/******************************************************/
//Author: Rajesh Ramachandran
//Found in: http://community.flexerasoftware.com/showthread.php?t=60963
//
//Arrays in InstallScript are not laid out like C/C++ arrays. InstallScript
//arrays are actually OleAutomation SAFEARRAYs. Hence to pass
//these arrays to .dll functions that expect a C style array requires some
//work(magic!). Look at the script below to see how that's done:
//
/******************************************************/

#include "ifx.h"

/*Dumps an array into a string. Elements are separated by a space*/
prototype STRING StreamArray(VARIANT);
function STRING StreamArray(array)
NUMBER i;
STRING s;
begin
for i = 0 to SizeOf(array) - 1
s = s + array(i) + " ";
endfor;

return s;
end;

/*Mirroring the C/C++ SAFEARRAY data structure*/
typedef _SAFEARRAY
begin
SHORT cDims;
SHORT fFeatures;
LONG cbElements;
LONG cLocks;
POINTER pvData;
/*rgsaBound omitted*/
end;

/*Mirroring the C/C++ VARIANT data structure*/
typedef _VARIANT
begin
SHORT vt;
SHORT wReserved1;
SHORT wReserved2;
SHORT wReserved3;
NUMBER theRealData; // The exact type of this member depends
on vt
end;


prototype POINTER Array2Pointer(BYREF VARIANT);

function POINTER Array2Pointer(array)
_VARIANT POINTER pVariant;
_SAFEARRAY POINTER pArray;
begin
pVariant = &array;
pArray = pVariant->theRealData;
return pArray->pvData;
end;

prototype BOOL PSAPI.EnumProcesses(POINTER, LONG, BYREF LONG);

function OnBegin()
LONG processIDs(512);
LONG cb, cbNeeded;
begin
cb = SizeOf(processIDs) * 4; // 4 = SizeOf DWORD

EnumProcesses(Array2Pointer(processIDs), cb, cbNeeded);

/*Shrink the Array to the no. of items returned by EnumProcesses
This is needed to prevent StreamArray from outputting junk*/
Resize(processIDs, cbNeeded / 4);

MessageBox(StreamArray(processIDs), INFORMATION);

abort;
end;

/*******************************************************************/
//
//The Array2Pointer function is the key here. When you declare an array variable
//what internally gets created is a VARIANT variable which holds the SAFEARRAY.
//Hence the Array2Pointer function *typecasts* the pointer to the array to a _VARIANT
//pointer to extract the SAFEARRAY pointer from it. The pointer to the actual data
//is extracted from the _SAFEARRAY pointer. _VARIANT & _SAFEARRAY are
//InstallScript typedefs which mirror the layout of their C/C++ counterparts.