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gecko-dev/js/public/Value.h

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
* vim: set ts=8 sts=4 et sw=4 tw=99:
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
/* JS::Value implementation. */
#ifndef js_Value_h
#define js_Value_h
#include "mozilla/Attributes.h"
#include "mozilla/Casting.h"
#include "mozilla/FloatingPoint.h"
#include "mozilla/Likely.h"
#include <limits> /* for std::numeric_limits */
#include "js-config.h"
#include "jstypes.h"
#include "js/GCAPI.h"
#include "js/RootingAPI.h"
#include "js/Utility.h"
namespace JS { class Value; }
/* JS::Value can store a full int32_t. */
#define JSVAL_INT_BITS 32
#define JSVAL_INT_MIN ((int32_t)0x80000000)
#define JSVAL_INT_MAX ((int32_t)0x7fffffff)
#if defined(JS_PUNBOX64)
# define JSVAL_TAG_SHIFT 47
#endif
// Use enums so that printing a JS::Value in the debugger shows nice
// symbolic type tags.
#if defined(_MSC_VER)
# define JS_ENUM_HEADER(id, type) enum id : type
# define JS_ENUM_FOOTER(id)
#else
# define JS_ENUM_HEADER(id, type) enum id
# define JS_ENUM_FOOTER(id) __attribute__((packed))
#endif
JS_ENUM_HEADER(JSValueType, uint8_t)
{
JSVAL_TYPE_DOUBLE = 0x00,
JSVAL_TYPE_INT32 = 0x01,
JSVAL_TYPE_UNDEFINED = 0x02,
JSVAL_TYPE_NULL = 0x03,
JSVAL_TYPE_BOOLEAN = 0x04,
JSVAL_TYPE_MAGIC = 0x05,
JSVAL_TYPE_STRING = 0x06,
JSVAL_TYPE_SYMBOL = 0x07,
JSVAL_TYPE_PRIVATE_GCTHING = 0x08,
JSVAL_TYPE_OBJECT = 0x0c,
/* These never appear in a jsval; they are only provided as an out-of-band value. */
JSVAL_TYPE_UNKNOWN = 0x20,
JSVAL_TYPE_MISSING = 0x21
} JS_ENUM_FOOTER(JSValueType);
static_assert(sizeof(JSValueType) == 1,
"compiler typed enum support is apparently buggy");
#if defined(JS_NUNBOX32)
JS_ENUM_HEADER(JSValueTag, uint32_t)
{
JSVAL_TAG_CLEAR = 0xFFFFFF80,
JSVAL_TAG_INT32 = JSVAL_TAG_CLEAR | JSVAL_TYPE_INT32,
JSVAL_TAG_UNDEFINED = JSVAL_TAG_CLEAR | JSVAL_TYPE_UNDEFINED,
JSVAL_TAG_NULL = JSVAL_TAG_CLEAR | JSVAL_TYPE_NULL,
JSVAL_TAG_BOOLEAN = JSVAL_TAG_CLEAR | JSVAL_TYPE_BOOLEAN,
JSVAL_TAG_MAGIC = JSVAL_TAG_CLEAR | JSVAL_TYPE_MAGIC,
JSVAL_TAG_STRING = JSVAL_TAG_CLEAR | JSVAL_TYPE_STRING,
JSVAL_TAG_SYMBOL = JSVAL_TAG_CLEAR | JSVAL_TYPE_SYMBOL,
JSVAL_TAG_PRIVATE_GCTHING = JSVAL_TAG_CLEAR | JSVAL_TYPE_PRIVATE_GCTHING,
JSVAL_TAG_OBJECT = JSVAL_TAG_CLEAR | JSVAL_TYPE_OBJECT
} JS_ENUM_FOOTER(JSValueTag);
static_assert(sizeof(JSValueTag) == sizeof(uint32_t),
"compiler typed enum support is apparently buggy");
#elif defined(JS_PUNBOX64)
JS_ENUM_HEADER(JSValueTag, uint32_t)
{
JSVAL_TAG_MAX_DOUBLE = 0x1FFF0,
JSVAL_TAG_INT32 = JSVAL_TAG_MAX_DOUBLE | JSVAL_TYPE_INT32,
JSVAL_TAG_UNDEFINED = JSVAL_TAG_MAX_DOUBLE | JSVAL_TYPE_UNDEFINED,
JSVAL_TAG_NULL = JSVAL_TAG_MAX_DOUBLE | JSVAL_TYPE_NULL,
JSVAL_TAG_BOOLEAN = JSVAL_TAG_MAX_DOUBLE | JSVAL_TYPE_BOOLEAN,
JSVAL_TAG_MAGIC = JSVAL_TAG_MAX_DOUBLE | JSVAL_TYPE_MAGIC,
JSVAL_TAG_STRING = JSVAL_TAG_MAX_DOUBLE | JSVAL_TYPE_STRING,
JSVAL_TAG_SYMBOL = JSVAL_TAG_MAX_DOUBLE | JSVAL_TYPE_SYMBOL,
JSVAL_TAG_PRIVATE_GCTHING = JSVAL_TAG_MAX_DOUBLE | JSVAL_TYPE_PRIVATE_GCTHING,
JSVAL_TAG_OBJECT = JSVAL_TAG_MAX_DOUBLE | JSVAL_TYPE_OBJECT
} JS_ENUM_FOOTER(JSValueTag);
static_assert(sizeof(JSValueTag) == sizeof(uint32_t),
"compiler typed enum support is apparently buggy");
JS_ENUM_HEADER(JSValueShiftedTag, uint64_t)
{
JSVAL_SHIFTED_TAG_MAX_DOUBLE = ((((uint64_t)JSVAL_TAG_MAX_DOUBLE) << JSVAL_TAG_SHIFT) | 0xFFFFFFFF),
JSVAL_SHIFTED_TAG_INT32 = (((uint64_t)JSVAL_TAG_INT32) << JSVAL_TAG_SHIFT),
JSVAL_SHIFTED_TAG_UNDEFINED = (((uint64_t)JSVAL_TAG_UNDEFINED) << JSVAL_TAG_SHIFT),
JSVAL_SHIFTED_TAG_NULL = (((uint64_t)JSVAL_TAG_NULL) << JSVAL_TAG_SHIFT),
JSVAL_SHIFTED_TAG_BOOLEAN = (((uint64_t)JSVAL_TAG_BOOLEAN) << JSVAL_TAG_SHIFT),
JSVAL_SHIFTED_TAG_MAGIC = (((uint64_t)JSVAL_TAG_MAGIC) << JSVAL_TAG_SHIFT),
JSVAL_SHIFTED_TAG_STRING = (((uint64_t)JSVAL_TAG_STRING) << JSVAL_TAG_SHIFT),
JSVAL_SHIFTED_TAG_SYMBOL = (((uint64_t)JSVAL_TAG_SYMBOL) << JSVAL_TAG_SHIFT),
JSVAL_SHIFTED_TAG_PRIVATE_GCTHING = (((uint64_t)JSVAL_TAG_PRIVATE_GCTHING) << JSVAL_TAG_SHIFT),
JSVAL_SHIFTED_TAG_OBJECT = (((uint64_t)JSVAL_TAG_OBJECT) << JSVAL_TAG_SHIFT)
} JS_ENUM_FOOTER(JSValueShiftedTag);
static_assert(sizeof(JSValueShiftedTag) == sizeof(uint64_t),
"compiler typed enum support is apparently buggy");
#endif
/*
* All our supported compilers implement C++11 |enum Foo : T| syntax, so don't
* expose these macros. (This macro exists *only* because gcc bug 51242
* <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51242> makes bit-fields of
* typed enums trigger a warning that can't be turned off. Don't expose it
* beyond this file!)
