Pass and return data to a Delphi-written UDF

Data
[UDF Series IV]: passing and returning data to a Delphi-written UDF
Warton Translation
Author: Chris Levesque, Tina Grubbe, Brett Bandy


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[Translator]:

I've translated a few articles about UDF, although some friends may get some help, but it's possible that the UDF
There are still some problems in understanding. Today, I translate two articles, both of which are from Mer System (http://www.mers.com)
, interested friends can view the original.


[Argument]:
When a dynamic-link library does not have special precautions for protected data values, our UDF has data results with parameter values or return values
May be in a protected exception or error result.

[Solution]:
Each date value is saved in two 32-bit integer types: A signed integer representing the date, and a representation
The unsigned integer of the time. Use the Delphi code to define this structure (ISC_QUAD) and the pointer to the structure (PISC_QUAD):
Type
{InterBase Date/time record}
Isc_quad = Record
Isc_quad_high:integer; Date
isc_quad_low:cardinal; Time
End
Pisc_quad = ^isc_quad;
To protect the return value, declare a thread-safe isc_quad variable outside the function definition so that it holds the return value (if the return value
is a date type of data).
Threadvar
Tempquad:isc_quad;
Then write your function so that the result points to the thread variable.

Defining functions
This function adds a existing date.
function Dayadd (var Days:integer; Ibdate pisc_quad): Pisc_quad; Cdecl Export

Begin
Tempquad.isc_quad_high: = Ibdate^.isc_quad_high + days;
Tempquad.isc_quad_low: = Ibdate^.isc_quad_low;
Result: = @tempquad;
End



The main source: MER Systems Inc. Http://www.mers.com