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#ifndef CharDistribution_h__

#define CharDistribution_h__

#include "nscore.h"

#define ENOUGH_DATA_THRESHOLD 1024

class CharDistributionAnalysis

{

public:

  CharDistributionAnalysis() {Reset();}

  //feed a block of data and do distribution analysis

  void HandleData(const char* aBuf, PRUint32 aLen) {}

  //Feed a character with known length

  void HandleOneChar(const char* aStr, PRUint32 aCharLen)

  {

    PRInt32 order;

    //we only care about 2-bytes character in our distribution analysis

    order = (aCharLen == 2) ? GetOrder(aStr) : -1;

    if (order >= 0)

    {

      mTotalChars++;

      //order is valid

      if ((PRUint32)order < mTableSize)

      {

        if (512 > mCharToFreqOrder[order])

          mFreqChars++;

      }

    }

  }

  //return confidence base on existing data

  float GetConfidence(PRBool aIsPreferredLanguage);

  //Reset analyser, clear any state 

  void      Reset(void) 

  {

    mDone = PR_FALSE;

    mTotalChars = 0;

    mFreqChars = 0;

  }

  //This function is for future extension. Caller can use this function to control

  //analyser's behavior

  void      SetOpion(){}

  //It is not necessary to receive all data to draw conclusion. For charset detection,

  // certain amount of data is enough

  PRBool GotEnoughData() {return mTotalChars > ENOUGH_DATA_THRESHOLD;}

protected:

  //we do not handle character base on its original encoding string, but 

  //convert this encoding string to a number, here called order.

  //This allow multiple encoding of a language to share one frequency table 

  virtual PRInt32 GetOrder(const char* str) {return -1;}

  //If this flag is set to PR_TRUE, detection is done and conclusion has been made

  PRBool   mDone;

  //The number of characters whose frequency order is less than 512

  PRUint32 mFreqChars;

  //Total character encounted.

  PRUint32 mTotalChars;

  //Mapping table to get frequency order from char order (get from GetOrder())

  const PRInt16  *mCharToFreqOrder;

  //Size of above table

  PRUint32 mTableSize;

  //This is a constant value varies from language to language, it is used in 

  //calculating confidence. See my paper for further detail.

  float    mTypicalDistributionRatio;

};

class EUCTWDistributionAnalysis: public CharDistributionAnalysis

{

public:

  EUCTWDistributionAnalysis();

protected:

  //for euc-TW encoding, we are interested 

  //  first  byte range: 0xc4 -- 0xfe

  //  second byte range: 0xa1 -- 0xfe

  //no validation needed here. State machine has done that

  PRInt32 GetOrder(const char* str) 

  { if ((unsigned char)*str >= (unsigned char)0xc4)  

      return 94*((unsigned char)str[0]-(unsigned char)0xc4) + (unsigned char)str[1] - (unsigned char)0xa1;

    else

      return -1;

  }

};

class EUCKRDistributionAnalysis : public CharDistributionAnalysis

{

public:

  EUCKRDistributionAnalysis();

protected:

  //for euc-KR encoding, we are interested 

  //  first  byte range: 0xb0 -- 0xfe

  //  second byte range: 0xa1 -- 0xfe

  //no validation needed here. State machine has done that

  PRInt32 GetOrder(const char* str) 

  { if ((unsigned char)*str >= (unsigned char)0xb0)  

      return 94*((unsigned char)str[0]-(unsigned char)0xb0) + (unsigned char)str[1] - (unsigned char)0xa1;

    else

      return -1;

  }

};

class GB2312DistributionAnalysis : public CharDistributionAnalysis

{

public:

  GB2312DistributionAnalysis();

protected:

  //for GB2312 encoding, we are interested 

  //  first  byte range: 0xb0 -- 0xfe

  //  second byte range: 0xa1 -- 0xfe

  //no validation needed here. State machine has done that

  PRInt32 GetOrder(const char* str) 

  { if ((unsigned char)*str >= (unsigned char)0xb0 && (unsigned char)str[1] >= (unsigned char)0xa1)  

      return 94*((unsigned char)str[0]-(unsigned char)0xb0) + (unsigned char)str[1] - (unsigned char)0xa1;

    else

      return -1;

  }

};

class Big5DistributionAnalysis : public CharDistributionAnalysis

{

public:

  Big5DistributionAnalysis();

protected:

  //for big5 encoding, we are interested 

  //  first  byte range: 0xa4 -- 0xfe

  //  second byte range: 0x40 -- 0x7e , 0xa1 -- 0xfe

  //no validation needed here. State machine has done that

  PRInt32 GetOrder(const char* str) 

  { if ((unsigned char)*str >= (unsigned char)0xa4)  

      if ((unsigned char)str[1] >= (unsigned char)0xa1)

        return 157*((unsigned char)str[0]-(unsigned char)0xa4) + (unsigned char)str[1] - (unsigned char)0xa1 +63;

      else

        return 157*((unsigned char)str[0]-(unsigned char)0xa4) + (unsigned char)str[1] - (unsigned char)0x40;

    else

      return -1;

  }

};

class SJISDistributionAnalysis : public CharDistributionAnalysis

{

public:

  SJISDistributionAnalysis();

protected:

  //for sjis encoding, we are interested 

  //  first  byte range: 0x81 -- 0x9f , 0xe0 -- 0xfe

  //  second byte range: 0x40 -- 0x7e,  0x81 -- oxfe

  //no validation needed here. State machine has done that

  PRInt32 GetOrder(const char* str) 

  { 

    PRInt32 order;

    if ((unsigned char)*str >= (unsigned char)0x81 && (unsigned char)*str <= (unsigned char)0x9f)  

      order = 188 * ((unsigned char)str[0]-(unsigned char)0x81);

    else if ((unsigned char)*str >= (unsigned char)0xe0 && (unsigned char)*str <= (unsigned char)0xef)  

      order = 188 * ((unsigned char)str[0]-(unsigned char)0xe0 + 31);

    else

      return -1;

    order += (unsigned char)*(str+1) - 0x40;

    if ((unsigned char)str[1] > (unsigned char)0x7f)

      order--;

    return order;

  }

};

class EUCJPDistributionAnalysis : public CharDistributionAnalysis

{

public:

  EUCJPDistributionAnalysis();

protected:

  //for euc-JP encoding, we are interested 

  //  first  byte range: 0xa0 -- 0xfe

  //  second byte range: 0xa1 -- 0xfe

  //no validation needed here. State machine has done that

  PRInt32 GetOrder(const char* str) 

  { if ((unsigned char)*str >= (unsigned char)0xa0)  

      return 94*((unsigned char)str[0]-(unsigned char)0xa1) + (unsigned char)str[1] - (unsigned char)0xa1;

    else

      return -1;

  }

};

#endif //CharDistribution_h__