Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Xml/System/Xml/XmlDownloadManagerAsync.cs

@@ -0,0 +1,74 @@
+
+namespace System.Xml    {
+
+    using System;
+    using System.IO;
+    using System.Security;
+    using System.Collections;
+    using System.Net;
+    using System.Net.Cache;
+    using System.Runtime.Versioning;
+    using System.Threading.Tasks;
+
+    //
+    // XmlDownloadManager
+    //
+    internal partial class XmlDownloadManager   {
+
+        [ResourceConsumption(ResourceScope.Machine)]
+        [ResourceExposure(ResourceScope.Machine)]
+        internal Task<Stream> GetStreamAsync(Uri uri, ICredentials credentials, IWebProxy proxy,
+            RequestCachePolicy cachePolicy) {
+            if (uri.Scheme == "file")   {
+                return Task.Run<Stream>(() => { return new FileStream(uri.LocalPath, FileMode.Open, FileAccess.Read, FileShare.Read, 1, true); });
+            }
+            else {
+                return GetNonFileStreamAsync(uri, credentials, proxy, cachePolicy);
+            }
+        }
+
+        private async Task<Stream> GetNonFileStreamAsync(Uri uri, ICredentials credentials, IWebProxy proxy,
+            RequestCachePolicy cachePolicy) {
+            WebRequest req = WebRequest.Create(uri);
+            if (credentials != null)    {
+                req.Credentials = credentials;
+            }
+            if (proxy != null)  {
+                req.Proxy = proxy;
+            }
+            if (cachePolicy != null)    {
+                req.CachePolicy = cachePolicy;
+            }
+
+            WebResponse resp = await Task<WebResponse>.Factory.FromAsync(req.BeginGetResponse, req.EndGetResponse, null).ConfigureAwait(false);
+            HttpWebRequest webReq = req as HttpWebRequest;
+            if (webReq != null) {
+                lock (this) {
+                    if (connections == null)    {
+                        connections = new Hashtable();
+                    }
+                    OpenedHost openedHost = (OpenedHost)connections[webReq.Address.Host];
+                    if (openedHost == null) {
+                        openedHost = new OpenedHost();
+                    }
+
+                    if (openedHost.nonCachedConnectionsCount < webReq.ServicePoint.ConnectionLimit - 1) {
+                        // we are not close to connection limit -> don't cache the stream
+                        if (openedHost.nonCachedConnectionsCount == 0)  {
+                            connections.Add(webReq.Address.Host, openedHost);
+                        }
+                        openedHost.nonCachedConnectionsCount++;
+                        return new XmlRegisteredNonCachedStream(resp.GetResponseStream(), this, webReq.Address.Host);
+                    }
+                    else {
+                        // cache the stream and save the connection for the next request
+                        return new XmlCachedStream(resp.ResponseUri, resp.GetResponseStream());
+                    }
+                }
+            }
+            else {
+                return resp.GetResponseStream();
+            }
+        }
+    }
+}