CODEWITHSUNDEEP
functionc-preprocessor
Tage
Tage

Reputation: 35

Function-like macro definition

The problem is, that I don't quite understand what the following definition does. Can somebody explain it to me?

#define Vpc3MemSet_( _pToVpc3Memory, _bValue, _wLength )\
           Vpc3MemSet( _pToVpc3Memory, _bValue, _wLength )

Upvotes: 1

Views: 132

Answers (2)

Tage
Tage

Reputation: 35

One more thing, however. This is the whole #define sequence:

#if VPC3_SERIAL_MODE


 #define CopyToVpc3_( _pToVpc3Memory, _pLocalMemory, _wLength )\
           CopyToVpc3( _pToVpc3Memory, _pLocalMemory, _wLength )

 #define CopyFromVpc3_( _pLocalMemory, _pToVpc3Memory, _wLength )\
           CopyFromVpc3( _pLocalMemory, _pToVpc3Memory, _wLength )

 #define Vpc3MemSet_( _pToVpc3Memory, _bValue, _wLength )\
           Vpc3MemSet( _pToVpc3Memory, _bValue, _wLength )

 #define Vpc3MemCmp_( _pToVpc3Memory1, _pToVpc3Memory2, _wLength )\
           Vpc3MemCmp( _pToVpc3Memory1, _pToVpc3Memory2, _wLength )

#else

 #define CopyToVpc3_( _pToVpc3Memory, _pLocalMemory, _wLength )\
           memcpy( _pToVpc3Memory, _pLocalMemory, _wLength )

 #define CopyFromVpc3_( _pLocalMemory, _pToVpc3Memory, _wLength )\
           memcpy( _pLocalMemory, _pToVpc3Memory, _wLength )

 #define Vpc3MemSet_( _pToVpc3Memory, _bValue, _wLength )\
           memset( _pToVpc3Memory, _bValue, _wLength )

 #define Vpc3MemCmp_( _pToVpc3Memory1, _pToVpc3Memory2, _wLength )\
           memcmp( _pToVpc3Memory1, _pToVpc3Memory2, _wLength )

#endif /* #if VPC3_SERIAL_MODE */

So the four functions have two definitions depending on whether you are in serial, or parallel mode. Yet, the memset() function is called in application source file, like the following:

 /*-----------------------------------------------------------------------*/
 /* init application data                                                 */
 /*-----------------------------------------------------------------------*/
  memset( &sDpAppl, 0, sizeof( sDpAppl ) );

 /*-----------------------------------------------------------------------*/
 /* initialize VPC3                                                       */
 /*-----------------------------------------------------------------------*/
 #if VPC3_SERIAL_MODE
  Vpc3AsicAddress = (VPC3_ADR)VPC3_ASIC_ADDRESS;
  pVpc3 = &sVpc3OnlyForInit;
  pDpSystem = &sDpSystemChannel1;

  memset( pVpc3, 0, sizeof( VPC3_STRUC ) );
#else
  pVpc3Channel1 = (VPC3_STRUC_PTR)VPC3_ASIC_ADDRESS;
  Vpc3AsicAddress = (VPC3_ADR)VPC3_ASIC_ADDRESS;
  pVpc3 = pVpc3Channel1;
  pDpSystem = &sDpSystemChannel1;
#endif//#if VPC3_SERIAL_MODE

As if this were a different function. Or, am I still missing something? :/ By the way, I am in serial mode and I already defined CopyToVpc3(), CopyFromVpc3(), Vpc3MemSet(), Vpc3MemCmp().

Upvotes: 0

clemens
clemens

Reputation: 17711

Your macro does nearly nothing. It replaces Vpc3MemSet_ (with underscore) by Vpc3MemSet (without underscore). Such macros usually make sense if there are different, platform-dependent variants (say for Linux, macOS, and Windows). For (fictional) example:

#ifdef __WINDOWS__
    #define Vpc3MemSet_( _pToVpc3Memory, _bValue, _wLength )\
       Vpc3MemSet( _pToVpc3Memory, _bValue, _wLength )
#else
    #define Vpc3MemSet_( _pToVpc3Memory, _bValue, _wLength )\
       memset(_pToVpc3Memory, _bValue, _wLength * sizeof(Vpc3))
#endif

You can call the platform-dependent function with the same macro call:

Vpc3MemSet_(memory, value, length);

This will expand to different function calls on Windows and Linux.

Upvotes: 1

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