1 files changed, 132 insertions, 0 deletions
diff --git a/gfx/2d/GenericRefCounted.h b/gfx/2d/GenericRefCounted.h
new file mode 100644
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+++ b/gfx/2d/GenericRefCounted.h
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+/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * 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/. */
+
+// This header provides virtual, non-templated alternatives to MFBT's RefCounted<T>.
+// It intentionally uses MFBT coding style with the intention of moving there
+// should there be other use cases for it.
+
+#ifndef MOZILLA_GENERICREFCOUNTED_H_
+#define MOZILLA_GENERICREFCOUNTED_H_
+
+#include "mozilla/RefPtr.h"
+#include "mozilla/RefCounted.h"
+
+namespace mozilla {
+
+/**
+ * Common base class for GenericRefCounted and GenericAtomicRefCounted.
+ *
+ * Having this shared base class, common to both the atomic and non-atomic
+ * cases, allows to have RefPtr's that don't care about whether the
+ * objects they're managing have atomic refcounts or not.
+ */
+class GenericRefCountedBase
+{
+  protected:
+    virtual ~GenericRefCountedBase() {};
+
+  public:
+    // AddRef() and Release() method names are for compatibility with nsRefPtr.
+    virtual void AddRef() = 0;
+
+    virtual void Release() = 0;
+
+    // ref() and deref() method names are for compatibility with wtf::RefPtr.
+    // No virtual keywords here: if a subclass wants to override the refcounting
+    // mechanism, it is welcome to do so by overriding AddRef() and Release().
+    void ref() { AddRef(); }
+    void deref() { Release(); }
+
+#ifdef MOZ_REFCOUNTED_LEAK_CHECKING
+    virtual const char* typeName() const = 0;
+    virtual size_t typeSize() const = 0;
+#endif
+};
+
+namespace detail {
+
+template<RefCountAtomicity Atomicity>
+class GenericRefCounted : public GenericRefCountedBase
+{
+  protected:
+    GenericRefCounted() : refCnt(0) { }
+
+    virtual ~GenericRefCounted() {
+      MOZ_ASSERT(refCnt == detail::DEAD);
+    }
+
+  public:
+    virtual void AddRef() override {
+      // Note: this method must be thread safe for GenericAtomicRefCounted.
+      MOZ_ASSERT(int32_t(refCnt) >= 0);
+#ifndef MOZ_REFCOUNTED_LEAK_CHECKING
+      ++refCnt;
+#else
+      const char* type = typeName();
+      uint32_t size = typeSize();
+      const void* ptr = this;
+      MozRefCountType cnt = ++refCnt;
+      detail::RefCountLogger::logAddRef(ptr, cnt, type, size);
+#endif
+    }
+
+    virtual void Release() override {
+      // Note: this method must be thread safe for GenericAtomicRefCounted.
+      MOZ_ASSERT(int32_t(refCnt) > 0);
+#ifndef MOZ_REFCOUNTED_LEAK_CHECKING
+      MozRefCountType cnt = --refCnt;
+#else
+      const char* type = typeName();
+      const void* ptr = this;
+      MozRefCountType cnt = --refCnt;
+      // Note: it's not safe to touch |this| after decrementing the refcount,
+      // except for below.
+      detail::RefCountLogger::logRelease(ptr, cnt, type);
+#endif
+      if (0 == cnt) {
+        // Because we have atomically decremented the refcount above, only
+        // one thread can get a 0 count here, so as long as we can assume that
+        // everything else in the system is accessing this object through
+        // RefPtrs, it's safe to access |this| here.
+#ifdef DEBUG
+        refCnt = detail::DEAD;
+#endif
+        delete this;
+      }
+    }
+
+    MozRefCountType refCount() const { return refCnt; }
+    bool hasOneRef() const {
+      MOZ_ASSERT(refCnt > 0);
+      return refCnt == 1;
+    }
+
+  private:
+    typename Conditional<Atomicity == AtomicRefCount, Atomic<MozRefCountType>, MozRefCountType>::Type refCnt;
+};
+
+} // namespace detail
+
+/**
+ * This reference-counting base class is virtual instead of
+ * being templated, which is useful in cases where one needs
+ * genericity at binary code level, but comes at the cost
+ * of a moderate performance and size overhead, like anything virtual.
+ */
+class GenericRefCounted : public detail::GenericRefCounted<detail::NonAtomicRefCount>
+{
+};
+
+/**
+ * GenericAtomicRefCounted is like GenericRefCounted, with an atomically updated
+ * reference counter.
+ */
+class GenericAtomicRefCounted : public detail::GenericRefCounted<detail::AtomicRefCount>
+{
+};
+
+} // namespace mozilla
+
+#endif