CSHARP-695: respect maxMessageSizeBytes when provided by the server.

MongoDB.Driver/CommandResults/IsMasterResult.cs

@@ -117,7 +117,13 @@ public int MaxBsonObjectSize
         /// </value>
         public int MaxMessageLength
         {
-            get { return Math.Max(MongoDefaults.MaxMessageLength, MaxBsonObjectSize + 1024); }
+            get
+            {
+                return Response.GetValue(
+                    "maxMessageSizeBytes",
+                    Math.Max(MongoDefaults.MaxMessageLength, MaxBsonObjectSize + 1024))
+                    .ToInt32();
+            }
         }
 
         /// <summary>

MongoDB.DriverUnitTests/CommandResults/IsMasterResultTests.cs

@@ -0,0 +1,72 @@
+/* Copyright 2010-2013 10gen Inc.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+* http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+using System;
+using MongoDB.Bson;
+using MongoDB.Driver;
+using NUnit.Framework;
+
+namespace MongoDB.DriverUnitTests.CommandResults
+{
+    [TestFixture]
+    public class IsMasterResultTests
+    {
+        [Test]
+        public void TestMaxMessageLengthWhenServerSupplied()
+        {
+            var command = new CommandDocument("ismaster", 1);
+            var document = new BsonDocument
+            {
+                { "ok", 1 },
+                { "maxMessageSizeBytes", 1000 },
+                { "maxBsonObjectSize", 1000 }
+            };
+            var result = new IsMasterResult();
+            result.Initialize(command, document);
+
+            Assert.AreEqual(1000, result.MaxMessageLength);
+        }
+
+        [Test]
+        public void TestMaxMessageLengthWhenNotServerSuppliedUsesMongoDefaultsWhenLargerThanMaxBsonObjectSize()
+        {
+            var command = new CommandDocument("ismaster", 1);
+            var document = new BsonDocument
+            {
+                { "ok", 1 },
+                { "maxBsonObjectSize", MongoDefaults.MaxMessageLength - 2048 }
+            };
+            var result = new IsMasterResult();
+            result.Initialize(command, document);
+
+            Assert.AreEqual(MongoDefaults.MaxMessageLength, result.MaxMessageLength);
+        }
+
+        [Test]
+        public void TestMaxMessageLengthWhenNotServerSuppliedUsesMaxBsonObjectSizeWhenLargerThanMongoDefaults()
+        {
+            var command = new CommandDocument("ismaster", 1);
+            var document = new BsonDocument
+            {
+                { "ok", 1 },
+                { "maxBsonObjectSize", MongoDefaults.MaxMessageLength }
+            };
+            var result = new IsMasterResult();
+            result.Initialize(command, document);
+
+            Assert.AreEqual(MongoDefaults.MaxMessageLength + 1024, result.MaxMessageLength);
+        }
+    }
+}

MongoDB.DriverUnitTests/MongoDB.DriverUnitTests.csproj

@@ -103,6 +103,7 @@
     <Compile Include="Builders\UpdateBuilderTests.cs" />
     <Compile Include="CommandResults\CollectionStatsResultTests.cs" />
     <Compile Include="CommandResults\CommandResultTests.cs" />
+    <Compile Include="CommandResults\IsMasterResultTests.cs" />
     <Compile Include="CommandResults\DatabaseStatsResultTests.cs" />
     <Compile Include="CommandResults\GetLastErrorResultTests.cs" />
     <Compile Include="CommandResults\ValidateCollectionResultTests.cs" />