pp_prg.txt

Przemyslaw Czerpak (druzus/at/priv.onet.pl)

In Harbour preprocessor can be used in PRG code.
This is list of PRG functions available for programmer.

   REQUEST __pp_StdRules
      It forces including standard std.ch rules in static binaries.
      Dynamic binaries linked with Harbour dynamic library always
      includes standard PP rules.


   __pp_Init( [<cIncludePath>] [, <cStdChFile> ] ) -> <pPP>
      Initialize new PP context and return pointer to it.
      when <cStdChFile> is empty string ("") then no default rules are
      used and only the dynamically created #defines like __HARBOUR__,
      __DATE__, __TIME__, __PLATFORM__* are registered.
      If <cStdChFile> is missing or NIL and standard PP rules from
      std.ch are included in binaries (REQUEST __pp_StdRules) then
      they are used.

   __pp_Path( <pPP>, <cPath> [, <lClearPrev>] ) -> NIL
      Add new (or replace previous) include paths.

   __pp_Reset( <pPP> )
      Reset the PP context (remove all rules added by user or
      preprocessed code)

   __pp_AddRule( <pPP>, <cDirective> )
      Preprocess and execute new preprocessor directive

   __pp_Process( <pPP>, <cCode> ) -> <cPreprocessedCode>
      Preprocess given code and return result

User can create more then one PP context and then use each of them
separately. Any modifications in one context have no effect in other
so different PP contexts can be used simultaneously in MT programs.
To free allocated PP context is enough to clear <pPP> variable.
When last instance of this variable in user code is cleared then
automatic destructor frees PP context with its all internal data
so even if variable is not explicitly cleared by assigning NIL but
is out of scope (e.g. local variable when program leaves the function)
PP context is freed.

Below is simple test program which preprocess file and executes
it's lines by macro compiler:


   /*** macro.dat ***/
   #define VALUE 123.45
   #xcommand INFO <data> => Alert( <data> )
   ? "Hello!"
   WAIT
   INFO "Let's test simple calculation."
   pow := 2
   ? "value =", VALUE
   ? "pow =", pow
   ? "value * pow =", VALUE * pow
   WAIT
   ? VALUE2  // generate RTE


   /*** testpp.prg ***/
   REQUEST __pp_StdRules
   REQUEST __Wait

   PROCEDURE Main()

      LOCAL cLine, pPP, oErr

      pPP := __pp_Init()
      BEGIN SEQUENCE WITH __BreakBlock()
         FOR EACH cLine IN hb_ATokens( __pp_Process( pPP, ;
               hb_MemoRead( "macro.dat" ) ), .T. )
            BEGIN SEQUENCE
               IF ! Empty( cLine )
                  &cLine
               ENDIF
            RECOVER USING oErr
               ? "MacroCompiler error at line:", ;
                  hb_ntos( cLine:__enumIndex() )
               ? cLine
               ? ErrMsg( oErr )
            END SEQUENCE
         NEXT
      RECOVER USING oErr
         ? ErrMsg( oErr )
      END SEQUENCE
      ?

      RETURN

   STATIC FUNCTION ErrMsg( oErr )
      RETURN "Error " + ;
         iif( HB_ISSTRING( oErr:subsystem ), ;
              oErr:subsystem, "???" ) + ;
         iif( HB_ISNUMERIC( oErr:subCode ), ;
              "/" + hb_ntos( oErr:subCode ), "/???" ) + ;
         iif( HB_ISSTRING( oErr:description ), ;
              " " + oErr:description, "" ) + ;
         iif( ! oErr:filename == "", ;
              " " + oErr:filename, ;
              iif( ! Empty( oErr:operation ), ;
                   " " + oErr:operation, "" ) )