gecko-dev/intl/uconv/ucvcn/nsHZToUnicode.cpp

/* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 *
 * The contents of this file are subject to the Netscape Public
 * License Version 1.1 (the "License"); you may not use this file
 * except in compliance with the License. You may obtain a copy of
 * the License at http://www.mozilla.org/NPL/
 *
 * Software distributed under the License is distributed on an "AS
 * IS" basis, WITHOUT WARRANTY OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * rights and limitations under the License.
 *
 * The Original Code is mozilla.org code.
 *
 * The Initial Developer of the Original Code is Netscape
 * Communications Corporation.  Portions created by Netscape are
 * Copyright (C) 1998 Netscape Communications Corporation. All
 * Rights Reserved.
 *
 * Contributor(s): 
 * 
 * This HZ to Unicode converter is a contribution from Intel Corporation to the mozilla 
 * project.
 */
/**
 * A character set converter from HZ to Unicode.
 * 
 *
 * @created         08/Sept/1999
 * @author  Yueheng Xu, Yueheng.Xu@intel.com
 *
 * Note: in this HZ-GB-2312 converter, we accept a string composed of 7-bit HZ 
 *       encoded Chinese chars,as it is defined in RFC1843 available at 
 *       http://www.cis.ohio-state.edu/htbin/rfc/rfc1843.html
 *       and RFC1842 available at http://www.cis.ohio-state.edu/htbin/rfc/rfc1842.html.
 *        
 *       In an effort to match the similar extended capability of Microsoft Internet Explorer
 *       5.0. We also accept the 8-bit GB encoded chars mixed in a HZ string.
 *       But this should not be a recommendedd practice for HTML authors.
 *
 *       The priority of converting are as follows: first convert 8-bit GB code; then,
 *       consume HZ ESC sequences such as '~{', '~}', '~~'; then, depending on the current
 *       state ( default to ASCII state ) of the string, each 7-bit char is converted as an 
 *       ASCII, or two 7-bit chars are converted into a Chinese character.
 */



#include "nsUCvCnDll.h"
#include "nsHZToUnicode.h"

#define _GBKU_TABLE_		// to use a shared GBKU table
#include "gbku.h"

//----------------------------------------------------------------------
// Class nsHZToUnicode [implementation]

//----------------------------------------------------------------------
// Subclassing of nsTablesDecoderSupport class [implementation]

NS_IMETHODIMP nsHZToUnicode::GetMaxLength(const char * aSrc, 
                                              PRInt32 aSrcLength, 
                                              PRInt32 * aDestLength)
{
  *aDestLength = aSrcLength;
  return NS_OK;
}
 

//convert the 7-bit HZ into an 8-bit GB index of the GBK table and get its unicode
void nsHZToUnicode::HZToUnicode(DByte *pGBCode, PRUnichar * pUnicode)
{
  //we are re-using the GBK's GB to Unicode mapping table.
  PRUint16 iGBKToUnicodeIndex = 0; 
  PRUint8 left, right;

  *pUnicode = 0xFFFF;
 
  if(pGBCode)	
    {
      left = pGBCode->leftbyte | 0x80; 
      right = pGBCode->rightbyte | 0x80;
      iGBKToUnicodeIndex = (left - 0x0081)*0x00BF + (right - 0x0040);
    }
 
  *pUnicode = GBKToUnicodeTable[iGBKToUnicodeIndex];
  
}

//convert the 8-bit GB index to its unicode by GBK table
void nsHZToUnicode::GBToUnicode(DByte *pGBCode, PRUnichar * pUnicode)
{
  //we are re-using the GBK's GB to Unicode mapping table.
  PRUint16 iGBKToUnicodeIndex = 0; 
  PRUint8 left, right;

  *pUnicode = 0xFFFF;
  
  if(pGBCode)	
    {
      left = pGBCode->leftbyte; 
      right = pGBCode->rightbyte;    
      iGBKToUnicodeIndex = (left - 0x0081)*0x00BF + (right - 0x0040);
    }

