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need guidence on testing

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This commit is contained in:
Giles Cope 2022-04-02 11:13:44 +01:00
parent 4bfea71637
commit 72a5e7e810
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GPG Key ID: 631F6352D4A949EF
1 changed files with 20 additions and 9 deletions
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29
library/core/src/num/mod.rs
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@ -1035,6 +1035,11 @@ macro_rules! impl_helper_for {
}
impl_helper_for! { i8 i16 i32 i64 i128 isize u8 u16 u32 u64 u128 usize }
#[inline(always)]
pub(crate) fn can_not_overflow<T>(radix: u32, is_signed_ty: bool, digits:&[u8]) -> bool {
radix <= 16 && digits.len() <= mem::size_of::<T>() * 2 - is_signed_ty as usize
}
fn from_str_radix<T: FromStrRadixHelper>(src: &str, radix: u32) -> Result<T, ParseIntError> {
use self::IntErrorKind::*;
use self::ParseIntError as PIE;
@ -1068,7 +1073,7 @@ fn from_str_radix<T: FromStrRadixHelper>(src: &str, radix: u32) -> Result<T, Par
let mut result = T::from_u32(0);
if radix <= 16 && digits.len() <= mem::size_of::<T>() * 2 - is_signed_ty as usize {
if can_not_overflow::<T>(radix, is_signed_ty, digits) {
// SAFETY: If the len of the str is short compared to the range of the type
// we are parsing into, then we can be certain that an overflow will not occur.
// This bound is when `radix.pow(digits.len()) - 1 <= T::MAX` but the condition
@ -1093,9 +1098,9 @@ fn from_str_radix<T: FromStrRadixHelper>(src: &str, radix: u32) -> Result<T, Par
run_unchecked_loop!(unchecked_sub)
};
}
} else {
} else {
macro_rules! run_checked_loop {
($checked_additive_op:ident, $overflow_err:ident) => {
($checked_additive_op:ident, $overflow_err:expr) => {
for &c in digits {
// When `radix` is passed in as a literal, rather than doing a slow `imul`
// the compiler can use shifts if `radix` can be expressed as a
@ -1110,17 +1115,23 @@ fn from_str_radix<T: FromStrRadixHelper>(src: &str, radix: u32) -> Result<T, Par
let mul = result.checked_mul(radix);
let x = (c as char).to_digit(radix).ok_or(PIE { kind: InvalidDigit })?;
result = mul.ok_or_else($overflow_err)?;
result = T::$checked_additive_op(&result, x).ok_or_else($overflow_err)?;
result = T::$checked_additive_op(&result, x).ok_or_else($overflow_err)?;
}
}
};
}
if is_positive {
let overflow_err = || PIE { kind: PosOverflow };
run_checked_loop!(checked_add, overflow_err)
run_checked_loop!(checked_add, || PIE { kind: PosOverflow })
} else {
let overflow_err = || PIE { kind: NegOverflow };
run_checked_loop!(checked_sub, overflow_err)
run_checked_loop!(checked_sub, || PIE { kind: NegOverflow })
};
}
Ok(result)
}
mod tests {
#[test]
fn test_can_not_overflow() {
assert_eq!(can_not_overflow::<i8>(10, true, "99".as_bytes()), true);
assert_eq!(can_not_overflow::<i8>(10, true, "129".as_bytes()), false);
}
}