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dbh_genkey(3)          DBHashTables Programmers' Manual          dbh_genkey(3)

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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
       conserve the order of the natural numbers, but which are optimized for
       construction of a balanced hash tree. In dbh_genkey the key is
       expressed 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
       numbers (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
       generated 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
       numbers {1, 2, 3, ...} where order is defined in two levels. In natural
       numbers there is only one level of order (defined by the > boolean
       operator). 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)

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