Dynamic Link Libraries (DLLs)

Note: 64-bit JMP cannot load 32-bit DLLs, and 32-bit JMP cannot load 64-bit DLLs. If you have a 32-bit DLL that you have used successfully in the past, but you are now using 64-bit JMP, you must recompile your DLL for 64-bit to be able to load it.

You can extend JMP functionality by using JMP Scripting Language (JSL) to load a DLL and call functions exported by that DLL. There is one JSL command and six messages that implement this functionality.

dll_obj = Load DLL("path" <, AutoDeclare(Boolean | Quiet | Verbose) |Quiet | Verbose > )

Load DLL() loads the DLL in the specified path. Use the AutoDeclare(Quiet) argument to suppress log window messaging.

Use the Declare Function message to define it and then call it.

dll_obj <<Declare Function("name", Convention(named_argument), Alias("string"), Arg(type, "string"), Returns(type), other_named_arguments)

The Alias defines an alternate name that you can use in JSL. For example, if you declared Alias("MsgBox") for a function that is named "Message Box" in the DLL, then you would call it as follows:

result = dll_obj <<MsgBox(...)

The named arguments for Convention are as follows:

•	STDCALL or PASCAL

•

CDECL

The type argument for both Arg and Returns can be one of the following:

Types for Arg and Returns
Int8	UInt8	Int16	UInt16
Int32	UInt32	Int64	UInt64
Float	Double	AnsiString	UnicodeString
Struct	IntPtr	UIntPtr	ObjPtr

See the DLL section of the JSL Syntax Reference for the Declare Function message arguments.

Finally, use the UnLoadDLL message to unload the DLL:

dll_obj << UnLoadDLL

Example

Suppose that you want the script to load a Windows 32-bit DLL or a 64-bit DLL based on the user’s computer. This example tests for the Windows operating system and then the computer processor’s bit level.

If( Host is( Windows ),

If(

Host is( Bits64 ),

// Load the 64-bit DLL.

dll_obj = Load DLL( "c:\Windows\System32\user32.dll" ),

// Load the 32-bit DLL.

dll_obj = Load DLL( "c:\Windows\SysWOW64\user32.dll"),

// If neither DLL is found, stop execution.

Throw

);

dll_obj <<DeclareFunction(

"MessageBoxW",

Convention( STDCALL ),

Alias( "MsgBox" ),

Arg( IntPtr, "hWnd" ),

Arg( UnicodeString, "message" ),

Arg( UnicodeString, "caption" ),

Arg( UInt32, "uType" ),

Returns( Int32 )

);

result = dll_obj << MsgBox(

"Here is a message from JMP.",

The Show Functions message sends any functions that have been declared using Declare Function to the log:

dll_obj << Show Functions;

If you are writing your own DLL, you can create functions in it using JSL. The Get Declaration JSL message sends any JSL functions in your DLL to the log:

dll_obj << Get Declaration JSL;

For Simple DLL Functions

If your DLL contains functions that are very simple, the Call DLL message declares the specified function with the specified signature, as shown in Signature Values.

dll_obj <<Call DLL(function_name, signature, arguments)

Signature Values
Signature	Argument is of Type
“v”	void
“c”	string
“n”	int

Then, the function is called, passing in the argument.

Example

// Load the DLL, given the specified path

dll_obj = Load DLL( "D:\Release\MyDLL.DLL" );

// Call the function inside the DLL named MyExportedFcn.

// This function takes one numeric as input and in this case,

// the value of the input argument is to be 654.

dll_obj << CallDLL( "MyExportedFcn", "n", 654 );

dll_obj << UnLoadDLL();

Effectively, what these two lines accomplish is to call MyExportedFcn, passing 654 as input to the function. Conceptually, it is as if the JSL script executed MyExportedFcn(654);