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fixup! factor::numeric::Montgomery: Fix overflow bug

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nicoo 2020-06-16 01:17:16 +02:00
parent 4851619d62
commit f1788d9e70
1 changed files with 9 additions and 9 deletions
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18
src/uu/factor/src/numeric.rs
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@ -80,16 +80,16 @@ impl Montgomery {
let (xnm, overflow) = (x as u128).overflowing_add(nm); // x + n*m let (xnm, overflow) = (x as u128).overflowing_add(nm); // x + n*m
debug_assert_eq!(xnm % (1 << 64), 0); debug_assert_eq!(xnm % (1 << 64), 0);
if !overflow { // (x + n*m) / R
let y = (xnm >> 64) as u64 + overflow as u64; // (x + n*m) / R // in case of overflow, this is (2¹²⁸ + xnm)/2⁶⁴ - n = xnm/2⁶⁴ + (2⁶⁴ - n)
if y >= *n { let y =
y - n (xnm >> 64) as u64 +
} else { if !overflow { 0 } else { n.wrapping_neg() };
y
} if y >= *n {
y - n
} else { } else {
// y = (2¹²⁸ + xnm)/2⁶⁴ - n = xnm/2⁶⁴ + (2⁶⁴ - n) y
(xnm >> 64) as u64 + n.wrapping_neg()
} }
} }
} }