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event_stream_handler.h
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1 // Copyright 2013 The Flutter Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #ifndef FLUTTER_SHELL_PLATFORM_COMMON_CLIENT_WRAPPER_INCLUDE_FLUTTER_EVENT_STREAM_HANDLER_H_
6 #define FLUTTER_SHELL_PLATFORM_COMMON_CLIENT_WRAPPER_INCLUDE_FLUTTER_EVENT_STREAM_HANDLER_H_
7
8 #include <memory>
9 #include <string>
10
11 #include "event_sink.h"
12
13 namespace flutter {
14
15 class EncodableValue;
16
17 template <typename T = EncodableValue>
18 struct StreamHandlerError {
19 const std::string error_code;
20 const std::string error_message;
21 const std::unique_ptr<T> error_details;
22
23 StreamHandlerError(const std::string& error_code,
24 const std::string& error_message,
25 std::unique_ptr<T>&& error_details)
26 : error_code(error_code),
27 error_message(error_message),
28 error_details(std::move(error_details)) {}
29 };
30
31 // Handler for stream setup and teardown requests.
32 // Implementations must be prepared to accept sequences of alternating calls to
33 // OnListen() and OnCancel(). Implementations should ideally consume no
34 // resources when the last such call is not OnListen(). In typical situations,
35 // this means that the implementation should register itself with
36 // platform-specific event sources OnListen() and deregister again OnCancel().
37 template <typename T = EncodableValue>
38 class StreamHandler {
39 public:
40 StreamHandler() = default;
41 virtual ~StreamHandler() = default;
42
43 // Prevent copying.
44 StreamHandler(StreamHandler const&) = delete;
45 StreamHandler& operator=(StreamHandler const&) = delete;
46
47 // Handles a request to set up an event stream. Returns nullptr on success,
48 // or an error on failure.
49 // |arguments| is stream configuration arguments and
50 // |events| is an EventSink for emitting events to the Flutter receiver.
51 std::unique_ptr<StreamHandlerError<T>> OnListen(
52 const T* arguments,
53 std::unique_ptr<EventSink<T>>&& events) {
54 return OnListenInternal(arguments, std::move(events));
55 }
56
57 // Handles a request to tear down the most recently created event stream.
58 // Returns nullptr on success, or an error on failure.
59 // |arguments| is stream configuration arguments.
60 std::unique_ptr<StreamHandlerError<T>> OnCancel(const T* arguments) {
61 return OnCancelInternal(arguments);
62 }
63
64 protected:
65 // Implementation of the public interface, to be provided by subclasses.
66 virtual std::unique_ptr<StreamHandlerError<T>> OnListenInternal(
67 const T* arguments,
68 std::unique_ptr<EventSink<T>>&& events) = 0;
69
70 // Implementation of the public interface, to be provided by subclasses.
71 virtual std::unique_ptr<StreamHandlerError<T>> OnCancelInternal(
72 const T* arguments) = 0;
73 };
74
75 } // namespace flutter
76
77 #endif // FLUTTER_SHELL_PLATFORM_COMMON_CLIENT_WRAPPER_INCLUDE_FLUTTER_EVENT_STREAM_HANDLER_H_
flutter::EventSink< T >
flutter::StreamHandler
Definition: event_stream_handler.h:38
flutter::StreamHandler::operator=
StreamHandler & operator=(StreamHandler const &)=delete
flutter::StreamHandler::OnListen
std::unique_ptr< StreamHandlerError< T > > OnListen(const T *arguments, std::unique_ptr< EventSink< T >> &&events)
Definition: event_stream_handler.h:51
flutter::StreamHandler::StreamHandler
StreamHandler()=default
flutter::StreamHandler::~StreamHandler
virtual ~StreamHandler()=default
flutter::StreamHandler::OnCancel
std::unique_ptr< StreamHandlerError< T > > OnCancel(const T *arguments)
Definition: event_stream_handler.h:60
flutter::StreamHandler::StreamHandler
StreamHandler(StreamHandler const &)=delete
flutter::StreamHandler::OnCancelInternal
virtual std::unique_ptr< StreamHandlerError< T > > OnCancelInternal(const T *arguments)=0
flutter::StreamHandler::OnListenInternal
virtual std::unique_ptr< StreamHandlerError< T > > OnListenInternal(const T *arguments, std::unique_ptr< EventSink< T >> &&events)=0
event_sink.h
flutter
Definition: accessibility_bridge.cc:14
flutter::StreamHandlerError
Definition: event_stream_handler.h:18
flutter::StreamHandlerError::error_code
const std::string error_code
Definition: event_stream_handler.h:19
flutter::StreamHandlerError::error_message
const std::string error_message
Definition: event_stream_handler.h:20
flutter::StreamHandlerError::StreamHandlerError
StreamHandlerError(const std::string &error_code, const std::string &error_message, std::unique_ptr< T > &&error_details)
Definition: event_stream_handler.h:23
flutter::StreamHandlerError::error_details
const std::unique_ptr< T > error_details
Definition: event_stream_handler.h:21