mirror of
https://github.com/mozilla/gecko-dev.git
synced 2024-11-26 22:32:46 +00:00
552 lines
17 KiB
C++
552 lines
17 KiB
C++
/* -*- 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/. */
|
|
|
|
/* ECMAScript conversion operations. */
|
|
|
|
#ifndef js_Conversions_h
|
|
#define js_Conversions_h
|
|
|
|
#include "mozilla/Casting.h"
|
|
#include "mozilla/FloatingPoint.h"
|
|
#include "mozilla/TypeTraits.h"
|
|
|
|
#include <math.h>
|
|
|
|
#include "jspubtd.h"
|
|
|
|
#include "js/RootingAPI.h"
|
|
#include "js/Value.h"
|
|
|
|
struct JSContext;
|
|
|
|
namespace js {
|
|
|
|
/* DO NOT CALL THIS. Use JS::ToBoolean. */
|
|
extern JS_PUBLIC_API(bool)
|
|
ToBooleanSlow(JS::HandleValue v);
|
|
|
|
/* DO NOT CALL THIS. Use JS::ToNumber. */
|
|
extern JS_PUBLIC_API(bool)
|
|
ToNumberSlow(JSContext* cx, JS::Value v, double* dp);
|
|
|
|
/* DO NOT CALL THIS. Use JS::ToInt8. */
|
|
extern JS_PUBLIC_API(bool)
|
|
ToInt8Slow(JSContext *cx, JS::HandleValue v, int8_t *out);
|
|
|
|
/* DO NOT CALL THIS. Use JS::ToInt16. */
|
|
extern JS_PUBLIC_API(bool)
|
|
ToInt16Slow(JSContext *cx, JS::HandleValue v, int16_t *out);
|
|
|
|
/* DO NOT CALL THIS. Use JS::ToInt32. */
|
|
extern JS_PUBLIC_API(bool)
|
|
ToInt32Slow(JSContext* cx, JS::HandleValue v, int32_t* out);
|
|
|
|
/* DO NOT CALL THIS. Use JS::ToUint32. */
|
|
extern JS_PUBLIC_API(bool)
|
|
ToUint32Slow(JSContext* cx, JS::HandleValue v, uint32_t* out);
|
|
|
|
/* DO NOT CALL THIS. Use JS::ToUint16. */
|
|
extern JS_PUBLIC_API(bool)
|
|
ToUint16Slow(JSContext* cx, JS::HandleValue v, uint16_t* out);
|
|
|
|
/* DO NOT CALL THIS. Use JS::ToInt64. */
|
|
extern JS_PUBLIC_API(bool)
|
|
ToInt64Slow(JSContext* cx, JS::HandleValue v, int64_t* out);
|
|
|
|
/* DO NOT CALL THIS. Use JS::ToUint64. */
|
|
extern JS_PUBLIC_API(bool)
|
|
ToUint64Slow(JSContext* cx, JS::HandleValue v, uint64_t* out);
|
|
|
|
/* DO NOT CALL THIS. Use JS::ToString. */
|
|
extern JS_PUBLIC_API(JSString*)
|
|
ToStringSlow(JSContext* cx, JS::HandleValue v);
|
|
|
|
/* DO NOT CALL THIS. Use JS::ToObject. */
|
|
extern JS_PUBLIC_API(JSObject*)
|
|
ToObjectSlow(JSContext* cx, JS::HandleValue v, bool reportScanStack);
|
|
|
|
} // namespace js
|
|
|
|
namespace JS {
|
|
|
|
namespace detail {
|
|
|
|
#ifdef JS_DEBUG
|
|
/*
|
|
* Assert that we're not doing GC on cx, that we're in a request as
|
|
* needed, and that the compartments for cx and v are correct.
|
|
* Also check that GC would be safe at this point.
|
|
*/
|
|
extern JS_PUBLIC_API(void)
|
|
AssertArgumentsAreSane(JSContext* cx, HandleValue v);
|
|
#else
|
|
inline void AssertArgumentsAreSane(JSContext* cx, HandleValue v)
|
|
{}
|
|
#endif /* JS_DEBUG */
|
|
|
|
} // namespace detail
|
|
|
|
/*
|
|
* ES6 draft 20141224, 7.1.1, second algorithm.
