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BrotliSharpLib

BrotliSharpLib is a full C# port of the brotli library/compression code by Google. It is intended to be a mostly 1:1 conversion of the original C code. All code is correct as of v0.6.0 of the reference implementation.

The projects targets .NET Framework 2.0 and thus uses a minimal set of APIs to ensure compatibility with a wide range of frameworks including .NET Standard and .NET Core. It also supports little-endian and big-endian architectures and is optimised for x86, x64 and ARM processors.

Currently the code only supports decompression and will implement compression in the future. The underlying APIs do support streams however, a proper Stream class won't be created until compression has been completed.

BrotliSharpLib is licensed under MIT.

Usage

Generic/basic usage:

byte[] brotliCompressedData = ...; // arbitary data source
byte[] uncompressedData = Brotli.DecompressBuffer(brotliCompressedData, 0, brotliCompressedData.Length);

Real-life example: The following allows for acceptance and decompression of brotli encoded web content via a HttpClient and falls back to gzip or deflate when required.

static class HttpClientEx
{
    private class BrotliCompressionHandler : DelegatingHandler
    {
        protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
        {
            request.Headers.AcceptEncoding.Add(new StringWithQualityHeaderValue("br"));
            var response = await base.SendAsync(request, cancellationToken);
            IEnumerable<string> ce;
            if (response.Content.Headers.TryGetValues("Content-Encoding", out ce) && ce.First() == "br")
            {
                var buffer = await response.Content.ReadAsByteArrayAsync();
                response.Content = new ByteArrayContent(Brotli.DecompressBuffer(buffer, 0, buffer.Length));
            }
            return response;
        }
    }

    public static HttpClient Create()
    {
        var handler = new HttpClientHandler();
        if (handler.SupportsAutomaticDecompression)
            handler.AutomaticDecompression = System.Net.DecompressionMethods.Deflate | System.Net.DecompressionMethods.GZip;
        return HttpClientFactory.Create(handler, new BrotliCompressionHandler());
    }
}

Performance

Considerations for Build

For optimal performance, ensure to build BrotliSharpLib in Release mode to enable all possible JIT optimisations.

Performance can also be further improved by building BrotliSharpLib using .NET Framework 4.5 or above (or any framework that supports AggressiveInlining). Selecting a specific target platform (instead of AnyCPU) where possible can also further improve performance. All of this however, is completely optional as BrotliSharpLib is designed to run in a wide range of contexts and configurations regardless.

Benchmark

On average, BrotliSharpLib runs about 11-12% faster than the standard C# decoding implementation provided by Google which is a straight auto-conversion of the Java port using sharpen.

The following are benchmark results using https://github.com/dotnet/BenchmarkDotNet with BrotliSharpLib and Google's C# implementation built against .NET Framework 4.6.1.

BenchmarkDotNet=v0.10.6, OS=Windows 10 Redstone 2 (10.0.15063)
Processor=Intel Core i5-6600K CPU 3.50GHz (Skylake), ProcessorCount=4
Frequency=3421875 Hz, Resolution=292.2374 ns, Timer=TSC
  [Host]       : Clr 4.0.30319.42000, 64bit RyuJIT-v4.7.2046.0
  LegacyJitX64 : Clr 4.0.30319.42000, 64bit LegacyJIT/clrjit-v4.7.2046.0;compatjit-v4.7.2046.0
  LegacyJitX86 : Clr 4.0.30319.42000, 32bit LegacyJIT-v4.7.2046.0
  RyuJitX64    : Clr 4.0.30319.42000, 64bit RyuJIT-v4.7.2046.0

Runtime=Clr
Method Job Jit Platform Mean Error StdDev
GoogleImpl LegacyJitX64 LegacyJit X64 12.49 ms 0.1086 ms 0.0907 ms
BrotliSharpLib LegacyJitX64 LegacyJit X64 11.20 ms 0.1380 ms 0.1290 ms
GoogleImpl LegacyJitX86 LegacyJit X86 16.16 ms 0.1305 ms 0.1156 ms
BrotliSharpLib LegacyJitX86 LegacyJit X86 14.02 ms 0.1395 ms 0.1305 ms
GoogleImpl RyuJitX64 RyuJit X64 12.75 ms 0.1556 ms 0.1456 ms
BrotliSharpLib RyuJitX64 RyuJit X64 11.63 ms 0.0785 ms 0.0735 ms