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WIP: Moving internals from Vec to Cow (Starting point for discussion) #286

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WIP: Moving internals from Vec to Cow (Starting point for discussion) #286

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77 changes: 56 additions & 21 deletions src/biguint.rs
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Original file line number Diff line number Diff line change
@@ -1,5 +1,5 @@
use crate::big_digit::{self, BigDigit};
use crate::std_alloc::{String, Vec};
use crate::std_alloc::{Cow, String, Vec};

use core::cmp;
use core::cmp::Ordering;
Expand Down Expand Up @@ -36,7 +36,7 @@ pub use self::iter::{U32Digits, U64Digits};

/// A big unsigned integer type.
pub struct BigUint {
data: Vec<BigDigit>,
data: Cow<'static, [BigDigit]>,
}

// Note: derived `Clone` doesn't specialize `clone_from`,
Expand Down Expand Up @@ -146,12 +146,19 @@ impl fmt::Octal for BigUint {
impl Zero for BigUint {
#[inline]
fn zero() -> BigUint {
BigUint { data: Vec::new() }
BigUint {
data: Cow::Borrowed(&[]),
}
}

#[inline]
fn set_zero(&mut self) {
self.data.clear();
match &mut self.data {
Cow::Borrowed(s) => {
*s = &[];
}
Cow::Owned(v) => v.clear(),
}
}

#[inline]
Expand All @@ -163,13 +170,22 @@ impl Zero for BigUint {
impl One for BigUint {
#[inline]
fn one() -> BigUint {
BigUint { data: vec![1] }
BigUint {
data: Cow::Borrowed(&[1]),
}
}

#[inline]
fn set_one(&mut self) {
self.data.clear();
self.data.push(1);
match &mut self.data {
Cow::Borrowed(s) => {
*s = &[1];
}
Cow::Owned(v) => {
v.clear();
v.push(1);
}
}
}

#[inline]
Expand Down Expand Up @@ -515,7 +531,10 @@ pub trait ToBigUint {
/// The digits are in little-endian base matching `BigDigit`.
#[inline]
pub(crate) fn biguint_from_vec(digits: Vec<BigDigit>) -> BigUint {
BigUint { data: digits }.normalized()
BigUint {
data: Cow::Owned(digits),
}
.normalized()
}

impl BigUint {
Expand Down Expand Up @@ -553,13 +572,15 @@ impl BigUint {
/// The base 2<sup>32</sup> digits are ordered least significant digit first.
#[inline]
pub fn assign_from_slice(&mut self, slice: &[u32]) {
self.data.clear();
let mut data = Vec::new();

#[cfg(not(u64_digit))]
self.data.extend_from_slice(slice);
data.extend_from_slice(slice);

#[cfg(u64_digit)]
self.data.extend(slice.chunks(2).map(u32_chunk_to_u64));
data.extend(slice.chunks(2).map(u32_chunk_to_u64));

self.data = Cow::Owned(data);

self.normalize();
}
Expand Down Expand Up @@ -755,7 +776,10 @@ impl BigUint {
/// ```
#[inline]
pub fn iter_u32_digits(&self) -> U32Digits<'_> {
U32Digits::new(self.data.as_slice())
U32Digits::new(match &self.data {
Cow::Borrowed(v) => v,
Cow::Owned(v) => v.as_slice(),
})
}

/// Returns an iterator of `u64` digits representation of the [`BigUint`] ordered least
Expand All @@ -774,7 +798,10 @@ impl BigUint {
/// ```
#[inline]
pub fn iter_u64_digits(&self) -> U64Digits<'_> {
U64Digits::new(self.data.as_slice())
U64Digits::new(match &self.data {
Cow::Borrowed(v) => v,
Cow::Owned(v) => v.as_slice(),
})
}

