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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at */
#ifndef nsSHistory_h
#define nsSHistory_h
#include "nsCOMPtr.h"
#include "nsDocShellLoadState.h"
#include "nsExpirationTracker.h"
#include "nsISHistory.h"
#include "nsSHEntryShared.h"
#include "nsSimpleEnumerator.h"
#include "nsTObserverArray.h"
#include "nsWeakReference.h"
#include "mozilla/dom/ipc/IdType.h"
#include "mozilla/LinkedList.h"
#include "mozilla/UniquePtr.h"
class nsIDocShell;
class nsDocShell;
class nsSHistoryObserver;
class nsISHEntry;
namespace mozilla {
namespace dom {
class LoadSHEntryResult;
} // namespace mozilla
class nsSHistory : public mozilla::LinkedListElement<nsSHistory>,
public nsISHistory,
public nsSupportsWeakReference {
// The timer based history tracker is used to evict bfcache on expiration.
class HistoryTracker final
: public nsExpirationTracker<mozilla::dom::SHEntrySharedParentState, 3> {
explicit HistoryTracker(nsSHistory* aSHistory, uint32_t aTimeout,
nsIEventTarget* aEventTarget)
: nsExpirationTracker(1000 * aTimeout / 2, "HistoryTracker",
aEventTarget) {
mSHistory = aSHistory;
virtual void NotifyExpired(
mozilla::dom::SHEntrySharedParentState* aObj) override {
// HistoryTracker is owned by nsSHistory; it always outlives HistoryTracker
// so it's safe to use raw pointer here.
nsSHistory* mSHistory;
// Structure used in SetChildHistoryEntry
struct SwapEntriesData {
ignoreBC; // constant; the browsing context to ignore
nsISHEntry* destTreeRoot; // constant; the root of the dest tree
nsISHEntry* destTreeParent; // constant; the node under destTreeRoot
// whose children will correspond to aEntry
explicit nsSHistory(mozilla::dom::BrowsingContext* aRootBC);
// One time initialization method
static nsresult Startup();
static void Shutdown();
static void UpdatePrefs();
// Max number of total cached content viewers. If the pref
// browser.sessionhistory.max_total_viewers is negative, then
// this value is calculated based on the total amount of memory.
// Otherwise, it comes straight from the pref.
static uint32_t GetMaxTotalViewers() { return sHistoryMaxTotalViewers; }
// Get the root SHEntry from a given entry.
static already_AddRefed<nsISHEntry> GetRootSHEntry(nsISHEntry* aEntry);
// Callback prototype for WalkHistoryEntries.
// `aEntry` is the child history entry, `aBC` is its corresponding browsing
// context, `aChildIndex` is the child's index in its parent entry, and
// `aData` is the opaque pointer passed to WalkHistoryEntries. Both structs
// that are passed as `aData` to this function have a field
// `aEntriesToUpdate`, which is an array of entries we need to update in
// docshell, if the 'SH in parent' pref is on (which implies that this method
// is executed in the parent)
typedef nsresult (*WalkHistoryEntriesFunc)(nsISHEntry* aEntry,
mozilla::dom::BrowsingContext* aBC,
int32_t aChildIndex, void* aData);
// Clone a session history tree for subframe navigation.
// The tree rooted at |aSrcEntry| will be cloned into |aDestEntry|, except
// for the entry with id |aCloneID|, which will be replaced with
// |aReplaceEntry|. |aSrcShell| is a (possibly null) docshell which
// corresponds to |aSrcEntry| via its mLSHE or mOHE pointers, and will
// have that pointer updated to point to the cloned history entry.
// If aCloneChildren is true then the children of the entry with id
// |aCloneID| will be cloned into |aReplaceEntry|.
static nsresult CloneAndReplace(nsISHEntry* aSrcEntry,
mozilla::dom::BrowsingContext* aOwnerBC,
uint32_t aCloneID, nsISHEntry* aReplaceEntry,
bool aCloneChildren, nsISHEntry** aDestEntry);
// Child-walking callback for CloneAndReplace
static nsresult CloneAndReplaceChild(nsISHEntry* aEntry,
mozilla::dom::BrowsingContext* aOwnerBC,
int32_t aChildIndex, void* aData);
// Child-walking callback for SetHistoryEntry
static nsresult SetChildHistoryEntry(nsISHEntry* aEntry,
mozilla::dom::BrowsingContext* aBC,
int32_t aEntryIndex, void* aData);
// For each child of aRootEntry, find the corresponding shell which is
// a child of aBC, and call aCallback. The opaque pointer aData
// is passed to the callback.
