diff options
| -rw-r--r-- | src/passwordmaker/base_conversion/iterative_conversion.rs | 19 |
1 files changed, 17 insertions, 2 deletions
diff --git a/src/passwordmaker/base_conversion/iterative_conversion.rs b/src/passwordmaker/base_conversion/iterative_conversion.rs index 438ef20..7d52e9b 100644 --- a/src/passwordmaker/base_conversion/iterative_conversion.rs +++ b/src/passwordmaker/base_conversion/iterative_conversion.rs @@ -17,6 +17,7 @@ pub(crate) struct IterativeBaseConversion<V,B>{ current_base_power : V, remaining_digits : usize, base : B, + switch_to_multiplication : bool, //count the number of divisions. After 1, current_value is smaller than max_base_power. After 2, it's safe to mutliply current_value by base. } impl<V,B> IterativeBaseConversion<V,B> @@ -32,6 +33,7 @@ impl<V,B> IterativeBaseConversion<V,B> current_base_power, remaining_digits: highest_fitting_exponent + 1, //to the power of 0 is a digit too. Soo, if base^n is the largest fitting exponent, n+1 digits. base, + switch_to_multiplication: false } } @@ -59,7 +61,8 @@ impl<V,B> IterativeBaseConversion<V,B> impl<V,B> std::iter::Iterator for IterativeBaseConversion<V,B> where V : for<'a> DivAssign<&'a B> + //used between steps to go to next-lower current_base_power RemAssignWithQuotient+ //used to get the result of each step. - TryInto<B> //used to convert the result of each step. We _know_ this cannot fail, but requiring Into would be wrong. + TryInto<B>, //used to convert the result of each step. We _know_ this cannot fail, but requiring Into would be wrong. + for<'a> &'a V : Mul<&'a B, Output = Option<V>> { type Item = B; @@ -69,7 +72,12 @@ impl<V,B> std::iter::Iterator for IterativeBaseConversion<V,B> } else { let result = self.current_value.rem_assign_with_quotient(&self.current_base_power); - self.current_base_power /= &self.base; + if self.switch_to_multiplication { + self.current_value = (&self.current_value * &self.base).expect("Cannot overflow."); + } else { + self.current_base_power /= &self.base; + self.switch_to_multiplication = true; + } self.remaining_digits = self.remaining_digits - 1; //this cannot ever yield None. @@ -171,4 +179,11 @@ mod iterative_conversion_tests{ // 3YPRS4FaC1KU assert_eq!(i.skip_while(|x| *x == 0_u64).collect::<Vec<_>>(), vec![3, 34, 25, 27, 28, 4, 15, 36, 12, 1, 20, 30]); } + #[test] + fn test_overflow_in_switch_to_multiplication(){ + //This should simply not overflow ever. + let i = IterativeBaseConversion::new(MyU128(u128::MAX), 40); + let result = i.skip_while(|x| *x == 0_u64).collect::<Vec<_>>(); + assert_eq!(result, vec![1, 8, 14, 11, 10, 3, 37, 5, 26, 17, 14, 0, 23, 37, 35, 24, 3, 11, 27, 20, 34, 18, 12, 6, 15]); + } }
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