Merge pull request #16631 from szehetner/Allocations

C#: Various allocation optimizations

4 files changed, 75 insertions, 9 deletions

diff --git a/src/csharp/Grpc.Core.Tests/MetadataTest.cs b/src/csharp/Grpc.Core.Tests/MetadataTest.cs
index 171c5c470e..d85d7572a6 100644
--- a/src/csharp/Grpc.Core.Tests/MetadataTest.cs
+++ b/src/csharp/Grpc.Core.Tests/MetadataTest.cs
@@ -73,6 +73,23 @@ namespace Grpc.Core.Tests
         }
 
         [Test]
+        public void KeysAreNormalized_UppercaseKey()
+        {
+            var uppercaseKey = "ABC";
+            var entry = new Metadata.Entry(uppercaseKey, "XYZ");
+            Assert.AreEqual("abc", entry.Key);
+        }
+
+        [Test]
+        public void KeysAreNormalized_LowercaseKey()
+        {
+            var lowercaseKey = "abc";
+            var entry = new Metadata.Entry(lowercaseKey, "XYZ");
+            // no allocation if key already lowercase
+            Assert.AreSame(lowercaseKey, entry.Key);
+        }
+
+        [Test]
         public void Entry_ConstructionPreconditions()
         {
             Assert.Throws(typeof(ArgumentNullException), () => new Metadata.Entry(null, "xyz"));
diff --git a/src/csharp/Grpc.Core/ClientBase.cs b/src/csharp/Grpc.Core/ClientBase.cs
index fac34071be..05edce7467 100644
--- a/src/csharp/Grpc.Core/ClientBase.cs
+++ b/src/csharp/Grpc.Core/ClientBase.cs
@@ -151,12 +151,12 @@ namespace Grpc.Core
         {
             private class ClientBaseConfigurationInterceptor : Interceptor
             {
-                readonly Func<IMethod, string, CallOptions, Tuple<string, CallOptions>> interceptor;
+                readonly Func<IMethod, string, CallOptions, ClientBaseConfigurationInfo> interceptor;
 
                 /// <summary>
                 /// Creates a new instance of ClientBaseConfigurationInterceptor given the specified header and host interceptor function.
                 /// </summary>
-                public ClientBaseConfigurationInterceptor(Func<IMethod, string, CallOptions, Tuple<string, CallOptions>> interceptor)
+                public ClientBaseConfigurationInterceptor(Func<IMethod, string, CallOptions, ClientBaseConfigurationInfo> interceptor)
                 {
                     this.interceptor = GrpcPreconditions.CheckNotNull(interceptor, nameof(interceptor));
                 }
@@ -166,7 +166,7 @@ namespace Grpc.Core
                     where TResponse : class
                 {
                     var newHostAndCallOptions = interceptor(context.Method, context.Host, context.Options);
-                    return new ClientInterceptorContext<TRequest, TResponse>(context.Method, newHostAndCallOptions.Item1, newHostAndCallOptions.Item2);
+                    return new ClientInterceptorContext<TRequest, TResponse>(context.Method, newHostAndCallOptions.Host, newHostAndCallOptions.CallOptions);
                 }
 
                 public override TResponse BlockingUnaryCall<TRequest, TResponse>(TRequest request, ClientInterceptorContext<TRequest, TResponse> context, BlockingUnaryCallContinuation<TRequest, TResponse> continuation)
@@ -195,6 +195,18 @@ namespace Grpc.Core
                 }
             }
 
+            internal struct ClientBaseConfigurationInfo
+            {
+                internal readonly string Host;
+                internal readonly CallOptions CallOptions;
+
+                internal ClientBaseConfigurationInfo(string host, CallOptions callOptions)
+                {
+                    Host = host;
+                    CallOptions = callOptions;
+                }
+            }
+
             readonly CallInvoker undecoratedCallInvoker;
             readonly string host;
 
@@ -206,7 +218,7 @@ namespace Grpc.Core
 
             internal CallInvoker CreateDecoratedCallInvoker()
             {
-                return undecoratedCallInvoker.Intercept(new ClientBaseConfigurationInterceptor((method, host, options) => Tuple.Create(this.host, options)));
+                return undecoratedCallInvoker.Intercept(new ClientBaseConfigurationInterceptor((method, host, options) => new ClientBaseConfigurationInfo(this.host, options)));
             }
 
             internal ClientBaseConfiguration WithHost(string host)
diff --git a/src/csharp/Grpc.Core/Internal/MarshalUtils.cs b/src/csharp/Grpc.Core/Internal/MarshalUtils.cs
index 3f9605bfdd..09ded1a036 100644
--- a/src/csharp/Grpc.Core/Internal/MarshalUtils.cs
+++ b/src/csharp/Grpc.Core/Internal/MarshalUtils.cs
@@ -35,6 +35,13 @@ namespace Grpc.Core.Internal
         /// </summary>
         public static string PtrToStringUTF8(IntPtr ptr, int len)
         {
+            if (len == 0)
+            {
+                return "";
+            }
+
+            // TODO(jtattermusch): once Span dependency is added,
+            // use Span-based API to decode the string without copying the buffer.
             var bytes = new byte[len];
             Marshal.Copy(ptr, bytes, 0, len);
             return EncodingUTF8.GetString(bytes);
diff --git a/src/csharp/Grpc.Core/Metadata.cs b/src/csharp/Grpc.Core/Metadata.cs
index 281952d6d4..a9aa2cbbfc 100644
--- a/src/csharp/Grpc.Core/Metadata.cs
+++ b/src/csharp/Grpc.Core/Metadata.cs
@@ -225,8 +225,6 @@ namespace Grpc.Core
         /// </summary>
         public class Entry
         {
-            private static readonly Regex ValidKeyRegex = new Regex("^[.a-z0-9_-]+$");
-
             readonly string key;
             readonly string value;
             readonly byte[] valueBytes;
@@ -358,10 +356,42 @@ namespace Grpc.Core
 
             private static string NormalizeKey(string key)
             {
-                var normalized = GrpcPreconditions.CheckNotNull(key, "key").ToLowerInvariant();
-                GrpcPreconditions.CheckArgument(ValidKeyRegex.IsMatch(normalized), 
+                GrpcPreconditions.CheckNotNull(key, "key");
+
+                GrpcPreconditions.CheckArgument(IsValidKey(key, out bool isLowercase), 
                     "Metadata entry key not valid. Keys can only contain lowercase alphanumeric characters, underscores, hyphens and dots.");
-                return normalized;
+                if (isLowercase)
+                {
+                    // save allocation of a new string if already lowercase
+                    return key;
+                }
+                
+                return key.ToLowerInvariant();
+            }
+
+            private static bool IsValidKey(string input, out bool isLowercase)
+            {
+                isLowercase = true;
+                for (int i = 0; i < input.Length; i++)
+                {
+                    char c = input[i];
+                    if ('a' <= c && c <= 'z' ||
+                        '0' <= c && c <= '9' ||
+                        c == '.' ||
+                        c == '_' || 
+                        c == '-' )
+                        continue;
+
+                    if ('A' <= c && c <= 'Z')
+                    {
+                        isLowercase = false;
+                        continue;
+                    }
+
+                    return false;
+                }
+
+                return true;
             }
 
             /// <summary>