1/*
2 * Copyright (C) 2013 Apple Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 *    notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 *    notice, this list of conditions and the following disclaimer in the
11 *    documentation and/or other materials provided with the distribution.
12 *
13 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
14 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
15 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
16 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
17 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
18 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
19 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
20 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
21 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
23 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
24 */
25
26#include "config.h"
27#include "PrototypeMap.h"
28
29#include "JSGlobalObject.h"
30#include "JSCInlines.h"
31
32namespace JSC {
33
34void PrototypeMap::addPrototype(JSObject* object)
35{
36    m_prototypes.add(object, object);
37
38    // Note that this method makes the somewhat odd decision to not check if this
39    // object currently has indexed accessors. We could do that check here, and if
40    // indexed accessors were found, we could tell the global object to have a bad
41    // time. But we avoid this, to allow the following to be always fast:
42    //
43    // 1) Create an object.
44    // 2) Give it a setter or read-only property that happens to have a numeric name.
45    // 3) Allocate objects that use this object as a prototype.
46    //
47    // This avoids anyone having a bad time. Even if the instance objects end up
48    // having indexed storage, the creation of indexed storage leads to a prototype
49    // chain walk that detects the presence of indexed setters and then does the
50    // right thing. As a result, having a bad time only happens if you add an
51    // indexed setter (or getter, or read-only field) to an object that is already
52    // used as a prototype.
53}
54
55Structure* PrototypeMap::emptyObjectStructureForPrototype(JSObject* prototype, unsigned inlineCapacity)
56{
57    StructureMap::AddResult addResult = m_structures.add(std::make_pair(prototype, inlineCapacity), nullptr);
58    if (!addResult.isNewEntry) {
59        ASSERT(isPrototype(prototype));
60        return addResult.iterator->value.get();
61    }
62
63    addPrototype(prototype);
64    Structure* structure = JSFinalObject::createStructure(
65        prototype->globalObject()->vm(), prototype->globalObject(), prototype, inlineCapacity);
66    addResult.iterator->value = Weak<Structure>(structure);
67    return structure;
68}
69
70void PrototypeMap::clearEmptyObjectStructureForPrototype(JSObject* object, unsigned inlineCapacity)
71{
72    m_structures.remove(std::make_pair(object, inlineCapacity));
73}
74
75} // namespace JSC
76