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mojo/public/cpp/bindings/synchronous_interface_ptr.h

-// Copyright 2016 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.
-
-#ifndef MOJO_PUBLIC_CPP_BINDINGS_SYNCHRONOUS_INTERFACE_PTR_H_
-#define MOJO_PUBLIC_CPP_BINDINGS_SYNCHRONOUS_INTERFACE_PTR_H_
-
-#include <cstddef>
-#include <memory>
-#include <utility>
-
-#include "mojo/public/cpp/bindings/interface_handle.h"
-#include "mojo/public/cpp/bindings/lib/message_header_validator.h"
-#include "mojo/public/cpp/bindings/lib/synchronous_connector.h"
-#include "mojo/public/cpp/bindings/message_validator.h"
-#include "mojo/public/cpp/environment/logging.h"
-#include "mojo/public/cpp/system/macros.h"
-
-namespace mojo {
-
-// A synchronous version of InterfacePtr. Interface message calls using a
-// SynchronousInterfacePtr will block if a response message is expected. This
-// class uses the generated synchronous versions of the mojo interfaces.
-//
-// To make a SynchronousInterfacePtr, use the |Create()| factory method and
-// supply the InterfaceHandle to it. Use |PassInterfaceHandle()| to extract the
-// InterfaceHandle.
-//
-// SynchronousInterfacePtr is thread-compatible (but not thread-safe).
-//
-// TODO(vardhan): Add support for InterfaceControlMessage methods.
-// TODO(vardhan): Message calls invoked on this class will return |false| if
-// there are any message pipe errors.  Should there be a better way to expose
-// underlying message pipe errors?
-template <typename Interface>
-class SynchronousInterfacePtr {
- public:
-  // Constructs an unbound SynchronousInterfacePtr.
-  SynchronousInterfacePtr() : version_(0) {}
-  SynchronousInterfacePtr(std::nullptr_t) : SynchronousInterfacePtr() {}
-
-  // Takes over the binding of another SynchronousInterfacePtr, and closes any
-  // message pipe already bound to this pointer.
-  SynchronousInterfacePtr(SynchronousInterfacePtr&& other) = default;
-
-  // Takes over the binding of another SynchronousInterfacePtr, and closes any
-  // message pipe already bound to this pointer.
-  SynchronousInterfacePtr& operator=(SynchronousInterfacePtr&& other) = default;
-
-  static SynchronousInterfacePtr<Interface> Create(
-      InterfaceHandle<Interface> handle) {
-    return SynchronousInterfacePtr<Interface>(std::move(handle));
-  }
-
-  // Closes the bound message pipe (if any).
-  void reset() { *this = SynchronousInterfacePtr<Interface>(); }
-
-  // Returns a raw pointer to the local proxy. Caller does not take ownership.
-  // Note that the local proxy is thread hostile, as stated above.
-  typename Interface::Synchronous_* get() { return proxy_.get(); }
-
-  typename Interface::Synchronous_* operator->() {
-    MOJO_DCHECK(connector_);
-    MOJO_DCHECK(proxy_);
-    return proxy_.get();
-  }
-  typename Interface::Synchronous_& operator*() { return *operator->(); }
-
-  // Returns whether or not this SynchronousInterfacePtr is bound to a message
-  // pipe.
-  bool is_bound() const { return connector_ && connector_->is_valid(); }
-  explicit operator bool() const { return is_bound(); }
-
-  uint32_t version() const { return version_; }
-
-  // Unbinds the SynchronousInterfacePtr and returns the underlying
-  // InterfaceHandle for the interface.
-  InterfaceHandle<Interface> PassInterfaceHandle() {
-    InterfaceHandle<Interface> handle(connector_->PassHandle(), version_);
-    reset();
-    return handle;
-  }
-
- private:
-  // We save the version_ here before we pass the underlying message pipe handle
-  // to |connector_|.
-  uint32_t version_;
-
-  // A simple I/O interface we supply to the generated |proxy_| so it doesn't
-  // have to know how to write mojo message.
-  std::unique_ptr<internal::SynchronousConnector> connector_;
-  // |proxy_| must outlive |connector_|, so make sure it is declared in this
-  // order.
-  std::unique_ptr<typename Interface::Synchronous_::Proxy_> proxy_;
-
-  SynchronousInterfacePtr(InterfaceHandle<Interface> handle)
-      : version_(handle.version()) {
-    connector_.reset(new internal::SynchronousConnector(handle.PassHandle()));
-
-    mojo::internal::MessageValidatorList validators;
-    validators.push_back(std::unique_ptr<mojo::internal::MessageValidator>(
-        new mojo::internal::MessageHeaderValidator));
-    validators.push_back(std::unique_ptr<mojo::internal::MessageValidator>(
-        new typename Interface::ResponseValidator_));
-
-    proxy_.reset(new typename Interface::Synchronous_::Proxy_(
-        connector_.get(), std::move(validators)));
-  }
-
-  MOJO_MOVE_ONLY_TYPE(SynchronousInterfacePtr);
-};
-
-// Creates a new message pipe over which Interface is to be served. Binds the
-// specified SynchronousInterfacePtr to one end of the message pipe, and returns
-// an InterfaceRequest bound to the other. The SynchronousInterfacePtr should be
-// passed to the client, and the InterfaceRequest should be passed to whatever
-// will provide the implementation. Unlike InterfacePtr<>, invocations on
-// SynchronousInterfacePtr<> will block until a response is received, so the
-// user must pass off InterfaceRequest<> to an implementation before issuing any
-// calls.
-//
-// Example:
-// ========
-// Given the following interface
-//   interface Echo {
-//     EchoString(string str) => (string value);
-//   }
-//
-// The client would have code similar to the following:
-//
-//   SynchronousInterfacePtr<Echo> client;
-//   InterfaceRequest<Echo> impl = GetSynchronousProxy(&client);
-//   // .. pass |impl| off to an implementation.
-//   mojo::String out;
-//   client->EchoString("hello!", &out);
-//
-// TODO(vardhan): Consider renaming this function, along with her sister
-// |GetProxy()| functions. Maybe `MakeSyncProxy()`?
-template <typename Interface>
-InterfaceRequest<Interface> GetSynchronousProxy(
-    SynchronousInterfacePtr<Interface>* ptr) {
-  InterfaceHandle<Interface> iface_handle;
-  auto retval = GetProxy(&iface_handle);
-  *ptr = SynchronousInterfacePtr<Interface>::Create(std::move(iface_handle));
-  return retval;
-}
-
-}  // namespace mojo
-
-#endif  // MOJO_PUBLIC_CPP_BINDINGS_SYNCHRONOUS_INTERFACE_PTR_H_