From 5a6564fa94d999ed4afdf272dd44ddc2f624d43d Mon Sep 17 00:00:00 2001
From: Doyle Thai <dyl.thai@gmail.com>
Date: Sat, 17 Jun 2017 22:25:29 +1000
Subject: [PATCH] Start creating multithreading work queue

---
 src/Win32DTRenderer.cpp | 122 +++++++++++++++++++++++++++++++++++-----
 src/dqn.h               |   5 +-
 2 files changed, 110 insertions(+), 17 deletions(-)

diff --git a/src/Win32DTRenderer.cpp b/src/Win32DTRenderer.cpp
index c19cad2..ef25f78 100644
--- a/src/Win32DTRenderer.cpp
+++ b/src/Win32DTRenderer.cpp
@@ -441,22 +441,65 @@ i32 Win32GetModuleDirectory(char *const buf, const u32 bufLen)
 	return lastSlashIndex;
 }
 
+typedef struct Win32Thread
+{
+	HANDLE handle;
+	i32    logicalIndex;
+	DWORD  id;
+} Win32Thread;
+
+typedef struct Win32ThreadContext
+{
+	Win32Thread *threadList;
+	i32 size;
+} Win32ThreadContext;
+
 typedef struct ThreadJob
 {
-	int numberToPrint;
+	i32 numberToPrint;
 } ThreadJob;
 
-typedef struct ThreadJobQueue {
-	ThreadJob *queue;
-	int        queueSize;
-} ThreadJobQueue;
+typedef struct Win32ThreadJobQueue {
+	ThreadJob *jobList;
 
-FILE_SCOPE ThreadJobQueue jobQueue[16];
+	LONG volatile jobInsertIndex;
+	LONG volatile currJobIndex;
+	LONG          size;
+} Win32ThreadJobQueue;
+
+FILE_SCOPE Win32ThreadJobQueue globalJobQueue;
+FILE_SCOPE Win32ThreadContext  globalThreadContext;
+FILE_SCOPE HANDLE              globalSemaphore;
+
+void PushThreadJob(Win32ThreadJobQueue *queue, ThreadJob job)
+{
+	DQN_ASSERT(queue->jobInsertIndex < queue->size);
+	queue->jobList[queue->jobInsertIndex] = job;
+
+	queue->jobInsertIndex++;
+	ReleaseSemaphore(globalSemaphore, 1, NULL);
+}
 
 DWORD WINAPI Win32ThreadCallback(void *lpParameter)
 {
-	OutputDebugString("Threaded Hello World!\n");
-	return 0;
+	Win32Thread *thread = (Win32Thread *)lpParameter;
+	DQN_ASSERT(thread);
+
+	for (;;)
+	{
+		if (globalJobQueue.currJobIndex < globalJobQueue.jobInsertIndex)
+		{
+			LONG workIndex = InterlockedIncrement(&globalJobQueue.currJobIndex) - 1;
+			ThreadJob job  = globalJobQueue.jobList[workIndex];
+
+			DqnWin32_OutputDebugString("Thread %d: Printing number: %d\n", thread->logicalIndex,
+			                           job.numberToPrint);
+		}
+		else
+		{
+			WaitForSingleObjectEx(globalSemaphore, INFINITE, false);
+		}
+	}
 }
 
 int WINAPI wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPWSTR lpCmdLine, int nShowCmd)
@@ -593,7 +636,7 @@ int WINAPI wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPWSTR lpCmdLi
 		////////////////////////////////////////////////////////////////////////
 		// Query CPU Cores
 		////////////////////////////////////////////////////////////////////////
-		i32 numCores        = 1;
+		i32 numCores        = 0;
 		i32 numLogicalCores = 0;
 
 		SYSTEM_INFO systemInfo;
@@ -648,18 +691,67 @@ int WINAPI wWinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPWSTR lpCmdLi
 		{
 			DQN_WIN32_ERROR_BOX("DqnMemStack_Push() failed", NULL);
 		}
+		DqnMemStackTempRegion_End(memRegion);
 