*/
#undef JS_ENUM_HEADER
#undef JS_ENUM_FOOTER
#if defined(JS_NUNBOX32)
#define JSVAL_TYPE_TO_TAG(type) ((JSValueTag)(JSVAL_TAG_CLEAR | (type)))
#define JSVAL_UPPER_EXCL_TAG_OF_PRIMITIVE_SET JSVAL_TAG_OBJECT
#define JSVAL_UPPER_INCL_TAG_OF_NUMBER_SET JSVAL_TAG_INT32
#define JSVAL_LOWER_INCL_TAG_OF_GCTHING_SET JSVAL_TAG_STRING
#elif defined(JS_PUNBOX64)
#define JSVAL_PAYLOAD_MASK 0x00007FFFFFFFFFFFLL
#define JSVAL_TAG_MASK 0xFFFF800000000000LL
#define JSVAL_TYPE_TO_TAG(type) ((JSValueTag)(JSVAL_TAG_MAX_DOUBLE | (type)))
#define JSVAL_TYPE_TO_SHIFTED_TAG(type) (((uint64_t)JSVAL_TYPE_TO_TAG(type)) << JSVAL_TAG_SHIFT)
#define JSVAL_UPPER_EXCL_TAG_OF_PRIMITIVE_SET JSVAL_TAG_OBJECT
#define JSVAL_UPPER_INCL_TAG_OF_NUMBER_SET JSVAL_TAG_INT32
#define JSVAL_LOWER_INCL_TAG_OF_GCTHING_SET JSVAL_TAG_STRING
#define JSVAL_UPPER_EXCL_SHIFTED_TAG_OF_PRIMITIVE_SET JSVAL_SHIFTED_TAG_OBJECT
#define JSVAL_UPPER_EXCL_SHIFTED_TAG_OF_NUMBER_SET JSVAL_SHIFTED_TAG_UNDEFINED
#define JSVAL_LOWER_INCL_SHIFTED_TAG_OF_GCTHING_SET JSVAL_SHIFTED_TAG_STRING
#endif /* JS_PUNBOX64 */
typedef enum JSWhyMagic
{
/** a hole in a native object's elements */
JS_ELEMENTS_HOLE,
/** there is not a pending iterator value */
JS_NO_ITER_VALUE,
/** exception value thrown when closing a generator */
JS_GENERATOR_CLOSING,
/** compiler sentinel value */
JS_NO_CONSTANT,
/** used in debug builds to catch tracing errors */
JS_THIS_POISON,
/** used in debug builds to catch tracing errors */
JS_ARG_POISON,
/** an empty subnode in the AST serializer */
JS_SERIALIZE_NO_NODE,
/** lazy arguments value on the stack */
JS_LAZY_ARGUMENTS,
/** optimized-away 'arguments' value */
JS_OPTIMIZED_ARGUMENTS,
/** magic value passed to natives to indicate construction */
JS_IS_CONSTRUCTING,
/** value of static block object slot */
JS_BLOCK_NEEDS_CLONE,
/** see class js::HashableValue */
JS_HASH_KEY_EMPTY,
/** error while running Ion code */
JS_ION_ERROR,
/** missing recover instruction result */
JS_ION_BAILOUT,
/** optimized out slot */
JS_OPTIMIZED_OUT,
/** uninitialized lexical bindings that produce ReferenceError on touch. */
JS_UNINITIALIZED_LEXICAL,
/** for local use */
JS_GENERIC_MAGIC,
JS_WHY_MAGIC_COUNT
} JSWhyMagic;
namespace js {
static inline JS::Value PoisonedObjectValue(uintptr_t poison);
} // namespace js
namespace JS {
static inline constexpr JS::Value UndefinedValue();
namespace detail {
constexpr int CanonicalizedNaNSignBit = 0;
constexpr uint64_t CanonicalizedNaNSignificand = 0x8000000000000ULL;
constexpr uint64_t CanonicalizedNaNBits =
mozilla::SpecificNaNBits<double,
detail::CanonicalizedNaNSignBit,
detail::CanonicalizedNaNSignificand>::value;
} // namespace detail
/**
* Returns a generic quiet NaN value, with all payload bits set to zero.
*
* Among other properties, this NaN's bit pattern conforms to JS::Value's
* bit pattern restrictions.
*/
static MOZ_ALWAYS_INLINE double
GenericNaN()
{
return mozilla::SpecificNaN<double>(detail::CanonicalizedNaNSignBit,
detail::CanonicalizedNaNSignificand);
}
/* MSVC with PGO miscompiles this function. */
#if defined(_MSC_VER)
# pragma optimize("g", off)
#endif
static inline double
CanonicalizeNaN(double d)
{
if (MOZ_UNLIKELY(mozilla::IsNaN(d)))
return GenericNaN();
return d;
}
#if defined(_MSC_VER)
# pragma optimize("", on)
#endif
/**
* JS::Value is the interface for a single JavaScript Engine value. A few
* general notes on JS::Value:
*
* - JS::Value has setX() and isX() members for X in
*
* { Int32, Double, String, Symbol, Boolean, Undefined, Null, Object, Magic }
*
* JS::Value also contains toX() for each of the non-singleton types.