  *pUnicode = GBKToUnicodeTable[iGBKToUnicodeIndex];
 
}


//Overwriting the ConvertNoBuff() in nsUCvCnSupport.cpp.
NS_IMETHODIMP nsHZToUnicode::ConvertNoBuff(const char* aSrc,
											   PRInt32 * aSrcLength,
											   PRUnichar *aDest,
											   PRInt32 * aDestLength)
{

#define HZ_STATE_GB		1
#define HZ_STATE_ASCII	2
#define HZ_STATE_TILD	3
#define HZLEAD1 '~'
#define HZLEAD2 '{'
#define HZLEAD3 '}'
#define HZLEAD4 '\n'

  static PRInt16 hz_state = HZ_STATE_ASCII;	// per HZ spec, default to ASCII state 
  PRInt32 i=0;
  PRInt32 iSrcLength = *aSrcLength;

  DByte *pSrcDBCode = (DByte *)aSrc;
  PRUnichar *pDestDBCode = (PRUnichar *)aDest;
  PRInt32 iDestlen = 0;
  PRUint8 ch1, ch2;
  nsresult res = NS_OK;

  for (i=0;i<iSrcLength;i++)
	{
      pSrcDBCode = (DByte *)aSrc;
      pDestDBCode = aDest;
      
      if ( iDestlen >= (*aDestLength) )
		{
          res = NS_OK_UDEC_MOREOUTPUT;
          break;
		}
      
      if ( *aSrc & 0x80 ) // if it is a 8-bit byte
		{
          // The source is a 8-bit GBCode
          GBToUnicode(pSrcDBCode, pDestDBCode);
          aSrc += 2;
          i++;
          iDestlen++;
          aDest++;
          *aSrcLength = i+1;
          continue;
		}
      
      // otherwise, it is a 7-bit byte 
      // The source will be an ASCII or a 7-bit HZ code depending on ch1
      
      ch1 = *aSrc;
      ch2	= *(aSrc+1);
      
      if (ch1 == HZLEAD1 )  // if it is lead by '~'
        {
          switch (ch2)
            {
            case HZLEAD2:	// we got a '~{'
              // we are switching to HZ state
              hz_state = HZ_STATE_GB;
              aSrc += 2;
              i++;
              break;
            case HZLEAD3:	// we got a '~}'
              // we are switching to ASCII state
              hz_state = HZ_STATE_ASCII;
              aSrc += 2;
              i++;
              break;
            case HZLEAD1:	// we got a '~~', process like an ASCII, but no state change
              aSrc++;
              *pDestDBCode = (PRUnichar) ( ((char)(*aSrc) )& 0x00ff);
              aSrc++;
              i++;
              iDestlen++;
              aDest++;
              break;
            case HZLEAD4:	// we got a "~\n", it means maintain double byte mode cross lines, ignore the '~' itself
              //  hz_state = HZ_STATE_GB; // I find that "~\n" should interpreted as line continuation without mode change
                                          // It should not be interpreted as line continuation with double byte mode on
              aSrc++;
              break;
            default:
              // undefined ESC sequence '~X' are ignored since this is a illegal combination 
              aSrc += 2;
              break;
            };

          continue;// go for next loop
        }

        // ch1 != '~'
        switch (hz_state)
          {
            case HZ_STATE_GB:
              // the following chars are HZ
              HZToUnicode(pSrcDBCode, pDestDBCode);
              aSrc += 2;
              i++;
              iDestlen++;
              aDest++;
              break;
            case HZ_STATE_ASCII:
            default:
              // default behavior also like an ASCII
              // when the source is an ASCII
              *pDestDBCode = (PRUnichar) ( ((char)(*aSrc) )& 0x00ff);
              aSrc++;
              iDestlen++;
              aDest++;
              break;
          }

        *aSrcLength = i+1;

    }// for loop

  *aDestLength = iDestlen;
        
  return NS_OK;
}