SST ShlWAPI TDllGetVersionProc Type

	(SST) ShlWAPI.pas Version 1.08

Developer Reference

TDllGetVersionProc Type Definition
Procedural type that defines the Microsoft recommendation and de-facto standard for a function that returns the version of a dynamic link library.

Scope
Global (i.e. pointer variables can be cast to this type and declared in any unit that uses/includes the unit in which the type was defined/declared).

Syntax
TYPE TDllGetVersionProc = FUNCTION(dllversioninfop : PDllVersionInfo) : HRESULT;

Parameters
dllversioninfop [in]	Pointer to, or address of a record/structore of type TDllVersionInfo or TDllVersionInfo2. .

Return Values
Returns S_OK (= 0) on success and, typically, a COM-defined error code on failure.

Remarks
This type is commonly used to type-cast a pointer variable to the entry point of the DllGetVersion function, previously acquired by means of the Windows, API function GetProcAddress, as a DllGetVersion function. Alternatively, it can also be used declare a variable in which to store the function's address directly. In this case, the function can subsequently be called by means of this variable without a type-cast.
Because the DllGetVersion function is an optional function that is not exported by all dlls, its existence and accessibility in both system and third party dlls can/should not be taken for granted and therefore has to be confirmed by means of the Windows, API function GetProcAddress, prior to calling the function itself.

Remarks

This type is commonly used to type-cast a pointer variable to the entry point of the DllGetVersion function, previously acquired by means of the Windows, API function GetProcAddress, as a DllGetVersion function. Alternatively, it can also be used declare a variable in which to store the function's address directly. In this case, the function can subsequently be called by means of this variable without a type-cast.

Because the DllGetVersion function is an optional function that is not exported by all dlls, its existence and accessibility in both system and third party dlls can/should not be taken for granted and therefore has to be confirmed by means of the Windows, API function GetProcAddress, prior to calling the function itself.

Example(s)
... Procedure CallDllGetVersion1(); Var dllhandle : HMODULE; Var dllverinforec : TDllVersionInfo; Var procaddr : POINTER; Var getverresult : HRESULT; begin dllhandle := 0; procaddr := NIL; FlllChar(dllverinforec, SizeOf(dllverinforec), #0); getverresult := 0; dllhandle := LoadLibrary('MyExampleDll.dll'); if (modulehandle <> 0) and (modulehandle <> INVALID_HANDLE_VALUE) then begin //Note, that the function name is case-sesitive ! procaddr := GetProcAddress(dllhandle, 'DllGetVersion'); if procaddr <> nil then begin dllverinforec.cbSize := SizeOf(dllverinforec); getverresult := TDllGetVersionProc(procaddr))(@dllverinforec); FreeLibrary(dllhandle); end; end; end; ... Procedure CallDllGetVersion2(); Var modulehandle : HMODULE; Var dllgetverfunc : TDllGetVersionProc; Var dllverinfo2rec : TDllVersionInfo2; Var getverresult : HRESULT; begin modulehandle := 0; procaddr := NIL; FlllChar(dllverinfo2rec, SizeOf(dllverinfo2rec), #0); getverresult := 0; //The following line assumes that the dll was already loaded //somewhere else in the program modulehandle := GetModuleHandle('MyExampleDll.dll'); if (modulehandle <> 0) and (modulehandle <> INVALID_HANDLE_VALUE) then begin //Don't forget that the function name is case-sesitive ! dllgetverfunc := GetProcAddress(dllhandle, 'DllGetVersion'); if @dllgetverfunc <> nil then begin dllverinfo2rec.info1.cbSize := SizeOf(dllverinfo2rec); getverresult := dllgetverfunc(@dllverinfo2rec); end; end; end;

Example(s)

... Procedure CallDllGetVersion1(); Var dllhandle : HMODULE; Var dllverinforec : TDllVersionInfo; Var procaddr : POINTER; Var getverresult : HRESULT; begin dllhandle := 0; procaddr := NIL; FlllChar(dllverinforec, SizeOf(dllverinforec), #0); getverresult := 0; dllhandle := LoadLibrary('MyExampleDll.dll'); if (modulehandle <> 0) and (modulehandle <> INVALID_HANDLE_VALUE) then begin //Note, that the function name is case-sesitive ! procaddr := GetProcAddress(dllhandle, 'DllGetVersion'); if procaddr <> nil then begin dllverinforec.cbSize := SizeOf(dllverinforec); getverresult := TDllGetVersionProc(procaddr))(@dllverinforec); FreeLibrary(dllhandle); end; end; end; ... Procedure CallDllGetVersion2(); Var modulehandle : HMODULE; Var dllgetverfunc : TDllGetVersionProc; Var dllverinfo2rec : TDllVersionInfo2; Var getverresult : HRESULT; begin modulehandle := 0; procaddr := NIL; FlllChar(dllverinfo2rec, SizeOf(dllverinfo2rec), #0); getverresult := 0; //The following line assumes that the dll was already loaded //somewhere else in the program modulehandle := GetModuleHandle('MyExampleDll.dll'); if (modulehandle <> 0) and (modulehandle <> INVALID_HANDLE_VALUE) then begin //Don't forget that the function name is case-sesitive ! dllgetverfunc := GetProcAddress(dllhandle, 'DllGetVersion'); if @dllgetverfunc <> nil then begin dllverinfo2rec.info1.cbSize := SizeOf(dllverinfo2rec); getverresult := dllgetverfunc(@dllverinfo2rec); end; end; end;

Requirements
Unit	Declared in ShlWAPI.pas
Library	ShlWAPI.dcu/ShlWAPI.obj

See Also
TDllVersionInfo, TDllVersionInfo2. MakeDllVerULL, DllGetVersion.

Windows APIs: DLLVERSIONINFO, DLLVERSIONINFO2, DllGetVersion, GetProcAddress.

Document/Contents version 1.00
Page/URI last updated on 07.12.2023

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