*
* - Magic is a singleton type whose payload contains either a JSWhyMagic "reason" for
* the magic value or a uint32_t value. By providing JSWhyMagic values when
* creating and checking for magic values, it is possible to assert, at
* runtime, that only magic values with the expected reason flow through a
* particular value. For example, if cx->exception has a magic value, the
* reason must be JS_GENERATOR_CLOSING.
*
* - The JS::Value operations are preferred. The JSVAL_* operations remain for
* compatibility; they may be removed at some point. These operations mostly
* provide similar functionality. But there are a few key differences. One
* is that JS::Value gives null a separate type.
* Also, to help prevent mistakenly boxing a nullable JSObject* as an object,
* Value::setObject takes a JSObject&. (Conversely, Value::toObject returns a
* JSObject&.) A convenience member Value::setObjectOrNull is provided.
*
* - JSVAL_VOID is the same as the singleton value of the Undefined type.
*
* - Note that JS::Value is 8 bytes on 32 and 64-bit architectures. Thus, on
* 32-bit user code should avoid copying jsval/JS::Value as much as possible,
* preferring to pass by const Value&.
*/
class MOZ_NON_PARAM alignas(8) Value
{
public:
#if defined(JS_NUNBOX32)
using PayloadType = uint32_t;
#elif defined(JS_PUNBOX64)
using PayloadType = uint64_t;
#endif
/*
* N.B. the default constructor leaves Value unitialized. Adding a default
* constructor prevents Value from being stored in a union.
*/
Value() = default;
Value(const Value& v) = default;
/**
* Returns false if creating a NumberValue containing the given type would
* be lossy, true otherwise.
*/
template <typename T>
static bool isNumberRepresentable(const T t) {
return T(double(t)) == t;
}
/*** Mutators ***/
void setNull() {
data.asBits = bitsFromTagAndPayload(JSVAL_TAG_NULL, 0);
}
void setUndefined() {
data.asBits = bitsFromTagAndPayload(JSVAL_TAG_UNDEFINED, 0);
}
void setInt32(int32_t i) {
data.asBits = bitsFromTagAndPayload(JSVAL_TAG_INT32, uint32_t(i));
}
int32_t& getInt32Ref() {
MOZ_ASSERT(isInt32());
return data.s.payload.i32;
}
void setDouble(double d) {
// Don't assign to data.asDouble to fix a miscompilation with
// GCC 5.2.1 and 5.3.1. See bug 1312488.
data = layout(d);
MOZ_ASSERT(isDouble());
}
void setNaN() {
setDouble(GenericNaN());
}
double& getDoubleRef() {
MOZ_ASSERT(isDouble());
return data.asDouble;
}
void setString(JSString* str) {
MOZ_ASSERT(js::gc::IsCellPointerValid(str));
data.asBits = bitsFromTagAndPayload(JSVAL_TAG_STRING, PayloadType(str));
}
void setSymbol(JS::Symbol* sym) {
MOZ_ASSERT(js::gc::IsCellPointerValid(sym));
data.asBits = bitsFromTagAndPayload(JSVAL_TAG_SYMBOL, PayloadType(sym));
}
void setObject(JSObject& obj) {
MOZ_ASSERT(js::gc::IsCellPointerValid(&obj));
#if defined(JS_PUNBOX64)
// VisualStudio cannot contain parenthesized C++ style cast and shift
// inside decltype in template parameter:
// AssertionConditionType<decltype((uintptr_t(x) >> 1))>
// It throws syntax error.
MOZ_ASSERT((((uintptr_t)&obj) >> JSVAL_TAG_SHIFT) == 0);
#endif
setObjectNoCheck(&obj);
}
private:
void setObjectNoCheck(JSObject* obj) {
data.asBits = bitsFromTagAndPayload(JSVAL_TAG_OBJECT, PayloadType(obj));
}
friend inline Value js::PoisonedObjectValue(uintptr_t poison);
public:
void setBoolean(bool b) {
data.asBits = bitsFromTagAndPayload(JSVAL_TAG_BOOLEAN, uint32_t(b));
}
void setMagic(JSWhyMagic why) {
data.asBits = bitsFromTagAndPayload(JSVAL_TAG_MAGIC, uint32_t(why));
}
void setMagicUint32(uint32_t payload) {
data.asBits = bitsFromTagAndPayload(JSVAL_TAG_MAGIC, payload);
}
bool setNumber(uint32_t ui) {
if (ui > JSVAL_INT_MAX) {
setDouble((double)ui);
return false;
} else {
setInt32((int32_t)ui);
return true;
}
}
bool setNumber(double d) {
int32_t i;
if (mozilla::NumberIsInt32(d, &i)) {
setInt32(i);
return true;
}
setDouble(d);
return false;
}
void setObjectOrNull(JSObject* arg) {
if (arg)
setObject(*arg);
else
setNull();
}
void swap(Value& rhs) {
uint64_t tmp = rhs.data.asBits;
rhs.data.asBits = data.asBits;
data.asBits = tmp;
}
private:
JSValueTag toTag() const {
#if defined(JS_NUNBOX32)
return data.s.tag;
#elif defined(JS_PUNBOX64)
return JSValueTag(data.asBits >> JSVAL_TAG_SHIFT);
#endif
}
public:
/*** JIT-only interfaces to interact with and create raw Values ***/
#if defined(JS_NUNBOX32)
PayloadType toNunboxPayload() const {
return static_cast<PayloadType>(data.s.payload.i32);
}
JSValueTag toNunboxTag() const {
return data.s.tag;
}
#elif defined(JS_PUNBOX64)
const void* bitsAsPunboxPointer() const {
return reinterpret_cast<void*>(data.asBits);
}
#endif
/*** Value type queries ***/
/*
* N.B. GCC, in some but not all cases, chooses to emit signed comparison
* of JSValueTag even though its underlying type has been forced to be
* uint32_t. Thus, all comparisons should explicitly cast operands to
* uint32_t.