static nsresult WalkHistoryEntries(nsISHEntry* aRootEntry,
mozilla::dom::BrowsingContext* aBC,
WalkHistoryEntriesFunc aCallback,
void* aData);
// This function finds all entries that are contiguous and same-origin with
// the aEntry. And call the aCallback on them, including the aEntry. This only
// works for the root entries. It will do nothing for non-root entries.
static void WalkContiguousEntries(
nsISHEntry* aEntry, const std::function<void(nsISHEntry*)>& aCallback);
nsTArray<nsCOMPtr<nsISHEntry>>& Entries() { return mEntries; }
void NotifyOnHistoryReplaceEntry();
void RemoveEntries(nsTArray<nsID>& aIDs, int32_t aStartIndex,
bool* aDidRemove);
// The size of the window of SHEntries which can have alive viewers in the
// bfcache around the currently active SHEntry.
// We try to keep viewers for SHEntries between index - VIEWER_WINDOW and
// index + VIEWER_WINDOW alive.
static const int32_t VIEWER_WINDOW = 3;
struct LoadEntryResult {
RefPtr<mozilla::dom::BrowsingContext> mBrowsingContext;
RefPtr<nsDocShellLoadState> mLoadState;
static void LoadURIs(nsTArray<LoadEntryResult>& aLoadResults);
static void LoadURIOrBFCache(LoadEntryResult& aLoadEntry);
// If this doesn't return an error then either aLoadResult is set to nothing,
// in which case the caller should ignore the load, or it returns a valid
// LoadEntryResult in aLoadResult which the caller should use to do the load.
nsresult Reload(uint32_t aReloadFlags,
nsTArray<LoadEntryResult>& aLoadResults);
nsresult ReloadCurrentEntry(nsTArray<LoadEntryResult>& aLoadResults);
nsresult GotoIndex(int32_t aIndex, nsTArray<LoadEntryResult>& aLoadResults,
bool aSameEpoch, bool aLoadCurrentEntry,
bool aUserActivation);
void WindowIndices(int32_t aIndex, int32_t* aOutStartIndex,
int32_t* aOutEndIndex);
void NotifyListenersContentViewerEvicted(uint32_t aNumEvicted);
int32_t Length() { return int32_t(mEntries.Length()); }
int32_t Index() { return mIndex; }
already_AddRefed<mozilla::dom::BrowsingContext> GetBrowsingContext() {
return mozilla::dom::BrowsingContext::Get(mRootBC);
bool HasOngoingUpdate() { return mHasOngoingUpdate; }
void SetHasOngoingUpdate(bool aVal) { mHasOngoingUpdate = aVal; }
void SetBrowsingContext(mozilla::dom::BrowsingContext* aRootBC) {
uint64_t newID = aRootBC ? aRootBC->Id() : 0;
if (mRootBC != newID) {
mRootBC = newID;
int32_t GetIndexForReplace() {
// Replace current entry in session history; If the requested index is
// valid, it indicates the loading was triggered by a history load, and
// we should replace the entry at requested index instead.
return mRequestedIndex == -1 ? mIndex : mRequestedIndex;
// Update the root browsing context state when adding, removing or
// replacing entries.
void UpdateRootBrowsingContextState() {
RefPtr<mozilla::dom::BrowsingContext> rootBC(GetBrowsingContext());
void GetEpoch(uint64_t& aEpoch,
mozilla::Maybe<mozilla::dom::ContentParentId>& aId) const {
aEpoch = mEpoch;
aId = mEpochParentId;
void SetEpoch(uint64_t aEpoch,
mozilla::Maybe<mozilla::dom::ContentParentId> aId) {
mEpoch = aEpoch;
mEpochParentId = aId;
void LogHistory();
virtual ~nsSHistory();
uint64_t mRootBC;
friend class nsSHistoryObserver;
void UpdateRootBrowsingContextState(
mozilla::dom::BrowsingContext* aBrowsingContext);
bool LoadDifferingEntries(nsISHEntry* aPrevEntry, nsISHEntry* aNextEntry,
mozilla::dom::BrowsingContext* aParent,
long aLoadType,
nsTArray<LoadEntryResult>& aLoadResults,
bool aLoadCurrentEntry, bool aUserActivation,
int32_t aOffset);
void InitiateLoad(nsISHEntry* aFrameEntry,
mozilla::dom::BrowsingContext* aFrameBC, long aLoadType,
nsTArray<LoadEntryResult>& aLoadResult,
bool aLoadCurrentEntry, bool aUserActivation,
int32_t aOffset);
nsresult LoadEntry(int32_t aIndex, long aLoadType, uint32_t aHistCmd,
nsTArray<LoadEntryResult>& aLoadResults, bool aSameEpoch,
bool aLoadCurrentEntry, bool aUserActivation);
// Find the history entry for a given bfcache entry. It only looks up between
// the range where alive viewers may exist (i.e nsSHistory::VIEWER_WINDOW).
