///////////////////////////////////////////////////////////////////////////
//
// Copyright (c) 2001-2011, Industrial Light & Magic, a division of Lucas
// Digital Ltd. LLC
// 
// All rights reserved.
// 
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
// *       Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// *       Redistributions in binary form must reproduce the above
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// in the documentation and/or other materials provided with the
// distribution.
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// 
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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///////////////////////////////////////////////////////////////////////////

#include <PyImathUtil.h>
#include <Iex.h>
#include <boost/python.hpp>
#include <pystate.h>

namespace PyImath {

PyAcquireLock::PyAcquireLock()
{
    _gstate = PyGILState_Ensure();
}

PyAcquireLock::~PyAcquireLock()
{
    PyGILState_Release(_gstate);
}

#ifdef PLATFORM_LINUX
// On Windows, this extern is not needed and produces a symbol mismatch at link time.
// We should verify that it's still needed on Linux for Python 2.6.
extern "C" PyThreadState *_PyThreadState_Current;
#endif

static bool
pyHaveLock()
{
    // This is very much dependent on the current Python
    // implementation of this functionality.  If we switch versions of
    // Python and the implementation changes, we'll have to change
    // this code as well and introduce a #define for the Python
    // version.
    
    if (!Py_IsInitialized())
	throw IEX_NAMESPACE::LogicExc("PyReleaseLock called without the interpreter initialized");

    PyThreadState *myThreadState = PyGILState_GetThisThreadState();

    // If the interpreter is initialized the gil is held if the
    // current thread's thread state is the current thread state
    return myThreadState != 0 && myThreadState == _PyThreadState_Current;
}

PyReleaseLock::PyReleaseLock()
{
    // only call PyEval_SaveThread if we have the interpreter lock held,
    // otherwise PyReleaseLock is a no-op.
    if (pyHaveLock())
        _save = PyEval_SaveThread();
    else
        _save = 0;
}

PyReleaseLock::~PyReleaseLock()
{
    if (_save != 0)
        PyEval_RestoreThread(_save);
}

} // namespace PyImath