From 39c002d52a8085fdde5cb08d768d78e9fe03fee0 Mon Sep 17 00:00:00 2001
From: greg <greg7mdp@gmail.com>
Date: Sat, 25 May 2019 16:01:53 -0400
Subject: [PATCH] std::shared_mutex support #11

---
 parallel_hashmap/phmap_base.h   | 25 +++++++++++++++++++++++++
 parallel_hashmap/phmap_config.h |  4 ++++
 2 files changed, 29 insertions(+)

diff --git a/parallel_hashmap/phmap_base.h b/parallel_hashmap/phmap_base.h
index 96b16e6..bbc6712 100644
--- a/parallel_hashmap/phmap_base.h
+++ b/parallel_hashmap/phmap_base.h
@@ -50,6 +50,10 @@
 
 #include "phmap_config.h"
 
+#ifdef PHMAP_HAVE_SHARED_MUTEX
+    #include <shared_mutex>  // after "phmap_config.h"
+#endif
+
 namespace phmap {
 
 template <class T> using Allocator = typename std::allocator<T>;
@@ -4898,6 +4902,27 @@ public:
     };
 #endif
 
+// --------------------------------------------------------------------------
+//         std::shared_mutex support (read and write lock support)
+// --------------------------------------------------------------------------
+#ifdef PHMAP_HAVE_SHARED_MUTEX
+
+    // ---------------------------------------------------------------------------
+    template <>
+    class  LockableImpl<std::shared_mutex> : public std::shared_mutex
+    {
+    public:
+        using mutex_type      = std::shared_mutex;
+        using Base            = LockableBaseImpl<std::shared_mutex>;
+        using SharedLock      = std::shared_lock<mutex_type>;
+        using UpgradeLock     = std::unique_lock<mutex_type>; // assume can't upgrade
+        using UniqueLock      = std::unique_lock<mutex_type>;
+        using SharedLocks     = typename Base::ReadLocks;
+        using UniqueLocks     = typename Base::WriteLocks;
+        using UpgradeToUnique = typename Base::DoNothing;  // we already have unique ownership
+    };
+#endif
+
 #endif // PHMAP_HAS_BOOST_THREAD_MUTEXES
 
 
diff --git a/parallel_hashmap/phmap_config.h b/parallel_hashmap/phmap_config.h
index a1705ad..f679f1a 100644
--- a/parallel_hashmap/phmap_config.h
+++ b/parallel_hashmap/phmap_config.h
@@ -311,6 +311,10 @@
     #define PHMAP_HAVE_STD_STRING_VIEW 1
 #endif
 
+#if (defined(_MSVC_LANG) && _MSVC_LANG >= 201402) || __cplusplus >= 201402
+    #define PHMAP_HAVE_SHARED_MUTEX 1
+#endif
+
 #ifndef PHMAP_HAVE_STD_STRING_VIEW
     #define PHMAP_HAVE_STD_STRING_VIEW 0
 #endif