*/
bool isUndefined() const {
#if defined(JS_NUNBOX32)
return toTag() == JSVAL_TAG_UNDEFINED;
#elif defined(JS_PUNBOX64)
return data.asBits == JSVAL_SHIFTED_TAG_UNDEFINED;
#endif
}
bool isNull() const {
#if defined(JS_NUNBOX32)
return toTag() == JSVAL_TAG_NULL;
#elif defined(JS_PUNBOX64)
return data.asBits == JSVAL_SHIFTED_TAG_NULL;
#endif
}
bool isNullOrUndefined() const {
return isNull() || isUndefined();
}
bool isInt32() const {
return toTag() == JSVAL_TAG_INT32;
}
bool isInt32(int32_t i32) const {
return data.asBits == bitsFromTagAndPayload(JSVAL_TAG_INT32, uint32_t(i32));
}
bool isDouble() const {
#if defined(JS_NUNBOX32)
return uint32_t(toTag()) <= uint32_t(JSVAL_TAG_CLEAR);
#elif defined(JS_PUNBOX64)
return (data.asBits | mozilla::DoubleTypeTraits::kSignBit) <= JSVAL_SHIFTED_TAG_MAX_DOUBLE;
#endif
}
bool isNumber() const {
#if defined(JS_NUNBOX32)
MOZ_ASSERT(toTag() != JSVAL_TAG_CLEAR);
return uint32_t(toTag()) <= uint32_t(JSVAL_UPPER_INCL_TAG_OF_NUMBER_SET);
#elif defined(JS_PUNBOX64)
return data.asBits < JSVAL_UPPER_EXCL_SHIFTED_TAG_OF_NUMBER_SET;
#endif
}
bool isString() const {
return toTag() == JSVAL_TAG_STRING;
}
bool isSymbol() const {
return toTag() == JSVAL_TAG_SYMBOL;
}
bool isObject() const {
#if defined(JS_NUNBOX32)
return toTag() == JSVAL_TAG_OBJECT;
#elif defined(JS_PUNBOX64)
MOZ_ASSERT((data.asBits >> JSVAL_TAG_SHIFT) <= JSVAL_TAG_OBJECT);
return data.asBits >= JSVAL_SHIFTED_TAG_OBJECT;
#endif
}
bool isPrimitive() const {
#if defined(JS_NUNBOX32)
return uint32_t(toTag()) < uint32_t(JSVAL_UPPER_EXCL_TAG_OF_PRIMITIVE_SET);
#elif defined(JS_PUNBOX64)
return data.asBits < JSVAL_UPPER_EXCL_SHIFTED_TAG_OF_PRIMITIVE_SET;
#endif
}
bool isObjectOrNull() const {
return isObject() || isNull();
}
bool isGCThing() const {
#if defined(JS_NUNBOX32)
/* gcc sometimes generates signed < without explicit casts. */
return uint32_t(toTag()) >= uint32_t(JSVAL_LOWER_INCL_TAG_OF_GCTHING_SET);
#elif defined(JS_PUNBOX64)
return data.asBits >= JSVAL_LOWER_INCL_SHIFTED_TAG_OF_GCTHING_SET;
#endif
}
bool isBoolean() const {
return toTag() == JSVAL_TAG_BOOLEAN;
}
bool isTrue() const {
return data.asBits == bitsFromTagAndPayload(JSVAL_TAG_BOOLEAN, uint32_t(true));
}
bool isFalse() const {
return data.asBits == bitsFromTagAndPayload(JSVAL_TAG_BOOLEAN, uint32_t(false));
}
bool isMagic() const {
return toTag() == JSVAL_TAG_MAGIC;
}
bool isMagic(JSWhyMagic why) const {
MOZ_ASSERT_IF(isMagic(), data.s.payload.why == why);
return isMagic();
}
JS::TraceKind traceKind() const {
MOZ_ASSERT(isGCThing());
static_assert((JSVAL_TAG_STRING & 0x03) == size_t(JS::TraceKind::String),
"Value type tags must correspond with JS::TraceKinds.");
static_assert((JSVAL_TAG_SYMBOL & 0x03) == size_t(JS::TraceKind::Symbol),
"Value type tags must correspond with JS::TraceKinds.");
static_assert((JSVAL_TAG_OBJECT & 0x03) == size_t(JS::TraceKind::Object),
"Value type tags must correspond with JS::TraceKinds.");
if (MOZ_UNLIKELY(isPrivateGCThing()))
return JS::GCThingTraceKind(toGCThing());
return JS::TraceKind(toTag() & 0x03);
}
JSWhyMagic whyMagic() const {
MOZ_ASSERT(isMagic());
return data.s.payload.why;
}
uint32_t magicUint32() const {
MOZ_ASSERT(isMagic());
return data.s.payload.u32;
}
/*** Comparison ***/
bool operator==(const Value& rhs) const {
return data.asBits == rhs.data.asBits;
}
bool operator!=(const Value& rhs) const {
return data.asBits != rhs.data.asBits;
}
friend inline bool SameType(const Value& lhs, const Value& rhs);
/*** Extract the value's typed payload ***/
int32_t toInt32() const {
MOZ_ASSERT(isInt32());
#if defined(JS_NUNBOX32)
return data.s.payload.i32;
#elif defined(JS_PUNBOX64)
return int32_t(data.asBits);
#endif
}
double toDouble() const {
MOZ_ASSERT(isDouble());
return data.asDouble;
}
double toNumber() const {
MOZ_ASSERT(isNumber());
return isDouble() ? toDouble() : double(toInt32());
}
JSString* toString() const {
MOZ_ASSERT(isString());
#if defined(JS_NUNBOX32)
return data.s.payload.str;
#elif defined(JS_PUNBOX64)
return reinterpret_cast<JSString*>(data.asBits & JSVAL_PAYLOAD_MASK);
#endif
}
JS::Symbol* toSymbol() const {
MOZ_ASSERT(isSymbol());
#if defined(JS_NUNBOX32)
return data.s.payload.sym;
#elif defined(JS_PUNBOX64)
return reinterpret_cast<JS::Symbol*>(data.asBits & JSVAL_PAYLOAD_MASK);
