/* -*- mode: c++; tab-width: 2; indent-tabs-mode: nil; -*-
Copyright (c) 2010-2012 Marcus Geelnard

This software is provided 'as-is', without any express or implied
warranty. In no event will the authors be held liable for any damages
arising from the use of this software.

Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it
freely, subject to the following restrictions:

    1. The origin of this software must not be misrepresented; you must not
    claim that you wrote the original software. If you use this software
    in a product, an acknowledgment in the product documentation would be
    appreciated but is not required.

    2. Altered source versions must be plainly marked as such, and must not be
    misrepresented as being the original software.

    3. This notice may not be removed or altered from any source
    distribution.
*/

#include <exception>

#if defined(_TTHREAD_POSIX_)
  #include <unistd.h>
  #include <map>
#elif defined(_TTHREAD_WIN32_)
  #include <process.h>
#endif


namespace tthread {

//------------------------------------------------------------------------------
// condition_variable
//------------------------------------------------------------------------------
// NOTE 1: The Win32 implementation of the condition_variable class is based on
// the corresponding implementation in GLFW, which in turn is based on a
// description by Douglas C. Schmidt and Irfan Pyarali:
// http://www.cs.wustl.edu/~schmidt/win32-cv-1.html
//
// NOTE 2: Windows Vista actually has native support for condition variables
// (InitializeConditionVariable, WakeConditionVariable, etc), but we want to
// be portable with pre-Vista Windows versions, so TinyThread++ does not use
// Vista condition variables.
//------------------------------------------------------------------------------

#if defined(_TTHREAD_WIN32_)
  #define _CONDITION_EVENT_ONE 0
  #define _CONDITION_EVENT_ALL 1
#endif

#if defined(_TTHREAD_WIN32_)
condition_variable::condition_variable() : mWaitersCount(0)
{
  mEvents[_CONDITION_EVENT_ONE] = CreateEvent(NULL, FALSE, FALSE, NULL);
  mEvents[_CONDITION_EVENT_ALL] = CreateEvent(NULL, TRUE, FALSE, NULL);
  InitializeCriticalSection(&mWaitersCountLock);
}
#endif

#if defined(_TTHREAD_WIN32_)
condition_variable::~condition_variable()
{
  CloseHandle(mEvents[_CONDITION_EVENT_ONE]);
  CloseHandle(mEvents[_CONDITION_EVENT_ALL]);
  DeleteCriticalSection(&mWaitersCountLock);
}
#endif

#if defined(_TTHREAD_WIN32_)
void condition_variable::_wait()
{
  // Wait for either event to become signaled due to notify_one() or
  // notify_all() being called
  int result = WaitForMultipleObjects(2, mEvents, FALSE, INFINITE);

  // Check if we are the last waiter
  EnterCriticalSection(&mWaitersCountLock);
  -- mWaitersCount;
  bool lastWaiter = (result == (WAIT_OBJECT_0 + _CONDITION_EVENT_ALL)) &&
                    (mWaitersCount == 0);
  LeaveCriticalSection(&mWaitersCountLock);

  // If we are the last waiter to be notified to stop waiting, reset the event
  if(lastWaiter)
    ResetEvent(mEvents[_CONDITION_EVENT_ALL]);
}
#endif

#if defined(_TTHREAD_WIN32_)
void condition_variable::notify_one()
{
  // Are there any waiters?
  EnterCriticalSection(&mWaitersCountLock);
  bool haveWaiters = (mWaitersCount > 0);
  LeaveCriticalSection(&mWaitersCountLock);

  // If we have any waiting threads, send them a signal
  if(haveWaiters)
    SetEvent(mEvents[_CONDITION_EVENT_ONE]);
}
#endif

#if defined(_TTHREAD_WIN32_)
void condition_variable::notify_all()
{
  // Are there any waiters?
  EnterCriticalSection(&mWaitersCountLock);
  bool haveWaiters = (mWaitersCount > 0);
  LeaveCriticalSection(&mWaitersCountLock);

  // If we have any waiting threads, send them a signal
  if(haveWaiters)
    SetEvent(mEvents[_CONDITION_EVENT_ALL]);
}
#endif


//------------------------------------------------------------------------------
// POSIX pthread_t to unique thread::id mapping logic.
// Note: Here we use a global thread safe std::map to convert instances of
// pthread_t to small thread identifier numbers (unique within one process).
// This method should be portable across different POSIX implementations.
//------------------------------------------------------------------------------

