jellyfin/MediaBrowser.Server.Implementations/HttpServer/ResponseFilter.cs

using MediaBrowser.Model.Logging;
using ServiceStack;
using ServiceStack.Web;
using System;
using System.Globalization;
using System.Net;
using System.Text;

namespace MediaBrowser.Server.Implementations.HttpServer
{
    public class ResponseFilter
    {
        private static readonly CultureInfo UsCulture = new CultureInfo("en-US");
        private readonly ILogger _logger;

        public ResponseFilter(ILogger logger)
        {
            _logger = logger;
        }

        /// <summary>
        /// Filters the response.
        /// </summary>
        /// <param name="req">The req.</param>
        /// <param name="res">The res.</param>
        /// <param name="dto">The dto.</param>
        public void FilterResponse(IRequest req, IResponse res, object dto)
        {
            // Try to prevent compatibility view
            res.AddHeader("X-UA-Compatible", "IE=Edge");

            var exception = dto as Exception;

            if (exception != null)
            {
                _logger.ErrorException("Error processing request for {0}", exception, req.RawUrl);

                if (!string.IsNullOrEmpty(exception.Message))
                {
                    var error = exception.Message.Replace(Environment.NewLine, " ");
                    error = RemoveControlCharacters(error);

                    res.AddHeader("X-Application-Error-Code", error);
                }
            }

            if (dto is CompressedResult)
            {
                // Per Google PageSpeed
                // This instructs the proxies to cache two versions of the resource: one compressed, and one uncompressed. 
                // The correct version of the resource is delivered based on the client request header. 
                // This is a good choice for applications that are singly homed and depend on public proxies for user locality.                        
                res.AddHeader("Vary", "Accept-Encoding");
            }

            var hasOptions = dto as IHasOptions;

            if (hasOptions != null)
            {
                // Content length has to be explicitly set on on HttpListenerResponse or it won't be happy
                string contentLength;

                if (hasOptions.Options.TryGetValue("Content-Length", out contentLength) && !string.IsNullOrEmpty(contentLength))
                {
                    var length = long.Parse(contentLength, UsCulture);

                    if (length > 0)
                    {
                        var response = (HttpListenerResponse)res.OriginalResponse;

                        response.ContentLength64 = length;
                       
                        // Disable chunked encoding. Technically this is only needed when using Content-Range, but
                        // anytime we know the content length there's no need for it
                        response.SendChunked = false;
                    }
                }
            }
        }

        /// <summary>
        /// Removes the control characters.
        /// </summary>
        /// <param name="inString">The in string.</param>
        /// <returns>System.String.</returns>
        private static string RemoveControlCharacters(string inString)
        {
            if (inString == null) return null;

            var newString = new StringBuilder();

            foreach (var ch in inString)
            {
                if (!char.IsControl(ch))
                {
                    newString.Append(ch);
                }
            }
            return newString.ToString();
        }
    }
}