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// Copyright © 2016–2023 Trevor Spiteri
// This program is free software: you can redistribute it and/or modify it under
// the terms of the GNU Lesser General Public License as published by the Free
// Software Foundation, either version 3 of the License, or (at your option) any
// later version.
//
// This program is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
// FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
// details.
//
// You should have received a copy of the GNU Lesser General Public License and
// a copy of the GNU General Public License along with this program. If not, see
// <https://www.gnu.org/licenses/>.
use crate::misc::NegAbs;
use crate::{Assign, Integer};
use az::{Az, Cast, WrappingCast};
use core::cell::UnsafeCell;
use core::ffi::c_int;
use core::mem;
use core::mem::MaybeUninit;
use core::ops::Deref;
use core::ptr::NonNull;
use gmp_mpfr_sys::gmp;
use gmp_mpfr_sys::gmp::{limb_t, mpz_t};
pub const LIMBS_IN_SMALL: usize = (128 / gmp::LIMB_BITS) as usize;
pub type Limbs = [MaybeUninit<limb_t>; LIMBS_IN_SMALL];
/**
A small integer that does not require any memory allocation.
This can be useful when you have a primitive integer type such as [`u64`] or
[`i8`], but need a reference to an [`Integer`].
If there are functions that take a [`u32`] or [`i32`] directly instead of an
[`Integer`] reference, using them can still be faster than using a
`SmallInteger`; the functions would still need to check for the size of an
[`Integer`] obtained using `SmallInteger`.
The `SmallInteger` type can be coerced to an [`Integer`], as it implements
<code>[Deref]\<[Target][Deref::Target] = [Integer]></code>.
# Examples
```rust
use rug::integer::SmallInteger;
use rug::Integer;
// `a` requires a heap allocation
let mut a = Integer::from(250);
// `b` can reside on the stack
let b = SmallInteger::from(-100);
a.lcm_mut(&b);
assert_eq!(a, 500);
// another computation:
a.lcm_mut(&SmallInteger::from(30));
assert_eq!(a, 1500);
```
*/
pub struct SmallInteger {
inner: UnsafeCell<mpz_t>,
limbs: Limbs,
}
impl Clone for SmallInteger {
fn clone(&self) -> SmallInteger {
SmallInteger {
inner: UnsafeCell::new(unsafe { *self.inner.get().cast_const() }),
limbs: self.limbs,
}
}
}
static_assert!(mem::size_of::<Limbs>() == 16);
// Safety: SmallInteger cannot be Sync because it contains an
// UnsafeCell which is written to then read without further
// protection, so it could lead to data races. But SmallInteger can be
// Send because if it is owned, no other reference can be used to
// modify the UnsafeCell.
unsafe impl Send for SmallInteger {}
impl Default for SmallInteger {
#[inline]
fn default() -> Self {
SmallInteger::new()
}
}
impl SmallInteger {
/// Creates a [`SmallInteger`] with value 0.
///
/// # Examples
///
/// ```rust
/// use rug::integer::SmallInteger;
/// let i = SmallInteger::new();
/// // Borrow i as if it were Integer.
/// assert_eq!(*i, 0);
/// ```
#[inline]
pub const fn new() -> Self {
SmallInteger {
inner: UnsafeCell::new(mpz_t {
alloc: LIMBS_IN_SMALL as c_int,
size: 0,
d: NonNull::dangling(),
}),
limbs: small_limbs![0],
}
}
/// Returns a mutable reference to an [`Integer`] for simple operations that
/// do not need to allocate more space for the number.
///
/// # Safety
///
/// It is undefined behavior to perform operations that reallocate the
/// internal data of the referenced [`Integer`] or to swap it with another
/// number.
///
/// Some GMP functions swap the allocations of their target operands;
/// calling such functions with the mutable reference returned by this
/// method can lead to undefined behavior.
///
/// # Examples
///
/// ```rust
/// use rug::integer::SmallInteger;
/// use rug::Assign;
/// let mut i = SmallInteger::from(1u64);
/// let capacity = i.capacity();
/// // another u64 will not require a reallocation
/// unsafe {
/// i.as_nonreallocating_integer().assign(2u64);
/// }
/// assert_eq!(*i, 2);
/// assert_eq!(i.capacity(), capacity);
/// ```
#[inline]
// Safety: after calling update_d(), self.inner.d points to the
// limbs so it is in a consistent state.
pub unsafe fn as_nonreallocating_integer(&mut self) -> &mut Integer {
self.update_d();
let ptr = cast_ptr_mut!(&mut self.inner, Integer);
unsafe { &mut *ptr }
}
#[inline]
fn update_d(&self) {
// Since this is borrowed, the limbs won't move around, and we can set
// the d field.
