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LibJS: Add spec comments to Value::to_i32{,_slow_case}()

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This commit is contained in:
Linus Groh 2022-12-10 00:01:05 +00:00
parent c2d33ec48a
commit f958b19b19
1 changed files with 16 additions and 4 deletions
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20
Userland/Libraries/LibJS/Runtime/Value.cpp
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@ -870,23 +870,35 @@ ThrowCompletionOr<PropertyKey> Value::to_property_key(VM& vm) const
return MUST(key.to_string(vm));
}
// 7.1.6 ToInt32 ( argument ), https://tc39.es/ecma262/#sec-toint32
ThrowCompletionOr<i32> Value::to_i32_slow_case(VM& vm) const
{
VERIFY(!is_int32());
double value = TRY(to_number(vm)).as_double();
if (!isfinite(value) || value == 0)
// 1. Let number be ? ToNumber(argument).
double number = TRY(to_number(vm)).as_double();
// 2. If number is not finite or number is either +0𝔽 or -0𝔽, return +0𝔽.
if (!isfinite(number) || number == 0)
return 0;
auto abs = fabs(value);
// 3. Let int be the mathematical value whose sign is the sign of number and whose magnitude is floor(abs(ℝ(number))).
auto abs = fabs(number);
auto int_val = floor(abs);
if (signbit(value))
if (signbit(number))
int_val = -int_val;
// 4. Let int32bit be int modulo 2^32.
auto remainder = fmod(int_val, 4294967296.0);
auto int32bit = remainder >= 0.0 ? remainder : remainder + 4294967296.0; // The notation “x modulo y” computes a value k of the same sign as y
// 5. If int32bit ≥ 2^31, return 𝔽(int32bit - 2^32); otherwise return 𝔽(int32bit).
if (int32bit >= 2147483648.0)
int32bit -= 4294967296.0;
return static_cast<i32>(int32bit);
}
// 7.1.6 ToInt32 ( argument ), https://tc39.es/ecma262/#sec-toint32
ThrowCompletionOr<i32> Value::to_i32(VM& vm) const
{
if (is_int32())