#endif
}
JSObject& toObject() const {
MOZ_ASSERT(isObject());
#if defined(JS_NUNBOX32)
return *data.s.payload.obj;
#elif defined(JS_PUNBOX64)
return *toObjectOrNull();
#endif
}
JSObject* toObjectOrNull() const {
MOZ_ASSERT(isObjectOrNull());
#if defined(JS_NUNBOX32)
return data.s.payload.obj;
#elif defined(JS_PUNBOX64)
uint64_t ptrBits = data.asBits & JSVAL_PAYLOAD_MASK;
MOZ_ASSERT((ptrBits & 0x7) == 0);
return reinterpret_cast<JSObject*>(ptrBits);
#endif
}
js::gc::Cell* toGCThing() const {
MOZ_ASSERT(isGCThing());
#if defined(JS_NUNBOX32)
return data.s.payload.cell;
#elif defined(JS_PUNBOX64)
uint64_t ptrBits = data.asBits & JSVAL_PAYLOAD_MASK;
MOZ_ASSERT((ptrBits & 0x7) == 0);
return reinterpret_cast<js::gc::Cell*>(ptrBits);
#endif
}
GCCellPtr toGCCellPtr() const {
return GCCellPtr(toGCThing(), traceKind());
}
bool toBoolean() const {
MOZ_ASSERT(isBoolean());
#if defined(JS_NUNBOX32)
return bool(data.s.payload.boo);
#elif defined(JS_PUNBOX64)
return bool(data.asBits & JSVAL_PAYLOAD_MASK);
#endif
}
uint32_t payloadAsRawUint32() const {
MOZ_ASSERT(!isDouble());
return data.s.payload.u32;
}
uint64_t asRawBits() const {
return data.asBits;
}
JSValueType extractNonDoubleType() const {
uint32_t type = toTag() & 0xF;
MOZ_ASSERT(type > JSVAL_TYPE_DOUBLE);
return JSValueType(type);
}
/*
* Private API
*
* Private setters/getters allow the caller to read/write arbitrary types
* that fit in the 64-bit payload. It is the caller's responsibility, after
* storing to a value with setPrivateX to read only using getPrivateX.
* Privates values are given a type which ensures they are not marked.
*/
void setPrivate(void* ptr) {
MOZ_ASSERT((uintptr_t(ptr) & 1) == 0);
#if defined(JS_NUNBOX32)
data.s.tag = JSValueTag(0);
data.s.payload.ptr = ptr;
#elif defined(JS_PUNBOX64)
data.asBits = uintptr_t(ptr) >> 1;
#endif
MOZ_ASSERT(isDouble());
}
void* toPrivate() const {
MOZ_ASSERT(isDouble());
#if defined(JS_NUNBOX32)
return data.s.payload.ptr;
#elif defined(JS_PUNBOX64)
MOZ_ASSERT((data.asBits & 0x8000000000000000ULL) == 0);
return reinterpret_cast<void*>(data.asBits << 1);
#endif
}
void setPrivateUint32(uint32_t ui) {
MOZ_ASSERT(uint32_t(int32_t(ui)) == ui);
setInt32(int32_t(ui));
}
uint32_t toPrivateUint32() const {
return uint32_t(toInt32());
}
/*
* Private GC Thing API
*
* Non-JSObject, JSString, and JS::Symbol cells may be put into the 64-bit
* payload as private GC things. Such Values are considered isGCThing(), and
* as such, automatically marked. Their traceKind() is gotten via their
* cells.
*/
void setPrivateGCThing(js::gc::Cell* cell) {
MOZ_ASSERT(JS::GCThingTraceKind(cell) != JS::TraceKind::String,
"Private GC thing Values must not be strings. Make a StringValue instead.");
MOZ_ASSERT(JS::GCThingTraceKind(cell) != JS::TraceKind::Symbol,
"Private GC thing Values must not be symbols. Make a SymbolValue instead.");
MOZ_ASSERT(JS::GCThingTraceKind(cell) != JS::TraceKind::Object,
"Private GC thing Values must not be objects. Make an ObjectValue instead.");
MOZ_ASSERT(js::gc::IsCellPointerValid(cell));
#if defined(JS_PUNBOX64)
// VisualStudio cannot contain parenthesized C++ style cast and shift
// inside decltype in template parameter:
// AssertionConditionType<decltype((uintptr_t(x) >> 1))>
// It throws syntax error.
MOZ_ASSERT((((uintptr_t)cell) >> JSVAL_TAG_SHIFT) == 0);
#endif
data.asBits = bitsFromTagAndPayload(JSVAL_TAG_PRIVATE_GCTHING, PayloadType(cell));
}
bool isPrivateGCThing() const {
return toTag() == JSVAL_TAG_PRIVATE_GCTHING;
}
const size_t* payloadWord() const {
#if defined(JS_NUNBOX32)
return &data.s.payload.word;
#elif defined(JS_PUNBOX64)
return &data.asWord;
#endif
}
const uintptr_t* payloadUIntPtr() const {
#if defined(JS_NUNBOX32)
return &data.s.payload.uintptr;
#elif defined(JS_PUNBOX64)
return &data.asUIntPtr;
#endif
}
#if !defined(_MSC_VER) && !defined(__sparc)
// Value must be POD so that MSVC will pass it by value and not in memory
// (bug 689101); the same is true for SPARC as well (bug 737344). More
// precisely, we don't want Value return values compiled as out params.
private:
#endif
#if MOZ_LITTLE_ENDIAN
# if defined(JS_NUNBOX32)
union layout {
uint64_t asBits;
struct {
union {
int32_t i32;
uint32_t u32;
uint32_t boo; // Don't use |bool| -- it must be four bytes.
