为什么在android possibleEncodings（）函数中需要反向拉丁-1到utf8？

Question

我在http://androidxref.com/4.0.4/xref/frameworks/base/media/libmedia/MediaScannerClient.cpp#95

中阅读了以下代码

static uint32_t possibleEncodings(const char* s)
{
    uint32_t result = kEncodingAll;
    // if s contains a native encoding, then it was mistakenly encoded in utf8 as if it were latin-1
    // so we need to reverse the latin-1 -> utf8 conversion to get the native chars back
    uint8_t ch1, ch2;
    uint8_t* chp = (uint8_t *)s;

    while ((ch1 = *chp++)) {
        if (ch1 & 0x80) {
            ch2 = *chp++;
            ch1 = ((ch1 << 6) & 0xC0) | (ch2 & 0x3F);
            // ch1 is now the first byte of the potential native char

            ch2 = *chp++;
            if (ch2 & 0x80)
                ch2 = ((ch2 << 6) & 0xC0) | (*chp++ & 0x3F);
            // ch2 is now the second byte of the potential native char
            int ch = (int)ch1 << 8 | (int)ch2;
            result &= findPossibleEncodings(ch);
        }
        // else ASCII character, which could be anything
    }

    return result;
}

为什么要使用上述逻辑将latin-1反转为utf8？