servable_handle.h

/* Copyright 2016 Google Inc. All Rights Reserved.
 
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 TENSORFLOW_SERVING_CORE_SERVABLE_HANDLE_H_
#define TENSORFLOW_SERVING_CORE_SERVABLE_HANDLE_H_
 
#include <algorithm>
#include <cstddef>
#include <memory>
#include <type_traits>
 
#include "tensorflow_serving/core/loader.h"
#include "tensorflow_serving/util/any_ptr.h"
 
namespace tensorflow {
namespace serving {
 
class UntypedServableHandle {
 public:
  virtual ~UntypedServableHandle() = default;
 
  virtual const ServableId& id() const = 0;
 
  virtual AnyPtr servable() = 0;
};
 
template <typename T>
class ServableHandle {
 public:
  static_assert(!std::is_pointer<T>::value,
                "Servables are implicitly passed as pointers, please use T "
                "instead of T*.");
 
  ServableHandle() = default;
 
  const ServableId& id() const { return untyped_handle_->id(); }
 
  // Smart pointer operations.
 
  T& operator*() const { return *get(); }
 
  T* operator->() const { return get(); }
 
  T* get() const { return servable_; }
 
  operator bool() const { return get() != nullptr; }
 
  // See the end of this file for comparison operators, which must be declared
  // at namespace scope to support left-hand-side arguments of different types.
 
 private:
  friend class Manager;
 
  explicit ServableHandle(std::unique_ptr<UntypedServableHandle> untyped_handle)
      : untyped_handle_(std::move(untyped_handle)),
        servable_(untyped_handle_ == nullptr
                      ? nullptr
                      : untyped_handle_->servable().get<T>()) {}
 
  std::unique_ptr<UntypedServableHandle> untyped_handle_;
  T* servable_ = nullptr;
};
 
class SharedPtrHandle final : public UntypedServableHandle {
 public:
  ~SharedPtrHandle() override = default;
 
  explicit SharedPtrHandle(const ServableId& id, std::shared_ptr<Loader> loader)
      : id_(id), loader_(std::move(loader)) {}
 
  AnyPtr servable() override { return loader_->servable(); }
 
  const ServableId& id() const override { return id_; }
 
 private:
  const ServableId id_;
  std::shared_ptr<Loader> loader_;
};
 
// We compare handles using both the servable pointer and the id. So if you
// share the same pointer amongst different versions, the handles won't be
// equal.
template <typename T, typename U>
constexpr bool operator==(const ServableHandle<T>& l,
                          const ServableHandle<U>& r) {
  return l.get() == r.get() && l.id() == r.id();
}
 
template <typename T, typename U>
constexpr bool operator!=(const ServableHandle<T>& l,
                          const ServableHandle<U>& r) {
  return !(l == r);
}
 
}  // namespace serving
}  // namespace tensorflow
 
#endif  // TENSORFLOW_SERVING_CORE_SERVABLE_HANDLE_H_