/**

 * WinPR: Windows Portable Runtime

 * Synchronization Functions

 *

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

 * Copyright 2016 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/synch.h>

#include "synch.h"

#include <winpr/crt.h>

#ifdef WINPR_SYNCHRONIZATION_BARRIER

#include <assert.h>

#include <winpr/sysinfo.h>

#include <winpr/library.h>

#include <winpr/interlocked.h>

#include <winpr/thread.h>

/**

 * WinPR uses the internal RTL_BARRIER struct members exactly like Windows:

 *

 * DWORD Reserved1:          number of threads that have not yet entered the barrier

 * DWORD Reserved2:          number of threads required to enter the barrier

 * ULONG_PTR Reserved3[2];   two synchronization events (manual reset events)

 * DWORD Reserved4;          number of processors

 * DWORD Reserved5;          spincount

 */

#ifdef _WIN32

static HMODULE g_Kernel32 = NULL;

static BOOL g_NativeBarrier = FALSE;

static INIT_ONCE g_InitOnce = INIT_ONCE_STATIC_INIT;

typedef BOOL(WINAPI* fnInitializeSynchronizationBarrier)(LPSYNCHRONIZATION_BARRIER lpBarrier,

                                                         LONG lTotalThreads, LONG lSpinCount);

typedef BOOL(WINAPI* fnEnterSynchronizationBarrier)(LPSYNCHRONIZATION_BARRIER lpBarrier,

                                                    DWORD dwFlags);

typedef BOOL(WINAPI* fnDeleteSynchronizationBarrier)(LPSYNCHRONIZATION_BARRIER lpBarrier);

static fnInitializeSynchronizationBarrier pfnInitializeSynchronizationBarrier = NULL;

static fnEnterSynchronizationBarrier pfnEnterSynchronizationBarrier = NULL;

static fnDeleteSynchronizationBarrier pfnDeleteSynchronizationBarrier = NULL;

static BOOL CALLBACK InitOnce_Barrier(PINIT_ONCE once, PVOID param, PVOID* context)

{

	g_Kernel32 = LoadLibraryA("kernel32.dll");

	if (!g_Kernel32)

		return TRUE;

	pfnInitializeSynchronizationBarrier = (fnInitializeSynchronizationBarrier)GetProcAddress(

	    g_Kernel32, "InitializeSynchronizationBarrier");

	pfnEnterSynchronizationBarrier =

	    (fnEnterSynchronizationBarrier)GetProcAddress(g_Kernel32, "EnterSynchronizationBarrier");

	pfnDeleteSynchronizationBarrier =

	    (fnDeleteSynchronizationBarrier)GetProcAddress(g_Kernel32, "DeleteSynchronizationBarrier");

	if (pfnInitializeSynchronizationBarrier && pfnEnterSynchronizationBarrier &&

	    pfnDeleteSynchronizationBarrier)

	{

		g_NativeBarrier = TRUE;

	}

	return TRUE;

}

#endif

BOOL WINAPI winpr_InitializeSynchronizationBarrier(LPSYNCHRONIZATION_BARRIER lpBarrier,

                                                   LONG lTotalThreads, LONG lSpinCount)

{

	SYSTEM_INFO sysinfo;

	HANDLE hEvent0;

	HANDLE hEvent1;

#ifdef _WIN32

	InitOnceExecuteOnce(&g_InitOnce, InitOnce_Barrier, NULL, NULL);

	if (g_NativeBarrier)

		return pfnInitializeSynchronizationBarrier(lpBarrier, lTotalThreads, lSpinCount);

#endif

	if (!lpBarrier || lTotalThreads < 1 || lSpinCount < -1)

	{

		SetLastError(ERROR_INVALID_PARAMETER);

		return FALSE;

	}

	ZeroMemory(lpBarrier, sizeof(SYNCHRONIZATION_BARRIER));

	if (lSpinCount == -1)

		lSpinCount = 2000;

	if (!(hEvent0 = CreateEvent(NULL, TRUE, FALSE, NULL)))

		return FALSE;

	if (!(hEvent1 = CreateEvent(NULL, TRUE, FALSE, NULL)))

	{

		CloseHandle(hEvent0);

		return FALSE;

	}

	GetNativeSystemInfo(&sysinfo);

	lpBarrier->Reserved1 = lTotalThreads;

	lpBarrier->Reserved2 = lTotalThreads;

	lpBarrier->Reserved3[0] = (ULONG_PTR)hEvent0;

	lpBarrier->Reserved3[1] = (ULONG_PTR)hEvent1;

	lpBarrier->Reserved4 = sysinfo.dwNumberOfProcessors;

	lpBarrier->Reserved5 = lSpinCount;

	return TRUE;

}

BOOL WINAPI winpr_EnterSynchronizationBarrier(LPSYNCHRONIZATION_BARRIER lpBarrier, DWORD dwFlags)

