/**

 * WinPR: Windows Portable Runtime

 * Synchronization Functions

 *

 * Copyright 2012 Marc-Andre Moreau <marcandre.moreau@gmail.com>

 * Copyright 2013 Norbert Federa <norbert.federa@thincast.com>

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

#ifdef HAVE_CONFIG_H

#include "config.h"

#endif

#include <winpr/tchar.h>

#include <winpr/synch.h>

#include <winpr/sysinfo.h>

#include <winpr/interlocked.h>

#include <winpr/thread.h>

#include "synch.h"

#ifdef HAVE_UNISTD_H

#include <unistd.h>

#endif

#if defined(__APPLE__)

#include <mach/task.h>

#include <mach/mach.h>

#include <mach/semaphore.h>

#endif

#ifndef _WIN32

#include "../log.h"

#define TAG WINPR_TAG("synch.critical")

VOID InitializeCriticalSection(LPCRITICAL_SECTION lpCriticalSection)

{

	InitializeCriticalSectionEx(lpCriticalSection, 0, 0);

}

BOOL InitializeCriticalSectionEx(LPCRITICAL_SECTION lpCriticalSection, DWORD dwSpinCount,

                                 DWORD Flags)

{

	/**

	 * See http://msdn.microsoft.com/en-us/library/ff541979(v=vs.85).aspx

	 * - The LockCount field indicates the number of times that any thread has

	 *   called the EnterCriticalSection routine for this critical section,

	 *   minus one. This field starts at -1 for an unlocked critical section.

	 *   Each call of EnterCriticalSection increments this value; each call of

	 *   LeaveCriticalSection decrements it.

	 * - The RecursionCount field indicates the number of times that the owning

	 *   thread has called EnterCriticalSection for this critical section.

	 */

	if (Flags != 0)

	{

		WLog_WARN(TAG, "Flags unimplemented");

	}

	lpCriticalSection->DebugInfo = NULL;

	lpCriticalSection->LockCount = -1;

	lpCriticalSection->SpinCount = 0;

	lpCriticalSection->RecursionCount = 0;

	lpCriticalSection->OwningThread = NULL;

	lpCriticalSection->LockSemaphore = (winpr_sem_t*)malloc(sizeof(winpr_sem_t));

	if (!lpCriticalSection->LockSemaphore)

		return FALSE;

#if defined(__APPLE__)

	if (semaphore_create(mach_task_self(), lpCriticalSection->LockSemaphore, SYNC_POLICY_FIFO, 0) !=

	    KERN_SUCCESS)

		goto out_fail;

#else

	if (sem_init(lpCriticalSection->LockSemaphore, 0, 0) != 0)

		goto out_fail;

#endif

	SetCriticalSectionSpinCount(lpCriticalSection, dwSpinCount);

	return TRUE;

out_fail:

	free(lpCriticalSection->LockSemaphore);

	return FALSE;

}

BOOL InitializeCriticalSectionAndSpinCount(LPCRITICAL_SECTION lpCriticalSection, DWORD dwSpinCount)

{

	return InitializeCriticalSectionEx(lpCriticalSection, dwSpinCount, 0);

}

DWORD SetCriticalSectionSpinCount(LPCRITICAL_SECTION lpCriticalSection, DWORD dwSpinCount)

{

#if !defined(WINPR_CRITICAL_SECTION_DISABLE_SPINCOUNT)

	SYSTEM_INFO sysinfo;

	DWORD dwPreviousSpinCount = lpCriticalSection->SpinCount;

	if (dwSpinCount)

	{

		/* Don't spin on uniprocessor systems! */

		GetNativeSystemInfo(&sysinfo);

		if (sysinfo.dwNumberOfProcessors < 2)

			dwSpinCount = 0;

	}

	lpCriticalSection->SpinCount = dwSpinCount;

	return dwPreviousSpinCount;

#else

	return 0;

#endif

}

static VOID _WaitForCriticalSection(LPCRITICAL_SECTION lpCriticalSection)

{

#if defined(__APPLE__)

	semaphore_wait(*((winpr_sem_t*)lpCriticalSection->LockSemaphore));

#else

	sem_wait((winpr_sem_t*)lpCriticalSection->LockSemaphore);

#endif

}

static VOID _UnWaitCriticalSection(LPCRITICAL_SECTION lpCriticalSection)

{

#if defined __APPLE__

	semaphore_signal(*((winpr_sem_t*)lpCriticalSection->LockSemaphore));

