DateInstanceCache.h [plain text]
#pragma once
#include "PureNaN.h"
#include <array>
#include <wtf/GregorianDateTime.h>
#include <wtf/HashFunctions.h>
#include <wtf/RefCounted.h>
namespace JSC {
class DateInstanceData : public RefCounted<DateInstanceData> {
public:
static Ref<DateInstanceData> create() { return adoptRef(*new DateInstanceData); }
static ptrdiff_t offsetOfGregorianDateTimeCachedForMS() { return OBJECT_OFFSETOF(DateInstanceData, m_gregorianDateTimeCachedForMS); }
static ptrdiff_t offsetOfCachedGregorianDateTime() { return OBJECT_OFFSETOF(DateInstanceData, m_cachedGregorianDateTime); }
static ptrdiff_t offsetOfGregorianDateTimeUTCCachedForMS() { return OBJECT_OFFSETOF(DateInstanceData, m_gregorianDateTimeUTCCachedForMS); }
static ptrdiff_t offsetOfCachedGregorianDateTimeUTC() { return OBJECT_OFFSETOF(DateInstanceData, m_cachedGregorianDateTimeUTC); }
double m_gregorianDateTimeCachedForMS { PNaN };
GregorianDateTime m_cachedGregorianDateTime;
double m_gregorianDateTimeUTCCachedForMS { PNaN };
GregorianDateTime m_cachedGregorianDateTimeUTC;
private:
DateInstanceData() = default;
};
class DateInstanceCache {
public:
DateInstanceCache()
{
reset();
}
void reset()
{
for (size_t i = 0; i < cacheSize; ++i)
m_cache[i].key = PNaN;
}
DateInstanceData* add(double d)
{
CacheEntry& entry = lookup(d);
if (d == entry.key)
return entry.value.get();
entry.key = d;
entry.value = DateInstanceData::create();
return entry.value.get();
}
private:
static const size_t cacheSize = 16;
struct CacheEntry {
double key;
RefPtr<DateInstanceData> value;
};
CacheEntry& lookup(double d) { return m_cache[WTF::FloatHash<double>::hash(d) & (cacheSize - 1)]; }
std::array<CacheEntry, cacheSize> m_cache;
};
}