Inroduction
Richard Peeters (r.peeters@pandora.be) has been working on a very interesting project to bring ISAM indexing to Liberty Basic using native LB code. His project is still in develpment, but really is promising.
I personally have been using this in some home grown projects and I am excited about where this is going. Richard may be submitting a proper newsletter article in the future (I hope) which details more about the project and its development. Until then I am offering the work in progress (with Richards permission). The function library is on page two. A sample test program using the function library is on page three.
All the functions depend on a global string array called globalinf$. It has four elements defined as:
Here is a run down of the function library:
------------------------------------------------------------------------------- function initfunclib use once in your program before using any of the functions in this library does some initialisations ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- function getcount used to get the number of records in the index parameters passed indexname$ = name of indexfile keylength = length of key returns nr of records in the index ------------------------------------------ ------------------------------------------------------------------------------- function index used to create an index on a file with fixed recordlengths (random or binary) the max number of records = 99999 parameters to be passed: filename$ = filename of file to be indexed reclen = recordlength indexname$= name of the indexfile to be created keybegin = the position in the record where the key begins keylength = length of the key unique = 0 = duplicate records allowed / 1 = no duplicates allowed the function returns the number of records indexed ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- function getkey used to search a key in an index parameters to be passed: indexname$= name of the indexfile to be searched keylength = length of the key key$ = key to search for the function returns the recordnr in the masterfile of the found key or if not found the negative recordnr after which it should have been if present ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- function lookup used to search part of a key in an index parameters to be passed: indexname$= name of the indexfile to be searched keylength = length of the key key$ = key to search for the function returns the recordnr in the referencefile of the 1st found key or if not found the negative recordnr after which it should have been if present ------------------------------------------------------------------------------- ------------------------------------------------------------------------------- function getfirst searches For the first key in the index with Name=indexname and keylength=keylength returns recordnr of record in masterfile ------------------------------------------------------------------------------- function getlast searches For the last key in the index with Name=indexname and keylength=keylength returns recordnr of record in masterfile ------------------------------------------------------------------------------- function getnext searches For the next key in the index from present position in globalinf$(2) with Name=indexname and keylength=keylength returns position in masterfile of next ------------------------------------------------------------------------------- function getprev searches For the previous key in the index from present position in globalinf$(2) with Name=indexname and keylength=keylength returns position in masterfile of previous