nancy-gzip.cs

public class NancyGzipCompression : IApplicationStartup
{
    public void Initialize(IPipelines pipelines)
    {
        pipelines.AfterRequest += CheckForCompression;
    }

    private static void CheckForCompression(NancyContext context)
    {
        if (!RequestIsGzipCompatible(context.Request))
        {
            return;
        }

        if (context.Response.StatusCode != HttpStatusCode.OK)
        {
            return;
        }

        if (!ResponseIsCompatibleMimeType(context.Response))
        {
            return;
        }

        if (ContentLengthIsTooSmall(context.Response))
        {
            return;
        }

        CompressResponse(context.Response);
    }

    private static void CompressResponse(Response response)
    {
        response.Headers["Content-Encoding"] = "gzip";

        var contents = response.Contents;
        response.Contents = responseStream =>
        {
            using (var compression = new GZipStream(responseStream, CompressionMode.Compress))
            {
                contents(compression);
            }
        };
    }

    private static bool ContentLengthIsTooSmall(Response response)
    {
        string contentLength;
        if (response.Headers.TryGetValue("Content-Length", out contentLength))
        {
            var length = long.Parse(contentLength);
            if (length < 4096)
            {
                return true;
            }
        }
        return false;
    }

    private static readonly List<string> ValidMimes = new List<string>
                                            {
                                                "application/json",
                                                "application/json; charset=utf-8"
                                            };

    private static bool ResponseIsCompatibleMimeType(Response response)
    {
        return ValidMimes.Any(x => x == response.ContentType);
    }

    private static bool RequestIsGzipCompatible(Request request)
    {
        return request.Headers.AcceptEncoding.Any(x => x.Contains("gzip"));
    }
}