编码字符之间的转换(C/C++)

最近一段做一些关于文字编码方面的东西，常常涉及到各种编码字符之间的转换。主要是做中日文方面的，包括中文gb2312, 日文JIS, SHIFT-JIS，以及他们和Unnicode码之间的转换。

一 GBK <==> Unicode

unsigned short GBK2UNI(unsigned short usGBK)
{
    unsigned char szEUC[2] = { usGBK >> 8, usGBK & 0xFF };
    unsigned short usUNI;
    MultiByteToWideChar(
        936,
        0,
        (LPCSTR)szEUC,
        2,
        &usUNI,
        1
    );
    return usUNI;
}

unsigned short UNI2GBK(unsigned short usUNI)
{
    unsigned char szGBK[3]={0};
    unsigned short wzUNI[2] = { usUNI, 0 };
    unsigned short usGBK;
    WideCharToMultiByte(
        936,
        0,
        wzUNI,
        2,
        (LPSTR)szGBK,
        2,
        0,
        0
    );
    usGBK = (szGBK[0] << 8) | szGBK[1];
    return usGBK;
}

二 SHIFT-JIS <==> Unicode
unsigned short SJIS2UNI(unsigned short usSJIS)
{
    unsigned char szEUC[2] = { usSJIS >> 8, usSJIS & 0xFF };
    unsigned short usUNI;
    MultiByteToWideChar(
        932,
        0,
        (LPCSTR)szEUC,
        2,
        &usUNI,
        1
    );
    return usUNI;
}

unsigned short UNI2SJIS(unsigned short usUNI)
{
    unsigned char szSJIS[3] = { 0 };
    unsigned short wzUNI[2] = { usUNI, 0 };
    unsigned short usSJIS;
    WideCharToMultiByte(
        932,
        0,
        wzUNI,
        2,
        (LPSTR)szSJIS,
        2,
        0,
        0
    );
    usSJIS = (szSJIS[0] << 8) | szSJIS[1];
    return usSJIS;
}

三 JIS <=> Unicode

unsigned short JIS2UNI(unsigned short usJIS)
{
    unsigned char szEUC[2] = { (usJIS | 0x8080) >> 8, (usJIS | 0x8080) & 0xFF };
    unsigned short usUNI;
    MultiByteToWideChar(
        20932,
        0,
        (LPCSTR)szEUC,
        2,
        &usUNI,
        1
    );
    return usUNI;
}
unsigned short UNI2JIS(unsigned short usUNI)
{
    unsigned char szJIS[3] = { 0 };
    unsigned short wzUNI[2] = { usUNI, 0 };
    unsigned short usJIS;
    WideCharToMultiByte(
        20932,
        0,
        wzUNI,
        2,
        (LPSTR)szJIS,
        2,
        0,
        0
    );
    usJIS = (szJIS[0] << 8) | szJIS[1];
    return usJIS;
}

四 JIS <=> SHIFT-JIS
unsigned short SJIS2JIS( unsigned short sjis )
{
    unsigned short ubyte, lbyte;


    if (((sjis >= 0x8140) && (sjis <= 0x9ffc)) ||
        ((sjis >= 0xe040) && (sjis <= 0xeffc)) )
    {
        ubyte = sjis >> 8;
        lbyte = sjis & 0x00ff;

        if ( (lbyte <= 0x3f) || (lbyte == 0x7f) ||
                (lbyte >= 0xfd) ) return 0;

        if ( ubyte >= 0xe0 ) ubyte -= 0xc0; else ubyte -= 0x80;
        ubyte = (ubyte << 1) + 0x1f;

        if ( lbyte >= 0x9f )
        {
            ubyte++;
            lbyte -= 0x7e;
        } else {
            if ( lbyte >= 0x80 ) lbyte--;
            lbyte -= 0x1f;
        }

        return ( ubyte << 8 ) + lbyte;

    } else {
        return 0;
    }
}

unsigned short JIS2SJIS( unsigned short jis )
{
    unsigned short     ubyte, lbyte;


    ubyte = jis >> 8;
    lbyte = jis & 0x00ff;

    lbyte += 0x1f;
    if ( lbyte >= 0x7f ) lbyte++;
    if ( lbyte <= 0x3f ) return 0;

    if ( (ubyte & 0x0001) == 0 )
    {
        lbyte = jis & 0x00ff;
        lbyte += 0x7e;
        ubyte--;
        if ( lbyte > 0xfd ) return 0;
    }

    ubyte -= 0x1f;
    ubyte = ubyte >> 1;
    ubyte += 0x80;
    if ( ubyte >= 0xa0 ) ubyte += 0x40;

    if ( ((ubyte >= 0x81) && (ubyte <= 0x9f)) ||
            ((ubyte >= 0xe0) && (ubyte <= 0xef)) )
    {
        return (ubyte << 8) + lbyte;
    } else {
        return 0;
    }
}