Berkeley DB

DB→set_h_hash

						#include <db.h>
						int
						DB→set_h_hash(DB *db,
						u_int32_t (*h_hash_fcn)(DB *, const void *bytes, u_int32_t length));
					

Description

Set a user-defined hash method; if no hash method is specified, a default hash method is used. Because no hash method performs equally well on all possible data, the user may find that the built-in hash method performs poorly with a particular data set. User-specified hash functions must take a pointer to a byte string and a length as arguments, and return a value of type u_int32_t. The hash function must handle any key values used by the application (possibly including zero-length keys).

If a hash method is specified, DB→open will attempt to determine whether the hash method specified is the same as the ...