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Fix to_signed_bytes_* for positive number with leading 0x80 #72

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Merged
bors merged 3 commits into from
Dec 14, 2018
Merged

Fix to_signed_bytes_* for positive number with leading 0x80 #72

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7993343
Fix `to_signed_bytes_*` for positive number with leading `0x80`
leoyvens Dec 14, 2018
443cc8e
Run rustfmt
leoyvens Dec 14, 2018
732e8e7
Test a range of round trips to/from_signed_bytes
cuviper Dec 14, 2018
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Run rustfmt
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@leoyvens
leoyvens committed Dec 14, 2018
commit 443cc8ea1f986a1503adfe75e55527b41d9adc4f
32 changes: 19 additions & 13 deletions src/bigint.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -710,9 +710,10 @@ impl ShlAssign<usize> for BigInt {
// Negative values need a rounding adjustment if there are any ones in the
// bits that are getting shifted out.
fn shr_round_down(i: &BigInt, rhs: usize) -> bool {
i.is_negative() && biguint::trailing_zeros(&i.data)
.map(|n| n < rhs)
.unwrap_or(false)
i.is_negative()
&& biguint::trailing_zeros(&i.data)
.map(|n| n < rhs)
.unwrap_or(false)
}

impl Shr<usize> for BigInt {
Expand Down Expand Up @@ -1126,15 +1127,13 @@ macro_rules! bigint_sub {
(_, NoSign) => $a_owned,
(NoSign, _) => -$b_owned,
// opposite signs => keep the sign of the left with the sum of magnitudes
(Plus, Minus) | (Minus, Plus) =>
BigInt::from_biguint($a.sign, $a_data + $b_data),
(Plus, Minus) | (Minus, Plus) => BigInt::from_biguint($a.sign, $a_data + $b_data),
// same sign => keep or toggle the sign of the left with the difference of magnitudes
(Plus, Plus) | (Minus, Minus) =>
match $a.data.cmp(&$b.data) {
Less => BigInt::from_biguint(-$a.sign, $b_data - $a_data),
Greater => BigInt::from_biguint($a.sign, $a_data - $b_data),
Equal => Zero::zero(),
},
(Plus, Plus) | (Minus, Minus) => match $a.data.cmp(&$b.data) {
Less => BigInt::from_biguint(-$a.sign, $b_data - $a_data),
Greater => BigInt::from_biguint($a.sign, $a_data - $b_data),
Equal => Zero::zero(),
},
}
};
}
Expand Down Expand Up @@ -2759,7 +2758,11 @@ impl BigInt {
pub fn to_signed_bytes_be(&self) -> Vec<u8> {
let mut bytes = self.data.to_bytes_be();
let first_byte = bytes.first().map(|v| *v).unwrap_or(0);
if first_byte > 0x7f && !(first_byte == 0x80 && bytes.iter().skip(1).all(Zero::is_zero) && self.sign == Sign::Minus) {
if first_byte > 0x7f
&& !(first_byte == 0x80
&& bytes.iter().skip(1).all(Zero::is_zero)
&& self.sign == Sign::Minus)
{
// msb used by magnitude, extend by 1 byte
bytes.insert(0, 0);
}
Expand All @@ -2783,7 +2786,10 @@ impl BigInt {
pub fn to_signed_bytes_le(&self) -> Vec<u8> {
let mut bytes = self.data.to_bytes_le();
let last_byte = bytes.last().map(|v| *v).unwrap_or(0);
if last_byte > 0x7f && !(last_byte == 0x80 && bytes.iter().rev().skip(1).all(Zero::is_zero) && self.sign == Sign::Minus)
if last_byte > 0x7f
&& !(last_byte == 0x80
&& bytes.iter().rev().skip(1).all(Zero::is_zero)
&& self.sign == Sign::Minus)
{
// msb used by magnitude, extend by 1 byte
bytes.push(0);
Expand Down
3 changes: 2 additions & 1 deletion src/biguint.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -135,7 +135,8 @@ fn from_bitwise_digits_le(v: &[u8], bits: usize) -> BigUint {
.iter()
.rev()
.fold(0, |acc, &c| (acc << bits) | c as BigDigit)
}).collect();
})
.collect();

BigUint::new(data)
}
Expand Down