Introduces QuicStreamSequencerBufferInterface with one implementation. Refactor, no behavior change.

net/quic/quic_stream_sequencer_buffer_interface.h

+#ifndef NET_QUIC_QUIC_STREAM_SEQUENCER_BUFFER_INTERFACE_H_
+#define NET_QUIC_QUIC_STREAM_SEQUENCER_BUFFER_INTERFACE_H_
+
+#include "net/quic/quic_frame_list.h"
+#include "net/quic/quic_protocol.h"
+
+using base::StringPiece;
+
+namespace net {
+
+// The QuicStreamSequencer uses an implementation of this interface to store
+// received data.
+class NET_EXPORT_PRIVATE QuicStreamSequencerBufferInterface {
+ public:
+  virtual ~QuicStreamSequencerBufferInterface() {}
+
+  // Free the space used to buffer data.
+  virtual void Clear() = 0;
+
+  // Returns true if there is nothing to read in this buffer.
+  virtual bool Empty() const = 0;
+
+  // Called to buffer new data received for this stream.  If the data was
+  // successfully buffered, returns QUIC_NO_ERROR and stores the number of
+  // bytes buffered in |bytes_buffered|. Returns an error otherwise.
+  // |timestamp| is the time the data arrived.
+  virtual QuicErrorCode OnStreamData(QuicStreamOffset offset,
+                                     StringPiece data,
+                                     QuicTime timestamp,
+                                     size_t* bytes_buffered) = 0;
+
+  // Reads from this buffer into given iovec array, up to number of iov_len
+  // iovec objects and returns the number of bytes read.
+  virtual size_t Readv(const struct iovec* iov, size_t iov_len) = 0;
+
+  // Returns the readable region of valid data in iovec format. The readable
+  // region is the buffer region where there is valid data not yet read by
+  // client.
+  // Returns the number of iovec entries in |iov| which were populated.
+  // If the region is empty, one iovec entry with 0 length
+  // is returned, and the function returns 0. If there are more readable
+  // regions than iov_size, the function only processes the first
+  // iov_size of them.
+  virtual int GetReadableRegions(struct iovec* iov, int iov_len) const = 0;
+
+  // Fills in one iovec with data which all arrived at the same time from the
+  // next readable region.
+  // Populates |timestamp| with the time that this data arrived.
+  // Returns false if there is no readable region available.
+  virtual bool GetReadableRegion(iovec* iov, QuicTime* timestamp) const = 0;
+
+  // Called after GetReadableRegions() to free up |bytes_used| space if these
+  // bytes are processed.
+  // Pre-requisite: bytes_used <= available bytes to read.
+  virtual bool MarkConsumed(size_t bytes_used) = 0;
+
+  // Deletes and records as consumed any buffered data and clear the buffer.
+  // (To be called only after sequencer's StopReading has been called.)
+  virtual size_t FlushBufferedFrames() = 0;
+
+  // Whether there are bytes can be read out.
+  virtual bool HasBytesToRead() const = 0;
+
+  // Count how many bytes have been consumed (read out of buffer).
+  virtual QuicStreamOffset BytesConsumed() const = 0;
+
+  // Count how many bytes are in buffer at this moment.
+  virtual size_t BytesBuffered() const = 0;
+};
+
+}  // namespace net
+
+#endif  // NET_QUIC_QUIC_STREAM_SEQUENCER_BUFFER_INTERFACE_H_