unsafe void decode_metadata()
{
byte x;
int i, id;
//bool first = true;
byte[] FLAC__STREAM_SYNC_STRING = new byte[] { (byte)'f', (byte)'L', (byte)'a', (byte)'C' };
byte[] ID3V2_TAG_ = new byte[] { (byte)'I', (byte)'D', (byte)'3' };
for (i = id = 0; i < 4; )
{
if (_IO.Read(_framesBuffer, 0, 1) == 0)
throw new Exception("FLAC stream not found");
x = _framesBuffer[0];
if (x == FLAC__STREAM_SYNC_STRING[i])
{
//first = true;
i++;
id = 0;
continue;
}
if (id < 3 && x == ID3V2_TAG_[id])
{
id++;
i = 0;
if (id == 3)
{
if (!skip_bytes(3))
throw new Exception("FLAC stream not found");
int skip = 0;
for (int j = 0; j < 4; j++)
{
if (0 == _IO.Read(_framesBuffer, 0, 1))
throw new Exception("FLAC stream not found");
skip <<= 7;
skip |= ((int)_framesBuffer[0] & 0x7f);
}
if (!skip_bytes(skip))
throw new Exception("FLAC stream not found");
}
continue;
}
id = 0;
if (x == 0xff) /* MAGIC NUMBER for the first 8 frame sync bits */
{
do
{
if (_IO.Read(_framesBuffer, 0, 1) == 0)
throw new Exception("FLAC stream not found");
x = _framesBuffer[0];
} while (x == 0xff);
if (x >> 2 == 0x3e) /* MAGIC NUMBER for the last 6 sync bits */
{
//_IO.Position -= 2;
// state = frame
throw new Exception("headerless file unsupported");
}
}
throw new Exception("FLAC stream not found");
}
do
{
fill_frames_buffer();
fixed (byte* buf = _framesBuffer)
{
BitReader bitreader = new BitReader(buf, _framesBufferOffset, _framesBufferLength - _framesBufferOffset);
bool is_last = bitreader.readbit() != 0;
MetadataType type = (MetadataType)bitreader.readbits(7);
int len = (int)bitreader.readbits(24);
if (type == MetadataType.StreamInfo)
{
const int FLAC__STREAM_METADATA_STREAMINFO_MIN_BLOCK_SIZE_LEN = 16; /* bits */
const int FLAC__STREAM_METADATA_STREAMINFO_MAX_BLOCK_SIZE_LEN = 16; /* bits */
const int FLAC__STREAM_METADATA_STREAMINFO_MIN_FRAME_SIZE_LEN = 24; /* bits */
const int FLAC__STREAM_METADATA_STREAMINFO_MAX_FRAME_SIZE_LEN = 24; /* bits */
const int FLAC__STREAM_METADATA_STREAMINFO_SAMPLE_RATE_LEN = 20; /* bits */
const int FLAC__STREAM_METADATA_STREAMINFO_CHANNELS_LEN = 3; /* bits */
const int FLAC__STREAM_METADATA_STREAMINFO_BITS_PER_SAMPLE_LEN = 5; /* bits */
const int FLAC__STREAM_METADATA_STREAMINFO_TOTAL_SAMPLES_LEN = 36; /* bits */
const int FLAC__STREAM_METADATA_STREAMINFO_MD5SUM_LEN = 128; /* bits */
min_block_size = bitreader.readbits(FLAC__STREAM_METADATA_STREAMINFO_MIN_BLOCK_SIZE_LEN);
max_block_size = bitreader.readbits(FLAC__STREAM_METADATA_STREAMINFO_MAX_BLOCK_SIZE_LEN);
min_frame_size = bitreader.readbits(FLAC__STREAM_METADATA_STREAMINFO_MIN_FRAME_SIZE_LEN);
max_frame_size = bitreader.readbits(FLAC__STREAM_METADATA_STREAMINFO_MAX_FRAME_SIZE_LEN);
int sample_rate = (int)bitreader.readbits(FLAC__STREAM_METADATA_STREAMINFO_SAMPLE_RATE_LEN);
int channels = 1 + (int)bitreader.readbits(FLAC__STREAM_METADATA_STREAMINFO_CHANNELS_LEN);
int bits_per_sample = 1 + (int)bitreader.readbits(FLAC__STREAM_METADATA_STREAMINFO_BITS_PER_SAMPLE_LEN);
pcm = new AudioPCMConfig(bits_per_sample, channels, sample_rate);
_sampleCount = (long)bitreader.readbits64(FLAC__STREAM_METADATA_STREAMINFO_TOTAL_SAMPLES_LEN);
bitreader.skipbits(FLAC__STREAM_METADATA_STREAMINFO_MD5SUM_LEN);
}
else if (type == MetadataType.Seektable)
{
int num_entries = len / 18;
seek_table = new SeekPoint[num_entries];
for (int e = 0; e < num_entries; e++)
{
seek_table[e].number = bitreader.read_long();
seek_table[e].offset = bitreader.read_long();
seek_table[e].framesize = (int)bitreader.read_ushort();
}
}
if (_framesBufferLength < 4 + len)
{
_IO.Position += 4 + len - _framesBufferLength;
_framesBufferLength = 0;
}
else
{
_framesBufferLength -= 4 + len;
_framesBufferOffset += 4 + len;
}
if (is_last)
break;
}
} while (true);
first_frame_offset = _IO.Position - _framesBufferLength;
}