Dafuq.cpp

s32 DecryptionCtx::DecryptRead(CInputStream& in, s32 key)
{
    int ret = 0;
    if (x20_encShift >= key)
    {
        int diff = x20_encShift - 0x20;
        int baseVal = -1;
        if (x20_encShift != 0x20)
            baseVal = 1 << (x20_encShift - 1);
        x20_encShift = key - x20_encShift;
        ret = baseVal | (x1c_encVal >> diff);
    }
    else
    {
        int diff = x20_encShift - key;
        int rem = x20_encShift - 0x20;
        int baseVal1 = -1;
        if (x20_encShift != 0x20)
            baseVal1 = 1 << (x20_encShift - 1);

        int bit = diff & 7;
        x20_encShift = 0;
        int count = (diff >> 3) + ((-bit | bit) >> 31);
        int baseVal2 = (baseVal1 & (x1c_encVal >> rem)) << diff;
        in.readBytesToBuf(&x1c_encVal, count);

        int baseVal3 = -1;
        if (diff != 0x20)
            baseVal3 = 1 << (diff - 1);

        int tmpShift = x20_encShift;
        x20_encShift = (count << 3);
        ret = baseVal2 | (baseVal3 & (x1c_encVal >> (diff - 0x20))) << tmpShift;
        x20_encShift = diff - x20_encShift;
        x1c_encVal = x1c_encVal >> diff;
    }

    return ret;
}