From 4f0afc78528416b00ef2b7007a520f668ceea343 Mon Sep 17 00:00:00 2001
From: Jan Tattermusch <jtattermusch@google.com>
Date: Tue, 23 Jun 2020 20:17:33 +0200
Subject: [PATCH] optimize WriteRawTag

---
 .../src/Google.Protobuf/WritingPrimitives.cs  | 63 +++++++++++++++++++
 1 file changed, 63 insertions(+)

diff --git a/csharp/src/Google.Protobuf/WritingPrimitives.cs b/csharp/src/Google.Protobuf/WritingPrimitives.cs
index 4323691bad..4ccad7376d 100644
--- a/csharp/src/Google.Protobuf/WritingPrimitives.cs
+++ b/csharp/src/Google.Protobuf/WritingPrimitives.cs
@@ -504,6 +504,20 @@ namespace Google.Protobuf
         /// Writes the given two-byte tag directly to the stream.
         /// </summary>
         public static void WriteRawTag(ref Span<byte> buffer, ref WriterInternalState state, byte b1, byte b2)
+        {
+            if (state.position + 2 > buffer.Length)
+            {
+                WriteRawTagSlowPath(ref buffer, ref state, b1, b2);
+            }
+            else
+            {
+                buffer[state.position++] = b1;
+                buffer[state.position++] = b2;
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private static void WriteRawTagSlowPath(ref Span<byte> buffer, ref WriterInternalState state, byte b1, byte b2)
         {
             WriteRawByte(ref buffer, ref state, b1);
             WriteRawByte(ref buffer, ref state, b2);
@@ -513,6 +527,21 @@ namespace Google.Protobuf
         /// Writes the given three-byte tag directly to the stream.
         /// </summary>
         public static void WriteRawTag(ref Span<byte> buffer, ref WriterInternalState state, byte b1, byte b2, byte b3)
+        {
+            if (state.position + 3 > buffer.Length)
+            {
+                WriteRawTagSlowPath(ref buffer, ref state, b1, b2, b3);
+            }
+            else
+            {
+                buffer[state.position++] = b1;
+                buffer[state.position++] = b2;
+                buffer[state.position++] = b3;
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private static void WriteRawTagSlowPath(ref Span<byte> buffer, ref WriterInternalState state, byte b1, byte b2, byte b3)
         {
             WriteRawByte(ref buffer, ref state, b1);
             WriteRawByte(ref buffer, ref state, b2);
@@ -523,6 +552,23 @@ namespace Google.Protobuf
         /// Writes the given four-byte tag directly to the stream.
         /// </summary>
         public static void WriteRawTag(ref Span<byte> buffer, ref WriterInternalState state, byte b1, byte b2, byte b3, byte b4)
+        {
+            if (state.position + 4 > buffer.Length)
+            {
+                WriteRawTagSlowPath(ref buffer, ref state, b1, b2, b3, b4);
+            }
+            else
+            {
+                buffer[state.position++] = b1;
+                buffer[state.position++] = b2;
+                buffer[state.position++] = b3;
+                buffer[state.position++] = b4;
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.NoInlining)]
+
+        private static void WriteRawTagSlowPath(ref Span<byte> buffer, ref WriterInternalState state, byte b1, byte b2, byte b3, byte b4)
         {
             WriteRawByte(ref buffer, ref state, b1);
             WriteRawByte(ref buffer, ref state, b2);
@@ -534,6 +580,23 @@ namespace Google.Protobuf
         /// Writes the given five-byte tag directly to the stream.
         /// </summary>
         public static void WriteRawTag(ref Span<byte> buffer, ref WriterInternalState state, byte b1, byte b2, byte b3, byte b4, byte b5)
+        {
+            if (state.position + 5 > buffer.Length)
+            {
+                WriteRawTagSlowPath(ref buffer, ref state, b1, b2, b3, b4, b5);
+            }
+            else
+            {
+                buffer[state.position++] = b1;
+                buffer[state.position++] = b2;
+                buffer[state.position++] = b3;
+                buffer[state.position++] = b4;
+                buffer[state.position++] = b5;
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.NoInlining)]
+        private static void WriteRawTagSlowPath(ref Span<byte> buffer, ref WriterInternalState state, byte b1, byte b2, byte b3, byte b4, byte b5)
         {
             WriteRawByte(ref buffer, ref state, b1);
             WriteRawByte(ref buffer, ref state, b2);