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diff --git a/third_party/libwebrtc/rtc_base/stream.h b/third_party/libwebrtc/rtc_base/stream.h
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+++ b/third_party/libwebrtc/rtc_base/stream.h
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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.
+ */
+
+#ifndef RTC_BASE_STREAM_H_
+#define RTC_BASE_STREAM_H_
+
+#include <memory>
+
+#include "rtc_base/buffer.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 };
+
+class RTC_EXPORT StreamInterface {
+ public:
+  virtual ~StreamInterface() {}
+
+  StreamInterface(const StreamInterface&) = delete;
+  StreamInterface& operator=(const StreamInterface&) = delete;
+
+  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;
+
+  // Return true if flush is successful.
+  virtual bool Flush();
+
+  //
+  // CONVENIENCE METHODS
+  //
+  // 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);
+
+ protected:
+  StreamInterface();
+};
+
+}  // namespace rtc
+
+#endif  // RTC_BASE_STREAM_H_