range of 0-2^32 (or whatever the size of an unsigned long
25 * is on your system) based on the id given. The faster the number changes
26 * the better in a general sence. The return value will be the index
27 * (after probing takes place) to the data assosiated with an id, so this
28 * function should always produce the same number for any given id.
29 *@param id The identifier to use to create a unique numerical identifier.
30 *@returns A mostly unique numerical identifier generated using the given
31 * id.
32 */
33 virtual unsigned long int hash( const void *id ) = 0;
34
35 /** This function must compare two ids in the format that this hashfunction
36 * accepts. For example, if the hash function hashes strings it should
37 * probably { return strcmp( id1, id2 ) == 0 }.
38 *@param id1 One value to use in the comparison
39 *@param id2 Another value to use in the comparison
40 *@returns True if the two values match, otherwise false.
41 */
42 virtual bool cmpIDs( const void *id1, const void *id2 ) = 0;
43
44// virtual void *createPersistantID( const void *id ) = 0;
45// virtual void destroyPersistantID( const void *id ) = 0;
46};
47
48#endif