/// <summary>Created compression stream on top of inner stream.</summary>
/// <param name="stream">Inner stream.</param>
/// <param name="settings">Compression settings.</param>
/// <param name="leaveOpen">Leave inner stream open after disposing.</param>
/// <returns>Compression stream.</returns>
public static LZ4EncoderStream Encode(
Stream stream, LZ4EncoderSettings settings = null, bool leaveOpen = false)
{
settings ??= LZ4EncoderSettings.Default;
var frameInfo = new LZ4Descriptor(
settings.ContentLength,
settings.ContentChecksum,
settings.ChainBlocks,
settings.BlockChecksum,
settings.Dictionary,
settings.BlockSize);
var level = settings.CompressionLevel;
var extraMemory = settings.ExtraMemory;
return(new LZ4EncoderStream(
stream,
frameInfo,
i => LZ4Encoder.Create(
i.Chaining, level, i.BlockSize, ExtraBlocks(i.BlockSize, extraMemory)),
leaveOpen));
}
private /*async*/ bool ReadFrame(Token token)
{
Stash.Clear();
var magic = /*await*/ TryPeek4(token);
if (!magic.HasValue)
{
return(false);
}
if (magic != 0x184D2204)
{
throw MagicNumberExpected();
}
var headerOffset = Stash.Length;
var FLG_BD = /*await*/ Peek2(token);
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?)/*await*/ Peek8(token) : null;
var dictionaryId = hasDictionary ? (uint?)/*await*/ Peek4(token) : null;
var actualHC = (byte)(DigestOfStash(headerOffset) >> 8);
var expectedHC = /*await*/ Peek1(token);
if (actualHC != expectedHC)
{
throw InvalidHeaderChecksum();
}
var blockSize = MaxBlockSize(blockSizeCode);
if (hasDictionary)
{
throw NotImplemented(
"Predefined dictionaries feature is not implemented"); // Peek4(dictionaryId);
}
// ReSharper disable once ExpressionIsAlwaysNull
_frameInfo = new LZ4Descriptor(
contentLength, contentChecksum, blockChaining, blockChecksum, dictionaryId,
blockSize);
_decoder = _decoderFactory(_frameInfo);
_buffer = new byte[blockSize];
return(true);
}