/// Returns the integer formatted as a string in the given radix.
Expand Down Expand Up @@ -851,10 +878,15 @@ impl BigUint {
fn normalize(&mut self) {
if let Some(&0) = self.data.last() {
let len = self.data.iter().rposition(|&d| d != 0).map_or(0, |i| i + 1);
self.data.truncate(len);
self.data.to_mut().truncate(len);
}
if self.data.len() < self.data.capacity() / 4 {
self.data.shrink_to_fit();
match &mut self.data {
Cow::Owned(v) => {
if v.len() < v.capacity() / 4 {
v.shrink_to_fit();
}
}
_ => {}
}
}

Expand Down Expand Up @@ -948,11 +980,11 @@ impl BigUint {
if value {
if digit_index >= self.data.len() {
let new_len = digit_index.saturating_add(1);
self.data.resize(new_len, 0);
self.data.to_mut().resize(new_len, 0);
}
self.data[digit_index] |= bit_mask;
self.data.to_mut()[digit_index] |= bit_mask;
} else if digit_index < self.data.len() {
self.data[digit_index] &= !bit_mask;
self.data.to_mut()[digit_index] &= !bit_mask;
// the top bit may have been cleared, so normalize
self.normalize();
}
Expand Down Expand Up @@ -998,15 +1030,18 @@ impl IntDigits for BigUint {
}
#[inline]
fn digits_mut(&mut self) -> &mut Vec<BigDigit> {
&mut self.data
self.data.to_mut()
}
#[inline]
fn normalize(&mut self) {
self.normalize();
}
#[inline]
fn capacity(&self) -> usize {
self.data.capacity()
match &self.data {
Cow::Borrowed(v) => v.len(),
Cow::Owned(v) => v.capacity(),
}
}
#[inline]
fn len(&self) -> usize {
Expand Down
30 changes: 16 additions & 14 deletions src/biguint/addition.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -99,14 +99,16 @@ impl AddAssign<&BigUint> for BigUint {
fn add_assign(&mut self, other: &BigUint) {
let self_len = self.data.len();
let carry = if self_len < other.data.len() {
let lo_carry = __add2(&mut self.data[..], &other.data[..self_len]);
self.data.extend_from_slice(&other.data[self_len..]);
__add2(&mut self.data[self_len..], &[lo_carry])
let lo_carry = __add2(&mut self.data.to_mut()[..], &other.data[..self_len]);
self.data
.to_mut()
.extend_from_slice(&other.data[self_len..]);
__add2(&mut self.data.to_mut()[self_len..], &[lo_carry])
} else {
__add2(&mut self.data[..], &other.data[..])
__add2(&mut self.data.to_mut()[..], &other.data[..])
};
if carry != 0 {
self.data.push(carry);
self.data.to_mut().push(carry);
}
}
}
Expand All @@ -132,12 +134,12 @@ impl AddAssign<u32> for BigUint {
fn add_assign(&mut self, other: u32) {
if other != 0 {
if self.data.is_empty() {
self.data.push(0);
self.data.to_mut().push(0);
}

let carry = __add2(&mut self.data, &[other as BigDigit]);
let carry = __add2(&mut self.data.to_mut(), &[other as BigDigit]);
if carry != 0 {
self.data.push(carry);
self.data.to_mut().push(carry);
}
}
}
Expand Down Expand Up @@ -177,12 +179,12 @@ impl AddAssign<u64> for BigUint {
fn add_assign(&mut self, other: u64) {
if other != 0 {
if self.data.is_empty() {
self.data.push(0);
self.data.to_mut().push(0);
}

let carry = __add2(&mut self.data, &[other as BigDigit]);
let carry = __add2(&mut self.data.to_mut(), &[other as BigDigit]);
if carry != 0 {
self.data.push(carry);
self.data.to_mut().push(carry);
}
}
}
Expand Down Expand Up @@ -233,12 +235,12 @@ impl AddAssign<u128> for BigUint {
*self += lo;
} else {
while self.data.len() < 2 {
self.data.push(0);
self.data.to_mut().push(0);
}

let carry = __add2(&mut self.data, &[lo, hi]);
let carry = __add2(&mut self.data.to_mut(), &[lo, hi]);
if carry != 0 {
self.data.push(carry);
self.data.to_mut().push(carry);
}
}
}
Expand Down
12 changes: 9 additions & 3 deletions src/biguint/arbitrary.rs
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Original file line number Diff line number Diff line change
@@ -1,9 +1,9 @@
use super::{biguint_from_vec, BigUint};

use crate::big_digit::BigDigit;
#[cfg(feature = "quickcheck")]
use crate::std_alloc::Box;
use crate::std_alloc::Vec;
#[cfg(feature = "quickcheck")]
use crate::std_alloc::{Box, Cow};

