Added ability for c# to redirect C core logs to arbitrary sink

src/csharp/Grpc.Core/Grpc.Core.csproj

@@ -1,4 +1,4 @@
-<?xml version="1.0" encoding="utf-8"?>
+<?xml version="1.0" encoding="utf-8"?>
 <Project DefaultTargets="Build" ToolsVersion="4.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <PropertyGroup>
     <Configuration Condition=" '$(Configuration)' == '' ">Debug</Configuration>
@@ -33,6 +33,7 @@
     <Reference Include="System" />
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="Internal\GrpcLog.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="RpcException.cs" />
     <Compile Include="Calls.cs" />
@@ -66,8 +67,4 @@
     <Compile Include="Utils\ExceptionHelper.cs" />
   </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
-  <ItemGroup>
-    <Folder Include="Internal\" />
-    <Folder Include="Utils\" />
-  </ItemGroup>
 </Project>

src/csharp/Grpc.Core/GrpcEnvironment.cs

@@ -107,6 +107,7 @@ namespace Grpc.Core
         /// </summary>
         private GrpcEnvironment()
         {
+            GrpcLog.RedirectNativeLogs(Console.Error);
             grpcsharp_init();
             threadPool = new GrpcThreadPool(THREAD_POOL_SIZE);
             threadPool.Start();

src/csharp/Grpc.Core/Internal/GrpcLog.cs

@@ -0,0 +1,94 @@
+#region Copyright notice and license
+
+// Copyright 2015, Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#endregion
+
+using System;
+using System.Collections.Concurrent;
+using System.Diagnostics;
+using System.IO;
+using System.Runtime.InteropServices;
+using System.Threading;
+
+namespace Grpc.Core.Internal
+{
+    internal delegate void GprLogDelegate(IntPtr fileStringPtr, Int32 line, UInt64 threadId, IntPtr severityStringPtr, IntPtr msgPtr);
+
+    /// <summary>
+    /// Logs from gRPC C core library can get lost if your application is not a console app.
+    /// This class allows redirection of logs to arbitrary destination.
+    /// </summary>
+    internal static class GrpcLog
+    {
+        static object staticLock = new object();
+        static GprLogDelegate writeCallback;
+        static TextWriter dest;
+
+        [DllImport("grpc_csharp_ext.dll")]
+        static extern void grpcsharp_redirect_log(GprLogDelegate callback);
+
+        /// <summary>
+        /// Sets text writer as destination for logs from native gRPC C core library.
+        /// Only first invocation has effect.
+        /// </summary>
+        /// <param name="textWriter"></param>
+        public static void RedirectNativeLogs(TextWriter textWriter)
+        {
+            lock (staticLock)
+            {
+                if (writeCallback == null)
+                {
+                    writeCallback = new GprLogDelegate(HandleWrite);
+                    dest = textWriter;
+                    grpcsharp_redirect_log(writeCallback);    
+                }
+            }
+        }
+
+        private static void HandleWrite(IntPtr fileStringPtr, Int32 line, UInt64 threadId, IntPtr severityStringPtr, IntPtr msgPtr)
+        {
+            try
+            {
+                // TODO: DateTime format used here is different than in C core.
+                dest.WriteLine(string.Format("{0}{1} {2} {3}:{4}: {5}", 
+                    Marshal.PtrToStringAnsi(severityStringPtr), DateTime.Now,  
+                    threadId,
+                    Marshal.PtrToStringAnsi(fileStringPtr), 
+                    line, 
+                    Marshal.PtrToStringAnsi(msgPtr)));
+            }
+            catch (Exception e)
+            {
+                Console.WriteLine("Caught exception in native callback " + e);
+            }
+        }
+    }
+}

src/csharp/ext/grpc_csharp_ext.c

@@ -35,9 +35,10 @@
 
 #include <grpc/support/port_platform.h>
 #include <grpc/support/alloc.h>
-#include <grpc/grpc.h>
 #include <grpc/support/log.h>
 #include <grpc/support/slice.h>
+#include <grpc/support/thd.h>
+#include <grpc/grpc.h>
 
 #include <string.h>
 
@@ -579,6 +580,27 @@ grpcsharp_server_request_call(grpc_server *server, grpc_completion_queue *cq,
       &(ctx->server_rpc_new.request_metadata), cq, ctx);
 }
 
+/* Logging */
+
+typedef void(GPR_CALLTYPE *grpcsharp_log_func)(const char *file,
+	                                           gpr_int32 line,
+											   gpr_uint64 thd_id,
+	                                           const char *severity_string,
+											   const char *msg);
+static grpcsharp_log_func log_func = NULL;
+
+/* Redirects gpr_log to log_func callback */
+static void grpcsharp_log_handler(gpr_log_func_args *args) {
+	log_func(args->file, args->line, gpr_thd_currentid(),
+		     gpr_log_severity_string(args->severity), args->message);
+}
+
+GPR_EXPORT void GPR_CALLTYPE
+grpcsharp_redirect_log(grpcsharp_log_func func) {
+	GPR_ASSERT(func);
+	log_func = func;
+	gpr_set_log_function(grpcsharp_log_handler);
+}
 
 /* For testing */
 GPR_EXPORT void GPR_CALLTYPE