#if defined(_TTHREAD_POSIX_)
static thread::id _pthread_t_to_ID(const pthread_t &aHandle)
{
  static mutex idMapLock;
  static std::map<pthread_t, unsigned long int> idMap;
  static unsigned long int idCount(1);

  lock_guard<mutex> guard(idMapLock);
  if(idMap.find(aHandle) == idMap.end())
    idMap[aHandle] = idCount ++;
  return thread::id(idMap[aHandle]);
}
#endif // _TTHREAD_POSIX_


//------------------------------------------------------------------------------
// thread
//------------------------------------------------------------------------------

/// Information to pass to the new thread (what to run).
struct _thread_start_info {
  void (*mFunction)(void *); ///< Pointer to the function to be executed.
  void * mArg;               ///< Function argument for the thread function.
  thread * mThread;          ///< Pointer to the thread object.
};

// Thread wrapper function.
#if defined(_TTHREAD_WIN32_)
unsigned WINAPI thread::wrapper_function(void * aArg)
#elif defined(_TTHREAD_POSIX_)
void * thread::wrapper_function(void * aArg)
#endif
{
  // Get thread startup information
  _thread_start_info * ti = (_thread_start_info *) aArg;

  try
  {
    // Call the actual client thread function
    ti->mFunction(ti->mArg);
  }
  catch(...)
  {
    // Uncaught exceptions will terminate the application (default behavior
    // according to C++11)
    std::terminate();
  }

  // The thread is no longer executing
  lock_guard<mutex> guard(ti->mThread->mDataMutex);
  ti->mThread->mNotAThread = true;

  // The thread is responsible for freeing the startup information
  delete ti;

  return 0;
}

thread::thread(void (*aFunction)(void *), void * aArg)
{
  // Serialize access to this thread structure
  lock_guard<mutex> guard(mDataMutex);

  // Fill out the thread startup information (passed to the thread wrapper,
  // which will eventually free it)
  _thread_start_info * ti = new _thread_start_info;
  ti->mFunction = aFunction;
  ti->mArg = aArg;
  ti->mThread = this;

  // The thread is now alive
  mNotAThread = false;

  // Create the thread
#if defined(_TTHREAD_WIN32_)
  mHandle = (HANDLE) _beginthreadex(0, 0, wrapper_function, (void *) ti, 0, &mWin32ThreadID);
#elif defined(_TTHREAD_POSIX_)
  if(pthread_create(&mHandle, NULL, wrapper_function, (void *) ti) != 0)
    mHandle = 0;
#endif

  // Did we fail to create the thread?
  if(!mHandle)
  {
    mNotAThread = true;
    delete ti;
  }
}

thread::~thread()
{
  if(joinable())
    std::terminate();
}

void thread::join()
{
  if(joinable())
  {
#if defined(_TTHREAD_WIN32_)
    WaitForSingleObject(mHandle, INFINITE);
    CloseHandle(mHandle);
#elif defined(_TTHREAD_POSIX_)
    pthread_join(mHandle, NULL);
#endif
  }
}

bool thread::joinable() const
{
  mDataMutex.lock();
  bool result = !mNotAThread;
  mDataMutex.unlock();
  return result;
}

void thread::detach()
{
  mDataMutex.lock();
  if(!mNotAThread)
  {
#if defined(_TTHREAD_WIN32_)
    CloseHandle(mHandle);
#elif defined(_TTHREAD_POSIX_)
    pthread_detach(mHandle);
#endif
    mNotAThread = true;
  }
  mDataMutex.unlock();
}

thread::id thread::get_id() const
{
  if(!joinable())
    return id();
#if defined(_TTHREAD_WIN32_)
  return id((unsigned long int) mWin32ThreadID);
#elif defined(_TTHREAD_POSIX_)
  return _pthread_t_to_ID(mHandle);
#endif
}

unsigned thread::hardware_concurrency()
{
#if defined(_TTHREAD_WIN32_)
  SYSTEM_INFO si;
  GetSystemInfo(&si);
  return (int) si.dwNumberOfProcessors;
#elif defined(_SC_NPROCESSORS_ONLN)
  return (int) sysconf(_SC_NPROCESSORS_ONLN);
#elif defined(_SC_NPROC_ONLN)
  return (int) sysconf(_SC_NPROC_ONLN);
#else
  // The standard requires this function to return zero if the number of
  // hardware cores could not be determined.
  return 0;
#endif
}


//------------------------------------------------------------------------------
// this_thread
//------------------------------------------------------------------------------

thread::id this_thread::get_id()
{
#if defined(_TTHREAD_WIN32_)
  return thread::id((unsigned long int) GetCurrentThreadId());
#elif defined(_TTHREAD_POSIX_)
  return _pthread_t_to_ID(pthread_self());
#endif
}

}
