Sybase 12.4.2 manual How parameters are passed to the external function, 271

CHAPTER 6 Using Procedures and Batches

How parameters are passed to the external function

SQL data types are mapped to their C equivalents as follows:

SQL data type	C data type
INTEGER	long (32 bits)
SMALLINT	short
REAL	float
CHAR( n )	char *

These are the only SQL data types you can use: using others produces an error.

Procedure parameters that are INOUT or OUT parameters are passed to the external function by reference. For example, the procedure

CREATE PROCEDURE dll_proc( INOUT xvar REAL )

EXTERNAL NAME ’function_name@library.dll’

has an associated C function parameter declaration of

function_name( float * xvar )

Procedure parameters that are IN parameters are passed to the external function by value. For example, the procedure

CREATE PROCEDURE dll_proc( IN xvar REAL )

EXTERNAL NAME ’function_name@library.dll’

has an associated external function parameter declaration of

function_name( float xvar )

Character data types are an exception to IN parameters being passed. They are always passed by reference, whether they are IN, OUT, or INOUT parameters. For example, the procedure

CREATE PROCEDURE dll_proc ( IN invar CHAR( 128 ) )

EXTERNAL NAME ’function_name@library.dll’

has the following external function parameter declaration

function_name( char * invar )

271