#[cfg(feature = "quickcheck")]
impl quickcheck::Arbitrary for BigUint {
Expand All @@ -14,7 +14,13 @@ impl quickcheck::Arbitrary for BigUint {

fn shrink(&self) -> Box<dyn Iterator<Item = Self>> {
// Use shrinker from Vec
Box::new(self.data.shrink().map(biguint_from_vec))
Box::new(
match &self.data {
Cow::Owned(v) => v.shrink(),
Cow::Borrowed(v) => v.to_vec().shrink(),
}
.map(biguint_from_vec),
)
}
}

Expand Down
12 changes: 6 additions & 6 deletions src/biguint/bits.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -35,10 +35,10 @@ impl BitAnd<&BigUint> for BigUint {
impl BitAndAssign<&BigUint> for BigUint {
#[inline]
fn bitand_assign(&mut self, other: &BigUint) {
for (ai, &bi) in self.data.iter_mut().zip(other.data.iter()) {
for (ai, &bi) in self.data.to_mut().iter_mut().zip(other.data.iter()) {
*ai &= bi;
}
self.data.truncate(other.data.len());
self.data.to_mut().truncate(other.data.len());
self.normalize();
}
}
Expand All @@ -57,12 +57,12 @@ impl BitOr<&BigUint> for BigUint {
impl BitOrAssign<&BigUint> for BigUint {
#[inline]
fn bitor_assign(&mut self, other: &BigUint) {
for (ai, &bi) in self.data.iter_mut().zip(other.data.iter()) {
for (ai, &bi) in self.data.to_mut().iter_mut().zip(other.data.iter()) {
*ai |= bi;
}
if other.data.len() > self.data.len() {
let extra = &other.data[self.data.len()..];
self.data.extend(extra.iter().cloned());
self.data.to_mut().extend(extra.iter().cloned());
}
}
}
Expand All @@ -81,12 +81,12 @@ impl BitXor<&BigUint> for BigUint {
impl BitXorAssign<&BigUint> for BigUint {
#[inline]
fn bitxor_assign(&mut self, other: &BigUint) {
for (ai, &bi) in self.data.iter_mut().zip(other.data.iter()) {
for (ai, &bi) in self.data.to_mut().iter_mut().zip(other.data.iter()) {
*ai ^= bi;
}
if other.data.len() > self.data.len() {
let extra = &other.data[self.data.len()..];
self.data.extend(extra.iter().cloned());
self.data.to_mut().extend(extra.iter().cloned());
}
self.normalize();
}
Expand Down
6 changes: 3 additions & 3 deletions src/biguint/convert.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -498,7 +498,7 @@ impl From<u64> for BigUint {
let mut ret: BigUint = Zero::zero();

while n != 0 {
ret.data.push(n as BigDigit);
ret.data.to_mut().push(n as BigDigit);
// don't overflow if BITS is 64:
n = (n >> 1) >> (big_digit::BITS - 1);
}
Expand All @@ -513,7 +513,7 @@ impl From<u128> for BigUint {
let mut ret: BigUint = Zero::zero();

while n != 0 {
ret.data.push(n as BigDigit);
ret.data.to_mut().push(n as BigDigit);
n >>= big_digit::BITS;
}

Expand Down Expand Up @@ -644,7 +644,7 @@ fn to_inexact_bitwise_digits_le(u: &BigUint, bits: u8) -> Vec<u8> {
let mut r = 0;
let mut rbits = 0;

for c in &u.data {
for c in u.data.iter() {
r |= *c << rbits;
rbits += big_digit::BITS;

Expand Down
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