|
|
*
|
|
* Most users shouldn't call this -- use JS::ToBoolean, ToNumber, or ToString
|
|
* instead. This will typically only be called from custom convert hooks that
|
|
* wish to fall back to the ES6 default conversion behavior shared by most
|
|
* objects in JS, codified as OrdinaryToPrimitive.
|
|
*/
|
|
extern JS_PUBLIC_API(bool)
|
|
OrdinaryToPrimitive(JSContext* cx, HandleObject obj, JSType type, MutableHandleValue vp);
|
|
|
|
/* ES6 draft 20141224, 7.1.2. */
|
|
MOZ_ALWAYS_INLINE bool
|
|
ToBoolean(HandleValue v)
|
|
{
|
|
if (v.isBoolean())
|
|
return v.toBoolean();
|
|
if (v.isInt32())
|
|
return v.toInt32() != 0;
|
|
if (v.isNullOrUndefined())
|
|
return false;
|
|
if (v.isDouble()) {
|
|
double d = v.toDouble();
|
|
return !mozilla::IsNaN(d) && d != 0;
|
|
}
|
|
if (v.isSymbol())
|
|
return true;
|
|
|
|
/* The slow path handles strings and objects. */
|
|
return js::ToBooleanSlow(v);
|
|
}
|
|
|
|
/* ES6 draft 20141224, 7.1.3. */
|
|
MOZ_ALWAYS_INLINE bool
|
|
ToNumber(JSContext* cx, HandleValue v, double* out)
|
|
{
|
|
detail::AssertArgumentsAreSane(cx, v);
|
|
|
|
if (v.isNumber()) {
|
|
*out = v.toNumber();
|
|
return true;
|
|
}
|
|
return js::ToNumberSlow(cx, v, out);
|
|
}
|
|
|
|
/* ES6 draft 20141224, ToInteger (specialized for doubles). */
|
|
inline double
|
|
ToInteger(double d)
|
|
{
|
|
if (d == 0)
|
|
return d;
|
|
|
|
if (!mozilla::IsFinite(d)) {
|
|
if (mozilla::IsNaN(d))
|
|
return 0;
|
|
return d;
|
|
}
|
|
|
|
return d < 0 ? ceil(d) : floor(d);
|
|
}
|
|
|
|
/* ES6 draft 20141224, 7.1.5. */
|
|
MOZ_ALWAYS_INLINE bool
|
|
ToInt32(JSContext* cx, JS::HandleValue v, int32_t* out)
|
|
{
|
|
detail::AssertArgumentsAreSane(cx, v);
|
|
|
|
if (v.isInt32()) {
|
|
*out = v.toInt32();
|
|
return true;
|
|
}
|
|
return js::ToInt32Slow(cx, v, out);
|
|
}
|
|
|
|
/* ES6 draft 20141224, 7.1.6. */
|
|
MOZ_ALWAYS_INLINE bool
|
|
ToUint32(JSContext* cx, HandleValue v, uint32_t* out)
|
|
{
|
|
detail::AssertArgumentsAreSane(cx, v);
|
|
|
|
if (v.isInt32()) {
|
|
*out = uint32_t(v.toInt32());
|
|
return true;
|
|
}
|
|
return js::ToUint32Slow(cx, v, out);
|
|
}
|
|
|
|
/* ES6 draft 20141224, 7.1.7. */
|
|
MOZ_ALWAYS_INLINE bool
|
|
ToInt16(JSContext *cx, JS::HandleValue v, int16_t *out)
|
|
{
|
|
detail::AssertArgumentsAreSane(cx, v);
|
|
|
|
if (v.isInt32()) {
|
|
*out = int16_t(v.toInt32());
|
|
return true;
|
|
}
|
|
return js::ToInt16Slow(cx, v, out);
|
|
}
|
|
|
|
/* ES6 draft 20141224, 7.1.8. */
|
|
MOZ_ALWAYS_INLINE bool
|
|
ToUint16(JSContext* cx, HandleValue v, uint16_t* out)
|
|
{
|
|
detail::AssertArgumentsAreSane(cx, v);
|
|
|
|
if (v.isInt32()) {
|
|
*out = uint16_t(v.toInt32());
|
|
return true;
|
|
}
|
|
return js::ToUint16Slow(cx, v, out);
|
|
}
|
|
|
|
/* ES6 draft 20141224, 7.1.9 */
|
|
MOZ_ALWAYS_INLINE bool
|
|
ToInt8(JSContext *cx, JS::HandleValue v, int8_t *out)
|
|
{
|
|
detail::AssertArgumentsAreSane(cx, v);
|
|
|
|
if (v.isInt32()) {
|
|
*out = int8_t(v.toInt32());
|
|
return true;
|
|
}
|
|
return js::ToInt8Slow(cx, v, out);
|
|
}
|
|
|
|
/*
|
|
* Non-standard, with behavior similar to that of ToInt32, except in its
|
|
* producing an int64_t.