JSString* str;
JS::Symbol* sym;
JSObject* obj;
js::gc::Cell* cell;
void* ptr;
JSWhyMagic why;
size_t word;
uintptr_t uintptr;
} payload;
JSValueTag tag;
} s;
double asDouble;
void* asPtr;
layout() = default;
explicit constexpr layout(uint64_t bits) : asBits(bits) {}
explicit constexpr layout(double d) : asDouble(d) {}
} data;
# elif defined(JS_PUNBOX64)
union layout {
uint64_t asBits;
#if !defined(_WIN64)
/* MSVC does not pack these correctly :-( */
struct {
uint64_t payload47 : 47;
JSValueTag tag : 17;
} debugView;
#endif
struct {
union {
int32_t i32;
uint32_t u32;
JSWhyMagic why;
} payload;
} s;
double asDouble;
void* asPtr;
size_t asWord;
uintptr_t asUIntPtr;
layout() = default;
explicit constexpr layout(uint64_t bits) : asBits(bits) {}
explicit constexpr layout(double d) : asDouble(d) {}
} data;
# endif /* JS_PUNBOX64 */
#else /* MOZ_LITTLE_ENDIAN */
# if defined(JS_NUNBOX32)
union layout {
uint64_t asBits;
struct {
JSValueTag tag;
union {
int32_t i32;
uint32_t u32;
uint32_t boo; // Don't use |bool| -- it must be four bytes.
JSString* str;
JS::Symbol* sym;
JSObject* obj;
js::gc::Cell* cell;
void* ptr;
JSWhyMagic why;
size_t word;
uintptr_t uintptr;
} payload;
} s;
double asDouble;
void* asPtr;
layout() = default;
explicit constexpr layout(uint64_t bits) : asBits(bits) {}
explicit constexpr layout(double d) : asDouble(d) {}
} data;
# elif defined(JS_PUNBOX64)
union layout {
uint64_t asBits;
struct {
JSValueTag tag : 17;
uint64_t payload47 : 47;
} debugView;
struct {
uint32_t padding;
union {
int32_t i32;
uint32_t u32;
JSWhyMagic why;
} payload;
} s;
double asDouble;
void* asPtr;
size_t asWord;
uintptr_t asUIntPtr;
layout() = default;
explicit constexpr layout(uint64_t bits) : asBits(bits) {}
explicit constexpr layout(double d) : asDouble(d) {}
} data;
# endif /* JS_PUNBOX64 */
#endif /* MOZ_LITTLE_ENDIAN */
private:
explicit constexpr Value(uint64_t asBits) : data(asBits) {}
explicit constexpr Value(double d) : data(d) {}
void staticAssertions() {
JS_STATIC_ASSERT(sizeof(JSValueType) == 1);
JS_STATIC_ASSERT(sizeof(JSValueTag) == 4);
JS_STATIC_ASSERT(sizeof(JSWhyMagic) <= 4);
JS_STATIC_ASSERT(sizeof(Value) == 8);
}
friend constexpr Value JS::UndefinedValue();
public:
static constexpr uint64_t
bitsFromTagAndPayload(JSValueTag tag, PayloadType payload)
{
#if defined(JS_NUNBOX32)
return (uint64_t(uint32_t(tag)) << 32) | payload;
#elif defined(JS_PUNBOX64)
return (uint64_t(uint32_t(tag)) << JSVAL_TAG_SHIFT) | payload;
#endif
}
static constexpr Value
fromTagAndPayload(JSValueTag tag, PayloadType payload)
{
return fromRawBits(bitsFromTagAndPayload(tag, payload));
}
static constexpr Value
fromRawBits(uint64_t asBits) {
return Value(asBits);
}
static constexpr Value
fromInt32(int32_t i) {
return fromTagAndPayload(JSVAL_TAG_INT32, uint32_t(i));
}
static constexpr Value
fromDouble(double d) {
return Value(d);
}
} JS_HAZ_GC_POINTER;
static_assert(sizeof(Value) == 8, "Value size must leave three tag bits, be a binary power, and is ubiquitously depended upon everywhere");
inline bool
IsOptimizedPlaceholderMagicValue(const Value& v)
{
if (v.isMagic()) {
MOZ_ASSERT(v.whyMagic() == JS_OPTIMIZED_ARGUMENTS || v.whyMagic() == JS_OPTIMIZED_OUT);
return true;
}
return false;
}
static MOZ_ALWAYS_INLINE void
ExposeValueToActiveJS(const Value& v)
{
#ifdef DEBUG
Value tmp = v;
MOZ_ASSERT(!js::gc::EdgeNeedsSweepUnbarrieredSlow(&tmp));
#endif
if (v.isGCThing())
js::gc::ExposeGCThingToActiveJS(GCCellPtr(v));
}
/************************************************************************/
static inline MOZ_MAY_CALL_AFTER_MUST_RETURN Value
NullValue()
{
Value v;
v.setNull();
return v;
}
static inline constexpr Value
UndefinedValue()
{
return Value::fromTagAndPayload(JSVAL_TAG_UNDEFINED, 0);
}
static inline constexpr Value
Int32Value(int32_t i32)
{
return Value::fromInt32(i32);
}
static inline Value
DoubleValue(double dbl)
{
Value v;
v.setDouble(dbl);
return v;
}
static inline Value
CanonicalizedDoubleValue(double d)
{
return MOZ_UNLIKELY(mozilla::IsNaN(d))
? Value::fromRawBits(detail::CanonicalizedNaNBits)
: Value::fromDouble(d);
}
static inline bool
IsCanonicalized(double d)
{
if (mozilla::IsInfinite(d) || mozilla::IsFinite(d))
return true;
uint64_t bits;
mozilla::BitwiseCast<uint64_t>(d, &bits);
return (bits & ~mozilla::DoubleTypeTraits::kSignBit) == detail::CanonicalizedNaNBits;
}
static inline Value
DoubleNaNValue()
{
Value v;
v.setNaN();
return v;
}
static inline Value
Float32Value(float f)
{
Value v;
v.setDouble(f);
return v;
}
static inline Value
StringValue(JSString* str)
{
Value v;
v.setString(str);
return v;
}
static inline Value
SymbolValue(JS::Symbol* sym)
{
Value v;
v.setSymbol(sym);
return v;
}
static inline Value
BooleanValue(bool boo)
{
Value v;
v.setBoolean(boo);
return v;
}
static inline Value
TrueValue()
{
Value v;
v.setBoolean(true);
return v;
}
static inline Value
FalseValue()
{
Value v;
v.setBoolean(false);
return v;
}
static inline Value
ObjectValue(JSObject& obj)
{
Value v;
v.setObject(obj);
return v;
}
static inline Value
MagicValue(JSWhyMagic why)
{
Value v;
v.setMagic(why);
return v;
}
static inline Value
MagicValueUint32(uint32_t payload)
{
Value v;
v.setMagicUint32(payload);
return v;
}
static inline Value
NumberValue(float f)
{
Value v;
v.setNumber(f);
return v;
}
static inline Value
NumberValue(double dbl)
{
Value v;
v.setNumber(dbl);
return v;
}
static inline Value
NumberValue(int8_t i)
{
return Int32Value(i);
}
static inline Value
NumberValue(uint8_t i)
{
return Int32Value(i);
}
static inline Value
NumberValue(int16_t i)
{
return Int32Value(i);
}
static inline Value
