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* Copyright 2004 The WebRTC Project Authors. All rights reserved.
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
#include <memory>
#include "rtc_base/buffer.h"
#include "rtc_base/constructor_magic.h"
#include "rtc_base/message_handler.h"
#include "rtc_base/system/rtc_export.h"
#include "rtc_base/third_party/sigslot/sigslot.h"
#include "rtc_base/thread.h"
namespace rtc {
// StreamInterface is a generic asynchronous stream interface, supporting read,
// write, and close operations, and asynchronous signalling of state changes.
// The interface is designed with file, memory, and socket implementations in
// mind. Some implementations offer extended operations, such as seeking.
// The following enumerations are declared outside of the StreamInterface
// class for brevity in use.
// The SS_OPENING state indicates that the stream will signal open or closed
// in the future.
enum StreamState { SS_CLOSED, SS_OPENING, SS_OPEN };
// Stream read/write methods return this value to indicate various success
// and failure conditions described below.
enum StreamResult { SR_ERROR, SR_SUCCESS, SR_BLOCK, SR_EOS };
// StreamEvents are used to asynchronously signal state transitionss. The flags
// may be combined.
// SE_OPEN: The stream has transitioned to the SS_OPEN state
// SE_CLOSE: The stream has transitioned to the SS_CLOSED state
// SE_READ: Data is available, so Read is likely to not return SR_BLOCK
// SE_WRITE: Data can be written, so Write is likely to not return SR_BLOCK
enum StreamEvent { SE_OPEN = 1, SE_READ = 2, SE_WRITE = 4, SE_CLOSE = 8 };
struct StreamEventData : public MessageData {
int events, error;
StreamEventData(int ev, int er) : events(ev), error(er) {}
class RTC_EXPORT StreamInterface : public MessageHandlerAutoCleanup {
~StreamInterface() override;
virtual StreamState GetState() const = 0;
// Read attempts to fill buffer of size buffer_len. Write attempts to send
// data_len bytes stored in data. The variables read and write are set only
// on SR_SUCCESS (see below). Likewise, error is only set on SR_ERROR.
// Read and Write return a value indicating:
// SR_ERROR: an error occurred, which is returned in a non-null error
// argument. Interpretation of the error requires knowledge of the
// stream's concrete type, which limits its usefulness.
// SR_SUCCESS: some number of bytes were successfully written, which is
// returned in a non-null read/write argument.
// SR_BLOCK: the stream is in non-blocking mode, and the operation would
// block, or the stream is in SS_OPENING state.
// SR_EOS: the end-of-stream has been reached, or the stream is in the
// SS_CLOSED state.
virtual StreamResult Read(void* buffer,
size_t buffer_len,
size_t* read,
int* error) = 0;
virtual StreamResult Write(const void* data,
size_t data_len,
size_t* written,
int* error) = 0;
// Attempt to transition to the SS_CLOSED state. SE_CLOSE will not be
// signalled as a result of this call.
virtual void Close() = 0;
// Streams may signal one or more StreamEvents to indicate state changes.
// The first argument identifies the stream on which the state change occured.
// The second argument is a bit-wise combination of StreamEvents.
// If SE_CLOSE is signalled, then the third argument is the associated error
// code. Otherwise, the value is undefined.
// Note: Not all streams will support asynchronous event signalling. However,
// SS_OPENING and SR_BLOCK returned from stream member functions imply that
// certain events will be raised in the future.
sigslot::signal3<StreamInterface*, int, int> SignalEvent;
// Like calling SignalEvent, but posts a message to the specified thread,
// which will call SignalEvent. This helps unroll the stack and prevent
// re-entrancy.
void PostEvent(Thread* t, int events, int err);
// Like the aforementioned method, but posts to the current thread.
void PostEvent(int events, int err);
// Return true if flush is successful.
virtual bool Flush();
// These methods are implemented in terms of other methods, for convenience.
// WriteAll is a helper function which repeatedly calls Write until all the
// data is written, or something other than SR_SUCCESS is returned. Note that
// unlike Write, the argument 'written' is always set, and may be non-zero
// on results other than SR_SUCCESS. The remaining arguments have the
// same semantics as Write.
StreamResult WriteAll(const void* data,
size_t data_len,
size_t* written,
int* error);
// MessageHandler Interface
void OnMessage(Message* msg) override;
// StreamAdapterInterface is a convenient base-class for adapting a stream.
// By default, all operations are pass-through. Override the methods that you
// require adaptation. Streams should really be upgraded to reference-counted.
// In the meantime, use the owned flag to indicate whether the adapter should
// own the adapted stream.
class StreamAdapterInterface : public StreamInterface,
public sigslot::has_slots<> {
explicit StreamAdapterInterface(StreamInterface* stream, bool owned = true);
// Core Stream Interface
StreamState GetState() const override;
StreamResult Read(void* buffer,
size_t buffer_len,
size_t* read,
int* error) override;
StreamResult Write(const void* data,
size_t data_len,
size_t* written,
int* error) override;
void Close() override;
bool Flush() override;
void Attach(StreamInterface* stream, bool owned = true);
StreamInterface* Detach();
~StreamAdapterInterface() override;
// Note that the adapter presents itself as the origin of the stream events,
// since users of the adapter may not recognize the adapted object.
virtual void OnEvent(StreamInterface* stream, int events, int err);
StreamInterface* stream() { return stream_; }
StreamInterface* stream_;
bool owned_;
} // namespace rtc
#endif // RTC_BASE_STREAM_H_