1 /*
2  *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
3  *
4  *  Use of this source code is governed by a BSD-style license
5  *  that can be found in the LICENSE file in the root of the source
6  *  tree. An additional intellectual property rights grant can be found
7  *  in the file PATENTS.  All contributing project authors may
8  *  be found in the AUTHORS file in the root of the source tree.
9  */
10 
11 #ifndef RTC_BASE_STREAM_H_
12 #define RTC_BASE_STREAM_H_
13 
14 #include <memory>
15 
16 #include "rtc_base/buffer.h"
17 #include "rtc_base/constructor_magic.h"
18 #include "rtc_base/message_handler.h"
19 #include "rtc_base/system/rtc_export.h"
20 #include "rtc_base/third_party/sigslot/sigslot.h"
21 #include "rtc_base/thread.h"
22 
23 namespace rtc {
24 
25 ///////////////////////////////////////////////////////////////////////////////
26 // StreamInterface is a generic asynchronous stream interface, supporting read,
27 // write, and close operations, and asynchronous signalling of state changes.
28 // The interface is designed with file, memory, and socket implementations in
29 // mind.  Some implementations offer extended operations, such as seeking.
30 ///////////////////////////////////////////////////////////////////////////////
31 
32 // The following enumerations are declared outside of the StreamInterface
33 // class for brevity in use.
34 
35 // The SS_OPENING state indicates that the stream will signal open or closed
36 // in the future.
37 enum StreamState { SS_CLOSED, SS_OPENING, SS_OPEN };
38 
39 // Stream read/write methods return this value to indicate various success
40 // and failure conditions described below.
41 enum StreamResult { SR_ERROR, SR_SUCCESS, SR_BLOCK, SR_EOS };
42 
43 // StreamEvents are used to asynchronously signal state transitionss.  The flags
44 // may be combined.
45 //  SE_OPEN: The stream has transitioned to the SS_OPEN state
46 //  SE_CLOSE: The stream has transitioned to the SS_CLOSED state
47 //  SE_READ: Data is available, so Read is likely to not return SR_BLOCK
48 //  SE_WRITE: Data can be written, so Write is likely to not return SR_BLOCK
49 enum StreamEvent { SE_OPEN = 1, SE_READ = 2, SE_WRITE = 4, SE_CLOSE = 8 };
50 
51 struct StreamEventData : public MessageData {
52   int events, error;
StreamEventDataStreamEventData53   StreamEventData(int ev, int er) : events(ev), error(er) {}
54 };
55 
56 class RTC_EXPORT StreamInterface : public MessageHandler {
57  public:
58   enum { MSG_POST_EVENT = 0xF1F1, MSG_MAX = MSG_POST_EVENT };
59 
60   ~StreamInterface() override;
61 
62   virtual StreamState GetState() const = 0;
63 
64   // Read attempts to fill buffer of size buffer_len.  Write attempts to send
65   // data_len bytes stored in data.  The variables read and write are set only
66   // on SR_SUCCESS (see below).  Likewise, error is only set on SR_ERROR.
67   // Read and Write return a value indicating:
68   //  SR_ERROR: an error occurred, which is returned in a non-null error
69   //    argument.  Interpretation of the error requires knowledge of the
70   //    stream's concrete type, which limits its usefulness.
71   //  SR_SUCCESS: some number of bytes were successfully written, which is
72   //    returned in a non-null read/write argument.
73   //  SR_BLOCK: the stream is in non-blocking mode, and the operation would
74   //    block, or the stream is in SS_OPENING state.
75   //  SR_EOS: the end-of-stream has been reached, or the stream is in the
76   //    SS_CLOSED state.
77   virtual StreamResult Read(void* buffer,
78                             size_t buffer_len,
79                             size_t* read,
80                             int* error) = 0;
81   virtual StreamResult Write(const void* data,
82                              size_t data_len,
83                              size_t* written,
84                              int* error) = 0;
85   // Attempt to transition to the SS_CLOSED state.  SE_CLOSE will not be
86   // signalled as a result of this call.
87   virtual void Close() = 0;
88 
89   // Streams may signal one or more StreamEvents to indicate state changes.
90   // The first argument identifies the stream on which the state change occured.
91   // The second argument is a bit-wise combination of StreamEvents.
92   // If SE_CLOSE is signalled, then the third argument is the associated error
93   // code.  Otherwise, the value is undefined.
94   // Note: Not all streams will support asynchronous event signalling.  However,
95   // SS_OPENING and SR_BLOCK returned from stream member functions imply that
96   // certain events will be raised in the future.
97   sigslot::signal3<StreamInterface*, int, int> SignalEvent;
98 
99   // Like calling SignalEvent, but posts a message to the specified thread,
100   // which will call SignalEvent.  This helps unroll the stack and prevent
101   // re-entrancy.
102   void PostEvent(Thread* t, int events, int err);
103   // Like the aforementioned method, but posts to the current thread.
104   void PostEvent(int events, int err);
105 
106   // Return true if flush is successful.
107   virtual bool Flush();
108 
109   //
110   // CONVENIENCE METHODS
111   //
112   // These methods are implemented in terms of other methods, for convenience.
113   //
114 
115   // WriteAll is a helper function which repeatedly calls Write until all the
116   // data is written, or something other than SR_SUCCESS is returned.  Note that
117   // unlike Write, the argument 'written' is always set, and may be non-zero
118   // on results other than SR_SUCCESS.  The remaining arguments have the
119   // same semantics as Write.
120   StreamResult WriteAll(const void* data,
121                         size_t data_len,
122                         size_t* written,
123                         int* error);
124 
125  protected:
126   StreamInterface();
127 
128   // MessageHandler Interface
129   void OnMessage(Message* msg) override;
130 
131  private:
132   RTC_DISALLOW_COPY_AND_ASSIGN(StreamInterface);
133 };
134 
135 ///////////////////////////////////////////////////////////////////////////////
136 // StreamAdapterInterface is a convenient base-class for adapting a stream.
137 // By default, all operations are pass-through.  Override the methods that you
138 // require adaptation.  Streams should really be upgraded to reference-counted.
139 // In the meantime, use the owned flag to indicate whether the adapter should
140 // own the adapted stream.
141 ///////////////////////////////////////////////////////////////////////////////
142 
143 class StreamAdapterInterface : public StreamInterface,
144                                public sigslot::has_slots<> {
145  public:
146   explicit StreamAdapterInterface(StreamInterface* stream, bool owned = true);
147 
148   // Core Stream Interface
149   StreamState GetState() const override;
150   StreamResult Read(void* buffer,
151                     size_t buffer_len,
152                     size_t* read,
153                     int* error) override;
154   StreamResult Write(const void* data,
155                      size_t data_len,
156                      size_t* written,
157                      int* error) override;
158   void Close() override;
159 
160   bool Flush() override;
161 
162   void Attach(StreamInterface* stream, bool owned = true);
163   StreamInterface* Detach();
164 
165  protected:
166   ~StreamAdapterInterface() override;
167 
168   // Note that the adapter presents itself as the origin of the stream events,
169   // since users of the adapter may not recognize the adapted object.
170   virtual void OnEvent(StreamInterface* stream, int events, int err);
stream()171   StreamInterface* stream() { return stream_; }
172 
173  private:
174   StreamInterface* stream_;
175   bool owned_;
176   RTC_DISALLOW_COPY_AND_ASSIGN(StreamAdapterInterface);
177 };
178 
179 }  // namespace rtc
180 
181 #endif  // RTC_BASE_STREAM_H_
182