/**

 * 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.

 */

#include <winpr/config.h>

#include <winpr/assert.h>

#include <winpr/tchar.h>

#include <winpr/synch.h>

#include <winpr/sysinfo.h>

#include <winpr/interlocked.h>

#include <winpr/thread.h>

#include "synch.h"

#ifdef WINPR_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)

{

  WINPR_ASSERT(lpCriticalSection);

  /**

   * 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(WINPR_ATTR_UNUSED LPCRITICAL_SECTION lpCriticalSection,

                                  WINPR_ATTR_UNUSED DWORD dwSpinCount)

{

  WINPR_ASSERT(lpCriticalSection);

#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

  // WLog_ERR("TODO", "TODO: implement");

  return 0;

#endif

}

static VOID WaitForCriticalSection(LPCRITICAL_SECTION lpCriticalSection)

{

  WINPR_ASSERT(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)

{

  WINPR_ASSERT(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)

{

  WINPR_ASSERT(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();

  WINPR_ASSERT(lpCriticalSection);

  /* 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)

{

  WINPR_ASSERT(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

  {

    (void)InterlockedDecrement(&lpCriticalSection->LockCount);

  }

}

VOID DeleteCriticalSection(LPCRITICAL_SECTION lpCriticalSection)

{

  WINPR_ASSERT(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