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EnableExplicit

;Hot Reload DLL
;Platform: Windows OS
;Author: Mijikai
;Version: Draft 1

;It works with a copy of the original library (which is created) either in the same or temp directory.
;The original libraries creation time is monitored to determine if it should be reloaded.

;Functions:
;- hrdLibrary()   to add libraries
;- hrdFunction()  to determine the function address within a library
;- hrdReload()    checks all added libraries and reloads them if needed

;Callback (Init function called when a library is loaded/reloaded):

;Procedure.i Callback(*Name.String,Handle.i,*Parameter)
;EndProcedure

Structure HOT_RELOAD_DLL
  handle.i
  name.s
  copy.s
  date.FILETIME
  *init
  *parameter
EndStructure

Global NewList hrd.HOT_RELOAD_DLL()

Procedure.i hrdReload()
  Protected wfa.WIN32_FILE_ATTRIBUTE_DATA
  Protected *str
  Protected error.i
  ForEach hrd()
    If GetFileAttributesEx_(hrd()\name,#Null,@wfa)
      If CompareMemory(@hrd()\date,@wfa\ftCreationTime,SizeOf(FILETIME)) = #Null
        CopyMemory(@wfa\ftCreationTime,@hrd()\date,SizeOf(FILETIME))
        If hrd()\handle
          FreeLibrary_(hrd()\handle)
          DeleteFile(hrd()\copy)
          hrd()\handle = #Null
        EndIf
        If CopyFile(hrd()\name,hrd()\copy)
          hrd()\handle = LoadLibrary_(hrd()\copy)
        EndIf
        If hrd()\handle
          *str = @hrd()\name
          CallFunctionFast(hrd()\init,@*str,hrd()\handle,hrd()\parameter)  
        Else
          error = #True
          Break
        EndIf
      EndIf  
    Else
      error = #True
      Break
    EndIf
  Next
  ProcedureReturn error
EndProcedure

Procedure.i hrdLibrary(Library.s,*Init,Temp.i = #False,*Parameter = #Null)
  Protected *hrd.HOT_RELOAD_DLL
  If Library And *Init
    If AddElement(hrd())
      hrd()\name = Library
      hrd()\copy = "hrd_" + Library
      If Temp
        hrd()\copy = GetTemporaryDirectory() + hrd()\copy
      EndIf
      hrd()\init = *Init
      hrd()\parameter = *Parameter
      *hrd = @hrd()
      If hrdReload() = #Null
        ProcedureReturn *hrd\handle
      EndIf
    EndIf
  EndIf
  ProcedureReturn #Null
EndProcedure

Procedure.i hrdFunction(Handle.i,Name.s)
  Protected *name.Ascii
  Protected *address
  *name = Ascii(Name)
  If *name
    *address = GetProcAddress_(Handle,*name)
    FreeMemory(*name)
  EndIf
  ProcedureReturn *address
EndProcedure

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EnableExplicit

XIncludeFile "hrd.pbi"

Global *hot;<- holds a function pointer (gets updated by the callback)

Procedure.i Init(*Name.String,Handle.i,*Parameter);<- callback used to update data/pointers
  *hot = hrdFunction(Handle,"Dummy")
  ProcedureReturn #Null
EndProcedure

Procedure.i Main()
  hrdLibrary("hot.dll",@Init());<- example dll
  If OpenWindow(0,#Null,#Null,200,100,#Null$,#PB_Window_SystemMenu|#PB_Window_ScreenCentered)
    ButtonGadget(1,20,30,160,30,"Test")
    Repeat
      If hrdReload();<- check if there where changes made to the library
        Break  
      EndIf
      Select WaitWindowEvent()
        Case #PB_Event_Gadget
          If EventGadget() = 1 And *hot
            CallFunctionFast(*hot)
          EndIf
        Case #PB_Event_CloseWindow
          Break
      EndSelect
    ForEver
    CloseWindow(0)
  EndIf
  ProcedureReturn #Null
EndProcedure

End Main()

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EnableExplicit

ProcedureDLL.i Dummy()
  MessageRequester("Message","Message :)")
  ProcedureReturn #Null
EndProcedure