1 files changed, 171 insertions, 0 deletions
diff --git a/src/core/lib/gprpp/orphanable.h b/src/core/lib/gprpp/orphanable.h
new file mode 100644
index 0000000000..50199730c9
--- /dev/null
+++ b/src/core/lib/gprpp/orphanable.h
@@ -0,0 +1,171 @@
+/*
+ *
+ * Copyright 2017 gRPC authors.
+ *
+ * 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.
+ *
+ */
+
+#ifndef GRPC_CORE_LIB_GPRPP_ORPHANABLE_H
+#define GRPC_CORE_LIB_GPRPP_ORPHANABLE_H
+
+#include <grpc/support/log.h>
+#include <grpc/support/sync.h>
+
+#include <memory>
+
+#include "src/core/lib/debug/trace.h"
+#include "src/core/lib/gprpp/abstract.h"
+#include "src/core/lib/gprpp/debug_location.h"
+#include "src/core/lib/gprpp/memory.h"
+
+namespace grpc_core {
+
+// A base class for orphanable objects, which have one external owner
+// but are not necessarily destroyed immediately when the external owner
+// gives up ownership.  Instead, the owner calls the object's Orphan()
+// method, and the object then takes responsibility for its own cleanup
+// and destruction.
+class Orphanable {
+ public:
+  // Gives up ownership of the object.  The implementation must arrange
+  // to eventually destroy the object without further interaction from the
+  // caller.
+  virtual void Orphan() GRPC_ABSTRACT;
+
+  // Not copyable or movable.
+  Orphanable(const Orphanable&) = delete;
+  Orphanable& operator=(const Orphanable&) = delete;
+
+  GRPC_ABSTRACT_BASE_CLASS
+
+ protected:
+  Orphanable() {}
+  virtual ~Orphanable() {}
+};
+
+template <typename T>
+class OrphanableDelete {
+ public:
+  void operator()(T* p) { p->Orphan(); }
+};
+
+template <typename T, typename Deleter = OrphanableDelete<T>>
+using OrphanablePtr = std::unique_ptr<T, Deleter>;
+
+template <typename T, typename... Args>
+inline OrphanablePtr<T> MakeOrphanable(Args&&... args) {
+  return OrphanablePtr<T>(New<T>(std::forward<Args>(args)...));
+}
+
+// A type of Orphanable with internal ref-counting.
+class InternallyRefCounted : public Orphanable {
+ public:
+  // Not copyable nor movable.
+  InternallyRefCounted(const InternallyRefCounted&) = delete;
+  InternallyRefCounted& operator=(const InternallyRefCounted&) = delete;
+
+  GRPC_ABSTRACT_BASE_CLASS
+
+ protected:
+  InternallyRefCounted() { gpr_ref_init(&refs_, 1); }
+  virtual ~InternallyRefCounted() {}
+
+  void Ref() { gpr_ref(&refs_); }
+
+  void Unref() {
+    if (gpr_unref(&refs_)) {
+      Delete(this);
+    }
+  }
+
+  // Allow Delete() to access destructor.
+  template <typename T>
+  friend void Delete(T*);
+
+ private:
+  gpr_refcount refs_;
+};
+
+// An alternative version of the InternallyRefCounted base class that
+// supports tracing.  This is intended to be used in cases where the
+// object will be handled both by idiomatic C++ code using smart
+// pointers and legacy code that is manually calling Ref() and Unref().
+// Once all of our code is converted to idiomatic C++, we may be able to
+// eliminate this class.
+class InternallyRefCountedWithTracing : public Orphanable {
+ public:
+  // Not copyable nor movable.
+  InternallyRefCountedWithTracing(const InternallyRefCountedWithTracing&) =
+      delete;
+  InternallyRefCountedWithTracing& operator=(
+      const InternallyRefCountedWithTracing&) = delete;
+
+  GRPC_ABSTRACT_BASE_CLASS
+
+ protected:
+  // Allow Delete() to access destructor.
+  template <typename T>
+  friend void Delete(T*);
+
+  InternallyRefCountedWithTracing()
+      : InternallyRefCountedWithTracing(static_cast<TraceFlag*>(nullptr)) {}
+
+  explicit InternallyRefCountedWithTracing(TraceFlag* trace_flag)
+      : trace_flag_(trace_flag) {
+    gpr_ref_init(&refs_, 1);
+  }
+
+#ifdef NDEBUG
+  explicit InternallyRefCountedWithTracing(DebugOnlyTraceFlag* trace_flag)
+      : InternallyRefCountedWithTracing() {}
+#endif
+
+  virtual ~InternallyRefCountedWithTracing() {}
+
+  void Ref() { gpr_ref(&refs_); }
+
+  void Ref(const DebugLocation& location, const char* reason) {
+    if (location.Log() && trace_flag_ != nullptr && trace_flag_->enabled()) {
+      gpr_atm old_refs = gpr_atm_no_barrier_load(&refs_.count);
+      gpr_log(GPR_DEBUG, "%s:%p %s:%d ref %" PRIdPTR " -> %" PRIdPTR " %s",
+              trace_flag_->name(), this, location.file(), location.line(),
+              old_refs, old_refs + 1, reason);
+    }
+    Ref();
+  }
+
+  void Unref() {
+    if (gpr_unref(&refs_)) {
+      Delete(this);
+    }
+  }
+
+  void Unref(const DebugLocation& location, const char* reason) {
+    if (location.Log() && trace_flag_ != nullptr && trace_flag_->enabled()) {
+      gpr_atm old_refs = gpr_atm_no_barrier_load(&refs_.count);
+      gpr_log(GPR_DEBUG, "%s:%p %s:%d unref %" PRIdPTR " -> %" PRIdPTR " %s",
+              trace_flag_->name(), this, location.file(), location.line(),
+              old_refs, old_refs - 1, reason);
+    }
+    Unref();
+  }
+
+ private:
+  TraceFlag* trace_flag_ = nullptr;
+  gpr_refcount refs_;
+};
+
+}  // namespace grpc_core
+
+#endif /* GRPC_CORE_LIB_GPRPP_ORPHANABLE_H */