|
|
*/
|
|
MOZ_ALWAYS_INLINE bool
|
|
ToInt64(JSContext* cx, HandleValue v, int64_t* out)
|
|
{
|
|
detail::AssertArgumentsAreSane(cx, v);
|
|
|
|
if (v.isInt32()) {
|
|
*out = int64_t(v.toInt32());
|
|
return true;
|
|
}
|
|
return js::ToInt64Slow(cx, v, out);
|
|
}
|
|
|
|
/*
|
|
* Non-standard, with behavior similar to that of ToUint32, except in its
|
|
* producing a uint64_t.
|
|
*/
|
|
MOZ_ALWAYS_INLINE bool
|
|
ToUint64(JSContext* cx, HandleValue v, uint64_t* out)
|
|
{
|
|
detail::AssertArgumentsAreSane(cx, v);
|
|
|
|
if (v.isInt32()) {
|
|
*out = uint64_t(v.toInt32());
|
|
return true;
|
|
}
|
|
return js::ToUint64Slow(cx, v, out);
|
|
}
|
|
|
|
/* ES6 draft 20141224, 7.1.12. */
|
|
MOZ_ALWAYS_INLINE JSString*
|
|
ToString(JSContext* cx, HandleValue v)
|
|
{
|
|
detail::AssertArgumentsAreSane(cx, v);
|
|
|
|
if (v.isString())
|
|
return v.toString();
|
|
return js::ToStringSlow(cx, v);
|
|
}
|
|
|
|
/* ES6 draft 20141224, 7.1.13. */
|
|
inline JSObject*
|
|
ToObject(JSContext* cx, HandleValue v)
|
|
{
|
|
detail::AssertArgumentsAreSane(cx, v);
|
|
|
|
if (v.isObject())
|
|
return &v.toObject();
|
|
return js::ToObjectSlow(cx, v, false);
|
|
}
|
|
|
|
namespace detail {
|
|
|
|
/*
|
|
* Convert a double value to ResultType (an unsigned integral type) using
|
|
* ECMAScript-style semantics (that is, in like manner to how ECMAScript's
|
|
* ToInt32 converts to int32_t).
|
|
*
|
|
* If d is infinite or NaN, return 0.
|
|
* Otherwise compute d2 = sign(d) * floor(abs(d)), and return the ResultType
|
|
* value congruent to d2 mod 2**(bit width of ResultType).
|
|
*
|
|
* The algorithm below is inspired by that found in
|
|
* <http://trac.webkit.org/changeset/67825/trunk/JavaScriptCore/runtime/JSValue.cpp>
|
|
* but has been generalized to all integer widths.
|
|
*/
|
|
template<typename ResultType>
|
|
inline ResultType
|
|
ToUintWidth(double d)
|
|
{
|
|
static_assert(mozilla::IsUnsigned<ResultType>::value,
|
|
"ResultType must be an unsigned type");
|
|
|
|
uint64_t bits = mozilla::BitwiseCast<uint64_t>(d);
|
|
unsigned DoubleExponentShift = mozilla::FloatingPoint<double>::kExponentShift;
|
|
|
|
// Extract the exponent component. (Be careful here! It's not technically
|
|
// the exponent in NaN, infinities, and subnormals.)
|
|
int_fast16_t exp =
|
|
int_fast16_t((bits & mozilla::FloatingPoint<double>::kExponentBits) >> DoubleExponentShift) -
|
|
int_fast16_t(mozilla::FloatingPoint<double>::kExponentBias);
|
|
|
|
// If the exponent's less than zero, abs(d) < 1, so the result is 0. (This
|
|
// also handles subnormals.)