#else

	sem_post((winpr_sem_t*)lpCriticalSection->LockSemaphore);

#endif

}

VOID EnterCriticalSection(LPCRITICAL_SECTION lpCriticalSection)

{

#if !defined(WINPR_CRITICAL_SECTION_DISABLE_SPINCOUNT)

	ULONG SpinCount = lpCriticalSection->SpinCount;

	/* If we're lucky or if the current thread is already owner we can return early */

	if (SpinCount && TryEnterCriticalSection(lpCriticalSection))

		return;

	/* Spin requested times but don't compete with another waiting thread */

	while (SpinCount-- && lpCriticalSection->LockCount < 1)

	{

		/* Atomically try to acquire and check the if the section is free. */

		if (InterlockedCompareExchange(&lpCriticalSection->LockCount, 0, -1) == -1)

		{

			lpCriticalSection->RecursionCount = 1;

			lpCriticalSection->OwningThread = (HANDLE)(ULONG_PTR)GetCurrentThreadId();

			return;

		}

		/* Failed to get the lock. Let the scheduler know that we're spinning. */

		if (sched_yield() != 0)

		{

			/**

			 * On some operating systems sched_yield is a stub.

			 * usleep should at least trigger a context switch if any thread is waiting.

			 * A ThreadYield() would be nice in winpr ...

			 */

			usleep(1);

		}

	}

#endif

	/* First try the fastest possible path to get the lock. */

	if (InterlockedIncrement(&lpCriticalSection->LockCount))

	{

		/* Section is already locked. Check if it is owned by the current thread. */

		if (lpCriticalSection->OwningThread == (HANDLE)(ULONG_PTR)GetCurrentThreadId())

		{

			/* Recursion. No need to wait. */

			lpCriticalSection->RecursionCount++;

			return;

		}

		/* Section is locked by another thread. We have to wait. */

		_WaitForCriticalSection(lpCriticalSection);

	}

	/* We got the lock. Own it ... */

	lpCriticalSection->RecursionCount = 1;

	lpCriticalSection->OwningThread = (HANDLE)(ULONG_PTR)GetCurrentThreadId();

}

BOOL TryEnterCriticalSection(LPCRITICAL_SECTION lpCriticalSection)

{

	HANDLE current_thread = (HANDLE)(ULONG_PTR)GetCurrentThreadId();

	/* Atomically acquire the the lock if the section is free. */

	if (InterlockedCompareExchange(&lpCriticalSection->LockCount, 0, -1) == -1)

	{

		lpCriticalSection->RecursionCount = 1;

		lpCriticalSection->OwningThread = current_thread;

		return TRUE;

	}

	/* Section is already locked. Check if it is owned by the current thread. */

	if (lpCriticalSection->OwningThread == current_thread)

	{

		/* Recursion, return success */

		lpCriticalSection->RecursionCount++;

		InterlockedIncrement(&lpCriticalSection->LockCount);

		return TRUE;

	}

	return FALSE;

}

VOID LeaveCriticalSection(LPCRITICAL_SECTION lpCriticalSection)

{

	/* Decrement RecursionCount and check if this is the last LeaveCriticalSection call ...*/

	if (--lpCriticalSection->RecursionCount < 1)

	{

		/* Last recursion, clear owner, unlock and if there are other waiting threads ... */

		lpCriticalSection->OwningThread = NULL;

		if (InterlockedDecrement(&lpCriticalSection->LockCount) >= 0)

		{

			/* ...signal the semaphore to unblock the next waiting thread */

			_UnWaitCriticalSection(lpCriticalSection);

		}

	}

	else

	{

		InterlockedDecrement(&lpCriticalSection->LockCount);

	}

}

VOID DeleteCriticalSection(LPCRITICAL_SECTION lpCriticalSection)

{

	lpCriticalSection->LockCount = -1;

	lpCriticalSection->SpinCount = 0;

	lpCriticalSection->RecursionCount = 0;

	lpCriticalSection->OwningThread = NULL;

	if (lpCriticalSection->LockSemaphore != NULL)

	{

#if defined __APPLE__

		semaphore_destroy(mach_task_self(), *((winpr_sem_t*)lpCriticalSection->LockSemaphore));

#else

		sem_destroy((winpr_sem_t*)lpCriticalSection->LockSemaphore);

#endif

		free(lpCriticalSection->LockSemaphore);

		lpCriticalSection->LockSemaphore = NULL;

	}

}

#endif