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
VisitTracker()19 VisitTracker::VisitTracker() {
20 }
21
~VisitTracker()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.
GetLastVisit(const void * host,int32 page_id,const GURL & referrer)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
AddVisit(const void * host,int32 page_id,const GURL & url,VisitID visit_id)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
NotifyRenderProcessHostDestruction(const void * host)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
CleanupTransitionList(TransitionList * transitions)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