From 186444853d1b1ed331bda3910fa020332259bb63 Mon Sep 17 00:00:00 2001
From: Jamie Reece Wilson <me@reece.sx>
Date: Sat, 21 Oct 2023 04:57:25 +0100
Subject: [PATCH] [+] LSLocalSemaphore (faster io semaphore)

---
 Source/IO/Loop/LSLocalSemaphore.cpp  | 172 +++++++++++++++++++++++++++
 Source/IO/Loop/LSLocalSemaphore.hpp  |  37 ++++++
 Source/IO/Loop/LSSemaphore.Linux.cpp |   4 +-
 Source/IO/Loop/LSSemaphore.NT.cpp    |   2 +
 4 files changed, 214 insertions(+), 1 deletion(-)
 create mode 100644 Source/IO/Loop/LSLocalSemaphore.cpp
 create mode 100644 Source/IO/Loop/LSLocalSemaphore.hpp

diff --git a/Source/IO/Loop/LSLocalSemaphore.cpp b/Source/IO/Loop/LSLocalSemaphore.cpp
new file mode 100644
index 00000000..89b6f9aa
--- /dev/null
+++ b/Source/IO/Loop/LSLocalSemaphore.cpp
@@ -0,0 +1,172 @@
+/***
+    Copyright (C) 2023 J Reece Wilson (a/k/a "Reece"). All rights reserved.
+
+    File: LSLocalSemaphore.cpp
+    Date: 2023-10-21
+    Author: Reece
+***/
+#include <RuntimeInternal.hpp>
+#include "LSLocalSemaphore.hpp"
+#include <Source/Threading/Primitives/SMTYield.hpp>
+
+namespace Aurora::IO::Loop
+{
+    static auto const kFutexBitWake	= 256u;
+
+    LSLocalSemaphore::LSLocalSemaphore()
+    {
+
+    }
+
+    LSLocalSemaphore::~LSLocalSemaphore()
+    {
+
+    }
+
+    bool LSLocalSemaphore::TryInit(AuUInt32 initialCount)
+    {
+        if (!LSSemaphore::TryInit(1))
+        {
+            return false;
+        }
+
+        this->uAtomicSemaphore = initialCount;
+
+        return true;
+    }
+
+    bool LSLocalSemaphore::OnTrigger(AuUInt handle)
+    {
+        if (AuAtomicLoad(&this->uAtomicWord) & kFutexBitWake)
+        {
+            AuAtomicSub(&this->uAtomicWord, kFutexBitWake);
+        }
+
+        return this->TryTakeNoSpin();
+    }
+
+    bool LSLocalSemaphore::AddOne()
+    {
+        AuAtomicAdd(&this->uAtomicSemaphore, 1u);
+
+        while (true)
+        {
+            auto uState = AuAtomicLoad(&this->uAtomicWord);
+ 
+            if (uState & kFutexBitWake)
+            {
+                if (AuAtomicCompareExchange(&this->uAtomicWord, uState, uState) == uState)
+                {
+                    return true;
+                }
+                else
+                {
+                    continue;
+                }
+            }
+
+            if (AuAtomicCompareExchange(&this->uAtomicWord, uState + kFutexBitWake, uState) == uState)
+            {
+                LSSemaphore::AddOne();
+                return true;
+            }
+        }
+    }
+
+    bool LSLocalSemaphore::IsSignaled()
+    {
+        return this->TryTake();
+    }
+
+    bool LSLocalSemaphore::WaitOn(AuUInt32 timeout)
+    {
+        return this->TryTakeWaitMS(timeout);
+    }
+
+    ELoopSource LSLocalSemaphore::GetType()
+    {
+        return ELoopSource::eSourceSemaphore;
+    }
+
+    bool LSLocalSemaphore::TryTakeNoSpin()
+    {
+        AuUInt32 uOld {};
+
+        while ((uOld = this->uAtomicSemaphore))
+        {
+            if (AuAtomicCompareExchange(&this->uAtomicSemaphore, uOld - 1, uOld) == uOld)
+            {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    bool LSLocalSemaphore::TryTakeSpin()
+    {
+        return Threading::Primitives::DoTryIf([&]
+        {
+            return this->TryTakeNoSpin();
+        });
+    }
+
+    bool LSLocalSemaphore::TryTake()
+    {
+        return this->TryTakeNoSpin();
+    }
+
+    bool LSLocalSemaphore::TryTakeWaitMS(AuUInt32 timeout)
+    {
+        auto uEndTime = AuTime::SteadyClockMS() + timeout;
+
+        if (this->TryTakeSpin())
+        {
+            return true;
+        }
+
+        while (!this->TryTakeNoSpin())
+        {
+            if (!timeout)
+            {
+                if (LSSemaphore::WaitOn(0))
+                {
+                    return true;
+                }
+            }
+            else
+            {
+                auto uStartTime = Time::SteadyClockNS();
+                if (uStartTime >= uEndTime)
+                {
+                    return false;
+                }
+
+                if (LSSemaphore::WaitOn(AuNSToMS<AuInt64>(uEndTime - uStartTime)))
+                {
+                    return true;
+                }
+            }
+        }
+
+        return true;
+    }
+
+    AUKN_SYM AuSPtr<ILSSemaphore> NewLSSemaphore(AuUInt32 initialCount)
+    {
+        auto pMutex = AuMakeShared<LSLocalSemaphore>();
+        if (!pMutex)
+        {
+            SysPushErrorGeneric();
+            return {};
+        }
+
+        if (!pMutex->TryInit(initialCount))
+        {
+            SysPushErrorNested();
+            return {};
+        }
+
+        return pMutex;
+    }
+}
\ No newline at end of file
diff --git a/Source/IO/Loop/LSLocalSemaphore.hpp b/Source/IO/Loop/LSLocalSemaphore.hpp
new file mode 100644
index 00000000..66884233
--- /dev/null
+++ b/Source/IO/Loop/LSLocalSemaphore.hpp
@@ -0,0 +1,37 @@
+/***
+    Copyright (C) 2023 J Reece Wilson (a/k/a "Reece"). All rights reserved.
+
+    File: LSLocalMutex.hpp
+    Date: 2023-10-21
+    Author: Reece
+***/
+#pragma once
+
+#include "LSSemaphore.hpp"
+
+namespace Aurora::IO::Loop
+{
+    struct LSLocalSemaphore : LSSemaphore
+    {
+        LSLocalSemaphore();
+        ~LSLocalSemaphore();
+    
+        bool TryInit(AuUInt32 initialCount);
+
+        bool IsSignaled() override;
+        bool WaitOn(AuUInt32 timeout) override;
+        ELoopSource GetType() override;
+
+        bool AddOne() override;
+
+        virtual bool OnTrigger(AuUInt handle) override;
+
+        bool TryTakeNoSpin();
+        bool TryTakeSpin();
+        bool TryTake();
+        bool TryTakeWaitMS(AuUInt32 timeout);
+
+        AuAUInt32 uAtomicWord {};
+        AuAUInt32 uAtomicSemaphore {};
+    };
+}
\ No newline at end of file
diff --git a/Source/IO/Loop/LSSemaphore.Linux.cpp b/Source/IO/Loop/LSSemaphore.Linux.cpp
index 981fc451..6e098d84 100644
--- a/Source/IO/Loop/LSSemaphore.Linux.cpp
+++ b/Source/IO/Loop/LSSemaphore.Linux.cpp
@@ -43,7 +43,7 @@ namespace Aurora::IO::Loop
     bool LSSemaphore::TryInit(AuUInt32 initialCount)
     {
         this->Init(initialCount);
-        return this->handle != -1;
+        return this->HasValidHandle();
     }
 
