DllManager is a predeclared class employing the Factory/Constructor (Create/Init) pattern. It wraps several DLL-related Windows APIs and a Scripting.Dictionary object for the <DLL name> → <DLL handle> mapping.
DllManager.Create & DllManager.Init The factory takes three optional arguments, passed to the constructor:
- DefaultPath (String) - the default DLL directory,
- DllNames (Variant, defaults to empty) - a single DLL name (String) or multiple DLL names (array),
- ResolvePath (Boolean, defaults to true) - indicates whether the factory should resolve the library path.
If DefaultPath is not provided or set to blank string, it defaults to "Library" & ThisWorkbook.VBProject.Name & "\dll" & ARCH, where ARCH is a conditionally declared constant set to "x32" for VBA-x32 and "x64" for VBA-x64. DefaultPath can be set/changed via its setter (Property Let) and reset with a blank string. The setter checks if the parameter holds a valid absolute or relative (w.r.t. ThisWorkbook.Path) path. If this check succeeds, SetDllDirectory API sets the default DLL search path.
DllNames accepts either a String containing a single DLL name (passed to DllManager.Load) or an array of String names (passed to DllManager.LoadMultiple).
ResolvePath is only honored if the second argument is a String (see DllManager.Load for further details).
DllManager.Load & DllManager.Free DllManager.Load loads individual libraries, taking three arguments:
- DllName (String, required) - the DLL name to be loaded,
- Path (String, defaults to DefaultPath) - the target DLL directory,
- ResolvePath (Boolean, defaults to true) - indicates whether Load should resolve the library path.
If Path is provided, it is used instead of the DefaultPath.
If ResolvePath is true, it checks if Path is a valid absolute or relative (w.r.t. ThisWorkbook.Path) path and, if this check passes, appends the DllName. Otherwise, Load appends DllName to Path without any checks.
Eventually, the LoadLibrary API loads the library.
DllManager.Free frees previously loaded library.
DllManager.LoadMultiple & DllManager.FreeMultiple take a 0-based array of DLL names to be loaded/freed (a ParamArray list is also accepted). If no argument is provided, LoadMultiple does nothing, but FreeMultiple frees all loaded libraries.
DllManager.GetDllPath takes a name of a previously loaded DLL and returns its file path.
DllManager.ProcAddressGet & DllManager.CacheProcPtr DllManager.ProcAddressGet takes two String arguments, the name of a previously loaded DLL library and a function name, and retrieves the entry pointer (RAM address) via Windows API. It also saves the retrieved address in the internal cache and uses it on subsequent requests. DllManager.CacheProcPtr also takes a function pointer as the third argument and saves it into the internal cache directly. This API can be used, for example, for tests involving DllManager.ProcAddressGet.
DllManager.IndirectCall wraps the DispCallFunc Windows API to make proxied DLL calls. It takes five arguments:
- ModuleName (String) - same as ProcAddressGet/CacheProcPtr,
- ProcName (String) - same as ProcAddressGet/CacheProcPtr,
- CallnigConv (CALLCONV Enum) - indicates calling convention of the called function,
- ReturnType (VbVarType Enum) - indicates type of the returned value,
- Arguments (array of Variant) - contains arguments to be passed to the called function from left to right.
The arguments should be prepared according to the called function specifications, providing addresses where necessary; IndirectCall cannot provide any assistance here.
DllManager.Class_Terminate calls FreeMultiple, freeing all loaded libraries.