root/chrome/browser/sync/sessions2/tab_node_pool2.cc

DEFINITIONS

1. TabIdToTag
2. AddTabNode
3. AssociateTabNode
4. GetFreeTabNode
5. FreeTabNode
6. FreeTabNodeInternal
7. IsUnassociatedTabNode
8. ReassociateTabNode
9. GetTabIdFromTabNodeId
10. DeleteUnassociatedTabNodes
11. Clear
12. Capacity
13. Empty
14. Full
15. SetMachineTag

// Copyright 2013 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/sync/sessions2/tab_node_pool2.h"

#include "base/format_macros.h"
#include "base/logging.h"
#include "base/strings/stringprintf.h"
#include "sync/api/sync_change.h"
#include "sync/api/sync_data.h"
#include "sync/internal_api/public/base/model_type.h"
#include "sync/protocol/session_specifics.pb.h"
#include "sync/protocol/sync.pb.h"

namespace browser_sync {

const size_t TabNodePool2::kFreeNodesLowWatermark = 25;
const size_t TabNodePool2::kFreeNodesHighWatermark = 100;

TabNodePool2::TabNodePool2()
    : max_used_tab_node_id_(kInvalidTabNodeID) {}

// static
// We start vending tab node IDs at 0.
const int TabNodePool2::kInvalidTabNodeID = -1;

TabNodePool2::~TabNodePool2() {}

// Static
std::string TabNodePool2::TabIdToTag(
    const std::string machine_tag, int tab_node_id) {
  return base::StringPrintf("%s %d", machine_tag.c_str(), tab_node_id);
}

void TabNodePool2::AddTabNode(int tab_node_id) {
  DCHECK_GT(tab_node_id, kInvalidTabNodeID);
  DCHECK(nodeid_tabid_map_.find(tab_node_id) == nodeid_tabid_map_.end());
  unassociated_nodes_.insert(tab_node_id);
  if (max_used_tab_node_id_ < tab_node_id)
    max_used_tab_node_id_ = tab_node_id;
}

void TabNodePool2::AssociateTabNode(int tab_node_id,
                                    SessionID::id_type tab_id) {
  DCHECK_GT(tab_node_id, kInvalidTabNodeID);
  // Remove sync node if it is in unassociated nodes pool.
  std::set<int>::iterator u_it = unassociated_nodes_.find(tab_node_id);
  if (u_it != unassociated_nodes_.end()) {
    unassociated_nodes_.erase(u_it);
  } else {
    // This is a new node association, the sync node should be free.
    // Remove node from free node pool and then associate it with the tab.
    std::set<int>::iterator it = free_nodes_pool_.find(tab_node_id);
    DCHECK(it != free_nodes_pool_.end());
    free_nodes_pool_.erase(it);
  }
  DCHECK(nodeid_tabid_map_.find(tab_node_id) == nodeid_tabid_map_.end());
  nodeid_tabid_map_[tab_node_id] = tab_id;
}

int TabNodePool2::GetFreeTabNode(syncer::SyncChangeList* append_changes) {
  DCHECK_GT(machine_tag_.length(), 0U);
  DCHECK(append_changes);
  if (free_nodes_pool_.empty()) {
    // Tab pool has no free nodes, allocate new one.
    int tab_node_id = ++max_used_tab_node_id_;
    std::string tab_node_tag = TabIdToTag(machine_tag_, tab_node_id);

    // We fill the new node with just enough data so that in case of a crash/bug
    // we can identify the node as our own on re-association and reuse it.
    sync_pb::EntitySpecifics entity;
    sync_pb::SessionSpecifics* specifics = entity.mutable_session();
    specifics->set_session_tag(machine_tag_);
    specifics->set_tab_node_id(tab_node_id);
    append_changes->push_back(syncer::SyncChange(
        FROM_HERE,
        syncer::SyncChange::ACTION_ADD,
        syncer::SyncData::CreateLocalData(tab_node_tag,
                                          tab_node_tag,
                                          entity)));

