DevTools: provide an option to return traces as streams

content/browser/devtools/devtools_io_context.h

+// Copyright 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.
+
+#include <map>
+
+#include "base/callback.h"
+#include "base/files/file.h"
+#include "base/memory/ref_counted_delete_on_message_loop.h"
+#include "base/memory/ref_counted_memory.h"
+
+namespace content {
+namespace devtools {
+
+class DevToolsIOContext {
+ public:
+  class Stream : public base::RefCountedDeleteOnMessageLoop<Stream> {
+   public:
+    enum Status {
+      StatusSuccess,
+      StatusEOF,
+      StatusFailure
+    };
+
+    using ReadCallback = base::Callback<
+        void(const scoped_refptr<base::RefCountedString>& data, int status)>;
+
+    void Read(off_t position, size_t max_size, ReadCallback callback);
+    void Append(const scoped_refptr<base::RefCountedString>& data);
+    const std::string& handle() const { return handle_; }
+
+   private:
+    Stream();
+    ~Stream();
+    friend class DevToolsIOContext;
+    friend class base::RefCountedDeleteOnMessageLoop<Stream>;
+    friend class base::DeleteHelper<Stream>;
+
+    void ReadOnFileThread(off_t pos, size_t max_size, ReadCallback callback);
+    void AppendOnFileThread(const scoped_refptr<base::RefCountedString>& data);
+    bool InitOnFileThreadIfNeeded();
+
+    const std::string handle_;
+    base::File file_;
+    bool had_errors_;
+    off_t last_read_pos_;
+  };
+
+  DevToolsIOContext();
+  ~DevToolsIOContext();
+
+  scoped_refptr<Stream> CreateTempFileBackedStream();
+  scoped_refptr<Stream> GetByHandle(const std::string& handle);
+  bool Close(const std::string& handle);
+  void DiscardAllStreams();
+
+ private:
+  using StreamsMap = std::map<std::string, scoped_refptr<Stream>>;
+  StreamsMap streams_;
+};
+
+}  // namespace devtools
+}  // namespace content