/* -*- Mode: C++; tab-width: 2; 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 Communicator client 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): 
 */

#include "nsUCS2BEToUnicode.h"
#include <string.h>
//----------------------------------------------------------------------
// Global functions and data [declaration]

static PRUint16 g_UCS2BEMappingTable[] = {
  0x0001, 0x0004, 0x0005, 0x0008, 0x0000, 0x0000, 0xFFFF, 0x0000
};

static PRInt16 g_UCS2BEShiftTable[] =  {
  0, u2BytesCharset, 
  ShiftCell(0,       0, 0, 0, 0, 0, 0, 0), 
};

//----------------------------------------------------------------------
// Class nsUCS2BEToUnicode [implementation]

nsUCS2BEToUnicode::nsUCS2BEToUnicode() 
: nsTableDecoderSupport((uShiftTable*) &g_UCS2BEShiftTable, 
                        (uMappingTable*) &g_UCS2BEMappingTable)
{
}

nsresult nsUCS2BEToUnicode::CreateInstance(nsISupports ** aResult) 
{
  *aResult = new nsUCS2BEToUnicode();
  return (*aResult == NULL)? NS_ERROR_OUT_OF_MEMORY : NS_OK;
}

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

NS_IMETHODIMP nsUCS2BEToUnicode::GetMaxLength(const char * aSrc, 
                                            PRInt32 aSrcLength, 
                                            PRInt32 * aDestLength)
{
  if(0 == (aSrcLength % 2)) 
  {
    *aDestLength = aSrcLength / 2;
    return NS_OK_UENC_EXACTLENGTH;
  } else {
    *aDestLength = (aSrcLength  + 1) / 2;
    return NS_OK;
  }
}


class nsUTF16SameEndianToUnicode : public nsBasicDecoderSupport
{
public:

  /**
   * Class constructor.
   */
  nsUTF16SameEndianToUnicode() { Reset();};

  NS_IMETHOD Convert(const char * aSrc, PRInt32 * aSrcLength,
      PRUnichar * aDest, PRInt32 * aDestLength); 
  NS_IMETHOD Reset();

protected:
  //--------------------------------------------------------------------
  // Subclassing of nsDecoderSupport class [declaration]

  NS_IMETHOD GetMaxLength(const char * aSrc, PRInt32 aSrcLength, 
      PRInt32 * aDestLength);
protected:
  PRUint8 mState;
  PRUint8 mData;
};


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

NS_IMETHODIMP nsUTF16SameEndianToUnicode::GetMaxLength(const char * aSrc, 
                                            PRInt32 aSrcLength, 
                                            PRInt32 * aDestLength)
{
  *aDestLength = (aSrcLength + ((1==mState)?1:0))/2;
  return NS_OK;
}
NS_IMETHODIMP nsUTF16SameEndianToUnicode::Convert(
      const char * aSrc, PRInt32 * aSrcLength,
      PRUnichar * aDest, PRInt32 * aDestLength)
{
  const char* src = aSrc;
  const char* srcEnd = aSrc + *aSrcLength;
  PRUnichar* dest = aDest;
  PRUnichar* destEnd = aDest + *aDestLength;
  PRInt32 copybytes;

  if(2 == mState) // first time called
  {
    // eleminate BOM
    if(0xFEFF == *((PRUnichar*)src)) {
      src+=2;
    } else if(0xFFFE == *((PRUnichar*)src)) {
      *aSrcLength=0;
      *aDestLength=0;
      return NS_ERROR_ILLEGAL_INPUT;
    }  
    mState=0;
  }

  if((1 == mState) && (src < srcEnd))
  {
    if(dest >= destEnd)
      goto error;
    if(src>=srcEnd)
      goto done;
    char tmpbuf[2];
    PRUnichar * up = (PRUnichar*) &tmpbuf[0];
    tmpbuf[0]= mData;
    tmpbuf[1]= *src++;
    *dest++ = *up;
  }
  
  copybytes = (destEnd-dest)*2;
  if(copybytes > (0xFFFE & (srcEnd-src)))
      copybytes = 0xFFFE & (srcEnd-src);
  memcpy(dest,src,copybytes);
  src +=copybytes;
  dest +=(copybytes/2);
  if(srcEnd==src)  {
     mState = 0;
  } else if(1 == (srcEnd-src) ) {
     mState = 1;
     mData  = *src++;
  } else  {
     goto error;
  }
  
done:
  *aDestLength = dest - aDest;
  *aSrcLength =  src  - aSrc; 
  return NS_OK;

error:
  *aDestLength = dest - aDest;
  *aSrcLength =  src  - aSrc; 
  return  NS_OK_UDEC_MOREOUTPUT;
}

NS_IMETHODIMP nsUTF16SameEndianToUnicode::Reset()
{
  mState =2;
  mData=0;
  return NS_OK;
}
class nsUTF16DiffEndianToUnicode : public nsUTF16SameEndianToUnicode
{
public:
  nsUTF16DiffEndianToUnicode() {};
  NS_IMETHOD Convert(const char * aSrc, PRInt32 * aSrcLength,
      PRUnichar * aDest, PRInt32 * aDestLength); 
};

NS_IMETHODIMP nsUTF16DiffEndianToUnicode::Convert(
      const char * aSrc, PRInt32 * aSrcLength,
      PRUnichar * aDest, PRInt32 * aDestLength)
{
  if(2 == mState) // first time called
  {
    if(0xFFFE == *((PRUnichar*)aSrc)) {
      aSrc+=2;
      *aSrcLength-=2;
    } else if(0xFEFF == *((PRUnichar*)aSrc)) {
      // eleminate BOM
      *aSrcLength=0;
      *aDestLength=0;
      return NS_ERROR_ILLEGAL_INPUT;
    }  
    mState=0;
  }
  nsresult res = nsUTF16SameEndianToUnicode::Convert(aSrc,aSrcLength, aDest, aDestLength);
  PRInt32 i;

  // copy
  char* p;
  p=(char*)aDest;
  for(i=*aDestLength; i>0 ;i--,p+=2)
  {
     char tmp = *(p+1);
     *(p+1) = *p;
     *(p)= tmp;
  }

  return res;
}
static char BOM[] = {(char)0xfe, (char)0xff};
#define IsBigEndian() (0xFEFF == *((PRUint16*)BOM))

nsresult NEW_UTF16BEToUnicode(nsISupports **aResult)
{
   if(IsBigEndian()) {
     *aResult = new nsUTF16SameEndianToUnicode();
   } else {
     *aResult = new nsUTF16DiffEndianToUnicode();
   }
   return (NULL == *aResult) ? NS_ERROR_OUT_OF_MEMORY : NS_OK;
}
nsresult NEW_UTF16LEToUnicode(nsISupports **aResult)
{
   if(IsBigEndian()) {
     *aResult = new nsUTF16DiffEndianToUnicode();
   } else {
     *aResult = new nsUTF16SameEndianToUnicode();
   }
   return (NULL == *aResult) ? NS_ERROR_OUT_OF_MEMORY : NS_OK;
}