// bslmt_muteximpl_win32.h                                            -*-C++-*-
#ifndef INCLUDED_BSLMT_MUTEXIMPL_WIN32
#define INCLUDED_BSLMT_MUTEXIMPL_WIN32

#include <bsls_ident.h>
BSLS_IDENT("$Id: $")

//@PURPOSE: Provide a win32 implementation of `bslmt::Mutex`.
//
//@CLASSES:
//  bslmt::MutexImpl<Platform::Win32Threads>: win32 specialization
//
//@SEE_ALSO: bslmt_mutex
//
//@DESCRIPTION: This component provides an implementation of `bslmt::Mutex` for
// Windows (win32), `bslmt::MutexImpl<Platform::Win32Threads>`, via the
// template specialization:
// ```
// bslmt::MutexImpl<Platform::Win32Threads>
// ```
// This template class should not be used (directly) by client code.  Clients
// should instead use `bslmt::Mutex`.
//
///Usage
///-----
// This component is an implementation detail of `bslmt` and is *not* intended
// for direct client use.  It is subject to change without notice.  As such, a
// usage example is not provided.

#include <bslscm_version.h>

#include <bslmt_platform.h>

#include <bsls_platform.h>

#ifdef BSLMT_PLATFORM_WIN32_THREADS

// Platform-specific implementation starts here.

// Rather than setting 'WINVER' or 'NTDDI_VERSION', just forward declare the
// Windows 2000 functions that are used.

struct _RTL_CRITICAL_SECTION;

typedef struct _RTL_CRITICAL_SECTION CRITICAL_SECTION, *LPCRITICAL_SECTION;
typedef int BOOL;
typedef unsigned long DWORD;

extern "C" {
    __declspec(dllimport) BOOL __stdcall InitializeCriticalSectionAndSpinCount(
                                    LPCRITICAL_SECTION lpCriticalSection,
                                    DWORD dwSpinCount);

    __declspec(dllimport) void __stdcall DeleteCriticalSection(
                                LPCRITICAL_SECTION lpCriticalSection);

    __declspec(dllimport) BOOL __stdcall TryEnterCriticalSection(
                                 LPCRITICAL_SECTION lpCriticalSection);

    __declspec(dllimport) void __stdcall EnterCriticalSection(
                                LPCRITICAL_SECTION lpCriticalSection);

    __declspec(dllimport) void __stdcall LeaveCriticalSection(
                                LPCRITICAL_SECTION lpCriticalSection);

}  // extern "C"

namespace BloombergLP {
namespace bslmt {

template <class THREAD_POLICY>
class MutexImpl;

                 // =======================================
                 // class MutexImpl<Platform::Win32Threads>
                 // =======================================

/// This class provides a full specialization of `MutexImpl` for Windows.
/// It provides an efficient proxy for Windows critical sections, and
/// related operations.  Note that the mutex implemented in this class is
/// *not* error checking, and is non-recursive.
/// TYPES
template <>
class MutexImpl<Platform::Win32Threads> {

  public:
    enum {
        // Size of the buffer allocated for the critical section, in
        // pointer-sized elements.  We have to make it public so we could
        // access it in a .cpp file to verify the size.

#ifdef BSLS_PLATFORM_CPU_64_BIT
        // 5*8 = 40 bytes
        k_CRITICAL_SECTION_BUFFER_SIZE = 5
#else
        // 6*4 = 24 bytes
        k_CRITICAL_SECTION_BUFFER_SIZE = 6
#endif
    };

  private:
    enum {
        // A Windows critical section has a configurable spin count.  A lock
        // operation spins this many iterations (on, presumably, some atomic
        // integer) before sleeping on the underlying primitive.

        k_SPIN_COUNT = 30
    };

    // DATA
    void *d_lock[k_CRITICAL_SECTION_BUFFER_SIZE];

    // NOT IMPLEMENTED
    MutexImpl(const MutexImpl&);
    MutexImpl& operator=(const MutexImpl&);

  public:
    // PUBLIC TYPES

    /// The underlying OS-level type.  Exposed so that other bslmt components
    /// can operate directly on this mutex.
    typedef _RTL_CRITICAL_SECTION NativeType;

    // CREATORS

    /// Create a mutex initialized to an unlocked state.
    MutexImpl();

    /// Destroy this mutex object.
    ~MutexImpl();

    // MANIPULATORS

    /// Acquire a lock on this mutex object.  If this object is currently
    /// locked, then suspend execution of the current thread until a lock
    /// can be acquired.  Note that the behavior is undefined if the calling
    /// thread already owns the lock on this mutex, and will likely result
    /// in a deadlock.
    void lock();

    /// Return a reference to the modifiable OS-level mutex underlying this
    /// object.  This method is intended only to support other bslmt
    /// components that must operate directly on this mutex.
    NativeType& nativeMutex();

    /// Attempt to acquire a lock on this mutex object.  Return 0 on
    /// success, and a non-zero value of this object is already locked, or
    /// if an error occurs.
    int tryLock();

    /// Release a lock on this mutex that was previously acquired through a
    /// successful call to `lock`, or `tryLock`.  The behavior is undefined,
    /// unless the calling thread currently owns the lock on this mutex.
    void unlock();
};

// ============================================================================
//                             INLINE DEFINITIONS
// ============================================================================

                 // ---------------------------------------
                 // class MutexImpl<Platform::Win32Threads>
                 // ---------------------------------------

// CREATORS
inline
MutexImpl<bslmt::Platform::Win32Threads>::MutexImpl()
{
    InitializeCriticalSectionAndSpinCount(
          reinterpret_cast<_RTL_CRITICAL_SECTION *>(d_lock), k_SPIN_COUNT);
}

inline
MutexImpl<bslmt::Platform::Win32Threads>::~MutexImpl()
{
    DeleteCriticalSection(
        reinterpret_cast<_RTL_CRITICAL_SECTION*>(d_lock));
}

// MANIPULATORS
inline
void MutexImpl<bslmt::Platform::Win32Threads>::lock()
{
    EnterCriticalSection(
        reinterpret_cast<_RTL_CRITICAL_SECTION*>(d_lock));
}

inline
MutexImpl<bslmt::Platform::Win32Threads>::NativeType&
MutexImpl<bslmt::Platform::Win32Threads>::nativeMutex()
{
    return *reinterpret_cast<_RTL_CRITICAL_SECTION*>(d_lock);
}

inline
int MutexImpl<bslmt::Platform::Win32Threads>::tryLock()
{
    return !TryEnterCriticalSection(
        reinterpret_cast<_RTL_CRITICAL_SECTION*>(d_lock));
}

inline
void MutexImpl<bslmt::Platform::Win32Threads>::unlock()
{
    LeaveCriticalSection(
        reinterpret_cast<_RTL_CRITICAL_SECTION*>(d_lock));
}

}  // close package namespace
}  // close enterprise namespace

#endif // BSLMT_PLATFORM_WIN32_THREADS

#endif

// ----------------------------------------------------------------------------
// Copyright 2015 Bloomberg Finance L.P.
//
// 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.
// ----------------------------- END-OF-FILE ----------------------------------
