1 // Copyright (c) 2011 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 // A RendererNetPredictor instance is maintained for each RenderThread. 6 // URL strings are typically added to the embedded queue during rendering. 7 // The first addition to the queue (transitioning from empty to having 8 // some names) causes a processing task to be added to the Renderer Thread. 9 // The processing task gathers all buffered names, and send them via IPC 10 // to the browser, so that DNS lookups can be performed before the user attempts 11 // to traverse a link. 12 // This class removed some duplicates, and discards numeric IP addresss 13 // (which wouldn't looked up in DNS anyway). 14 // To limit the time during the processing task (and avoid stalling the Render 15 // thread), several limits are placed on how much of the queue to process. 16 // If the processing task is not able to completely empty the queue, it 17 // schedules a future continuation of the task, and keeps the map of already 18 // sent names. If the entire queue is processed, then the list of "sent names" 19 // is cleared so that future gatherings might again pass along the same names. 20 21 #ifndef CHROME_RENDERER_NET_RENDERER_NET_PREDICTOR_H_ 22 #define CHROME_RENDERER_NET_RENDERER_NET_PREDICTOR_H_ 23 24 #include <map> 25 #include <string> 26 27 #include "base/basictypes.h" 28 #include "base/memory/weak_ptr.h" 29 #include "chrome/renderer/net/predictor_queue.h" 30 31 class RendererNetPredictor { 32 public: 33 RendererNetPredictor(); 34 ~RendererNetPredictor(); 35 36 // Push a name into the queue to be resolved. 37 void Resolve(const char* name, size_t length); 38 39 // SubmitHosts processes the buffered names, and submits them for DNS 40 // prefetching. 41 // Note that browser process may decide which names should be looked up (to 42 // pre-warm the cache) based on what has been (or not been) looked up 43 // recently. 44 // If sending for DNS lookup is incomplete (queue is not empty, or not all 45 // names in map are sent, or ...) then a task to continue processing is 46 // sent to our thread loop. 47 void SubmitHostnames(); 48 49 // The following is private, but exposed for testing purposes only. 50 static bool is_numeric_ip(const char* name, size_t length); 51 52 private: 53 // ExtractBufferedNames pulls names from queue into the map, reducing or 54 // eliminating a waiting queue. 55 // The size_goal argument can be used to reduce the amount of 56 // processing done in this method, and can leave some data 57 // in the buffer under some circumstances. 58 // If size_goal is zero, then extraction proceeds until 59 // the queue is empty. If size goal is positive, then 60 // extraction continues until the domain_map_ contains 61 // at least the specified number of names, or the buffer is empty. 62 void ExtractBufferedNames(size_t size_goal = 0); 63 64 // DnsPrefetchNames does not check the buffer, and just sends names 65 // that are already collected in the domain_map_ for DNS lookup. 66 // If max_count is zero, then all available names are sent; and 67 // if positive, then at most max_count names will be sent. 68 void DnsPrefetchNames(size_t max_count = 0); 69 70 // Reset() restores initial state provided after construction. 71 // This discards ALL queue entries, and map entries. 72 void Reset(); 73 74 // We use c_string_queue_ to hold lists of names supplied typically) by the 75 // renderer. It queues the names, at minimal cost to the renderer's thread, 76 // and allows this class to process them when time permits (in a later task). 77 DnsQueue c_string_queue_; 78 79 80 // domain_map_ contains (for each domain) one of the next two constants, 81 // depending on whether we have asked the browser process to do the actual 82 // DNS lookup. 83 static const int kLookupRequested = 0x1; 84 static const int kPending = 0x0; 85 typedef std::map<std::string, int> DomainUseMap; 86 DomainUseMap domain_map_; 87 88 // Cache a tally of the count of names that haven't yet been sent 89 // for DNS pre-fetching. Note that we *could* recalculate this 90 // count by iterating over domain_map_, looking for even values. 91 size_t new_name_count_; 92 93 // We have some metrics to examine performance. We might use 94 // these metrics to modify buffer counts etc. some day. 95 int buffer_full_discard_count_; 96 int numeric_ip_discard_count_; 97 98 base::WeakPtrFactory<RendererNetPredictor> weak_factory_; 99 100 DISALLOW_COPY_AND_ASSIGN(RendererNetPredictor); 101 }; // class RendererNetPredictor 102 103 #endif // CHROME_RENDERER_NET_RENDERER_NET_PREDICTOR_H_ 104