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+// Copyright (c) 2010 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.
+
+// A RendererNetPredictor instance is maintained for each RenderThread.
+// URL strings are typically added to the embedded queue during rendering.
+// The first addition to the queue (transitioning from empty to having
+// some names) causes a processing task to be added to the Renderer Thread.
+// The processing task gathers all buffered names, and send them via IPC
+// to the browser, so that DNS lookups can be performed before the user attempts
+// to traverse a link.
+// This class removed some duplicates, and discards numeric IP addresss
+// (which wouldn't looked up in DNS anyway).
+// To limit the time during the processing task (and avoid stalling the Render
+// thread), several limits are placed on how much of the queue to process.
+// If the processing task is not able to completely empty the queue, it
+// schedules a future continuation of the task, and keeps the map of already
+// sent names.  If the entire queue is processed, then the list of "sent names"
+// is cleared so that future gatherings might again pass along the same names.
+
+#ifndef CHROME_RENDERER_NET_RENDERER_NET_PREDICTOR_H_
+#define CHROME_RENDERER_NET_RENDERER_NET_PREDICTOR_H_
+
+#include <map>
+#include <string>
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/task.h"
+#include "chrome/renderer/net/predictor_queue.h"
+
+// Global API consists to do Prefetching in renderer.  This uses IPC to reach
+// the Browser's global functions.
+void DnsPrefetchCString(const char* hostname, size_t length);
+
+class RendererNetPredictor {
+ public:
+  RendererNetPredictor();
+
+  ~RendererNetPredictor() {}
+
+  // Push a name into the queue to be resolved.
+  void Resolve(const char* name, size_t length);
+
+  // SubmitHosts processes the buffered names, and submits them for DNS
+  // prefetching.
+  // Note that browser process may decide which names should be looked up (to
+  // pre-warm the cache) based on what has been (or not been) looked up
+  // recently.
+  // If sending for DNS lookup is incomplete (queue is not empty, or not all
+  // names in map are sent, or ...) then a task to continue processing is
+  // sent to our thread loop.
+  void SubmitHostnames();
+
+  // The following is private, but exposed for testing purposes only.
+  static bool is_numeric_ip(const char* name, size_t length);
+
+ private:
+  // ExtractBufferedNames pulls names from queue into the map, reducing or
+  // eliminating a waiting queue.
+  // The size_goal argument can be used to reduce the amount of
+  // processing done in this method, and can leave some data
+  // in the buffer under some circumstances.
+  // If size_goal is zero, then extraction proceeds until
+  // the queue is empty.  If size goal is positive, then
+  // extraction continues until the domain_map_ contains
+  // at least the specified number of names, or the buffer is empty.
+  void ExtractBufferedNames(size_t size_goal = 0);
+
+  // DnsPrefetchNames does not check the buffer, and just sends names
+  // that are already collected in the domain_map_ for DNS lookup.
+  // If max_count is zero, then all available names are sent; and
+  // if positive, then at most max_count names will be sent.
+  void DnsPrefetchNames(size_t max_count = 0);
+
+  // Reset() restores initial state provided after construction.
+  // This discards ALL queue entries, and map entries.
+  void Reset();
+
+  // We use c_string_queue_ to hold lists of names supplied typically) by the
+  // renderer.  It queues the names, at minimal cost to the renderer's thread,
+  // and allows this class to process them when time permits (in a later task).
+  DnsQueue c_string_queue_;
+
+
+  // domain_map_ contains (for each domain) one of the next two constants,
+  // depending on whether we have asked the browser process to do the actual
+  // DNS lookup.
+  static const int kLookupRequested = 0x1;
+  static const int kPending = 0x0;
+  typedef std::map<std::string, int> DomainUseMap;
+  DomainUseMap domain_map_;
+
+  // Cache a tally of the count of names that haven't yet been sent
+  // for DNS pre-fetching.  Note that we *could* recalculate this
+  // count by iterating over domain_map_, looking for even values.
+  size_t new_name_count_;
+
+  // We have some metrics to examine performance.  We might use
+  // these metrics to modify buffer counts etc. some day.
+  int buffer_full_discard_count_;
+  int numeric_ip_discard_count_;
+
+  ScopedRunnableMethodFactory<RendererNetPredictor> renderer_predictor_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(RendererNetPredictor);
+};  // class RendererNetPredictor
+
+#endif  // CHROME_RENDERER_NET_RENDERER_NET_PREDICTOR_H_