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Tip revision: 0f7f9fad114b25dcae74e0d7f14d5359c64e174e authored by ffxbld on 07 July 2015, 02:40:09 UTC
Added FENNEC_39_0_1_RELEASE FENNEC_39_0_1_BUILD2 tag(s) for changeset 96c214a15c79. DONTBUILD CLOSED TREE a=release
Added FENNEC_39_0_1_RELEASE FENNEC_39_0_1_BUILD2 tag(s) for changeset 96c214a15c79. DONTBUILD CLOSED TREE a=release
Tip revision: 0f7f9fa
jsweakmap.h
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
* vim: set ts=8 sts=4 et sw=4 tw=99:
* 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 http://mozilla.org/MPL/2.0/. */
#ifndef jsweakmap_h
#define jsweakmap_h
#include "jscompartment.h"
#include "jsfriendapi.h"
#include "jsobj.h"
#include "gc/Marking.h"
#include "gc/StoreBuffer.h"
#include "js/HashTable.h"
namespace js {
// A subclass template of js::HashMap whose keys and values may be garbage-collected. When
// a key is collected, the table entry disappears, dropping its reference to the value.
//
// More precisely:
//
// A WeakMap entry is collected if and only if either the WeakMap or the entry's key
// is collected. If an entry is not collected, it remains in the WeakMap and it has a
// strong reference to the value.
//
// You must call this table's 'trace' method when the object of which it is a part is
// reached by the garbage collection tracer. Once a table is known to be live, the
// implementation takes care of the iterative marking needed for weak tables and removing
// table entries when collection is complete.
// The value for the next pointer for maps not in the map list.
static WeakMapBase * const WeakMapNotInList = reinterpret_cast<WeakMapBase*>(1);
typedef HashSet<WeakMapBase*, DefaultHasher<WeakMapBase*>, SystemAllocPolicy> WeakMapSet;
// Common base class for all WeakMap specializations. The collector uses this to call
// their markIteratively and sweep methods.
class WeakMapBase {
public:
WeakMapBase(JSObject* memOf, JSCompartment* c);
virtual ~WeakMapBase();
void trace(JSTracer* tracer);
// Garbage collector entry points.
// Unmark all weak maps in a compartment.
static void unmarkCompartment(JSCompartment* c);
// Mark all the weakmaps in a compartment.
static void markAll(JSCompartment* c, JSTracer* tracer);
// Check all weak maps in a compartment that have been marked as live in this garbage
// collection, and mark the values of all entries that have become strong references
// to them. Return true if we marked any new values, indicating that we need to make
// another pass. In other words, mark my marked maps' marked members' mid-collection.
static bool markCompartmentIteratively(JSCompartment* c, JSTracer* tracer);
// Add zone edges for weakmaps with key delegates in a different zone.
static bool findZoneEdgesForCompartment(JSCompartment* c);
// Sweep the weak maps in a compartment, removing dead weak maps and removing
// entries of live weak maps whose keys are dead.
static void sweepCompartment(JSCompartment* c);
// Trace all delayed weak map bindings. Used by the cycle collector.
static void traceAllMappings(WeakMapTracer* tracer);
bool isInList() { return next != WeakMapNotInList; }
// Save information about which weak maps are marked for a compartment.
static bool saveCompartmentMarkedWeakMaps(JSCompartment* c, WeakMapSet& markedWeakMaps);
// Restore information about which weak maps are marked for many compartments.
static void restoreCompartmentMarkedWeakMaps(WeakMapSet& markedWeakMaps);
// Remove a weakmap from its compartment's weakmaps list.
static void removeWeakMapFromList(WeakMapBase* weakmap);
protected:
// Instance member functions called by the above. Instantiations of WeakMap override
// these with definitions appropriate for their Key and Value types.
virtual void nonMarkingTraceKeys(JSTracer* tracer) = 0;
virtual void nonMarkingTraceValues(JSTracer* tracer) = 0;
virtual bool markIteratively(JSTracer* tracer) = 0;
virtual bool findZoneEdges() = 0;
virtual void sweep() = 0;
virtual void traceMappings(WeakMapTracer* tracer) = 0;
virtual void finish() = 0;
// Object that this weak map is part of, if any.
