From 9248dcf07ec5c0499e6cc7e7555a746c58130934 Mon Sep 17 00:00:00 2001
From: greg7mdp <greg7mdp@gmail.com>
Date: Sun, 19 Nov 2023 18:14:48 -0500
Subject: [PATCH] Add support for Windows `phmap::srwlock`

---
 examples/lazy_emplace_l.cc    | 11 +----------
 parallel_hashmap/phmap_base.h | 37 +++++++++++++++++++++++++++++++++++
 2 files changed, 38 insertions(+), 10 deletions(-)

diff --git a/examples/lazy_emplace_l.cc b/examples/lazy_emplace_l.cc
index beb5f2f..392428f 100644
--- a/examples/lazy_emplace_l.cc
+++ b/examples/lazy_emplace_l.cc
@@ -8,18 +8,9 @@
 #include <vector>
 #include <ppl.h>
 
-class srwlock {
-    SRWLOCK _lock;
-
-public:
-    srwlock()     { InitializeSRWLock(&_lock); }
-    void lock()   { AcquireSRWLockExclusive(&_lock); }
-    void unlock() { ReleaseSRWLockExclusive(&_lock); }
-};
-
 using Map =  phmap::parallel_flat_hash_map<std::string, int, phmap::priv::hash_default_hash<std::string>,
                                            phmap::priv::hash_default_eq<std::string>,
-                                           std::allocator<std::pair<const std::string, int>>, 8, srwlock>;
+                                           std::allocator<std::pair<const std::string, int>>, 8, phmap::srwlock>;
 
 class Dict
 {
diff --git a/parallel_hashmap/phmap_base.h b/parallel_hashmap/phmap_base.h
index 89597ab..db4f767 100644
--- a/parallel_hashmap/phmap_base.h
+++ b/parallel_hashmap/phmap_base.h
@@ -5000,6 +5000,7 @@ public:
 
 // --------------------------------------------------------------------------
 //         Abseil Mutex support (read and write lock support)
+//         use: `phmap::AbslMutex` instead of `std::mutex`
 // --------------------------------------------------------------------------
 #ifdef ABSL_SYNCHRONIZATION_MUTEX_H_
     
@@ -5030,6 +5031,42 @@ public:
 
 #endif
 
+// --------------------------------------------------------------------------
+//         Microsoft SRWLOCK support (read and write lock support)
+//         use: `phmap::srwlock` instead of `std::mutex`
+// --------------------------------------------------------------------------
+#if defined(_MSVC_LANG) && defined(SRWLOCK_INIT)
+
+    class srwlock {
+        SRWLOCK _lock;
+    public:
+        srwlock()              { InitializeSRWLock(&_lock); }
+        void lock()            { AcquireSRWLockExclusive(&_lock); }
+        void unlock()          { ReleaseSRWLockExclusive(&_lock); }
+        bool try_lock()        { return !!TryAcquireSRWLockExclusive(&_lock); }
+        void lock_shared()     { AcquireSRWLockShared(&_lock); }
+        void unlock_shared()   { ReleaseSRWLockShared(&_lock); }
+        bool try_lock_shared() { return !!TryAcquireSRWLockShared(&_lock); }
+    };
+
+
+    template<>
+    class LockableImpl<srwlock> : public srwlock
+    {
+    public:
+        using mutex_type    = srwlock;
+        using Base          = LockableBaseImpl<srwlock>;
+        using SharedLock    = typename Base::ReadLock;
+        using ReadWriteLock = typename Base::ReadWriteLock;
+        using UpgradeLock   = typename Base::WriteLock;
+        using UniqueLock    = typename Base::WriteLock;
+        using SharedLocks   = typename Base::ReadLocks;
+        using UniqueLocks   = typename Base::WriteLocks;
+        using UpgradeToUnique = typename Base::DoNothing; // we already have unique ownership
+    };
+
+#endif
+
 // --------------------------------------------------------------------------
 //         Boost shared_mutex support (read and write lock support)
 // --------------------------------------------------------------------------