/*
 * $Id$
 */

/*
 * Harbour Project source code: 
 *   CT3 string functions
 *     - CHAREVEN()
 *     - CHARODD()
 *
 * Copyright 2000-2001 Viktor Szakats <viktor.szakats@syenar.hu>
 *
 * Merged into one file for optimization and some small corrections:
 * (c) 2001 IntTec GmbH, Neunlindenstr 32, 79106 Freiburg, Germany
 *          Author: Martin Vogel <vogel@inttec.de>
 *
 * www - http://www.harbour-project.org
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this software; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
 * Boston, MA 02111-1307 USA (or visit the web site http://www.gnu.org/).
 *
 * As a special exception, the Harbour Project gives permission for
 * additional uses of the text contained in its release of Harbour.
 *
 * The exception is that, if you link the Harbour libraries with other
 * files to produce an executable, this does not by itself cause the
 * resulting executable to be covered by the GNU General Public License.
 * Your use of that executable is in no way restricted on account of
 * linking the Harbour library code into it.
 *
 * This exception does not however invalidate any other reasons why
 * the executable file might be covered by the GNU General Public License.
 *
 * This exception applies only to the code released by the Harbour
 * Project under the name Harbour.  If you copy code from other
 * Harbour Project or Free Software Foundation releases into a copy of
 * Harbour, as the General Public License permits, the exception does
 * not apply to the code that you add in this way.  To avoid misleading
 * anyone as to the status of such modified files, you must delete
 * this exception notice from them.
 *
 * If you write modifications of your own for Harbour, it is your choice
 * whether to permit this exception to apply to your modifications.
 * If you do not wish that, delete this exception notice.
 *
 */

#include "ct.h"

#define DO_CHAREVOD_CHAREVEN   0
#define DO_CHAREVOD_CHARODD    1

/* helper function */
static void do_charevod( int iSwitch )
{
   if( ISCHAR( 1 ) )
   {
      char *pcString = hb_parc( 1 );
      size_t sLen = hb_parclen( 1 );
      char *pcResult;
      size_t sPos, sResultPos;

      if( sLen == 0 )
      {
         int iArgErrorMode = ct_getargerrormode();

         if( iArgErrorMode != CT_ARGERR_IGNORE )
         {
            ct_error( ( USHORT ) iArgErrorMode, EG_ARG,
                      iSwitch == DO_CHAREVOD_CHAREVEN ?
                      CT_ERROR_CHAREVEN : CT_ERROR_CHARODD,
                      NULL, HB_ERR_FUNCNAME, 0, EF_CANDEFAULT,
                      HB_ERR_ARGS_BASEPARAMS );
         }
         hb_retc( NULL );
         return;
      }

      pcResult = ( char * ) hb_xgrab( ( sLen + 1 ) / 2 );

      if( iSwitch == DO_CHAREVOD_CHAREVEN )
         sPos = 1;
      else
         sPos = 0;

      sResultPos = 0;
      for( ; sPos < sLen; sPos += 2 )
         pcResult[sResultPos++] = pcString[sPos];

      if( sResultPos == 0 )
         hb_retc( NULL );
      else
         hb_retclen( pcResult, sResultPos );

      hb_xfree( pcResult );
   }
   else
   {
      PHB_ITEM pSubst = NULL;
      int iArgErrorMode = ct_getargerrormode();

      if( iArgErrorMode != CT_ARGERR_IGNORE )
      {
         pSubst = ct_error_subst( ( USHORT ) iArgErrorMode, EG_ARG,
                                  iSwitch == DO_CHAREVOD_CHAREVEN ?
                                  CT_ERROR_CHAREVEN : CT_ERROR_CHARODD, NULL,
                                  HB_ERR_FUNCNAME, 0, EF_CANSUBSTITUTE,
                                  HB_ERR_ARGS_BASEPARAMS );
      }

      if( pSubst != NULL )
         hb_itemReturnRelease( pSubst );
      else
         hb_retc( NULL );
   }
}


/*  $DOC$
 *  $FUNCNAME$
 *      CHAREVEN()
 *  $CATEGORY$
 *      CT3 string functions
 *  $ONELINER$
 *      Returns the characters on the even positions in a string
 *  $SYNTAX$
 *      CHAREVEN (<cString>) --> cEvenString
 *  $ARGUMENTS$
 *      <cString>      processed string
 *  $RETURNS$
 *      <cEvenString>  a string containing all character from even positions
 *                     in <cString>
 *  $DESCRIPTION$
 *      The CHAREVEN() function looks for the characters on the even positions
 *      in a given string, collects them and returns them as a string.
 *  $EXAMPLES$
 *      ? CHAREVEN (" H E L L O !") -> "HELLO!"
 *  $TESTS$
 *      CHAREVEN (" 1 2 3 4 5") == "12345"
 *      CHAREVEN (" 1 2 3 4 ") == "1234"
 *      CHAREVEN (" ") == ""
 *  $STATUS$
 *      Ready
 *  $COMPLIANCE$
 *      CHAREVEN() is compatible with CT3's CHAREVEN().
 *  $PLATFORMS$
 *      All
 *  $FILES$
 *      Source is charevod.c, library is ct3.
 *  $SEEALSO$
 *      CHARODD()  CHARMIX()
 *  $END$
 */

HB_FUNC( CHAREVEN )
{
   do_charevod( DO_CHAREVOD_CHAREVEN );
}


/*  $DOC$
 *  $FUNCNAME$
 *      CHARODD()
 *  $CATEGORY$
 *      CT3 string functions
 *  $ONELINER$
 *      Returns the characters on the odd positions in a string
 *  $SYNTAX$
 *      CHARODD (<cString>) --> cOddString
 *  $ARGUMENTS$
 *      <cString>      processed string
 *  $RETURNS$
 *      <cOddString>  a string containing all character from odd positions
 *                    in <cString>
 *  $DESCRIPTION$
 *      The CHARODD() function looks for the characters on the odd positions
 *      in a given string, collects them and returns them as a string.
 *  $EXAMPLES$
 *      ? CHARODD ("H E L L O ! ") -> "HELLO!"
 *  $TESTS$
 *      CHARODD ("1A2B3C4D5E") == "12345"
 *      CHARODD ("1A2B3C4D5")  == "12345"
 *  $STATUS$
 *      Ready
 *  $COMPLIANCE$
 *      CHARODD() is compatible with CT3's CHARODD().
 *  $PLATFORMS$
 *      All
 *  $FILES$
 *      Source is charevod.c, library is ct3.
 *  $SEEALSO$
 *      CHAREVEN()  CHARMIX()
 *  $END$
 */

HB_FUNC( CHARODD )
{
   do_charevod( DO_CHAREVOD_CHARODD );
}
