Add out-of-process memory logging stream parsing.

chrome/profiling/memlog_stream_parser.h

+// Copyright 2017 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 CHROME_PROFILING_MEMLOG_STREAM_PARSER_H_
+#define CHROME_PROFILING_MEMLOG_STREAM_PARSER_H_
+
+#include <deque>
+
+#include "base/macros.h"
+#include "chrome/profiling/memlog_receiver.h"
+#include "chrome/profiling/memlog_stream_receiver.h"
+
+namespace profiling {
+
+// Parses a memory stream. Refcounted via StreamReceiver.
+class MemlogStreamParser : public MemlogStreamReceiver {
+ public:
+  // Receiver must outlive this class.
+  explicit MemlogStreamParser(MemlogReceiver* receiver);
+  ~MemlogStreamParser() override;
+
+  // StreamReceiver implementation.
+  void OnStreamData(std::unique_ptr<char[]> data, size_t sz) override;
+  void OnStreamComplete() override;
+
+ private:
+  struct Block {
+    Block(std::unique_ptr<char[]> d, size_t s);
+
+    std::unique_ptr<char[]> data;
+    size_t size;
+  };
+
+  enum ReadStatus {
+    READ_OK,      // Read OK.
+    READ_ERROR,   // Fatal error, don't send more data.
+    READ_NO_DATA  // Not enough data, try again when we get more
+  };
+
+  // Returns true if the given number of bytes are available now.
+  bool AreBytesAvailable(size_t count) const;
+
+  // Returns false if not enough bytes are available. On failure, the dest
+  // buffer will be in an undefined state (it may be written partially).
+  bool PeekBytes(size_t count, void* dest) const;
+  bool ReadBytes(size_t count, void* dest);
+  void ConsumeBytes(size_t count);  // Bytes must be available.
+
+  ReadStatus ParseHeader();
+  ReadStatus ParseAlloc();
+  ReadStatus ParseFree();
+
+  MemlogReceiver* receiver_;  // Not owned by this class.
+
+  std::deque<Block> blocks_;
+
+  bool received_header_ = false;
+
+  // Current offset into blocks_[0] of the next packet to process.
+  size_t block_zero_offset_ = 0;
+
+  DISALLOW_COPY_AND_ASSIGN(MemlogStreamParser);
+};
+
+}  // namespace profiling
+
+#endif  // CHROME_PROFILING_MEMLOG_STREAM_PARSER_H_