TnbStringCipher.h

[詳解]

#pragma once
#include "TnbStr.h"
#include "TnbException.h"
 
 
 
//TNB Library
namespace TNB
{
 
 
 
class CStringCipher
{
public:
 
    void SetKey(const CAscii& ascKey)
    {
        m_ascKey = ascKey;
    }
 
    CAscii Encode(LPCSTR lpsz) const
    {
        return m_Shift(lpsz, true);
    }
 
    CAscii Decode(LPCSTR lpsz) const
    {
        return m_Shift(lpsz, false);
    }
 
private:
    static int ms_RangeShift(int c, int iShift, int iMin, int iMax)
    {
        ASSERTLIB(iMin < iMax);
        if ( c < iMin || c > iMax )
        {
            return -1;
        }
        int iRange = iMax - iMin;
        if ( iShift >= 0 )
        {
            iShift %= iRange;
        }
        else
        {
            iShift = -((-iShift) % iRange);
        }
        //
        int iCode = (c - iMin) + iShift;
        while ( iCode < 0x0000 )
        {
            iCode += iRange;
        }
        while ( iCode >= iRange )
        {
            iCode -= iRange;
        }
        ASSERTLIB( (iCode + iMin) >= iMin && (iCode + iMin) < iMax ); 
        return iCode + iMin;
    }
 
    static BYTE ms_ShiftChar(BYTE c, int iShift)
    {
        int r = ms_RangeShift(c, iShift, 0x20, 0x80); 
        if ( r < 0 ) { r = ms_RangeShift(c, iShift, 0x81, 0x9F); }
        if ( r < 0 ) { r = ms_RangeShift(c, iShift, 0xA0, 0xDF); }
        if ( r < 0 ) { r = ms_RangeShift(c, iShift, 0xE0, 0xFB); }
        return ( r < 0 ) ? c : static_cast<BYTE>(r);
    }
 
    CAscii m_Shift(LPCSTR lpsz, bool boIsEnc) const
    {
        if ( m_ascKey.IsEmpty() )
        {
            ASSERT0(false, "CCipherData", "暗号、復号キーが指定されていません。");
            throw CEmptyException();
        }
        const BYTE* B = reinterpret_cast<const BYTE*>(LPCSTR(m_ascKey));
        size_t iKeySize = m_ascKey.GetLength();
        CAscii str;
        size_t iLen = STRLIB::GetLen(lpsz);
        if ( iLen > 0 )
        {
            char* P = str.GetBuffer(iLen);
            if ( boIsEnc )
            {
                loop ( i, iLen )
                {
                    P[i] = ms_ShiftChar(lpsz[i], B[i % iKeySize]);
                }
            }
            else
            {
                loop ( i, iLen )
                {
                    P[i] = ms_ShiftChar(lpsz[i], -B[i % iKeySize]);
                }
            }
            P[iLen] = 0;
            str.ReleaseBuffer();
        }
        return str;
    }
 
    CAscii      m_ascKey;               
};
 
 
 
};//TNB