From 43583a174849d655f02c1f8a886ba405c9d25d88 Mon Sep 17 00:00:00 2001
From: Jamie Reece Wilson <me@reece.sx>
Date: Fri, 1 Dec 2023 01:12:18 +0000
Subject: [PATCH] [+] IRWLock::CheckSelfThreadIsWriter

---
 .../Aurora/Threading/Primitives/RWLock.hpp    | 22 +++++++++++++------
 Source/Threading/Primitives/AuRWLock.cpp      |  7 ++++++
 Source/Threading/Primitives/AuRWLock.hpp      |  2 ++
 3 files changed, 24 insertions(+), 7 deletions(-)

diff --git a/Include/Aurora/Threading/Primitives/RWLock.hpp b/Include/Aurora/Threading/Primitives/RWLock.hpp
index 511b32d4..07814726 100644
--- a/Include/Aurora/Threading/Primitives/RWLock.hpp
+++ b/Include/Aurora/Threading/Primitives/RWLock.hpp
@@ -13,16 +13,17 @@ namespace Aurora::Threading::Primitives
     {
         /**
          * @brief Returns a complete IWaitable interface for reantrant access to the protected resources.
-         *        Once a thread takes exclusive access of the resource, only it shall pass read
+         *        Once a thread takes exclusive access of the resource, only it shall pass read. Noting this 
+         *        is critical section behaviour, not mutex behaviour.
          * @return 
-        */
+         */
         virtual IWaitable *AsReadable() = 0;
         
         /**
          * @brief Returns a complete IWaitable interface for exclusive thread access to the protected resources
          *        
          * @return 
-        */
+         */
         virtual IWaitable *AsWritable() = 0;
 
         /**
@@ -31,20 +32,27 @@ namespace Aurora::Threading::Primitives
          *        You must be careful to consider how this is used to prevent dead-locks
          * @param timeout in relative nanoseconds
          * @return 
-        */
+         */
         virtual bool UpgradeReadToWrite(AuUInt64 timeout) = 0;
 
         /**
          * @brief Reverses UpgradeReadToWrite.
          * @return 
-        */
+         */
         virtual bool DowngradeWriteToRead() = 0;
+
+        /**
+         * @brief Checks if the current thread has acquired a critical-section lock on the mutually exclusive resource 
+         * @return 
+         */
+        virtual bool CheckSelfThreadIsWriter() = 0;
     };
 
-    /// Allows AsReadable entrancy as AsWritable lock
+    /// Allows AsReadable() holder entrancy as AsWritable() lock
+    /// Check CheckSelfThreadIsWriter() before any lock guards, if non-reentrant mutual exclusion is desired.
     AUKN_SHARED_SOO_NCM(RWLock, IRWLock, kPrimitiveSizeRWLock);
 
-    /// Allows AsWritable reentrancy, and allows AsReadable entrancy as AsWritable lock
+    /// Allows AsWritable() holder reentrancy, and allows AsReadable() holder entrancy as AsWritable() lock
     AUKN_SHARED_SOO_NCM(RWRenterableLock, IRWLock, kPrimitiveSizeRWLock);
     
 }
\ No newline at end of file
diff --git a/Source/Threading/Primitives/AuRWLock.cpp b/Source/Threading/Primitives/AuRWLock.cpp
index fa2d267a..f0650408 100644
--- a/Source/Threading/Primitives/AuRWLock.cpp
+++ b/Source/Threading/Primitives/AuRWLock.cpp
@@ -934,6 +934,13 @@ namespace Aurora::Threading::Primitives
         return &this->write_;
     }
 
+
+    template<bool bIsWriteRecursionAllowed>
+    bool RWLockImpl<bIsWriteRecursionAllowed>::CheckSelfThreadIsWriter()
+    {
+        return this->reentrantWriteLockHandle_ == GetThreadCookie();
+    }
+
     AUKN_SYM IRWLock *RWLockNew()
     {
         return _new RWLockImpl<false>();
diff --git a/Source/Threading/Primitives/AuRWLock.hpp b/Source/Threading/Primitives/AuRWLock.hpp
index da803b2c..47b3996e 100644
--- a/Source/Threading/Primitives/AuRWLock.hpp
+++ b/Source/Threading/Primitives/AuRWLock.hpp
@@ -90,6 +90,8 @@ namespace Aurora::Threading::Primitives
         IWaitable *AsReadable() override;
         IWaitable *AsWritable() override;
 
+        bool CheckSelfThreadIsWriter() override;
+
         auline ConditionVariableInternal &GetCondition();
         auline ConditionVariableInternal &GetConditionWriter();