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LibJS: Add spec comments to Value::to_i16()

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This commit is contained in:
Linus Groh 2022-12-10 00:01:31 +00:00
parent 1ef2b43e4c
commit b8ae9ca206
1 changed files with 13 additions and 4 deletions
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17
Userland/Libraries/LibJS/Runtime/Value.cpp
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@ -933,15 +933,24 @@ ThrowCompletionOr<u32> Value::to_u32(VM& vm) const
// 7.1.8 ToInt16 ( argument ), https://tc39.es/ecma262/#sec-toint16
ThrowCompletionOr<i16> Value::to_i16(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 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 int16bit be int modulo 2^16.
auto remainder = fmod(int_val, 65536.0);
auto int16bit = remainder >= 0.0 ? remainder : remainder + 65536.0; // The notation “x modulo y” computes a value k of the same sign as y
// 5. If int16bit ≥ 2^15, return 𝔽(int16bit - 2^16); otherwise return 𝔽(int16bit).
if (int16bit >= 32768.0)
int16bit -= 65536.0;
return static_cast<i16>(int16bit);