121 lines
4.9 KiB
C++
121 lines
4.9 KiB
C++
/*
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* Copyright 2004 The WebRTC Project Authors. All rights reserved.
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*
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* Use of this source code is governed by a BSD-style license
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* that can be found in the LICENSE file in the root of the source
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* tree. An additional intellectual property rights grant can be found
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* in the file PATENTS. All contributing project authors may
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* be found in the AUTHORS file in the root of the source tree.
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*/
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#ifndef RTC_BASE_STREAM_H_
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#define RTC_BASE_STREAM_H_
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#include <memory>
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#include "rtc_base/buffer.h"
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#include "rtc_base/constructor_magic.h"
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#include "rtc_base/message_handler.h"
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#include "rtc_base/system/rtc_export.h"
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#include "rtc_base/third_party/sigslot/sigslot.h"
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#include "rtc_base/thread.h"
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namespace rtc {
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///////////////////////////////////////////////////////////////////////////////
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// StreamInterface is a generic asynchronous stream interface, supporting read,
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// write, and close operations, and asynchronous signalling of state changes.
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// The interface is designed with file, memory, and socket implementations in
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// mind. Some implementations offer extended operations, such as seeking.
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///////////////////////////////////////////////////////////////////////////////
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// The following enumerations are declared outside of the StreamInterface
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// class for brevity in use.
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// The SS_OPENING state indicates that the stream will signal open or closed
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// in the future.
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enum StreamState { SS_CLOSED, SS_OPENING, SS_OPEN };
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// Stream read/write methods return this value to indicate various success
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// and failure conditions described below.
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enum StreamResult { SR_ERROR, SR_SUCCESS, SR_BLOCK, SR_EOS };
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// StreamEvents are used to asynchronously signal state transitionss. The flags
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// may be combined.
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// SE_OPEN: The stream has transitioned to the SS_OPEN state
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// SE_CLOSE: The stream has transitioned to the SS_CLOSED state
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// SE_READ: Data is available, so Read is likely to not return SR_BLOCK
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// SE_WRITE: Data can be written, so Write is likely to not return SR_BLOCK
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enum StreamEvent { SE_OPEN = 1, SE_READ = 2, SE_WRITE = 4, SE_CLOSE = 8 };
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class RTC_EXPORT StreamInterface {
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public:
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virtual ~StreamInterface() {}
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virtual StreamState GetState() const = 0;
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// Read attempts to fill buffer of size buffer_len. Write attempts to send
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// data_len bytes stored in data. The variables read and write are set only
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// on SR_SUCCESS (see below). Likewise, error is only set on SR_ERROR.
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// Read and Write return a value indicating:
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// SR_ERROR: an error occurred, which is returned in a non-null error
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// argument. Interpretation of the error requires knowledge of the
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// stream's concrete type, which limits its usefulness.
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// SR_SUCCESS: some number of bytes were successfully written, which is
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// returned in a non-null read/write argument.
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// SR_BLOCK: the stream is in non-blocking mode, and the operation would
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// block, or the stream is in SS_OPENING state.
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// SR_EOS: the end-of-stream has been reached, or the stream is in the
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// SS_CLOSED state.
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virtual StreamResult Read(void* buffer,
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size_t buffer_len,
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size_t* read,
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int* error) = 0;
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virtual StreamResult Write(const void* data,
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size_t data_len,
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size_t* written,
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int* error) = 0;
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// Attempt to transition to the SS_CLOSED state. SE_CLOSE will not be
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// signalled as a result of this call.
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virtual void Close() = 0;
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// Streams may signal one or more StreamEvents to indicate state changes.
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// The first argument identifies the stream on which the state change occured.
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// The second argument is a bit-wise combination of StreamEvents.
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// If SE_CLOSE is signalled, then the third argument is the associated error
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// code. Otherwise, the value is undefined.
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// Note: Not all streams will support asynchronous event signalling. However,
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// SS_OPENING and SR_BLOCK returned from stream member functions imply that
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// certain events will be raised in the future.
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sigslot::signal3<StreamInterface*, int, int> SignalEvent;
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// Return true if flush is successful.
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virtual bool Flush();
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//
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// CONVENIENCE METHODS
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//
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// These methods are implemented in terms of other methods, for convenience.
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//
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// WriteAll is a helper function which repeatedly calls Write until all the
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// data is written, or something other than SR_SUCCESS is returned. Note that
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// unlike Write, the argument 'written' is always set, and may be non-zero
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// on results other than SR_SUCCESS. The remaining arguments have the
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// same semantics as Write.
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StreamResult WriteAll(const void* data,
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size_t data_len,
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size_t* written,
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int* error);
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protected:
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StreamInterface();
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private:
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RTC_DISALLOW_COPY_AND_ASSIGN(StreamInterface);
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};
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} // namespace rtc
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#endif // RTC_BASE_STREAM_H_
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