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14.4 TOS2WIN

Tos2Win Cookie

To ascertain which Tos2Win version and which features are present, as of Version 1.19 a cookie '_T2W' exists with a pointer to the following data structure:

1 x Word Length of the structure
1 x Word Version in BCD i.e. $0119 = Version 1.19
1 x Long Offset of the Atari memory in PC memory for recalculation of pointers
4 x Long Bit-fields for individual T2W features


Call PC-DLLs as of Version 1.19J

In TOS2WIN all PC calls are introduced with the sequence $4858, which is followed by the group code (e.g. $5043) for the DLL functions, and is terminated with the function number (e.g. $0000).

So a call of a DLL function would look as follows: 

Function start
                    .
                    .
                    .
                  $4858
                  $5043
                  $0000
                    .
                    .
                    .
Function end       RTS

The parameters for the function lie from a7 + 4 onwards. This means placing all required parameters on the stack (always only LONGwords) and then a bsr to function start.

All pointers passed to the PC function to values in Atari memory have to be corrected with an offset. Atari address + offset = PC address. One can get the offset either via the Tos2Win cookie or via the DLL function $0000. The offset does not alter during the runtime of the program.

DLL function

$0000 LONG HoleOffset()
 
Return value: Returns in d0 the offset for recalculation

This function can also be used to ascertain whether the following functions are present. Just load register d0 with zero and call the function. If there is still zero in d0, then the functions are not implemented.
 
$0001 LONG OpenLibrary(Name)
 
Name : Pointer to a NULL-terminated string that contains the name of the desired DLL, e.g. 'GDI32.DLL' (the pointer must be corrected with the offset)
Return value: Returns in d0 a handle to the DLL
$0002 VOID CloseLibrary(Handle)
 
Handle : Handle to the DLL to be closed; when the internal Windows counter has reached zero, the DLL is removed from memory
$0003 LONG GetFunctionAdress(Handle,Name)
 
Handle : Handle for the DLL
Name : Pointer to a NULL-terminated string that contains the name of the function (pointer has to be corrected)
Return value: Address of the function in PC memory
$0004 LONG CallLibraryFunction(Adr,Number,.....)
 
Adr : Address of the desired function
Number : Number of parameters passed to the PC function
.... : The corresponding parameters (pointers have to be corrected)
Return value: Possible return value of the PC function
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