    // Grow the pool by 1 since we created a new node.
    DVLOG(1) << "Adding sync node " << tab_node_id
             << " to tab node id pool";
    free_nodes_pool_.insert(tab_node_id);
    return tab_node_id;
  } else {
    // Return the next free node.
    return *free_nodes_pool_.begin();
  }
}

void TabNodePool2::FreeTabNode(int tab_node_id,
                               syncer::SyncChangeList* append_changes) {
  DCHECK(append_changes);
  TabNodeIDToTabIDMap::iterator it = nodeid_tabid_map_.find(tab_node_id);
  DCHECK(it != nodeid_tabid_map_.end());
  nodeid_tabid_map_.erase(it);
  FreeTabNodeInternal(tab_node_id, append_changes);
}

void TabNodePool2::FreeTabNodeInternal(
    int tab_node_id,
    syncer::SyncChangeList* append_changes) {
  DCHECK(free_nodes_pool_.find(tab_node_id) == free_nodes_pool_.end());
  DCHECK(append_changes);
  free_nodes_pool_.insert(tab_node_id);

  // If number of free nodes exceed kFreeNodesHighWatermark,
  // delete sync nodes till number reaches kFreeNodesLowWatermark.
  // Note: This logic is to mitigate temporary disassociation issues with old
  // clients: http://crbug.com/259918. Newer versions do not need this.
  if (free_nodes_pool_.size() > kFreeNodesHighWatermark) {
    for (std::set<int>::iterator free_it = free_nodes_pool_.begin();
         free_it != free_nodes_pool_.end();) {
      const std::string tab_node_tag = TabIdToTag(machine_tag_, *free_it);
      append_changes->push_back(syncer::SyncChange(
          FROM_HERE,
          syncer::SyncChange::ACTION_DELETE,
          syncer::SyncData::CreateLocalDelete(tab_node_tag,
                                              syncer::SESSIONS)));
      free_nodes_pool_.erase(free_it++);
      if (free_nodes_pool_.size() <= kFreeNodesLowWatermark) {
        return;
      }
    }
  }
}

bool TabNodePool2::IsUnassociatedTabNode(int tab_node_id) {
  return unassociated_nodes_.find(tab_node_id) != unassociated_nodes_.end();
}

void TabNodePool2::ReassociateTabNode(int tab_node_id,
                                      SessionID::id_type tab_id) {
  // Remove from list of unassociated sync_nodes if present.
  std::set<int>::iterator it = unassociated_nodes_.find(tab_node_id);
  if (it != unassociated_nodes_.end()) {
    unassociated_nodes_.erase(it);
  } else {
    // tab_node_id must be an already associated node.
    DCHECK(nodeid_tabid_map_.find(tab_node_id) != nodeid_tabid_map_.end());
  }
  nodeid_tabid_map_[tab_node_id] = tab_id;
}

SessionID::id_type TabNodePool2::GetTabIdFromTabNodeId(
    int tab_node_id) const {
  TabNodeIDToTabIDMap::const_iterator it = nodeid_tabid_map_.find(tab_node_id);
  if (it != nodeid_tabid_map_.end()) {
    return it->second;
  }
  return kInvalidTabID;
}

void TabNodePool2::DeleteUnassociatedTabNodes(
    syncer::SyncChangeList* append_changes) {
  for (std::set<int>::iterator it = unassociated_nodes_.begin();
       it != unassociated_nodes_.end();) {
    FreeTabNodeInternal(*it, append_changes);
    unassociated_nodes_.erase(it++);
  }
  DCHECK(unassociated_nodes_.empty());
}

// Clear tab pool.
void TabNodePool2::Clear() {
  unassociated_nodes_.clear();
  free_nodes_pool_.clear();
  nodeid_tabid_map_.clear();
  max_used_tab_node_id_ = kInvalidTabNodeID;
}

size_t TabNodePool2::Capacity() const {
  return nodeid_tabid_map_.size() + unassociated_nodes_.size() +
         free_nodes_pool_.size();
}

bool TabNodePool2::Empty() const { return free_nodes_pool_.empty(); }

bool TabNodePool2::Full() { return nodeid_tabid_map_.empty(); }

void TabNodePool2::SetMachineTag(const std::string& machine_tag) {
  machine_tag_ = machine_tag;
}

}  // namespace browser_sync