Prototypes

Prototype.<type> name(<parameter>, [, <parameter> [= DefaultValue]...])

For advanced programmers. Prototype allows to declare a type which will map a function. It's useful when used with a variable, to do a function pointer (the variable value will be the address the function to call, and can be changed at will).

This feature can replace the OpenLibrary() and CallFunction() sequence as it has some advantages: type checking is done, number of of parameters is validated.

Unlike CallFunction(), it can deal with double, float and quad variables without any problem. To get easily the pointer of a library function, use GetFunction().

The last parameters can have a default value (need to be a constant expression), so if these parameters are omitted when the function is called, the default value will be used.

By default the function will use the standard call convention (stdcall). If the function pointer will be a C one, the PrototypeC variant should be used instead.

The pseudotypes can be used for the parameters, but not for the returned value.

Example:

  Prototype.l ProtoMessageBox(Window.l, Body$, Title$, Flags.l = 0)

  If OpenLibrary(0, "User32.dll")
   
    ; 'MsgBox' is a variable with a 'ProtoMessageBox' type
    ;
    MsgBox.ProtoMessageBox = GetFunction(0, "MessageBoxA")
    
    MsgBox(0, "Hello", "World") ; We don't specify the flags
  EndIf
    

Example: With pseudotypes

  ; We use the 'p-unicode' pseudotype for the string parameters, as
  ; MessageBoxW() is an unicode only function. The compiler will 
  ; automatically converts the strings to unicode when needed.
  ;
  Prototype.l ProtoMessageBoxW(Window.l, Body.p-unicode, Title.p-unicode, Flags.l = 0)

  If OpenLibrary(0, "User32.dll")
   
    ; 'MsgBox' is a variable with a 'ProtoMessageBoxW' type
    ;
    MsgBox.ProtoMessageBoxW = GetFunction(0, "MessageBoxW")
    
    MsgBox(0, "Hello", "World") ; We don't specify the flags
  EndIf