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LibJS: Add spec comments to Value::to_u8_clamp()

This commit is contained in:
Linus Groh 2022-12-10 00:02:28 +00:00
parent fff5fe44c1
commit 34e372cbff

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@ -1033,21 +1033,39 @@ ThrowCompletionOr<u8> Value::to_u8(VM& vm) const
// 7.1.12 ToUint8Clamp ( argument ), https://tc39.es/ecma262/#sec-touint8clamp
ThrowCompletionOr<u8> Value::to_u8_clamp(VM& vm) const
{
// 1. Let number be ? ToNumber(argument).
auto number = TRY(to_number(vm));
// 2. If number is NaN, return +0𝔽.
if (number.is_nan())
return 0;
double value = number.as_double();
// 3. If (number) ≤ 0, return +0𝔽.
if (value <= 0.0)
return 0;
// 4. If (number) ≥ 255, return 255𝔽.
if (value >= 255.0)
return 255;
// 5. Let f be floor((number)).
auto int_val = floor(value);
// 6. If f + 0.5 < (number), return 𝔽(f + 1).
if (int_val + 0.5 < value)
return static_cast<u8>(int_val + 1.0);
// 7. If (number) < f + 0.5, return 𝔽(f).
if (value < int_val + 0.5)
return static_cast<u8>(int_val);
// 8. If f is odd, return 𝔽(f + 1).
if (fmod(int_val, 2.0) == 1.0)
return static_cast<u8>(int_val + 1.0);
// 9. Return 𝔽(f).
return static_cast<u8>(int_val);
}