NumberValue(uint16_t i)
{
return Int32Value(i);
}
static inline Value
NumberValue(int32_t i)
{
return Int32Value(i);
}
static inline constexpr Value
NumberValue(uint32_t i)
{
return i <= JSVAL_INT_MAX
? Int32Value(int32_t(i))
: Value::fromDouble(double(i));
}
namespace detail {
template <bool Signed>
class MakeNumberValue
{
public:
template<typename T>
static inline Value create(const T t)
{
Value v;
if (JSVAL_INT_MIN <= t && t <= JSVAL_INT_MAX)
v.setInt32(int32_t(t));
else
v.setDouble(double(t));
return v;
}
};
template <>
class MakeNumberValue<false>
{
public:
template<typename T>
static inline Value create(const T t)
{
Value v;
if (t <= JSVAL_INT_MAX)
v.setInt32(int32_t(t));
else
v.setDouble(double(t));
return v;
}
};
} // namespace detail
template <typename T>
static inline Value
NumberValue(const T t)
{
MOZ_ASSERT(Value::isNumberRepresentable(t), "value creation would be lossy");
return detail::MakeNumberValue<std::numeric_limits<T>::is_signed>::create(t);
}
static inline Value
ObjectOrNullValue(JSObject* obj)
{
Value v;
v.setObjectOrNull(obj);
return v;
}
static inline Value
PrivateValue(void* ptr)
{
Value v;
v.setPrivate(ptr);
return v;
}
static inline Value
PrivateUint32Value(uint32_t ui)
{
Value v;
v.setPrivateUint32(ui);
return v;
}
static inline Value
PrivateGCThingValue(js::gc::Cell* cell)
{
Value v;
v.setPrivateGCThing(cell);
return v;
}
inline bool
SameType(const Value& lhs, const Value& rhs)
{
#if defined(JS_NUNBOX32)
JSValueTag ltag = lhs.toTag(), rtag = rhs.toTag();
return ltag == rtag || (ltag < JSVAL_TAG_CLEAR && rtag < JSVAL_TAG_CLEAR);
#elif defined(JS_PUNBOX64)
return (lhs.isDouble() && rhs.isDouble()) ||
(((lhs.data.asBits ^ rhs.data.asBits) & 0xFFFF800000000000ULL) == 0);
#endif
}
} // namespace JS
/************************************************************************/
namespace JS {
JS_PUBLIC_API(void) HeapValuePostBarrier(Value* valuep, const Value& prev, const Value& next);
template <>
struct GCPolicy<JS::Value>
{
static Value initial() { return UndefinedValue(); }
static void trace(JSTracer* trc, Value* v, const char* name) {
js::UnsafeTraceManuallyBarrieredEdge(trc, v, name);
}
static bool isTenured(const Value& thing) {
return !thing.isGCThing() || !IsInsideNursery(thing.toGCThing());
}
static bool isValid(const Value& value) {
return !value.isGCThing() || js::gc::IsCellPointerValid(value.toGCThing());
}
};
} // namespace JS
namespace js {
template <>
struct BarrierMethods<JS::Value>
{
static gc::Cell* asGCThingOrNull(const JS::Value& v) {
return v.isGCThing() ? v.toGCThing() : nullptr;
}
static void postBarrier(JS::Value* v, const JS::Value& prev, const JS::Value& next) {
JS::HeapValuePostBarrier(v, prev, next);
}
static void exposeToJS(const JS::Value& v) {
JS::ExposeValueToActiveJS(v);
}
};
template <class Wrapper> class MutableValueOperations;
/**
* A class designed for CRTP use in implementing the non-mutating parts of the
* Value interface in Value-like classes. Wrapper must be a class inheriting
* ValueOperations<Wrapper> with a visible get() method returning a const
* reference to the Value abstracted by Wrapper.
*/
template <class Wrapper>
class WrappedPtrOperations<JS::Value, Wrapper>
{
const JS::Value& value() const { return static_cast<const Wrapper*>(this)->get(); }
public:
bool isUndefined() const { return value().isUndefined(); }
bool isNull() const { return value().isNull(); }
bool isBoolean() const { return value().isBoolean(); }
bool isTrue() const { return value().isTrue(); }
bool isFalse() const { return value().isFalse(); }
bool isNumber() const { return value().isNumber(); }
bool isInt32() const { return value().isInt32(); }
bool isInt32(int32_t i32) const { return value().isInt32(i32); }
bool isDouble() const { return value().isDouble(); }
bool isString() const { return value().isString(); }
bool isSymbol() const { return value().isSymbol(); }
bool isObject() const { return value().isObject(); }
bool isMagic() const { return value().isMagic(); }
bool isMagic(JSWhyMagic why) const { return value().isMagic(why); }
bool isGCThing() const { return value().isGCThing(); }
bool isPrimitive() const { return value().isPrimitive(); }
bool isNullOrUndefined() const { return value().isNullOrUndefined(); }
bool isObjectOrNull() const { return value().isObjectOrNull(); }
bool toBoolean() const { return value().toBoolean(); }
double toNumber() const { return value().toNumber(); }
int32_t toInt32() const { return value().toInt32(); }
double toDouble() const { return value().toDouble(); }
JSString* toString() const { return value().toString(); }
JS::Symbol* toSymbol() const { return value().toSymbol(); }
JSObject& toObject() const { return value().toObject(); }
JSObject* toObjectOrNull() const { return value().toObjectOrNull(); }
gc::Cell* toGCThing() const { return value().toGCThing(); }
JS::TraceKind traceKind() const { return value().traceKind(); }
void* toPrivate() const { return value().toPrivate(); }
uint32_t toPrivateUint32() const { return value().toPrivateUint32(); }
uint64_t asRawBits() const { return value().asRawBits(); }
JSValueType extractNonDoubleType() const { return value().extractNonDoubleType(); }
JSWhyMagic whyMagic() const { return value().whyMagic(); }
uint32_t magicUint32() const { return value().magicUint32(); }
};
/**
* A class designed for CRTP use in implementing all the mutating parts of the
* Value interface in Value-like classes. Wrapper must be a class inheriting
* MutableWrappedPtrOperations<Wrapper> with visible get() methods returning const and
* non-const references to the Value abstracted by Wrapper.
