/*
 * $Id$
 */

/*
 * Harbour Project source code: 
 *   CT3 string functions
 *     - CHARSWAP()
 *     - WORDSWAP()
 *
 * Copyright 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"


/* defines */
#define DO_CHARSWAP_CHARSWAP          0
#define DO_CHARSWAP_WORDSWAP          1
#define DO_CHARSWAP_WORDSWAP_CHARSWAP 2

/* helper function for the charswap and wordswap functions */
static void do_charswap( int iSwitch )
{
   int iNoRet;

   /* suppress return value ? */
   iNoRet = ct_getref() && ISBYREF( 1 );

   /* param check */
   if( ISCHAR( 1 ) )
   {
      char *pcString = hb_parc( 1 );
      size_t sStrLen = ( size_t ) hb_parclen( 1 );
      char *pcRet;
      size_t sRetIndex = 0;
      int iShift, iMod;
      char *pcSub;

      if( sStrLen == 0 )
      {
         if( iNoRet )
            hb_ret();
         else
            hb_retc( NULL );
         return;
      }

      if( iSwitch == DO_CHARSWAP_WORDSWAP )
      {
         iShift = 4;
         if( ISLOG( 2 ) && hb_parl( 2 ) )
         {
            iSwitch = DO_CHARSWAP_WORDSWAP_CHARSWAP;
         }
      }
      else
      {
         iShift = 2;
      }

      pcRet = ( char * ) hb_xgrab( sStrLen );

      for( pcSub = pcString; pcSub < pcString + sStrLen + 1 - iShift; pcSub += iShift )
      {
         switch ( iSwitch )
         {
            case DO_CHARSWAP_WORDSWAP:
               pcRet[sRetIndex++] = pcSub[2];
               pcRet[sRetIndex++] = pcSub[3];
               pcRet[sRetIndex++] = pcSub[0];
               pcRet[sRetIndex++] = pcSub[1];
               break;

            case DO_CHARSWAP_WORDSWAP_CHARSWAP:
               pcRet[sRetIndex++] = pcSub[3];
               pcRet[sRetIndex++] = pcSub[2];
               /* no 'break' here !! */
            case DO_CHARSWAP_CHARSWAP:
               pcRet[sRetIndex++] = pcSub[1];
               pcRet[sRetIndex++] = pcSub[0];
         }
      }

      /* copy rest of string */
      if( ( iSwitch == DO_CHARSWAP_WORDSWAP ) || ( iSwitch == DO_CHARSWAP_WORDSWAP_CHARSWAP ) )
      {
         iMod = sStrLen % 4;
      }
      else
      {
         iMod = sStrLen % 2;
      }

      for( pcSub = pcString + sStrLen - iMod; pcSub < pcString + sStrLen; pcSub++ )
      {
         pcRet[sRetIndex++] = *pcSub;
      }

      /* return string */
      if( ISBYREF( 1 ) )
      {
         hb_storclen( pcRet, sRetIndex, 1 );
      }

      if( iNoRet )
         hb_retl( 0 );
      else
         hb_retclen( pcRet, sRetIndex );
      hb_xfree( pcRet );
   }
   else                         /* if (ISCHAR (1)) */
   {
      PHB_ITEM pSubst = NULL;
      int iArgErrorMode = ct_getargerrormode();

      if( iArgErrorMode != CT_ARGERR_IGNORE )
      {
         if( iSwitch == DO_CHARSWAP_CHARSWAP )
         {
            pSubst = ct_error_subst( ( USHORT ) iArgErrorMode, EG_ARG,
                                     CT_ERROR_CHARSWAP,
                                     NULL, "CHARSWAP", 0, EF_CANSUBSTITUTE,
                                     HB_ERR_ARGS_BASEPARAMS );
         }
         else
         {
            pSubst = ct_error_subst( ( USHORT ) iArgErrorMode, EG_ARG,
                                     CT_ERROR_WORDSWAP,
                                     NULL, "WORDSWAP", 0, EF_CANSUBSTITUTE,
                                     HB_ERR_ARGS_BASEPARAMS );
         }
      }

      if( pSubst != NULL )
         hb_itemReturnRelease( pSubst );
      else if( iNoRet )
         hb_retl( 0 );
      else
         hb_retc( NULL );
   }
}


