/**************************************************************
 * 
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 * 
 *************************************************************/



#include "system.h"

#include <osl/mutex.h>
#include <osl/diagnose.h>

/*
	Implementation notes:
	The void* hidden by oslMutex points to a WIN32
	CRITICAL_SECTION structure.
*/

typedef struct _oslMutexImpl {
	CRITICAL_SECTION	m_Mutex;
	int 				m_Locks;
	DWORD				m_Owner;
	DWORD				m_Requests;
} oslMutexImpl;

static BOOL (WINAPI *lpfTryEnterCriticalSection)(LPCRITICAL_SECTION)
	= (BOOL (WINAPI *)(LPCRITICAL_SECTION))0xFFFFFFFF;

static CRITICAL_SECTION MutexLock;

/*****************************************************************************/
/* osl_createMutex */
/*****************************************************************************/
oslMutex SAL_CALL osl_createMutex(void)
{
	oslMutexImpl *pMutexImpl;

	/* Window 95 does not support "TryEnterCriticalSection" */

	if (lpfTryEnterCriticalSection ==
				(BOOL (WINAPI *)(LPCRITICAL_SECTION))0xFFFFFFFF)
	{
		OSVERSIONINFO VersionInformation = 

		{
			sizeof(OSVERSIONINFO),
			0, 
	    	0, 
	    	0,
	    	0, 
	    	"",
		};

		/* ts: Window 98 does not support "TryEnterCriticalSection" but export the symbol !!!
		   calls to that symbol always returns FALSE */
		if (
			GetVersionEx(&VersionInformation) &&
			(VersionInformation.dwPlatformId == VER_PLATFORM_WIN32_NT)
		   )
		{
			lpfTryEnterCriticalSection = (BOOL (WINAPI *)(LPCRITICAL_SECTION))
					GetProcAddress(GetModuleHandle("KERNEL32"),
								   "TryEnterCriticalSection");
		}
		else
		{
			lpfTryEnterCriticalSection = (BOOL (WINAPI *)(LPCRITICAL_SECTION))NULL;
		}


		InitializeCriticalSection(&MutexLock);
	}

	pMutexImpl= calloc(sizeof(oslMutexImpl), 1);

	OSL_ASSERT(pMutexImpl); /* alloc successful? */

	InitializeCriticalSection(&pMutexImpl->m_Mutex);

	return (oslMutex)pMutexImpl;
}

/*****************************************************************************/
/* osl_destroyMutex */
/*****************************************************************************/
void SAL_CALL osl_destroyMutex(oslMutex Mutex)
{
	oslMutexImpl *pMutexImpl = (oslMutexImpl *)Mutex;

	if (pMutexImpl)
	{
		DeleteCriticalSection(&pMutexImpl->m_Mutex);
		free(pMutexImpl);
	}
}

/*****************************************************************************/
/* osl_acquireMutex */
/*****************************************************************************/
sal_Bool SAL_CALL osl_acquireMutex(oslMutex Mutex)
{
	oslMutexImpl *pMutexImpl = (oslMutexImpl *)Mutex;

	OSL_ASSERT(Mutex);

	if (lpfTryEnterCriticalSection == NULL)
	{
		EnterCriticalSection(&MutexLock);
		pMutexImpl->m_Requests++;
		LeaveCriticalSection(&MutexLock);

		EnterCriticalSection(&pMutexImpl->m_Mutex);

		EnterCriticalSection(&MutexLock);
		pMutexImpl->m_Requests--;
		if (pMutexImpl->m_Locks++ == 0)
			pMutexImpl->m_Owner = GetCurrentThreadId();
		LeaveCriticalSection(&MutexLock);
	}
	else
		EnterCriticalSection(&pMutexImpl->m_Mutex);

	return sal_True;
}

/*****************************************************************************/
/* osl_tryToAcquireMutex */
/*****************************************************************************/
sal_Bool SAL_CALL osl_tryToAcquireMutex(oslMutex Mutex)
{
	sal_Bool 	 ret = sal_False;
	oslMutexImpl *pMutexImpl = (oslMutexImpl *)Mutex;

	OSL_ASSERT(Mutex);

	if (lpfTryEnterCriticalSection != NULL)
		return (sal_Bool)(lpfTryEnterCriticalSection(&pMutexImpl->m_Mutex) != FALSE);
	else
	{
		EnterCriticalSection(&MutexLock);

		if ( ((pMutexImpl->m_Requests == 0) && (pMutexImpl->m_Locks == 0)) ||
			 (pMutexImpl->m_Owner == GetCurrentThreadId()) )
			ret = osl_acquireMutex(Mutex);

		LeaveCriticalSection(&MutexLock);
	}

	return ret;
}

/*****************************************************************************/
/* osl_releaseMutex */
/*****************************************************************************/
sal_Bool SAL_CALL osl_releaseMutex(oslMutex Mutex)
{
	oslMutexImpl *pMutexImpl = (oslMutexImpl *)Mutex;

	OSL_ASSERT(Mutex);

	if (lpfTryEnterCriticalSection == NULL)
	{
		EnterCriticalSection(&MutexLock);

		if (--(pMutexImpl->m_Locks) == 0)
			pMutexImpl->m_Owner = 0;

		LeaveCriticalSection(&MutexLock);
	}

	LeaveCriticalSection(&pMutexImpl->m_Mutex);

	return sal_True;
}

/*****************************************************************************/
/* osl_getGlobalMutex */
/*****************************************************************************/

/* initialized in dllentry.c */
oslMutex g_Mutex;

oslMutex * SAL_CALL osl_getGlobalMutex(void) 
{
	return &g_Mutex;
}