text: /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
   * vim: set ts=8 sts=4 et sw=4 tw=99:
   * This Source Code Form is subject to the terms of the Mozilla Public
   * License, v. 2.0. If a copy of the MPL was not distributed with this
   * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
  
  #ifndef js_RefCounted_h
  #define js_RefCounted_h
  
  #include "mozilla/Atomics.h"
  #include "mozilla/RefCountType.h"
  
  #include "js/Utility.h"
  
  // These types implement the same interface as mozilla::(Atomic)RefCounted and
  // must be used instead of mozilla::(Atomic)RefCounted for everything in
  // SpiderMonkey. There are two reasons:
  //  - Release() needs to call js_delete, not delete
  //  - SpiderMonkey does not have MOZILLA_INTERNAL_API defined which can lead
  //    to ODR violations that show up as spurious leak reports when ref-counted
  //    types are allocated by SpiderMonkey and released by Gecko (or vice versa).
  
  namespace js {
  
  template <typename T>
  class RefCounted
  {
      static const MozRefCountType DEAD = 0xffffdead;
  
    protected:
      RefCounted() : mRefCnt(0) {}
      ~RefCounted() { MOZ_ASSERT(mRefCnt == DEAD); }
  
    public:
      void AddRef() const
      {
          MOZ_ASSERT(int32_t(mRefCnt) >= 0);
          ++mRefCnt;
      }
  
      void Release() const
      {
        MOZ_ASSERT(int32_t(mRefCnt) > 0);
        MozRefCountType cnt = --mRefCnt;
        if (0 == cnt) {
  #ifdef DEBUG
            mRefCnt = DEAD;
  #endif
            js_delete(const_cast<T*>(static_cast<const T*>(this)));
        }
      }
  
    private:
      mutable MozRefCountType mRefCnt;
  };
  
  template <typename T>
  class AtomicRefCounted
  {
      // On 64-bit systems, if the refcount type is small (say, 32 bits), there's
      // a risk that it could overflow.  So require it to be large enough.
  
      static_assert(sizeof(MozRefCountType) == sizeof(uintptr_t),
                    "You're at risk for ref count overflow.");
  
      static const MozRefCountType DEAD = ~MozRefCountType(0xffff) | 0xdead;
  
    protected:
      AtomicRefCounted() : mRefCnt(0) {}
      ~AtomicRefCounted() { MOZ_ASSERT(mRefCnt == DEAD); }
  
    public:
      void AddRef() const
      {
          ++mRefCnt;
          MOZ_ASSERT(mRefCnt != DEAD);
      }
  
      void Release() const
      {
          MOZ_ASSERT(mRefCnt != 0);
          MozRefCountType cnt = --mRefCnt;
          if (0 == cnt) {
  #ifdef DEBUG
              mRefCnt = DEAD;
  #endif
              js_delete(const_cast<T*>(static_cast<const T*>(this)));
          }
      }
  
    private:
      mutable mozilla::Atomic<MozRefCountType> mRefCnt;
  };
  
  } // namespace js
  
  #endif /* js_RefCounted_h */
  