1 // Copyright (c) 2006-2008 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 #include "chrome/browser/history/visit_tracker.h" 6 7 #include "base/stl_util-inl.h" 8 9 namespace history { 10 11 // When the list gets longer than 'MaxItems', CleanupTransitionList will resize 12 // the list down to 'ResizeTo' size. This is so we only do few block moves of 13 // the data rather than constantly shuffle stuff around in the vector. 14 static const size_t kMaxItemsInTransitionList = 96; 15 static const size_t kResizeBigTransitionListTo = 64; 16 COMPILE_ASSERT(kResizeBigTransitionListTo < kMaxItemsInTransitionList, 17 max_items_must_be_larger_than_resize_to); 18 19 VisitTracker::VisitTracker() { 20 } 21 22 VisitTracker::~VisitTracker() { 23 STLDeleteContainerPairSecondPointers(hosts_.begin(), hosts_.end()); 24 } 25 26 // This function is potentially slow because it may do up to two brute-force 27 // searches of the transitions list. This transitions list is kept to a 28 // relatively small number by CleanupTransitionList so it shouldn't be a big 29 // deal. However, if this ends up being noticable for performance, we may want 30 // to optimize lookup. 31 VisitID VisitTracker::GetLastVisit(const void* host, 32 int32 page_id, 33 const GURL& referrer) { 34 if (referrer.is_empty() || !host) 35 return 0; 36 37 HostList::iterator i = hosts_.find(host); 38 if (i == hosts_.end()) 39 return 0; // We don't have any entries for this host. 40 TransitionList& transitions = *i->second; 41 42 // Recall that a page ID is associated with a single session history entry. 43 // In the case of automatically loaded iframes, many visits/URLs can have the 44 // same page ID. 45 // 46 // We search backwards, starting at the current page ID, for the referring 47 // URL. This won't always be correct. For example, if a render process has 48 // the same page open in two different tabs, or even in two different frames, 49 // we can get confused about which was which. We can have the renderer 50 // report more precise referrer information in the future, but this is a 51 // hard problem and doesn't affect much in terms of real-world issues. 52 // 53 // We assume that the page IDs are increasing over time, so larger IDs than 54 // the current input ID happened in the future (this will occur if the user 55 // goes back). We can ignore future transitions because if you navigate, go 56 // back, and navigate some more, we'd like to have one node with two out 57 // edges in our visit graph. 58 for (int i = static_cast<int>(transitions.size()) - 1; i >= 0; i--) { 59 if (transitions[i].page_id <= page_id && transitions[i].url == referrer) { 60 // Found it. 61 return transitions[i].visit_id; 62 } 63 } 64 65 // We can't find the referrer. 66 return 0; 67 } 68 69 void VisitTracker::AddVisit(const void* host, 70 int32 page_id, 71 const GURL& url, 72 VisitID visit_id) { 73 TransitionList* transitions = hosts_[host]; 74 if (!transitions) { 75 transitions = new TransitionList; 76 hosts_[host] = transitions; 77 } 78 79 Transition t; 80 t.url = url; 81 t.page_id = page_id; 82 t.visit_id = visit_id; 83 transitions->push_back(t); 84 85 CleanupTransitionList(transitions); 86 } 87 88 void VisitTracker::NotifyRenderProcessHostDestruction(const void* host) { 89 HostList::iterator i = hosts_.find(host); 90 if (i == hosts_.end()) 91 return; // We don't have any entries for this host. 92 93 delete i->second; 94 hosts_.erase(i); 95 } 96 97 98 void VisitTracker::CleanupTransitionList(TransitionList* transitions) { 99 if (transitions->size() <= kMaxItemsInTransitionList) 100 return; // Nothing to do. 101 102 transitions->erase(transitions->begin(), 103 transitions->begin() + kResizeBigTransitionListTo); 104 } 105 106 } // namespace history 107
