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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#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, uint32_t aLen) {}
//Feed a character with known length
void HandleOneChar(const char* aStr, uint32_t aCharLen)
{
int32_t 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 ((uint32_t)order < mTableSize)
{
if (512 > mCharToFreqOrder[order])
mFreqChars++;
}
}
}
//return confidence base on existing data
float GetConfidence(void);
//Reset analyser, clear any state
void Reset()
{
mDone = false;
mTotalChars = 0;
mFreqChars = 0;
mDataThreshold = 0;
}
//It is not necessary to receive all data to draw conclusion. For charset detection,
// certain amount of data is enough
bool 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 int32_t GetOrder(const char* str) {return -1;}
//If this flag is set to true, detection is done and conclusion has been made
bool mDone;
//The number of characters whose frequency order is less than 512
uint32_t mFreqChars;
//Total character encounted.
uint32_t mTotalChars;
//Number of hi-byte characters needed to trigger detection
uint32_t mDataThreshold;
//Mapping table to get frequency order from char order (get from GetOrder())
const int16_t *mCharToFreqOrder;
//Size of above table
uint32_t 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
int32_t 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
int32_t 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
int32_t 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
int32_t 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
int32_t GetOrder(const char* str)
{
int32_t 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
int32_t 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__
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