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/* -*- 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 jsweakcache_h
#define jsweakcache_h
#include "jsapi.h"
#include "jscntxt.h"
#include "jsobj.h"
#include "gc/Marking.h"
namespace js {
// A WeakCache is used to map a key to a value similar to an HashMap except
// that its entries are garbage collected. An entry is kept as long as
// both the key and value are marked.
//
// No mark function is provided with this weak container. However, this weak
// container should take part in the sweep phase.
template <class Key, class Value,
class HashPolicy = DefaultHasher<Key>,
class AllocPolicy = RuntimeAllocPolicy>
class WeakCache : public HashMap<Key, Value, HashPolicy, AllocPolicy> {
private:
typedef HashMap<Key, Value, HashPolicy, AllocPolicy> Base;
typedef typename Base::Range Range;
typedef typename Base::Enum Enum;
public:
explicit WeakCache(JSRuntime *rt) : Base(rt) { }
explicit WeakCache(JSContext *cx) : Base(cx) { }
public:
// Sweep all entries which have unmarked key or value.
void sweep(FreeOp *fop) {
// Remove all entries whose keys/values remain unmarked.
for (Enum e(*this); !e.empty(); e.popFront()) {
// Checking IsMarked() may update the location of the Key (or Value).
// Pass in a stack local, then manually update the backing heap store.
Key k(e.front().key);
bool isKeyDying = gc::IsAboutToBeFinalized(&k);
if (isKeyDying || gc::IsAboutToBeFinalized(e.front().value)) {
e.removeFront();
} else {
// Potentially update the location of the Key.
// The Value had its heap addresses correctly passed to IsMarked(),
// and therefore has already been updated if necessary.
// e.rekeyFront(k);
}
}
#if DEBUG
// Once we've swept, all remaining edges should stay within the
// known-live part of the graph.
for (Range r = Base::all(); !r.empty(); r.popFront()) {
Key k(r.front().key);
JS_ASSERT(!gc::IsAboutToBeFinalized(&k));
JS_ASSERT(!gc::IsAboutToBeFinalized(r.front().value));
// Assert that IsMarked() did not perform relocation.
JS_ASSERT(k == r.front().key);
}
#endif
}
};
// A WeakValueCache is similar to a WeakCache, except keys are never marked.
// This is useful for weak maps where the keys are primitive values such as uint32_t.
template <class Key, class Value,
class HashPolicy = DefaultHasher<Key>,
class AllocPolicy = RuntimeAllocPolicy>
class WeakValueCache : public HashMap<Key, Value, HashPolicy, AllocPolicy>
{
public:
typedef HashMap<Key, Value, HashPolicy, AllocPolicy> Base;
typedef typename Base::Range Range;
typedef typename Base::Enum Enum;
explicit WeakValueCache(JSRuntime *rt) : Base(rt) { }
explicit WeakValueCache(JSContext *cx) : Base(cx) { }
public:
// Sweep all entries which have unmarked key or value.
void sweep(FreeOp *fop) {
// Remove all entries whose values remain unmarked.
for (Enum e(*this); !e.empty(); e.popFront()) {
if (gc::IsAboutToBeFinalized(e.front().value))
e.removeFront();
}
#if DEBUG
// Once we've swept, all remaining edges should stay within the
// known-live part of the graph.
for (Range r = Base::all(); !r.empty(); r.popFront())
JS_ASSERT(!gc::IsAboutToBeFinalized(r.front().value));
#endif
}
};
} // namespace js
#endif /* jsweakcache_h */