Prep work for win7-specific condition variable

base/synchronization/condition_variable.h

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // ConditionVariable wraps pthreads condition variable synchronization or, on
 // Windows, simulates it.  This functionality is very helpful for having
 // several threads wait for an event, as is common with a thread pool managed
 // by a master.  The meaning of such an event in the (worker) thread pool
 // scenario is that additional tasks are now available for processing.  It is
 // used in Chrome in the DNS prefetching system to notify worker threads that
@@ skipping 50 matching lines @@
 //
 // For a discussion of the many very subtle implementation details, see the FAQ
 // at the end of condition_variable_win.cc.
 
 #ifndef BASE_SYNCHRONIZATION_CONDITION_VARIABLE_H_
 #define BASE_SYNCHRONIZATION_CONDITION_VARIABLE_H_
 #pragma once
 
 #include "build/build_config.h"
 
-#if defined(OS_WIN)
-#include <windows.h>
-#elif defined(OS_POSIX)
+#if defined(OS_POSIX)
 #include <pthread.h>
 #endif
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
 #include "base/synchronization/lock.h"
 
 namespace base {
 
+class ConditionVarImpl;
 class TimeDelta;
 
 class BASE_EXPORT ConditionVariable {
  public:
   // Construct a cv for use with ONLY one user lock.
   explicit ConditionVariable(Lock* user_lock);
 
   ~ConditionVariable();
 
   // Wait() releases the caller's critical section atomically as it starts to
   // sleep, and the reacquires it when it is signaled.
   void Wait();
   void TimedWait(const TimeDelta& max_time);
 
   // Broadcast() revives all waiting threads.
   void Broadcast();
   // Signal() revives one waiting thread.
   void Signal();
 
  private:
 
 #if defined(OS_WIN)
-
-  // Define Event class that is used to form circularly linked lists.
-  // The list container is an element with NULL as its handle_ value.
-  // The actual list elements have a non-zero handle_ value.
-  // All calls to methods MUST be done under protection of a lock so that links
-  // can be validated.  Without the lock, some links might asynchronously
-  // change, and the assertions would fail (as would list change operations).
-  class Event {
-   public:
-    // Default constructor with no arguments creates a list container.
-    Event();
-    ~Event();
-
-    // InitListElement transitions an instance from a container, to an element.
-    void InitListElement();
-
-    // Methods for use on lists.
-    bool IsEmpty() const;
-    void PushBack(Event* other);
-    Event* PopFront();
-    Event* PopBack();
-
-    // Methods for use on list elements.
-    // Accessor method.
-    HANDLE handle() const;
-    // Pull an element from a list (if it's in one).
-    Event* Extract();
-
-    // Method for use on a list element or on a list.
-    bool IsSingleton() const;
-
-   private:
-    // Provide pre/post conditions to validate correct manipulations.
-    bool ValidateAsDistinct(Event* other) const;
-    bool ValidateAsItem() const;
-    bool ValidateAsList() const;
-    bool ValidateLinks() const;
-
-    HANDLE handle_;
-    Event* next_;
-    Event* prev_;
-    DISALLOW_COPY_AND_ASSIGN(Event);
-  };
-
-  // Note that RUNNING is an unlikely number to have in RAM by accident.
-  // This helps with defensive destructor coding in the face of user error.
-  enum RunState { SHUTDOWN = 0, RUNNING = 64213 };
-
-  // Internal implementation methods supporting Wait().
-  Event* GetEventForWaiting();
-  void RecycleEvent(Event* used_event);
-
-  RunState run_state_;
-
-  // Private critical section for access to member data.
-  base::Lock internal_lock_;
-
-  // Lock that is acquired before calling Wait().
-  base::Lock& user_lock_;
-
-  // Events that threads are blocked on.
-  Event waiting_list_;
-
-  // Free list for old events.
-  Event recycling_list_;
-  int recycling_list_size_;
-
-  // The number of allocated, but not yet deleted events.
-  int allocation_counter_;
-
+  ConditionVarImpl* impl_;
 #elif defined(OS_POSIX)
-
   pthread_cond_t condition_;
   pthread_mutex_t* user_mutex_;
 #if !defined(NDEBUG)
   base::Lock* user_lock_;     // Needed to adjust shadow lock state on wait.
 #endif
 
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(ConditionVariable);
 };
 
 }  // namespace base
 
 #endif  // BASE_SYNCHRONIZATION_CONDITION_VARIABLE_H_