RelocatablePtrObject memberOf;
// Compartment that this weak map is part of.
JSCompartment* compartment;
// Link in a list of all WeakMaps in a compartment, headed by
// JSCompartment::gcWeakMapList. The last element of the list has nullptr as
// its next. Maps not in the list have WeakMapNotInList as their next.
WeakMapBase* next;
// Whether this object has been traced during garbage collection.
bool marked;
};
template <class Key, class Value,
class HashPolicy = DefaultHasher<Key> >
class WeakMap : public HashMap<Key, Value, HashPolicy, RuntimeAllocPolicy>, public WeakMapBase
{
public:
typedef HashMap<Key, Value, HashPolicy, RuntimeAllocPolicy> Base;
typedef typename Base::Enum Enum;
typedef typename Base::Lookup Lookup;
typedef typename Base::Range Range;
typedef typename Base::Ptr Ptr;
typedef typename Base::AddPtr AddPtr;
explicit WeakMap(JSContext* cx, JSObject* memOf = nullptr)
: Base(cx->runtime()), WeakMapBase(memOf, cx->compartment()) { }
bool init(uint32_t len = 16) {
if (!Base::init(len))
return false;
next = compartment->gcWeakMapList;
compartment->gcWeakMapList = this;
marked = JS::IsIncrementalGCInProgress(compartment->runtimeFromMainThread());
return true;
}
// Overwritten to add a read barrier to prevent an incorrectly gray value
// from escaping the weak map. See the comment before UnmarkGrayChildren in
// gc/Marking.cpp
Ptr lookup(const Lookup& l) const {
Ptr p = Base::lookup(l);
if (p)
exposeGCThingToActiveJS(p->value());
return p;
}
AddPtr lookupForAdd(const Lookup& l) const {
AddPtr p = Base::lookupForAdd(l);
if (p)
exposeGCThingToActiveJS(p->value());
return p;
}
Ptr lookupWithDefault(const Key& k, const Value& defaultValue) {
Ptr p = Base::lookupWithDefault(k, defaultValue);
if (p)
exposeGCThingToActiveJS(p->value());
return p;
}
private:
void exposeGCThingToActiveJS(const JS::Value& v) const { JS::ExposeValueToActiveJS(v); }
void exposeGCThingToActiveJS(JSObject* obj) const { JS::ExposeObjectToActiveJS(obj); }
bool markValue(JSTracer* trc, Value* x) {
if (gc::IsMarked(x))
return false;
gc::Mark(trc, x, "WeakMap entry value");
MOZ_ASSERT(gc::IsMarked(x));
return true;
}
void nonMarkingTraceKeys(JSTracer* trc) {
for (Enum e(*this); !e.empty(); e.popFront()) {
Key key(e.front().key());
gc::Mark(trc, &key, "WeakMap entry key");
if (key != e.front().key())
entryMoved(e, key);
}
}
void nonMarkingTraceValues(JSTracer* trc) {
for (Range r = Base::all(); !r.empty(); r.popFront())
gc::Mark(trc, &r.front().value(), "WeakMap entry value");
}
bool keyNeedsMark(JSObject* key) {
if (JSWeakmapKeyDelegateOp op = key->getClass()->ext.weakmapKeyDelegateOp) {
JSObject* delegate = op(key);
/*
* Check if the delegate is marked with any color to properly handle
* gray marking when the key's delegate is black and the map is
* gray.
*/
return delegate && gc::IsObjectMarked(&delegate);
}
return false;
}
bool keyNeedsMark(gc::Cell* cell) {
return false;
}
bool markIteratively(JSTracer* trc) {
bool markedAny = false;
for (Enum e(*this); !e.empty(); e.popFront()) {
/* If the entry is live, ensure its key and value are marked. */
Key key(e.front().key());
if (gc::IsMarked(const_cast<Key*>(&key))) {
if (markValue(trc, &e.front().value()))
markedAny = true;
if (e.front().key() != key)
entryMoved(e, key);
} else if (keyNeedsMark(key)) {
gc::Mark(trc, &e.front().value(), "WeakMap entry value");
gc::Mark(trc, &key, "proxy-preserved WeakMap entry key");
if (e.front().key() != key)
entryMoved(e, key);
markedAny = true;
}
key.unsafeSet(nullptr);
}
return markedAny;
}
bool findZoneEdges() {
// This is overridden by ObjectValueMap.
return true;
}
void sweep() {
/* Remove all entries whose keys remain unmarked. */
for (Enum e(*this); !e.empty(); e.popFront()) {
Key k(e.front().key());
if (gc::IsAboutToBeFinalized(&k))
e.removeFront();
else if (k != e.front().key())
entryMoved(e, k);
}
/*
* Once we've swept, all remaining edges should stay within the
* known-live part of the graph.
