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dbh_genkey(3) DBHashTables Programmers' Manual dbh_genkey(3) - NAME dbh_genkey, dbh_genkey2, dbh_orderkey - generate cuantified or ordered keys SYNOPSIS #include <dbh.h> void dbh_genkey (unsigned char *key, unsigned char length, unsigned int n); void dbh_genkey2 (unsigned char *key, unsigned char length, unsigned int n); void dbh_orderkey (unsigned char *key, unsigned char length, unsigned int n, unsigned char base); DESCRIPTION dbh_genkey and dbh_genkey2 obtain a key from a secuential series of natural numbers (positive integers without zero) which does not con- serve the order of the natural numbers, but which are optimized for construction of a balanced hash tree. In dbh_genkey the key is ex- pressed in cuantified numbers based on the 0 digit. In dbh_genkey2 the key is expressed in cuantified numbers based on the A symbol. dbh_orderkey will obtain a key from a secuential series of natural num- bers (positive integers without zero) which conserves the order of the natural numbers. This function generates a key that belongs to a finite subset of the cuantified numbers, but which preserves the order of the natural numbers (up to the supreme, of course). In these functions key is pointer to the address where to put the gen- erated key, length is the key length, and n is the natural number for which to generate the key. For dbh_orderkey base is the number system base to use. This will equal the maximum number of nodes per branch. This ---along with the keylength--- will define a maximum number of records for the DBHashTable. RETURN VALUE These functions do not return any value. NOTES Cuantified numbers are an alternate way to view the set of natural num- bers {1, 2, 3, ...} where order is defined in two levels. In natural numbers there is only one level of order (defined by the > boolean op- erator). In cuantified numbers the first level of order is defined by the cuanta or quantity. The cuanta is obtained by adding all the digits of the cuantified number. Thus, for example, 10022, 5, 32, and 11111 are all equal at the first level of order since they all add up to 5. The second level or order may be obtained in different manners. In functions dbh_genkey and dbh_genkey2 the corresponding order of the natural numbers from which they are associated is not conserved. In dbh_orderkey the corresponding order of the natural numbers from which they are associated is conserved, but at a price. The base, or maximum value each digit may reach, must be defined. This effectively puts a limit on the number of keys which may be generated for a given number of digits. When a DBHashTable is constructed with cuantified keys, the maximum amount of disk access instructions generated to access any given record is equal to the cuanta of the cuantified number represented by the key. This allows a DBHashTable to be constructed with minimum access time across all records. SEE ALSO dbh (0), dbh_update (3), dbh_load (3) Author Edscott Wilson Garcia <edscott@xfce.org> DBHashTables DBH dbh_genkey(3)
NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | SEE ALSO | Author
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