*/
template <class Wrapper>
class MutableWrappedPtrOperations<JS::Value, Wrapper> : public WrappedPtrOperations<JS::Value, Wrapper>
{
JS::Value& value() { return static_cast<Wrapper*>(this)->get(); }
public:
void setNull() { value().setNull(); }
void setUndefined() { value().setUndefined(); }
void setInt32(int32_t i) { value().setInt32(i); }
void setDouble(double d) { value().setDouble(d); }
void setNaN() { setDouble(JS::GenericNaN()); }
void setBoolean(bool b) { value().setBoolean(b); }
void setMagic(JSWhyMagic why) { value().setMagic(why); }
bool setNumber(uint32_t ui) { return value().setNumber(ui); }
bool setNumber(double d) { return value().setNumber(d); }
void setString(JSString* str) { this->value().setString(str); }
void setSymbol(JS::Symbol* sym) { this->value().setSymbol(sym); }
void setObject(JSObject& obj) { this->value().setObject(obj); }
void setObjectOrNull(JSObject* arg) { this->value().setObjectOrNull(arg); }
void setPrivate(void* ptr) { this->value().setPrivate(ptr); }
void setPrivateUint32(uint32_t ui) { this->value().setPrivateUint32(ui); }
void setPrivateGCThing(js::gc::Cell* cell) { this->value().setPrivateGCThing(cell); }
};
/*
* Augment the generic Heap<T> interface when T = Value with
* type-querying, value-extracting, and mutating operations.
*/
template <typename Wrapper>
class HeapBase<JS::Value, Wrapper> : public WrappedPtrOperations<JS::Value, Wrapper>
{
void setBarriered(const JS::Value& v) {
*static_cast<JS::Heap<JS::Value>*>(this) = v;
}
public:
void setNull() { setBarriered(JS::NullValue()); }
void setUndefined() { setBarriered(JS::UndefinedValue()); }
void setInt32(int32_t i) { setBarriered(JS::Int32Value(i)); }
void setDouble(double d) { setBarriered(JS::DoubleValue(d)); }
void setNaN() { setDouble(JS::GenericNaN()); }
void setBoolean(bool b) { setBarriered(JS::BooleanValue(b)); }
void setMagic(JSWhyMagic why) { setBarriered(JS::MagicValue(why)); }
void setString(JSString* str) { setBarriered(JS::StringValue(str)); }
void setSymbol(JS::Symbol* sym) { setBarriered(JS::SymbolValue(sym)); }
void setObject(JSObject& obj) { setBarriered(JS::ObjectValue(obj)); }
void setPrivateGCThing(js::gc::Cell* cell) { setBarriered(JS::PrivateGCThingValue(cell)); }
bool setNumber(uint32_t ui) {
if (ui > JSVAL_INT_MAX) {
setDouble((double)ui);
return false;
} else {
setInt32((int32_t)ui);
return true;
}
}
bool setNumber(double d) {
int32_t i;
if (mozilla::NumberIsInt32(d, &i)) {
setInt32(i);
return true;
}
setDouble(d);
return false;
}
void setObjectOrNull(JSObject* arg) {
if (arg)
setObject(*arg);
else
setNull();
}
};
/*
* If the Value is a GC pointer type, convert to that type and call |f| with
* the pointer. If the Value is not a GC type, calls F::defaultValue.
*/
template <typename F, typename... Args>
auto
DispatchTyped(F f, const JS::Value& val, Args&&... args)
-> decltype(f(static_cast<JSObject*>(nullptr), mozilla::Forward<Args>(args)...))
{
if (val.isString()) {
JSString* str = val.toString();
MOZ_ASSERT(gc::IsCellPointerValid(str));
return f(str, mozilla::Forward<Args>(args)...);
}
if (val.isObject()) {
JSObject* obj = &val.toObject();
MOZ_ASSERT(gc::IsCellPointerValid(obj));
return f(obj, mozilla::Forward<Args>(args)...);
}
if (val.isSymbol()) {
JS::Symbol* sym = val.toSymbol();
MOZ_ASSERT(gc::IsCellPointerValid(sym));
return f(sym, mozilla::Forward<Args>(args)...);
}
if (MOZ_UNLIKELY(val.isPrivateGCThing())) {
MOZ_ASSERT(gc::IsCellPointerValid(val.toGCThing()));
return DispatchTyped(f, val.toGCCellPtr(), mozilla::Forward<Args>(args)...);
}
MOZ_ASSERT(!val.isGCThing());
return F::defaultValue(val);
}
template <class S> struct VoidDefaultAdaptor { static void defaultValue(const S&) {} };
template <class S> struct IdentityDefaultAdaptor { static S defaultValue(const S& v) {return v;} };
template <class S, bool v> struct BoolDefaultAdaptor { static bool defaultValue(const S&) { return v; } };
static inline JS::Value
PoisonedObjectValue(uintptr_t poison)
{
JS::Value v;
v.setObjectNoCheck(reinterpret_cast<JSObject*>(poison));
return v;
}
} // namespace js
#ifdef DEBUG
namespace JS {
MOZ_ALWAYS_INLINE bool
ValueIsNotGray(const Value& value)
{
if (!value.isGCThing())
return true;
return CellIsNotGray(value.toGCThing());
}
MOZ_ALWAYS_INLINE bool
ValueIsNotGray(const Heap<Value>& value)
{
return ValueIsNotGray(value.unbarrieredGet());
}
} // namespace JS
#endif
/************************************************************************/
namespace JS {
extern JS_PUBLIC_DATA(const HandleValue) NullHandleValue;
extern JS_PUBLIC_DATA(const HandleValue) UndefinedHandleValue;
extern JS_PUBLIC_DATA(const HandleValue) TrueHandleValue;
extern JS_PUBLIC_DATA(const HandleValue) FalseHandleValue;
} // namespace JS
#endif /* js_Value_h */
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