relnote: refactoring the buffering logic in QUIC's stream sequencer.

net/quic/quic_frame_list.h

+// Copyright (c) 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef NET_QUIC_QUIC_FRAME_LIST_H_
+#define NET_QUIC_QUIC_FRAME_LIST_H_
+
+#include "net/quic/quic_frame_list.h"
+#include "net/quic/quic_protocol.h"
+
+using base::StringPiece;
+using std::string;
+using std::list;
+
+namespace net {
+
+namespace test {
+class QuicStreamSequencerPeer;
+}
+
+class NET_EXPORT_PRIVATE QuicFrameList {
+ public:
+  // A contiguous segment received by a QUIC stream.
+  struct FrameData {
+    FrameData(QuicStreamOffset offset, string segment);
+
+    const QuicStreamOffset offset;
+    string segment;
+  };
+
+  explicit QuicFrameList();
+
+  ~QuicFrameList();
+
+  // Clear the buffer such that it is in its initial, newly constructed state.
+  void Clear() { frame_list_.clear(); }
+
+  // Returns true if there is nothing to read in this buffer.
+  bool Empty() const { return frame_list_.empty(); }
+
+  // Write the supplied data to this buffer. If the write was successful,
+  // return the number of bytes written in |bytes_written|.
+  // Return QUIC_INVALID_STREAM_DATA if |data| overlaps with existing data.
+  // No data will be written.
+  // Return QUIC_NO_ERROR, if |data| is duplicated with data written previously,
+  // and |bytes_written| = 0
+  QuicErrorCode WriteAtOffset(QuicStreamOffset offset,
+                              StringPiece data,
+                              size_t* bytes_written);
+
+  // Read from this buffer into given iovec array, upto number of iov_len iovec
+  // objects.
+  // Returns the number of bytes read into iov.
+  size_t ReadvAndInvalidate(const struct iovec* iov, size_t iov_len);
+
+  // 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. ReadAndInvalidate() and WriteAtOffset() change the readable region.
+  // The return value of this function is the number of iovec entries
+  // filled into in iov. 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.
+  int GetReadableRegions(struct iovec* iov, int iov_len) const;
+
+  // Called after GetReadableRegions() to accumulate total_bytes_read_ and free
+  // up block when all data in it have been read out.
+  // Pre-requisite: bytes_used <= ReadableBytes()
+  bool IncreaseTotalReadAndInvalidate(size_t bytes_used);
+
+  // Whether there are bytes can be read out (offset == total_bytes_read_)
+  bool HasBytesToRead() const;
+
+  size_t size() const { return frame_list_.size(); }
+
+  QuicStreamOffset total_bytes_read() const { return total_bytes_read_; }
+
+ private:
+  friend class test::QuicStreamSequencerPeer;
+
+  list<FrameData>::iterator FindInsertionPoint(QuicStreamOffset offset,
+                                               size_t len);
+
+  bool FrameOverlapsBufferedData(
+      QuicStreamOffset offset,
+      size_t data_len,
+      list<FrameData>::const_iterator insertion_point) const;
+
+  bool IsDuplicate(QuicStreamOffset offset,
+                   size_t data_len,
+                   list<FrameData>::const_iterator insertion_point) const;
+
+  list<FrameData> frame_list_;
+  QuicStreamOffset total_bytes_read_ = 0;
+};
+
+}  // namespace net_quic
+
+#endif  // NET_QUIC_QUIC_FRAME_LIST_H_