/*
    Copyright 2005-2010 Intel Corporation.  All Rights Reserved.

    This file is part of Threading Building Blocks.

    Threading Building Blocks is free software; you can redistribute it
    and/or modify it under the terms of the GNU General Public License
    version 2 as published by the Free Software Foundation.

    Threading Building Blocks is distributed in the hope that it will be
    useful, but WITHOUT ANY WARRANTY; without even the implied warranty
    of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with Threading Building Blocks; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA

    As a special exception, you may use this file as part of a free software
    library without restriction.  Specifically, if other files instantiate
    templates or use macros or inline functions from this file, or you compile
    this file and link it with other files to produce an executable, this
    file does not by itself cause the resulting executable to be covered by
    the GNU General Public License.  This exception does not however
    invalidate any other reasons why the executable file might be covered by
    the GNU General Public License.
*/

#ifndef _TBB_tbb_main_H
#define _TBB_tbb_main_H

#include "tbb/atomic.h"

namespace tbb {

namespace internal {

void DoOneTimeInitializations ();

//------------------------------------------------------------------------
// __TBB_InitOnce
//------------------------------------------------------------------------

//! Class that supports TBB initialization. 
/** It handles acquisition and release of global resources (e.g. TLS) during startup and shutdown,
    as well as synchronization for DoOneTimeInitializations. */
class __TBB_InitOnce {
    friend void DoOneTimeInitializations();
    friend void ITT_DoUnsafeOneTimeInitialization ();

    static atomic<int> count;

    //! Platform specific code to acquire resources.
    static void acquire_resources();

    //! Platform specific code to release resources.
    static void release_resources();

    //! Specifies if the one-time initializations has been done.
    static bool InitializationDone;

    // Scenarios are possible when tools interop has to be initialized before the
    // TBB itself. This imposes a requirement that the global initialization lock 
    // has to support valid static initialization, and does not issue any tool
    // notifications in any build mode.
    typedef unsigned char mutex_type;

    // Global initialization lock
    static mutex_type InitializationLock;

public:
    static void lock()   { __TBB_LockByte( InitializationLock ); }

    static void unlock() { __TBB_store_with_release( InitializationLock, 0 ); }

    static bool initialization_done() { return __TBB_load_with_acquire(InitializationDone); }

    //! Add initial reference to resources. 
    /** We assume that dynamic loading of the library prevents any other threads 
        from entering the library until this constructor has finished running. **/
    __TBB_InitOnce() { add_ref(); }

    //! Remove the initial reference to resources.
    /** This is not necessarily the last reference if other threads are still running. **/
    ~__TBB_InitOnce() {
        remove_ref();
        // We assume that InitializationDone is not set after file-scope destructors
        // start running, and thus no race on InitializationDone is possible.
        if( initialization_done() ) {
            // Remove an extra reference that was added in DoOneTimeInitializations.
            remove_ref();  
        }
    } 
    //! Add reference to resources.  If first reference added, acquire the resources.
    static void add_ref();

    //! Remove reference to resources.  If last reference removed, release the resources.
    static void remove_ref();
}; // class __TBB_InitOnce


} // namespace internal

} // namespace tbb

#endif /* _TBB_tbb_main_H */