     bool LSSemaphore::IsSignaledNonblocking()
@@ -85,6 +85,7 @@ namespace Aurora::IO::Loop
         return ELoopSource::eSourceSemaphore;
     }
 
+#if 0
     AUKN_SYM AuSPtr<ILSSemaphore> NewLSSemaphore(AuUInt32 initialCount)
     {
         auto pSemaphore = AuMakeShared<LSSemaphore>(initialCount);
@@ -100,4 +101,5 @@ namespace Aurora::IO::Loop
 
         return pSemaphore;
     }
+#endif
 }
\ No newline at end of file
diff --git a/Source/IO/Loop/LSSemaphore.NT.cpp b/Source/IO/Loop/LSSemaphore.NT.cpp
index 44cbd4f1..ae8475f5 100644
--- a/Source/IO/Loop/LSSemaphore.NT.cpp
+++ b/Source/IO/Loop/LSSemaphore.NT.cpp
@@ -57,6 +57,7 @@ namespace Aurora::IO::Loop
         return true;
     }
 
+#if 0
     AUKN_SYM AuSPtr<ILSSemaphore>   NewLSSemaphore(AuUInt32 initialCount)
     {
         AuSPtr<LSSemaphore> ret;
@@ -70,4 +71,5 @@ namespace Aurora::IO::Loop
 
         return AuMakeShared<LSSemaphore>(semaphore);
     }
+#endif
 }
\ No newline at end of file