*/
assertEntriesNotAboutToBeFinalized();
}
void finish() {
Base::finish();
}
/* memberOf can be nullptr, which means that the map is not part of a JSObject. */
void traceMappings(WeakMapTracer* tracer) {
for (Range r = Base::all(); !r.empty(); r.popFront()) {
gc::Cell* key = gc::ToMarkable(r.front().key());
gc::Cell* value = gc::ToMarkable(r.front().value());
if (key && value) {
tracer->callback(tracer, memberOf,
JS::GCCellPtr(r.front().key()),
JS::GCCellPtr(r.front().value()));
}
}
}
/* Rekey an entry when moved, ensuring we do not trigger barriers. */
void entryMoved(Enum& eArg, const Key& k) {
typedef typename HashMap<typename Unbarriered<Key>::type,
typename Unbarriered<Value>::type,
typename Unbarriered<HashPolicy>::type,
RuntimeAllocPolicy>::Enum UnbarrieredEnum;
UnbarrieredEnum& e = reinterpret_cast<UnbarrieredEnum&>(eArg);
e.rekeyFront(reinterpret_cast<const typename Unbarriered<Key>::type&>(k));
}
protected:
void assertEntriesNotAboutToBeFinalized() {
#if DEBUG
for (Range r = Base::all(); !r.empty(); r.popFront()) {
Key k(r.front().key());
MOZ_ASSERT(!gc::IsAboutToBeFinalized(&k));
MOZ_ASSERT(!gc::IsAboutToBeFinalized(&r.front().value()));
MOZ_ASSERT(k == r.front().key());
}
#endif
}
};
/*
* At times, you will need to ignore barriers when accessing WeakMap entries.
* Localize the templatized casting craziness here.
*/
template <class Key, class Value>
static inline gc::HashKeyRef<HashMap<Key, Value, DefaultHasher<Key>, RuntimeAllocPolicy>, Key>
UnbarrieredRef(WeakMap<PreBarriered<Key>, RelocatablePtr<Value>>* map, Key key)
{
/*
* Some compilers complain about instantiating the WeakMap class for
* unbarriered type arguments, so we cast to a HashMap instead. Because of
* WeakMap's multiple inheritance, we need to do this in two stages, first
* to the HashMap base class and then to the unbarriered version.
*/
typedef typename WeakMap<PreBarriered<Key>, RelocatablePtr<Value>>::Base BaseMap;
auto baseMap = static_cast<BaseMap*>(map);
typedef HashMap<Key, Value, DefaultHasher<Key>, RuntimeAllocPolicy> UnbarrieredMap;
typedef gc::HashKeyRef<UnbarrieredMap, Key> UnbarrieredKeyRef;
return UnbarrieredKeyRef(reinterpret_cast<UnbarrieredMap*>(baseMap), key);
}
/* WeakMap methods exposed so they can be installed in the self-hosting global. */
extern JSObject*
InitBareWeakMapCtor(JSContext* cx, js::HandleObject obj);
extern bool
WeakMap_has(JSContext* cx, unsigned argc, Value* vp);
extern bool
WeakMap_get(JSContext* cx, unsigned argc, Value* vp);
extern bool
WeakMap_set(JSContext* cx, unsigned argc, Value* vp);
extern bool
WeakMap_delete(JSContext* cx, unsigned argc, Value* vp);
extern bool
WeakMap_clear(JSContext* cx, unsigned argc, Value* vp);
extern JSObject*
InitWeakMapClass(JSContext* cx, HandleObject obj);
} /* namespace js */
#endif /* jsweakmap_h */