private bool ReadFrame()
{
FlushPeek();
var magic = TryPeek32();
if (!magic.HasValue)
{
return(false);
}
if (magic != 0x184D2204)
{
throw MagicNumberExpected();
}
FlushPeek();
var FLG_BD = Peek16();
var FLG = FLG_BD & 0xFF;
var BD = (FLG_BD >> 8) & 0xFF;
var version = (FLG >> 6) & 0x11;
if (version != 1)
{
throw UnknownFrameVersion(version);
}
var blockChaining = ((FLG >> 5) & 0x01) == 0;
var blockChecksum = ((FLG >> 4) & 0x01) != 0;
var hasContentSize = ((FLG >> 3) & 0x01) != 0;
var contentChecksum = ((FLG >> 2) & 0x01) != 0;
var hasDictionary = (FLG & 0x01) != 0;
var blockSizeCode = (BD >> 4) & 0x07;
var contentLength = hasContentSize ? (long?)Peek64() : null;
var dictionaryId = hasDictionary ? (uint?)Peek32() : null;
var actualHC = (byte)(XXH32.DigestOf(_buffer16, 0, _index16) >> 8);
var expectedHC = Peek8();
if (actualHC != expectedHC)
{
throw InvalidHeaderChecksum();
}
var blockSize = MaxBlockSize(blockSizeCode);
if (hasDictionary)
{
throw NotImplemented(
"Predefined dictionaries feature is not implemented"); // Write32(dictionaryId);
}
// ReSharper disable once ExpressionIsAlwaysNull
_frameInfo = new LZ4Descriptor(
contentLength, contentChecksum, blockChaining, blockChecksum, dictionaryId,
blockSize);
_decoder = _decoderFactory(_frameInfo);
_buffer = new byte[blockSize];
return(true);
}
