nsSJISProber.cpp

/*  -*- C++ -*-
    SPDX-FileCopyrightText: 1998 Netscape Communications Corporation <developer@mozilla.org>
 
    SPDX-License-Identifier: MIT
*/
 
// for S-JIS encoding, observe characteristic:
// 1, kana character (or hankaku?) often have high frequency of appearance
// 2, kana character often exist in group
// 3, certain combination of kana is never used in japanese language
 
#include "nsSJISProber.h"
 
namespace kencodingprober
{
void nsSJISProber::Reset(void)
{
    mCodingSM->Reset();
    mState = eDetecting;
    mContextAnalyser.Reset();
    mDistributionAnalyser.Reset();
}
 
nsProbingState nsSJISProber::HandleData(const char *aBuf, unsigned int aLen)
{
    if (aLen == 0) {
        return mState;
    }
 
    for (unsigned int i = 0; i < aLen; i++) {
        const nsSMState codingState = mCodingSM->NextState(aBuf[i]);
        if (codingState == eError) {
            mState = eNotMe;
            break;
        }
        if (codingState == eItsMe) {
            mState = eFoundIt;
            break;
        }
        if (codingState == eStart) {
            unsigned int charLen = mCodingSM->GetCurrentCharLen();
            if (i == 0) {
                mLastChar[1] = aBuf[0];
                mContextAnalyser.HandleOneChar(mLastChar + 2 - charLen, charLen);
                mDistributionAnalyser.HandleOneChar(mLastChar, charLen);
            } else {
                mContextAnalyser.HandleOneChar(aBuf + i + 1 - charLen, charLen);
                mDistributionAnalyser.HandleOneChar(aBuf + i - 1, charLen);
            }
        }
    }
 
    mLastChar[0] = aBuf[aLen - 1];
 
    if (mState == eDetecting) {
        if (mContextAnalyser.GotEnoughData() && GetConfidence() > SHORTCUT_THRESHOLD) {
            mState = eFoundIt;
        }
    }
 
    return mState;
}
 
float nsSJISProber::GetConfidence(void)
{
    float contxtCf = mContextAnalyser.GetConfidence();
    float distribCf = mDistributionAnalyser.GetConfidence();
 
    return (contxtCf > distribCf ? contxtCf : distribCf);
}
}