|
|
if (exp < 0)
|
|
return 0;
|
|
|
|
uint_fast16_t exponent = mozilla::AssertedCast<uint_fast16_t>(exp);
|
|
|
|
// If the exponent is greater than or equal to the bits of precision of a
|
|
// double plus ResultType's width, the number is either infinite, NaN, or
|
|
// too large to have lower-order bits in the congruent value. (Example:
|
|
// 2**84 is exactly representable as a double. The next exact double is
|
|
// 2**84 + 2**32. Thus if ResultType is int32_t, an exponent >= 84 implies
|
|
// floor(abs(d)) == 0 mod 2**32.) Return 0 in all these cases.
|
|
const size_t ResultWidth = CHAR_BIT * sizeof(ResultType);
|
|
if (exponent >= DoubleExponentShift + ResultWidth)
|
|
return 0;
|
|
|
|
// The significand contains the bits that will determine the final result.
|
|
// Shift those bits left or right, according to the exponent, to their
|
|
// locations in the unsigned binary representation of floor(abs(d)).
|
|
static_assert(sizeof(ResultType) <= sizeof(uint64_t),
|
|
"Left-shifting below would lose upper bits");
|
|
ResultType result = (exponent > DoubleExponentShift)
|
|
? ResultType(bits << (exponent - DoubleExponentShift))
|
|
: ResultType(bits >> (DoubleExponentShift - exponent));
|
|
|
|
// Two further complications remain. First, |result| may contain bogus
|
|
// sign/exponent bits. Second, IEEE-754 numbers' significands (excluding
|
|
// subnormals, but we already handled those) have an implicit leading 1
|
|
// which may affect the final result.
|
|
//
|
|
// It may appear that there's complexity here depending on how ResultWidth
|
|
// and DoubleExponentShift relate, but it turns out there's not.
|
|
//
|
|
// Assume ResultWidth < DoubleExponentShift:
|
|
// Only right-shifts leave bogus bits in |result|. For this to happen,
|
|
// we must right-shift by > |DoubleExponentShift - ResultWidth|, implying
|
|
// |exponent < ResultWidth|.
|
|
// The implicit leading bit only matters if it appears in the final
|
|
// result -- if |2**exponent mod 2**ResultWidth != 0|. This implies
|
|
// |exponent < ResultWidth|.
|
|
// Otherwise assume ResultWidth >= DoubleExponentShift:
|
|
// Any left-shift less than |ResultWidth - DoubleExponentShift| leaves
|
|
// bogus bits in |result|. This implies |exponent < ResultWidth|. Any
|
|
// right-shift less than |ResultWidth| does too, which implies
|
|
// |DoubleExponentShift - ResultWidth < exponent|. By assumption, then,
|
|
// |exponent| is negative, but we excluded that above. So bogus bits
|
|
// need only |exponent < ResultWidth|.
|
|
// The implicit leading bit matters identically to the other case, so
|
|
// again, |exponent < ResultWidth|.
|
|
if (exponent < ResultWidth) {
|
|
ResultType implicitOne = ResultType(1) << exponent;
|
|
result &= implicitOne - 1; // remove bogus bits
|
|
result += implicitOne; // add the implicit bit
|
|
}
|
|
|
|
// Compute the congruent value in the signed range.
