Merge "FLAC: support files which has ID3v2 tag or Last-metadata-block flag is 1"

bool SniffFLAC(DataSourceHelper *source, float *confidence)

{

    // FLAC header.

    // Skip ID3 tags

    off64_t pos = 0;

    uint8_t header[10];

    for (;;) {

        if (source->readAt(pos, header, sizeof(header)) != sizeof(header)) {

            return false; // no more file to read.

        }

        // check for ID3 tag

        if (memcmp("ID3", header, 3) != 0) {

            break; // not an ID3 tag.

        }

        // skip the ID3v2 data and check again

        const unsigned id3Len = 10 +

                (((header[6] & 0x7f) << 21)

                 | ((header[7] & 0x7f) << 14)

                 | ((header[8] & 0x7f) << 7)

                 | (header[9] & 0x7f));

        pos += id3Len;

        ALOGV("skipped ID3 tag of len %u new starting offset is %#016llx",

                id3Len, (long long)pos);

    }

    // Check FLAC header.

    // https://xiph.org/flac/format.html#stream

    //

    // Note: content stored big endian.

    // 4            8         metadata type STREAMINFO (0) (note: OR with 0x80 if last metadata)

    // 5            24        size of metadata, for STREAMINFO (0x22).

    // Android is LE, so express header as little endian int64 constant.

    constexpr int64_t flacHeader = (0x22LL << 56) | 'CaLf';

    constexpr int64_t flacHeader2 = flacHeader | (0x80LL << 32); // alternate form (last metadata)

    int64_t header;

    if (source->readAt(0, &header, sizeof(header)) != sizeof(header)

            || (header != flacHeader && header != flacHeader2)) {

    if (memcmp("fLaC\x00\x00\x00\x22", header, 8) != 0 &&

        memcmp("fLaC\x80\x00\x00\x22", header, 8) != 0) {

        return false;

    }