{

	LONG remainingThreads;

	HANDLE hCurrentEvent;

	HANDLE hDormantEvent;

#ifdef _WIN32

	if (g_NativeBarrier)

		return pfnEnterSynchronizationBarrier(lpBarrier, dwFlags);

#endif

	if (!lpBarrier)

		return FALSE;

	/**

	 * dwFlags according to

	 * https://msdn.microsoft.com/en-us/library/windows/desktop/hh706889(v=vs.85).aspx

	 *

	 * SYNCHRONIZATION_BARRIER_FLAGS_BLOCK_ONLY (0x01)

	 * Specifies that the thread entering the barrier should block

	 * immediately until the last thread enters the barrier.

	 *

	 * SYNCHRONIZATION_BARRIER_FLAGS_SPIN_ONLY (0x02)

	 * Specifies that the thread entering the barrier should spin until the

	 * last thread enters the barrier, even if the spinning thread exceeds

	 * the barrier's maximum spin count.

	 *

	 * SYNCHRONIZATION_BARRIER_FLAGS_NO_DELETE (0x04)

	 * Specifies that the function can skip the work required to ensure

	 * that it is safe to delete the barrier, which can improve

	 * performance. All threads that enter this barrier must specify the

	 * flag; otherwise, the flag is ignored. This flag should be used only

	 * if the barrier will never be deleted.

	 */

	hCurrentEvent = (HANDLE)lpBarrier->Reserved3[0];

	hDormantEvent = (HANDLE)lpBarrier->Reserved3[1];

	remainingThreads = InterlockedDecrement((LONG*)&lpBarrier->Reserved1);

	assert(remainingThreads >= 0);

	if (remainingThreads > 0)

	{

		DWORD dwProcessors = lpBarrier->Reserved4;

		BOOL spinOnly = dwFlags & SYNCHRONIZATION_BARRIER_FLAGS_SPIN_ONLY;

		BOOL blockOnly = dwFlags & SYNCHRONIZATION_BARRIER_FLAGS_BLOCK_ONLY;

		BOOL block = TRUE;

		/**

		 * If SYNCHRONIZATION_BARRIER_FLAGS_SPIN_ONLY is set we will

		 * always spin and trust that the user knows what he/she/it

		 * is doing. Otherwise we'll only spin if the flag

		 * SYNCHRONIZATION_BARRIER_FLAGS_BLOCK_ONLY is not set and

		 * the number of remaining threads is less than the number

		 * of processors.

		 */

		if (spinOnly || (((ULONG)remainingThreads < dwProcessors) && !blockOnly))

		{

			DWORD dwSpinCount = lpBarrier->Reserved5;

			DWORD sp = 0;

			/**

			 * nb: we must let the compiler know that our comparand

			 * can change between the iterations in the loop below

			 */

			volatile ULONG_PTR* cmp = &lpBarrier->Reserved3[0];

			/* we spin until the last thread _completed_ the event switch */

			while ((block = (*cmp == (ULONG_PTR)hCurrentEvent)))

				if (!spinOnly && ++sp > dwSpinCount)

					break;

		}

		if (block)

			WaitForSingleObject(hCurrentEvent, INFINITE);

		return FALSE;

	}

	/* reset the dormant event first */

	ResetEvent(hDormantEvent);

	/* reset the remaining counter */

	lpBarrier->Reserved1 = lpBarrier->Reserved2;

	/* switch events - this will also unblock the spinning threads */

	lpBarrier->Reserved3[1] = (ULONG_PTR)hCurrentEvent;

	lpBarrier->Reserved3[0] = (ULONG_PTR)hDormantEvent;

	/* signal the blocked threads */

	SetEvent(hCurrentEvent);

	return TRUE;

}

BOOL WINAPI winpr_DeleteSynchronizationBarrier(LPSYNCHRONIZATION_BARRIER lpBarrier)

{

#ifdef _WIN32

	if (g_NativeBarrier)

		return pfnDeleteSynchronizationBarrier(lpBarrier);

#endif

	/**

	 * According to https://msdn.microsoft.com/en-us/library/windows/desktop/hh706887(v=vs.85).aspx

	 * Return value:

	 * The DeleteSynchronizationBarrier function always returns TRUE.

	 */

	if (!lpBarrier)

		return TRUE;

	while (lpBarrier->Reserved1 != lpBarrier->Reserved2)

		SwitchToThread();

	if (lpBarrier->Reserved3[0])

		CloseHandle((HANDLE)lpBarrier->Reserved3[0]);

	if (lpBarrier->Reserved3[1])

		CloseHandle((HANDLE)lpBarrier->Reserved3[1]);

	ZeroMemory(lpBarrier, sizeof(SYNCHRONIZATION_BARRIER));

	return TRUE;

}

#endif