|
|
return (bits & mozilla::FloatingPoint<double>::kSignBit) ? ~result + 1 : result;
|
|
}
|
|
|
|
template<typename ResultType>
|
|
inline ResultType
|
|
ToIntWidth(double d)
|
|
{
|
|
static_assert(mozilla::IsSigned<ResultType>::value,
|
|
"ResultType must be a signed type");
|
|
|
|
const ResultType MaxValue = (1ULL << (CHAR_BIT * sizeof(ResultType) - 1)) - 1;
|
|
const ResultType MinValue = -MaxValue - 1;
|
|
|
|
typedef typename mozilla::MakeUnsigned<ResultType>::Type UnsignedResult;
|
|
UnsignedResult u = ToUintWidth<UnsignedResult>(d);
|
|
if (u <= UnsignedResult(MaxValue))
|
|
return static_cast<ResultType>(u);
|
|
return (MinValue + static_cast<ResultType>(u - MaxValue)) - 1;
|
|
}
|
|
|
|
} // namespace detail
|
|
|
|
/* ES5 9.5 ToInt32 (specialized for doubles). */
|
|
inline int32_t
|
|
ToInt32(double d)
|
|
{
|
|
// clang crashes compiling this when targeting arm-darwin:
|
|
// https://llvm.org/bugs/show_bug.cgi?id=22974
|
|
#if defined (__arm__) && defined (__GNUC__) && !defined(__APPLE__)
|
|
int32_t i;
|
|
uint32_t tmp0;
|
|
uint32_t tmp1;
|
|
uint32_t tmp2;
|
|
asm (
|
|
// We use a pure integer solution here. In the 'softfp' ABI, the argument
|
|
// will start in r0 and r1, and VFP can't do all of the necessary ECMA
|
|
// conversions by itself so some integer code will be required anyway. A
|
|
// hybrid solution is faster on A9, but this pure integer solution is
|
|
// notably faster for A8.
|
|
|
|
// %0 is the result register, and may alias either of the %[QR]1 registers.
|
|
// %Q4 holds the lower part of the mantissa.
|
|
// %R4 holds the sign, exponent, and the upper part of the mantissa.
|
|
// %1, %2 and %3 are used as temporary values.
|
|
|
|
// Extract the exponent.
|
|
" mov %1, %R4, LSR #20\n"
|
|
" bic %1, %1, #(1 << 11)\n" // Clear the sign.
|
|
|
|
// Set the implicit top bit of the mantissa. This clobbers a bit of the
|
|
// exponent, but we have already extracted that.
|
|
" orr %R4, %R4, #(1 << 20)\n"
|
|
|
|
// Special Cases
|
|
// We should return zero in the following special cases:
|
|
// - Exponent is 0x000 - 1023: +/-0 or subnormal.
|
|
// - Exponent is 0x7ff - 1023: +/-INFINITY or NaN
|
|
// - This case is implicitly handled by the standard code path anyway,
|
|
// as shifting the mantissa up by the exponent will result in '0'.
|
|
//
|
|
// The result is composed of the mantissa, prepended with '1' and
|
|
// bit-shifted left by the (decoded) exponent. Note that because the r1[20]
|
|
// is the bit with value '1', r1 is effectively already shifted (left) by
|
|
// 20 bits, and r0 is already shifted by 52 bits.
|
|
|
|
// Adjust the exponent to remove the encoding offset. If the decoded
|
|
// exponent is negative, quickly bail out with '0' as such values round to
|
|
// zero anyway. This also catches +/-0 and subnormals.
|
|
" sub %1, %1, #0xff\n"
|
|
" subs %1, %1, #0x300\n"
|
|
" bmi 8f\n"
|
|
|
|
// %1 = (decoded) exponent >= 0
|
|
// %R4 = upper mantissa and sign
|
|
|
|
// ---- Lower Mantissa ----
|
|
" subs %3, %1, #52\n" // Calculate exp-52
|
|
" bmi 1f\n"
|
|
|
|
// Shift r0 left by exp-52.
|
|
// Ensure that we don't overflow ARM's 8-bit shift operand range.
|
|
// We need to handle anything up to an 11-bit value here as we know that
|
|
// 52 <= exp <= 1024 (0x400). Any shift beyond 31 bits results in zero
|
|
// anyway, so as long as we don't touch the bottom 5 bits, we can use
|
|
// a logical OR to push long shifts into the 32 <= (exp&0xff) <= 255 range.
|
|
" bic %2, %3, #0xff\n"
|
|
" orr %3, %3, %2, LSR #3\n"
|
|
// We can now perform a straight shift, avoiding the need for any
|
|
// conditional instructions or extra branches.
|
|
" mov %Q4, %Q4, LSL %3\n"
|
|
" b 2f\n"
|
|
"1:\n" // Shift r0 right by 52-exp.
|
|
// We know that 0 <= exp < 52, and we can shift up to 255 bits so 52-exp
|
|
// will always be a valid shift and we can sk%3 the range check for this case.