nsresult FindEntryForBFCache(mozilla::dom::SHEntrySharedParentState* aEntry,
nsISHEntry** aResult, int32_t* aResultIndex);
// Evict content viewers in this window which don't lie in the "safe" range
// around aIndex.
virtual void EvictOutOfRangeWindowContentViewers(int32_t aIndex);
void EvictContentViewerForEntry(nsISHEntry* aEntry);
static void GloballyEvictContentViewers();
static void GloballyEvictAllContentViewers();
// Calculates a max number of total
// content viewers to cache, based on amount of total memory
static uint32_t CalcMaxTotalViewers();
nsresult LoadNextPossibleEntry(int32_t aNewIndex, long aLoadType,
uint32_t aHistCmd,
nsTArray<LoadEntryResult>& aLoadResults,
bool aLoadCurrentEntry, bool aUserActivation);
// aIndex is the index of the entry which may be removed.
// If aKeepNext is true, aIndex is compared to aIndex + 1,
// otherwise comparison is done to aIndex - 1.
bool RemoveDuplicate(int32_t aIndex, bool aKeepNext);
// We need to update entries in docshell and browsing context.
// If our docshell is located in parent or 'SH in parent' pref is off we can
// update it directly, Otherwise, we have two choices. If the browsing context
// that owns the docshell is in the same process as the process who called us
// over IPC, then we save entries that need to be updated in a list, and once
// we have returned from the IPC call, we update the docshell in the child
// process. Otherwise, if the browsing context is in a different process, we
// do a nested IPC call to that process to update the docshell in that
// process.
static void HandleEntriesToSwapInDocShell(mozilla::dom::BrowsingContext* aBC,
nsISHEntry* aOldEntry,
nsISHEntry* aNewEntry);
void UpdateEntryLength(nsISHEntry* aOldEntry, nsISHEntry* aNewEntry,
bool aMove);
bool mHasOngoingUpdate;
nsTArray<nsCOMPtr<nsISHEntry>> mEntries; // entries are never null
// Track all bfcache entries and evict on expiration.
mozilla::UniquePtr<HistoryTracker> mHistoryTracker;
int32_t mIndex; // -1 means "no index"
int32_t mRequestedIndex; // -1 means "no requested index"
// Session History listeners
nsAutoTObserverArray<nsWeakPtr, 2> mListeners;
nsID mRootDocShellID;
// Max viewers allowed total, across all SHistory objects
static int32_t sHistoryMaxTotalViewers;
// The epoch (and id) tell us what navigations occured within the same
// event-loop spin in the child. We need to know this in order to
// implement spec requirements for dropping pending navigations when we
// do a history navigation, if it's not same-document. Content processes
// update the epoch via a runnable on each ::Go (including AsyncGo).
uint64_t mEpoch = 0;
mozilla::Maybe<mozilla::dom::ContentParentId> mEpochParentId;
// CallerWillNotifyHistoryIndexAndLengthChanges is used to prevent
// SHistoryChangeNotifier to send automatic index and length updates.
// When that is done, it is up to the caller to explicitly send those updates.
// This is needed in cases when the update is a reaction to some change in a
// child process and child process passes a changeId to the parent side.
class MOZ_STACK_CLASS CallerWillNotifyHistoryIndexAndLengthChanges {
explicit CallerWillNotifyHistoryIndexAndLengthChanges(
nsISHistory* aSHistory) {
nsSHistory* shistory = static_cast<nsSHistory*>(aSHistory);
if (shistory && !shistory->HasOngoingUpdate()) {
mSHistory = shistory;
~CallerWillNotifyHistoryIndexAndLengthChanges() {
if (mSHistory) {
RefPtr<nsSHistory> mSHistory;
inline nsISupports* ToSupports(nsSHistory* aObj) {
return static_cast<nsISHistory*>(aObj);
#endif /* nsSHistory */