 		////////////////////////////////////////////////////////////////////////
 		// Threading
 		////////////////////////////////////////////////////////////////////////
-		const i32 USE_DEFAULT_STACK_SIZE = 0;
-		void *threadParam                = NULL;
-		DWORD threadId;
+		const i32 QUEUE_SIZE = 20;
+		globalJobQueue.jobList = (ThreadJob *)DqnMemStack_Push(&globalPlatformMemory.tempStack,
+		                                                       sizeof(ThreadJob) * QUEUE_SIZE);
 
-		HANDLE threadHandle = CreateThread(NULL, USE_DEFAULT_STACK_SIZE, Win32ThreadCallback,
-		                                   threadParam, 0, &threadId);
+		if (globalJobQueue.jobList)
+		{
+			// NOTE: (numCores - 1), 1 core is already exclusively for main thread
+			i32 availableThreads = (numCores - 1) * numLogicalCores;
+			// TODO(doyle): Logic for single core/thread processors
+			DQN_ASSERT(availableThreads > 0);
 
-		DqnMemStackTempRegion_End(memRegion);
+			globalSemaphore = CreateSemaphore(NULL, 0, availableThreads, NULL);
+			if (globalSemaphore)
+			{
+				// Create jobs
+				globalJobQueue.size = QUEUE_SIZE;
+				for (i32 i = 0; i < 10; i++)
+				{
+					ThreadJob job     = {};
+					job.numberToPrint = i;
+					PushThreadJob(&globalJobQueue, job);
+				}
+
+				// Create threads
+				globalThreadContext.threadList = (Win32Thread *)DqnMemStack_Push(
+				    &globalPlatformMemory.tempStack, sizeof(Win32Thread) * availableThreads);
+				if (globalThreadContext.threadList)
+				{
+					globalThreadContext.size = availableThreads;
+					for (i32 i = 0; i < globalThreadContext.size; i++)
+					{
+						const i32 USE_DEFAULT_STACK_SIZE = 0;
+						Win32Thread *thread              = &globalThreadContext.threadList[i];
+						thread->logicalIndex             = i;
+						thread->handle =
+						    CreateThread(NULL, USE_DEFAULT_STACK_SIZE, Win32ThreadCallback,
+						                 (void *)thread, 0, &thread->id);
+
+						if (!thread->handle)
+						{
+							DqnWin32_DisplayLastError("CreateThread() failed");
+						}
+					}
+				}
+				else
+				{
+					// TODO(doyle): Failed allocation
+				}
+
+			}
+			else
+			{
+				// TODO(doyle): Semaphore failed.
+				DqnWin32_DisplayLastError("CreateSemaphore() failed");
+			}
+		}
 	}
 
 	////////////////////////////////////////////////////////////////////////////
diff --git a/src/dqn.h b/src/dqn.h
index 16b3086..4a70e7f 100644
--- a/src/dqn.h
+++ b/src/dqn.h
@@ -1686,9 +1686,10 @@ DQN_FILE_SCOPE void DqnMemStackTempRegion_End(DqnMemStackTempRegion region)
 	{
 		DQN_ASSERT(stack->block->used >= region.used);
 		stack->block->used = region.used;
-		DQN_ASSERT(stack->tempRegionCount >= 0);
 	}
+
 	stack->tempRegionCount--;
+	DQN_ASSERT(stack->tempRegionCount >= 0);
 }
 
 #ifdef DQN_CPP_MODE
@@ -3321,7 +3322,7 @@ DQN_FILE_SCOPE void DqnWin32_DisplayErrorCode(const DWORD error, const char *con
 
 DQN_FILE_SCOPE void DqnWin32_OutputDebugString(const char *const formatStr, ...)
 {
-	LOCAL_PERSIST char str[1024] = {0};
+	char str[1024] = {0};
 
 	va_list argList;
 	va_start(argList, formatStr);