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// Copyright 2018 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef V8_OBJECTS_SMI_H_
#define V8_OBJECTS_SMI_H_
#include "src/common/globals.h"
#include "src/objects/heap-object.h"
// Has to be the last include (doesn't have include guards):
#include "src/objects/object-macros.h"
namespace v8 {
namespace internal {
// Smi represents integer Numbers that can be stored in 31 bits.
// Smis are immediate which means they are NOT allocated in the heap.
// The ptr_ value has the following format: [31 bit signed int] 0
// For long smis it has the following format:
// [32 bit signed int] [31 bits zero padding] 0
// Smi stands for small integer.
class Smi : public Object {
public:
// This replaces the OBJECT_CONSTRUCTORS macro, because Smis are special
// in that we want them to be constexprs.
constexpr Smi() : Object() {}
explicit constexpr Smi(Address ptr) : Object(ptr) {
#if V8_CAN_HAVE_DCHECK_IN_CONSTEXPR
DCHECK(HAS_SMI_TAG(ptr));
#endif
}
Smi* operator->() { return this; }
const Smi* operator->() const { return this; }
// Returns the integer value.
inline int value() const { return Internals::SmiValue(ptr()); }
inline Smi ToUint32Smi() {
if (value() <= 0) return Smi::FromInt(0);
return Smi::FromInt(static_cast<uint32_t>(value()));
}
// Convert a Smi object to an int.
static inline int ToInt(const Object object) {
return Smi::cast(object).value();
}
// Convert a value to a Smi object.
static inline constexpr Smi FromInt(int value) {
#if V8_CAN_HAVE_DCHECK_IN_CONSTEXPR
DCHECK(Smi::IsValid(value));
#endif
return Smi(Internals::IntToSmi(value));
}
static inline Smi FromIntptr(intptr_t value) {
DCHECK(Smi::IsValid(value));
int smi_shift_bits = kSmiTagSize + kSmiShiftSize;
return Smi((static_cast<Address>(value) << smi_shift_bits) | kSmiTag);
}
// Given {value} in [0, 2^31-1], force it into Smi range by changing at most
// the MSB (leaving the lower 31 bit unchanged).
static inline Smi From31BitPattern(int value) {
return Smi::FromInt((value << (32 - kSmiValueSize)) >>
(32 - kSmiValueSize));
}
template <typename E,
typename = typename std::enable_if<std::is_enum<E>::value>::type>
static inline Smi FromEnum(E value) {
STATIC_ASSERT(sizeof(E) <= sizeof(int));
return FromInt(static_cast<int>(value));
}
// Returns whether value can be represented in a Smi.
static inline bool constexpr IsValid(intptr_t value) {
#if V8_CAN_HAVE_DCHECK_IN_CONSTEXPR
DCHECK(Internals::IsValidSmi(value) ==
(value >= kMinValue && value <= kMaxValue));
#endif
return Internals::IsValidSmi(value);
}
// Compare two Smis x, y as if they were converted to strings and then
// compared lexicographically. Returns:
// -1 if x < y.
// 0 if x == y.
// 1 if x > y.
// Returns the result (a tagged Smi) as a raw Address for ExternalReference
// usage.
V8_EXPORT_PRIVATE static Address LexicographicCompare(Isolate* isolate, Smi x,
Smi y);
DECL_CAST(Smi)
// Dispatched behavior.
V8_EXPORT_PRIVATE void SmiPrint(std::ostream& os) const; // NOLINT
DECL_VERIFIER(Smi)
// C++ does not allow us to have an object of type Smi within class Smi,
// so the kZero value has type Object. Consider it deprecated; new code
// should use zero() instead.
V8_EXPORT_PRIVATE static constexpr Object kZero = Object(0);
// If you need something with type Smi, call zero() instead. Since it is
// a constexpr, "calling" it is just as efficient as reading kZero.
static inline constexpr Smi zero() { return Smi::FromInt(0); }
static constexpr int kMinValue = kSmiMinValue;
static constexpr int kMaxValue = kSmiMaxValue;
};
CAST_ACCESSOR(Smi)
} // namespace internal
} // namespace v8
#include "src/objects/object-macros-undef.h"
#endif // V8_OBJECTS_SMI_H_
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