Open MySQL UDF & Plugin Library

Extending MyUDFLib :

After all, you have to refer to MySQL manual Chapter ( Extending MySQL) to know every thing you need about how adding new UDF Functions.

And, There are two ways to add new functions to MySQL:

Through the MySQL standar user-defined function (UDF) interface ways,

or using the UDF function definition/wrapper FUNCTION C macro. FUNCTION is set on MYSQL_UDF_API.h and do all the works for us (xxx_init, xxx_deinit, export as extern, ...), that I know isn't the best solution, but in some ways, Zend have the same view point :P :

     
     +----------------------------------------------------------------------+
     | FUNCTION(                                                            |
     |   name       , => function name                                      |
     |   type       , => function type retrun(STRING|REAL|LONG)             |
     |   /S;|R;|I;/ , => args->arg_type pattern (S:STRING;I:INTEGER;R:REAL) |
     |   arg_count  , => args->arg_count min , must be > 0                  |
     |   maybe_null , => initid->maybe_null (1|0)                           |
     |   max_length , => initid->max_length, -1 to no max                   |
     |   "USAGE: .."  => String to be used as error message                 |
     | )                                                                    |
     +----------------------------------------------------------------------+

For example :
str_replace is a part of MyUDFLib::LibString and use BString library.
needed args is :

Function name assignation as MySQL Server will call it : str_replace
Type : str_replace will reteurn a STRING
We have a very simple parametres pattern to check ("S;S;S;I") : first arg is STRING arg, the 2 is STRING, .., and the last is an INTEGER.
str_replace need 4 args min
str_replace will return String of 255 byte long.

And some help to display as error message, but one should try to keep the error message less than 80 bytes long! as a lucky MySQL developer say.

 /******************************************************************************
** str_replace
**   use BString::extern int bfindreplace (bstring b, const_bstring find,
**                           const_bstring replace, int position);
**   Replace all occurrences of the find substring with a replace bstring 
**   after a given position in the bstring b.
******************************************************************************/
// {{{
	FUNCTION( str_replace, STRING, "S;S;S;I", 4, 1, 255, 
    "USAGE: STRING str_replace(STRING str, STRING find, STRING replace, INT pos)" )
	{
		bstring       string_1 = bfromcstr ( ARGV(0) );
		bstring       string_2 = bfromcstr ( ARGV(1) );
		bstring       string_3 = bfromcstr ( ARGV(2) );
		long long     pos      = *((long long*) ARGV(1) );  

		bfindreplace ( string_1, string_2, string_3, pos ); 

		RETURN_STRING( bdata( string_1 ) );
    }

// }}}

MySQL UDF Library ( How to Extend )