(gdbm.info.gz) Sequential

Info Catalog

(gdbm.info.gz) Delete

(gdbm.info.gz) Top

(gdbm.info.gz) Reorganization

 
 Sequential access to records.
 *****************************
 
    The next two functions allow for accessing all items in the
 database. This access is not `key' sequential, but it is guaranteed to
 visit every `key' in the database once. The order has to do with the
 hash values.  `gdbm_firstkey' starts the visit of all keys in the
 database.  `gdbm_nextkey' finds and reads the next entry in the hash
 structure for `dbf'.
 
      key = gdbm_firstkey(dbf);
      
      nextkey = gdbm_nextkey(dbf, key);
 
    The parameters are:
 
 GDBM_FILE dbf
      The pointer returned by `gdbm_open'.
 
 datum `key'
 
 datum nextkey
      The `key' data.
 
    The return values are both datum. If `key'.dptr or nextkey.dptr is
 NULL, there is no first `key' or next `key'. Again notice that dptr
 points to data allocated by malloc and `gdbm' will not free it for you.
 
    These functions were intended to visit the database in read-only
 algorithms, for instance, to validate the database or similar
 operations.
 
    File `visiting' is based on a `hash table'. `gdbm_delete'
 re-arranges the hash table to make sure that any collisions in the
 table do not leave some item `un-findable'. The original key order is
 NOT guaranteed to remain unchanged in ALL instances. It is possible
 that some key will not be visited if a loop like the following is
 executed:
 
         key = gdbm_firstkey ( dbf );
         while ( key.dptr ) {
            nextkey = gdbm_nextkey ( dbf, key );
            if ( some condition ) {
               gdbm_delete ( dbf, key );
               free ( key.dptr );
            }
            key = nextkey;
         }
 

Info Catalog

(gdbm.info.gz) Delete

(gdbm.info.gz) Top

(gdbm.info.gz) Reorganization