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/*
* Copyright (C) 2025 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "config.h"
#include <wtf/CompactPtr.h>
#include <wtf/AccessibleAddress.h>
#include <wtf/HashMap.h>
#include <wtf/Lock.h>
#include <wtf/NeverDestroyed.h>
#include <wtf/SegmentedVector.h>
#include <wtf/Threading.h>
namespace WTF {
#if HAVE(36BIT_ADDRESS)
struct OutsizedCompactPtrManager {
HashMap<void*, OutsizedCompactPtr::Encoded> addedPointers;
SegmentedVector<void*> outsizedPointers;
};
static Lock outsizedCompactPtrLock;
static OutsizedCompactPtrManager* outsizedCompactPtrManager;
static void ensureOutsizedCompactPtrManager()
{
static std::once_flag onceFlag;
std::call_once(onceFlag, [] {
// WTF::initialize() is only needed to ensure that lowestAccessibleAddress()
// is ready for use.
WTF::initialize();
RELEASE_ASSERT(lowestAccessibleAddress() >= OutsizedCompactPtr::addressRangeForOutsizedPtrEncoding);
static NeverDestroyed<OutsizedCompactPtrManager> manager;
outsizedCompactPtrManager = &manager.get();
});
}
OutsizedCompactPtr::Encoded OutsizedCompactPtr::encode(void* ptr)
{
if (!outsizedCompactPtrManager)
ensureOutsizedCompactPtrManager();
Locker locker { outsizedCompactPtrLock };
auto& addedPointers = outsizedCompactPtrManager->addedPointers;
auto iter = addedPointers.find(ptr);
if (iter != addedPointers.end())
return iter->value;
auto& outsizedPointers = outsizedCompactPtrManager->outsizedPointers;
size_t entryIndex = outsizedPointers.size();
Encoded encoded = entryIndex + OutsizedCompactPtr::minEncoding;
RELEASE_ASSERT(encoded < OutsizedCompactPtr::maxEncoding, encoded, OutsizedCompactPtr::maxEncoding);
addedPointers.add(ptr, encoded);
outsizedPointers.append(ptr);
return encoded;
}
void* OutsizedCompactPtr::decode(uint32_t encoded)
{
Locker locker { outsizedCompactPtrLock };
auto& outsizedPointers = outsizedCompactPtrManager->outsizedPointers;
size_t entryIndex = encoded - OutsizedCompactPtr::minEncoding;
RELEASE_ASSERT(entryIndex < outsizedPointers.size(), entryIndex, outsizedPointers.size());
return outsizedPointers[entryIndex];
}
#endif // HAVE(36BIT_ADDRESS)
} // namespace WTF
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