|
|
" rsb %3, %1, #52\n"
|
|
" mov %Q4, %Q4, LSR %3\n"
|
|
|
|
// %1 = (decoded) exponent
|
|
// %R4 = upper mantissa and sign
|
|
// %Q4 = partially-converted integer
|
|
|
|
"2:\n"
|
|
// ---- Upper Mantissa ----
|
|
// This is much the same as the lower mantissa, with a few different
|
|
// boundary checks and some masking to hide the exponent & sign bit in the
|
|
// upper word.
|
|
// Note that the upper mantissa is pre-shifted by 20 in %R4, but we shift
|
|
// it left more to remove the sign and exponent so it is effectively
|
|
// pre-shifted by 31 bits.
|
|
" subs %3, %1, #31\n" // Calculate exp-31
|
|
" mov %1, %R4, LSL #11\n" // Re-use %1 as a temporary register.
|
|
" bmi 3f\n"
|
|
|
|
// Shift %R4 left by exp-31.
|
|
// Avoid overflowing the 8-bit shift range, as before.
|
|
" bic %2, %3, #0xff\n"
|
|
" orr %3, %3, %2, LSR #3\n"
|
|
// Perform the shift.
|
|
" mov %2, %1, LSL %3\n"
|
|
" b 4f\n"
|
|
"3:\n" // Shift r1 right by 31-exp.
|
|
// We know that 0 <= exp < 31, and we can shift up to 255 bits so 31-exp
|
|
// will always be a valid shift and we can skip the range check for this case.
|
|
" rsb %3, %3, #0\n" // Calculate 31-exp from -(exp-31)
|
|
" mov %2, %1, LSR %3\n" // Thumb-2 can't do "LSR %3" in "orr".
|
|
|
|
// %Q4 = partially-converted integer (lower)
|
|
// %R4 = upper mantissa and sign
|
|
// %2 = partially-converted integer (upper)
|
|
|
|
"4:\n"
|
|
// Combine the converted parts.
|
|
" orr %Q4, %Q4, %2\n"
|
|
// Negate the result if we have to, and move it to %0 in the process. To
|
|
// avoid conditionals, we can do this by inverting on %R4[31], then adding
|
|
// %R4[31]>>31.
|
|
" eor %Q4, %Q4, %R4, ASR #31\n"
|
|
" add %0, %Q4, %R4, LSR #31\n"
|
|
" b 9f\n"
|
|
"8:\n"
|
|
// +/-INFINITY, +/-0, subnormals, NaNs, and anything else out-of-range that
|
|
// will result in a conversion of '0'.
|
|
" mov %0, #0\n"
|
|
"9:\n"
|
|
: "=r" (i), "=&r" (tmp0), "=&r" (tmp1), "=&r" (tmp2), "=&r" (d)
|
|
: "4" (d)
|
|
: "cc"
|
|
);
|
|
return i;
|
|
#else
|
|
return detail::ToIntWidth<int32_t>(d);
|
|
#endif
|
|
}
|
|
|
|
/* ES5 9.6 (specialized for doubles). */
|
|
inline uint32_t
|
|
ToUint32(double d)
|
|
{
|
|
return detail::ToUintWidth<uint32_t>(d);
|
|
}
|
|
|
|
/* WEBIDL 4.2.4 */
|
|
inline int8_t
|
|
ToInt8(double d)
|
|
{
|
|
return detail::ToIntWidth<int8_t>(d);
|
|
}
|
|
|
|
/* WEBIDL 4.2.6 */
|
|
inline int16_t
|
|
ToInt16(double d)
|
|
{
|
|
return detail::ToIntWidth<int16_t>(d);
|
|
}
|
|
|
|
/* WEBIDL 4.2.10 */
|
|
inline int64_t
|
|
ToInt64(double d)
|
|
{
|
|
return detail::ToIntWidth<int64_t>(d);
|
|
}
|
|
|
|
/* WEBIDL 4.2.11 */
|
|
inline uint64_t
|
|
ToUint64(double d)
|
|
{
|
|
return detail::ToUintWidth<uint64_t>(d);
|
|
}
|
|
|
|
} // namespace JS
|
|
|
|
#endif /* js_Conversions_h */
|