From e4fda7d5bb8964b8e6cdd867c66f731b78b087ac Mon Sep 17 00:00:00 2001
From: Will <will@bluechilli.com>
Date: Thu, 1 Nov 2018 13:07:17 +1100
Subject: [PATCH] GetInstance() - avoid locking

---
 .gitignore                             |  1 +
 csharp/PhoneNumbers/PhoneNumberUtil.cs | 16 ++++++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/.gitignore b/.gitignore
index 31a08b7..2cbb0e8 100644
--- a/.gitignore
+++ b/.gitignore
@@ -42,6 +42,7 @@ build/
 *.pidb
 *.log
 *.scc
+*/.vs/*
 
 # Visual C++ cache files
 ipch/
diff --git a/csharp/PhoneNumbers/PhoneNumberUtil.cs b/csharp/PhoneNumbers/PhoneNumberUtil.cs
index ca81e69..98356b5 100644
--- a/csharp/PhoneNumbers/PhoneNumberUtil.cs
+++ b/csharp/PhoneNumbers/PhoneNumberUtil.cs
@@ -857,6 +857,14 @@ public IReadOnlyDictionary<int, List<String>> CallingCodeToRegion
         public static PhoneNumberUtil GetInstance(String baseFileLocation,
             Dictionary<int, List<String>> countryCallingCodeToRegionCodeMap)
         {
+            //double-check on purpose to avoid locking
+            //Storing value in a temp variable first, because it can get reset to null.
+            var i = instance_;
+            if (i != null)
+            {
+                return i;
+            }
+
             lock (thisLock)
             {
                 if (instance_ == null)
@@ -909,6 +917,14 @@ public Dictionary<int, PhoneMetadata>.KeyCollection GetSupportedGlobalNetworkCal
         */
         public static PhoneNumberUtil GetInstance()
         {
+            //double-check on purpose to avoid locking
+            //Storing value in a temp variable first, because it can get reset to null.
+            var i = instance_;
+            if (i != null)
+            {
+                return i;
+            }
+
             lock (thisLock)
             {
                 if (instance_ == null)