// Copyright (c) 2006-2008 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 "chrome/browser/history/visit_tracker.h"
#include "base/stl_util.h"
namespace history {
// When the list gets longer than 'MaxItems', CleanupTransitionList will resize
// the list down to 'ResizeTo' size. This is so we only do few block moves of
// the data rather than constantly shuffle stuff around in the vector.
static const size_t kMaxItemsInTransitionList = 96;
static const size_t kResizeBigTransitionListTo = 64;
COMPILE_ASSERT(kResizeBigTransitionListTo < kMaxItemsInTransitionList,
max_items_must_be_larger_than_resize_to);
VisitTracker::VisitTracker() {
}
VisitTracker::~VisitTracker() {
STLDeleteContainerPairSecondPointers(hosts_.begin(), hosts_.end());
}
// This function is potentially slow because it may do up to two brute-force
// searches of the transitions list. This transitions list is kept to a
// relatively small number by CleanupTransitionList so it shouldn't be a big
// deal. However, if this ends up being noticable for performance, we may want
// to optimize lookup.
VisitID VisitTracker::GetLastVisit(const void* host,
int32 page_id,
const GURL& referrer) {
if (referrer.is_empty() || !host)
return 0;
HostList::iterator i = hosts_.find(host);
if (i == hosts_.end())
return 0; // We don't have any entries for this host.
TransitionList& transitions = *i->second;
// Recall that a page ID is associated with a single session history entry.
// In the case of automatically loaded iframes, many visits/URLs can have the
// same page ID.
//
// We search backwards, starting at the current page ID, for the referring
// URL. This won't always be correct. For example, if a render process has
// the same page open in two different tabs, or even in two different frames,
// we can get confused about which was which. We can have the renderer
// report more precise referrer information in the future, but this is a
// hard problem and doesn't affect much in terms of real-world issues.
//
// We assume that the page IDs are increasing over time, so larger IDs than
// the current input ID happened in the future (this will occur if the user
// goes back). We can ignore future transitions because if you navigate, go
// back, and navigate some more, we'd like to have one node with two out
// edges in our visit graph.
for (int i = static_cast<int>(transitions.size()) - 1; i >= 0; i--) {
if (transitions[i].page_id <= page_id && transitions[i].url == referrer) {
// Found it.
return transitions[i].visit_id;
}
}
// We can't find the referrer.
return 0;
}
void VisitTracker::AddVisit(const void* host,
int32 page_id,
const GURL& url,
VisitID visit_id) {
TransitionList* transitions = hosts_[host];
if (!transitions) {
transitions = new TransitionList;
hosts_[host] = transitions;
}
Transition t;
t.url = url;
t.page_id = page_id;
t.visit_id = visit_id;
transitions->push_back(t);
CleanupTransitionList(transitions);
}
void VisitTracker::NotifyRenderProcessHostDestruction(const void* host) {
HostList::iterator i = hosts_.find(host);
if (i == hosts_.end())
return; // We don't have any entries for this host.
delete i->second;
hosts_.erase(i);
}
void VisitTracker::CleanupTransitionList(TransitionList* transitions) {
if (transitions->size() <= kMaxItemsInTransitionList)
return; // Nothing to do.
transitions->erase(transitions->begin(),
transitions->begin() + kResizeBigTransitionListTo);
}
} // namespace history