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LibJS: Add spec comments to Value::to_u8()

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This commit is contained in:
Linus Groh 2022-12-10 00:02:10 +00:00
parent 2a3f150ab8
commit fff5fe44c1
1 changed files with 13 additions and 4 deletions
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17
Userland/Libraries/LibJS/Runtime/Value.cpp
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@ -1009,15 +1009,24 @@ ThrowCompletionOr<i8> Value::to_i8(VM& vm) const
// 7.1.11 ToUint8 ( argument ), https://tc39.es/ecma262/#sec-touint8
ThrowCompletionOr<u8> Value::to_u8(VM& vm) const
{
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 int_val = floor(fabs(value));
if (signbit(value))
// 3. Let int be the mathematical value whose sign is the sign of number and whose magnitude is floor(abs(ℝ(number))).
auto int_val = floor(fabs(number));
if (signbit(number))
int_val = -int_val;
// 4. Let int8bit be int modulo 2^8.
auto int8bit = fmod(int_val, NumericLimits<u8>::max() + 1.0);
if (int8bit < 0)
int8bit += NumericLimits<u8>::max() + 1.0;
// 5. Return 𝔽(int8bit).
return static_cast<u8>(int8bit);
}