/*  $DOC$
 *  $FUNCNAME$
 *      CHARSWAP()
 *  $CATEGORY$
 *      CT3 string functions
 *  $ONELINER$
 *      Swap neighbouring characters in a string
 *  $SYNTAX$
 *      CHARSWAP (<[@]cString>) -> cSwappedString
 *  $ARGUMENTS$
 *      <[@]cString>      is the string that should be processed
 *  $RETURNS$
 *      <cSwappedString>  a string where neighbour characters are swapped
 *  $DESCRIPTION$
 *      The CHARSWAP() function loops through <cString> in steps of two
 *      characters and exchanges the characters from the odd and the even
 *      positions.
 *      By setting the CSETREF() switch to .T., one can omit the return value
 *      of this functin, but one must then pass <cString> by reference.
 *  $EXAMPLES$
 *      ? CHARSWAP("0123456789")   // "1032547698"
 *      ? CHARSWAP("ABCDEFGHIJK")  // "BADCFEHGJIK"
 *  $TESTS$
 *      CHARSWAP("0123456789")  == "1032547698"
 *      CHARSWAP("ABCDEFGHIJK") == "BADCFEHGJIK"
 *  $STATUS$
 *      Ready
 *  $COMPLIANCE$
 *      CHARSWAP() is compatible with CT3's CHARSWAP().
 *  $PLATFORMS$
 *      All
 *  $FILES$
 *      Source is charswap.c, library is libct.
 *  $SEEALSO$
 *      WORDSWAP(),CSETREF()
 *  $END$
 */

HB_FUNC( CHARSWAP )
{
   do_charswap( DO_CHARSWAP_CHARSWAP );
}


/*  $DOC$
 *  $FUNCNAME$
 *      WORDSWAP()
 *  $CATEGORY$
 *      CT3 string functions
 *  $ONELINER$
 *      Swap neighbouring double characters in a string
 *  $SYNTAX$
 *      WORDSWAP (<[@]cString> [, <lSwapCharacters>]) -> cSwappedString
 *  $ARGUMENTS$
 *      <[@]cString>         is the string that should be processed
 *      [<lSwapCharacters>]  specifies whether an additional swap should be
 *                           done within the double characters
 *                           Default: .F., no additional swap
 *  $RETURNS$
 *      <cSwappedString>  a string where neighbouring double characters are
 *                        swapped
 *  $DESCRIPTION$
 *      The WORDSWAP() function loops through <cString> in steps of four
 *      characters and exchanges the double characters from the first and
 *      second position with the one from the third and forth position.
 *      Additionally the function can perform a swap of the both char of
 *      each double character.
 *      By setting the CSETREF() switch to .T., one can omit the return value
 *      of this functin, but one must then pass <cString> by reference.
 *  $EXAMPLES$
 *      ? WORDSWAP("1234567890")        // "3412785690"
 *      ? WORDSWAP("1234567890", .t.)   // "4321876590"
 *  $TESTS$
 *      WORDSWAP("1234567890")      == "3412785690"
 *      WORDSWAP("1234567890", .t.) == "4321876590"
 *  $STATUS$
 *      Ready
 *  $COMPLIANCE$
 *      WORDSWAP() is compatible with CT3's WORDSWAP().
 *  $PLATFORMS$
 *      All
 *  $FILES$
 *      Source is charswap.c, library is libct.
 *  $SEEALSO$
 *      CHARSWAP(),CSETREF()
 *  $END$
 */

HB_FUNC( WORDSWAP )
{
   do_charswap( DO_CHARSWAP_WORDSWAP );
}
