The Tor Browser / file comparison
comparison: js/src/jsweakcache.h
js/src/jsweakcache.h
- branch
- TOR_BUG_9701
- changeset 15
- b8a032363ba2
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| -1:000000000000 | 0:91033e604afa |
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| 1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- | |
| 2 * vim: set ts=8 sts=4 et sw=4 tw=99: | |
| 3 * This Source Code Form is subject to the terms of the Mozilla Public | |
| 4 * License, v. 2.0. If a copy of the MPL was not distributed with this | |
| 5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ | |
| 6 | |
| 7 #ifndef jsweakcache_h | |
| 8 #define jsweakcache_h | |
| 9 | |
| 10 #include "jscntxt.h" | |
| 11 #include "gc/Marking.h" | |
| 12 #include "js/HashTable.h" | |
| 13 #include "vm/Runtime.h" | |
| 14 | |
| 15 namespace js { | |
| 16 | |
| 17 // A WeakCache is used to map a key to a value similar to an HashMap except | |
| 18 // that its entries are garbage collected. An entry is kept as long as | |
| 19 // both the key and value are marked. | |
| 20 // | |
| 21 // No mark function is provided with this weak container. However, this weak | |
| 22 // container should take part in the sweep phase. | |
| 23 template <class Key, class Value, | |
| 24 class HashPolicy = DefaultHasher<Key>, | |
| 25 class AllocPolicy = RuntimeAllocPolicy> | |
| 26 class WeakCache : public HashMap<Key, Value, HashPolicy, AllocPolicy> { | |
| 27 private: | |
| 28 typedef HashMap<Key, Value, HashPolicy, AllocPolicy> Base; | |
| 29 typedef typename Base::Range Range; | |
| 30 typedef typename Base::Enum Enum; | |
| 31 | |
| 32 public: | |
| 33 explicit WeakCache(JSRuntime *rt) : Base(rt) { } | |
| 34 explicit WeakCache(JSContext *cx) : Base(cx->runtime()) { } | |
| 35 | |
| 36 public: | |
| 37 // Sweep all entries which have unmarked key or value. | |
| 38 void sweep(FreeOp *fop) { | |
| 39 // Remove all entries whose keys/values remain unmarked. | |
| 40 for (Enum e(*this); !e.empty(); e.popFront()) { | |
| 41 // Checking IsMarked() may update the location of the Key (or Value). | |
| 42 // Pass in a stack local, then manually update the backing heap store. | |
| 43 Key k(e.front().key); | |
| 44 bool isKeyDying = gc::IsAboutToBeFinalized(&k); | |
| 45 | |
| 46 if (isKeyDying || gc::IsAboutToBeFinalized(e.front().value)) { | |
| 47 e.removeFront(); | |
| 48 } else { | |
| 49 // Potentially update the location of the Key. | |
| 50 // The Value had its heap addresses correctly passed to IsMarked(), | |
| 51 // and therefore has already been updated if necessary. | |
| 52 // e.rekeyFront(k); | |
| 53 } | |
| 54 } | |
| 55 | |
| 56 #if DEBUG | |
| 57 // Once we've swept, all remaining edges should stay within the | |
| 58 // known-live part of the graph. | |
| 59 for (Range r = Base::all(); !r.empty(); r.popFront()) { | |
| 60 Key k(r.front().key); | |
| 61 | |
| 62 JS_ASSERT(!gc::IsAboutToBeFinalized(&k)); | |
| 63 JS_ASSERT(!gc::IsAboutToBeFinalized(r.front().value)); | |
| 64 | |
| 65 // Assert that IsMarked() did not perform relocation. | |
| 66 JS_ASSERT(k == r.front().key); | |
| 67 } | |
| 68 #endif | |
| 69 } | |
| 70 }; | |
| 71 | |
| 72 // A WeakValueCache is similar to a WeakCache, except keys are never marked. | |
| 73 // This is useful for weak maps where the keys are primitive values such as uint32_t. | |
| 74 template <class Key, class Value, | |
| 75 class HashPolicy = DefaultHasher<Key>, | |
| 76 class AllocPolicy = RuntimeAllocPolicy> | |
| 77 class WeakValueCache : public HashMap<Key, Value, HashPolicy, AllocPolicy> | |
| 78 { | |
| 79 public: | |
| 80 typedef HashMap<Key, Value, HashPolicy, AllocPolicy> Base; | |
| 81 typedef typename Base::Range Range; | |
| 82 typedef typename Base::Enum Enum; | |
| 83 | |
| 84 explicit WeakValueCache(JSRuntime *rt) : Base(rt) { } | |
| 85 explicit WeakValueCache(JSContext *cx) : Base(cx->runtime()) { } | |
| 86 | |
| 87 public: | |
| 88 // Sweep all entries which have unmarked key or value. | |
| 89 void sweep(FreeOp *fop) { | |
| 90 // Remove all entries whose values remain unmarked. | |
| 91 for (Enum e(*this); !e.empty(); e.popFront()) { | |
| 92 if (gc::IsAboutToBeFinalized(e.front().value())) | |
| 93 e.removeFront(); | |
| 94 } | |
| 95 | |
| 96 #if DEBUG | |
| 97 // Once we've swept, all remaining edges should stay within the | |
| 98 // known-live part of the graph. | |
| 99 for (Range r = Base::all(); !r.empty(); r.popFront()) | |
| 100 JS_ASSERT(!gc::IsAboutToBeFinalized(r.front().value())); | |
| 101 #endif | |
| 102 } | |
| 103 }; | |
| 104 | |
| 105 } // namespace js | |
| 106 | |
| 107 #endif /* jsweakcache_h */ |
