DLL vs LIB

[jorge.posadas]

Grupo,

Hace muchisimo tiempo que usando clipper logre hace una libreria, encadenarla a mis PRG y luego usarla, ahora con el nacimiento de HMG, he leido sobre DLL mi pregunta es:

Cual es la diferencia entre DLL y LIB?
Cuando se debe usar LIB y cuando una DLL
Hay ventas de una sobre la otra?

Y por terminar,

Ejemplo,

LnCustomerId :=GetNextNumber("customer_id")


*------------------------------------------------------------------------------*
FUNCTION GetNextNumber(PsModule)
*------------------------------------------------------------------------------*
LdDateSQL := "DATE('NOW')"
LsTimeSQL := "TIME('NOW','LOCALTIME')"
LsModule := C2SQL(PsModule)
GnNextNumber := 0
IF .NOT. ConectMe()
MsgExclamation ("No me pude conectar a la base de datos")
RETURN NIL
ELSE
GsRead := "SELECT Module, Last_Number, "
GsRead += "(Last_Number + Sequence_Count) AS [Next_Number] "
GsRead += "FROM Folios WHERE LOWER(Module) = LOWER(&LsModule)"
IF TryToLock()
aTableNextNum := sql(oDataBase,GsRead)
IF LEN(aTableNextNum) = 0
MsgExclamation("No se encontro el modulo para la numeracion")
DeleteFileLock()
RETURN NIL
EndIf
GnNextNumber := aTableNextNum[1,3]
GsQueryInsert := "UPDATE Folios SET "
GsQueryInsert += "Last_Number = (Last_Number + Sequence_Count), "
GsQueryInsert += "Modify_Date = "+LdDateSQL +", "
GsQueryInsert += "Modify_Time = "+LsTimeSQL
GsQueryInsert += "WHERE LOWER(Module) = LOWER(&LsModule)"
IF .NOT. BeforeSave(GsQueryInsert)
MsgExclamation ("Error al tratar de obtener el folio siguiente.")
ENDIF
DeleteFileLock()
ENDIF
ENDIF
RETURN ( VAL(GnNextNumber ))

Pregunta: Como convierto esa pequea function en DLL y como se debe de llamar en un PRG.

De antemano agradezco la ayuda.

[Rathinagiri]

Difference between DLL and LIB:

DLL is dynamically linked library (ie., linked at the runtime). LIB is statically linked library inside the EXE.

DLL can be reused by many EXE files. LIB once attached to the EXE can be used by only that EXE.

Other than that, I don't see much of a difference between these two.

[serge_girard]

Thanks for clarification Rathi!

Serge

[mol]

Can sb. place small sample how to load dll into .exe and later unload it?
Regards, Marek

[mlnr]

Code: Select all

If !File("example.dll")
  MsgInfo ('Missing file: EXAMPLE.DLL')
  ReleaseAllWindows()
Endif
regikez:=ErrorBlock({ |objerr| ujkez(objerr,.T.) })
Begin Sequence
   jDll := hb_libLoad( hb_DirBase() + "example.dll" )
   IF !Empty( jDll )
      hb_DynCall( { "VerzioSzam", jDll, HB_DYN_CALLCONV_CDECL, HB_DYN_CTYPE_DOUBLE},@DllVersion)
      If DllVersion>1.1
         PcNev := hb_DynCall( { "PcNeve", jDll, hb_bitOr( HB_DYN_CALLCONV_STDCALL, HB_DYN_ENC_UTF16, HB_DYN_CTYPE_CHAR_PTR ),HB_DYN_CTYPE_CHAR_PTR },'*' )
      EndIf
    Else
      MsgInfo ('The program was not able to start correctly' + Chr(13) + Chr(10) + ' Please install .net framework 4' )
   EndIf
Recover Using objlocal
End Sequence
ErrorBlock(regikez) 

unload:

hb_libFree( hLib )

[Anand]

Difference between DLL and LIB:

DLL is dynamically linked library (ie., linked at the runtime). LIB is statically linked library inside the EXE.

DLL can be reused by many EXE files. LIB once attached to the EXE can be used by only that EXE.

Further with what Rathi said, calling functions in a DLL is same like calling in your codes, if the dll is linked statically with lib. Whereas calling the function requires dllcall with defined parameters if it is dynamically linked.

Regards,

Anand

[srvet_claudio]

The only advantage of the dll is when a very large library is shared by multiple applications or require frequent updating in library functions, so the dll is used in the practice only by software developers for programmers.

[Rathinagiri]

Rightly said Claudio.

[jorge.posadas]

Grupo,

Gracias a todos por sus comentarios, ahora me tocara investigar COMO se crea una DLL y luego el COMO se usa en mis aplicaciones

[Carlos Britos]

Grupo,

Gracias a todos por sus comentarios, ahora me tocara investigar COMO se crea una DLL y luego el COMO se usa en mis aplicaciones

Hi Jorge

Crear una dll con harbour no es una tarea sencilla, aunque si es posble. Deberas manejar mucho el codigo C. La gran pregunta es si se justifica todo ese trabajo para cargar una funcion.

Usarla es muy sencillo hay varios ejemplos en los samples.

Create a DLL with harbour is not easy, but not impossible. You have to do a lot of work with C code. The big question is if this big job paid for it, just to load one function.

Using dll is very simple, you can find many samples in the Samples folder.