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/*
* Copyright (C) 2021 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.
*/
#pragma once
#include "ExceptionExpectation.h"
#include "ExceptionHelpers.h"
#include "JSCJSValueInlines.h"
#include "JSObject.h"
#include "VMTrapsInlines.h"
namespace JSC {
ALWAYS_INLINE bool areKeysEqual(JSGlobalObject* globalObject, JSValue a, JSValue b)
{
// We want +0 and -0 to be compared to true here. sameValue() itself doesn't
// guarantee that, however, we normalize all keys before comparing and storing
// them in the map. The normalization will convert -0.0 and 0.0 to the integer
// representation for 0.
return sameValue(globalObject, a, b);
}
// Note that normalization is inlined in DFG's NormalizeMapKey.
// Keep in sync with the implementation of DFG and FTL normalization.
ALWAYS_INLINE JSValue normalizeMapKey(JSValue key)
{
if (!key.isNumber()) {
if (key.isHeapBigInt())
return tryConvertToBigInt32(key.asHeapBigInt());
return key;
}
if (key.isInt32())
return key;
double d = key.asDouble();
if (std::isnan(d))
return jsNaN();
int i = static_cast<int>(d);
if (i == d) {
// When a key is -0, we convert it to positive zero.
// When a key is the double representation for an integer, we convert it to an integer.
return jsNumber(i);
}
// This means key is definitely not negative zero, and it's definitely not a double representation of an integer.
return key;
}
ALWAYS_INLINE uint32_t wangsInt64Hash(uint64_t key)
{
key += ~(key << 32);
key ^= (key >> 22);
key += ~(key << 13);
key ^= (key >> 8);
key += (key << 3);
key ^= (key >> 15);
key += ~(key << 27);
key ^= (key >> 31);
return static_cast<unsigned>(key);
}
ALWAYS_INLINE uint32_t jsMapHash(JSBigInt* bigInt)
{
return bigInt->hash();
}
template<ExceptionExpectation expection>
ALWAYS_INLINE uint32_t jsMapHashImpl(JSGlobalObject* globalObject, VM& vm, JSValue value)
{
ASSERT_WITH_MESSAGE(normalizeMapKey(value) == value, "We expect normalized values flowing into this function.");
if (value.isString()) {
auto scope = DECLARE_THROW_SCOPE(vm);
auto wtfString = asString(value)->value(globalObject);
if constexpr (expection == ExceptionExpectation::CanThrow)
RETURN_IF_EXCEPTION(scope, UINT_MAX);
else
EXCEPTION_ASSERT_UNUSED(scope, !scope.exception());
return wtfString->impl()->hash();
}
if (value.isHeapBigInt())
return jsMapHash(value.asHeapBigInt());
return wangsInt64Hash(JSValue::encode(value));
}
ALWAYS_INLINE uint32_t jsMapHash(JSGlobalObject* globalObject, VM& vm, JSValue value)
{
return jsMapHashImpl<ExceptionExpectation::CanThrow>(globalObject, vm, value);
}
ALWAYS_INLINE uint32_t jsMapHashForAlreadyHashedValue(JSGlobalObject* globalObject, VM& vm, JSValue value)
{
return jsMapHashImpl<ExceptionExpectation::ShouldNotThrow>(globalObject, vm, value);
}
ALWAYS_INLINE std::optional<uint32_t> concurrentJSMapHash(JSValue key)
{
key = normalizeMapKey(key);
if (key.isString()) {
JSString* string = asString(key);
if (string->length() > 10 * 1024)
return std::nullopt;
const StringImpl* impl = string->tryGetValueImpl();
if (!impl)
return std::nullopt;
return impl->concurrentHash();
}
if (key.isHeapBigInt())
return key.asHeapBigInt()->concurrentHash();
uint64_t rawValue = JSValue::encode(key);
return wangsInt64Hash(rawValue);
}
static constexpr uint32_t hashMapInitialCapacity = 4;
ALWAYS_INLINE uint32_t shouldShrink(uint32_t capacity, uint32_t keyCount)
{
return 8 * keyCount <= capacity && capacity > hashMapInitialCapacity;
}
ALWAYS_INLINE uint32_t shouldRehash(uint32_t capacity, uint32_t keyCount, uint32_t deleteCount)
{
return 2 * (keyCount + deleteCount) >= capacity;
}
ALWAYS_INLINE uint32_t nextCapacity(uint32_t capacity, uint32_t keyCount)
{
if (!capacity)
return hashMapInitialCapacity;
if (shouldShrink(capacity, keyCount)) {
ASSERT((capacity / 2) >= hashMapInitialCapacity);
return capacity / 2;
}
if (3 * keyCount <= capacity && capacity > 64) {
// We stay at the same size if rehashing would cause us to be no more than
// 1/3rd full. This comes up for programs like this:
// Say the hash table grew to a key count of 64, causing it to grow to a capacity of 256.
// Then, the table added 63 items. The load is now 127. Then, 63 items are deleted.
// The load is still 127. Then, another item is added. The load is now 128, and we
// decide that we need to rehash. The key count is 65, almost exactly what it was
// when we grew to a capacity of 256. We don't really need to grow to a capacity
// of 512 in this situation. Instead, we choose to rehash at the same size. This
// will bring the load down to 65. We rehash into the same size when we determine
// that the new load ratio will be under 1/3rd. (We also pick a minumum capacity
// at which this rule kicks in because otherwise we will be too sensitive to rehashing
// at the same capacity).
return capacity;
}
return Checked<uint32_t>(capacity) * 2;
}
} // namespace JSC
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