//
// However, if there already exists a reference created with Deref, we
// must not set the d field as that reference contains its d field
// without the UnsafeCell wrapping. So we first check whether the d
// field is already set correctly. If not, then there is no existing
// reference created with Deref yet, so we can set the d field.
let d = NonNull::<[MaybeUninit<limb_t>]>::from(&self.limbs[..]).cast();
// Safety: self is not Sync, so we can write to d without causing a data race.
unsafe {
if (*self.inner.get().cast_const()).d != d {
(*self.inner.get()).d = d;
}
}
}
}
impl Deref for SmallInteger {
type Target = Integer;
#[inline]
fn deref(&self) -> &Integer {
self.update_d();
let ptr = cast_ptr!(&self.inner, Integer);
// Safety: since we called update_d, the inner pointer is pointing
// to the limbs and the number is in a consistent state.
unsafe { &*ptr }
}
}
/// Types implementing this trait can be converted to [`SmallInteger`].
///
/// The following are implemented when `T` implements `ToSmall`:
/// * <code>[Assign][`Assign`]\<T> for [SmallInteger][`SmallInteger`]</code>
/// * <code>[From][`From`]\<T> for [SmallInteger][`SmallInteger`]</code>
///
/// This trait is sealed and cannot be implemented for more types; it is
/// implemented for [`bool`] and the unsigned integer types [`u8`], [`u16`],
/// [`u32`], [`u64`], [`u128`] and [`usize`].
pub trait ToSmall: SealedToSmall {}
pub trait SealedToSmall: Sized {
fn copy(self, size: &mut c_int, limbs: &mut Limbs);
fn is_zero(&self) -> bool;
}
macro_rules! is_zero {
() => {
#[inline]
fn is_zero(&self) -> bool {
*self == 0
}
};
}
macro_rules! signed {
($($I:ty)*) => { $(
impl ToSmall for $I {}
impl SealedToSmall for $I {
#[inline]
fn copy(self, size: &mut c_int, limbs: &mut Limbs) {
let (neg, abs) = self.neg_abs();
abs.copy(size, limbs);
if neg {
*size = -*size;
}
}
is_zero! {}
}
)* };
}
macro_rules! one_limb {
($($U:ty)*) => { $(
impl ToSmall for $U {}
impl SealedToSmall for $U {
#[inline]
fn copy(self, size: &mut c_int, limbs: &mut Limbs) {
if self == 0 {
*size = 0;
} else {
*size = 1;
limbs[0] = MaybeUninit::new(self.into());
}
}
is_zero! {}
}
)* };
}
signed! { i8 i16 i32 i64 i128 isize }
impl ToSmall for bool {}
impl SealedToSmall for bool {
#[inline]
fn copy(self, size: &mut c_int, limbs: &mut Limbs) {
if !self {
*size = 0;
} else {
*size = 1;
limbs[0] = MaybeUninit::new(1);
}
}
#[inline]
fn is_zero(&self) -> bool {
!*self
}
}
one_limb! { u8 u16 u32 }
#[cfg(gmp_limb_bits_64)]
one_limb! { u64 }
#[cfg(gmp_limb_bits_32)]
impl ToSmall for u64 {}
#[cfg(gmp_limb_bits_32)]
impl SealedToSmall for u64 {
#[inline]
fn copy(self, size: &mut c_int, limbs: &mut Limbs) {
if self == 0 {
*size = 0;
} else if self <= 0xffff_ffff {
*size = 1;
limbs[0] = MaybeUninit::new(self.wrapping_cast());
} else {
*size = 2;
limbs[0] = MaybeUninit::new(self.wrapping_cast());
limbs[1] = MaybeUninit::new((self >> 32).wrapping_cast());
}
}
is_zero! {}
}
impl ToSmall for u128 {}
impl SealedToSmall for u128 {
#[cfg(gmp_limb_bits_64)]
#[inline]
fn copy(self, size: &mut c_int, limbs: &mut Limbs) {
if self == 0 {
*size = 0;
} else if self <= 0xffff_ffff_ffff_ffff {
*size = 1;
limbs[0] = MaybeUninit::new(self.wrapping_cast());
} else {
*size = 2;
limbs[0] = MaybeUninit::new(self.wrapping_cast());
limbs[1] = MaybeUninit::new((self >> 64).wrapping_cast());
}
}
#[cfg(gmp_limb_bits_32)]
#[inline]
fn copy(self, size: &mut c_int, limbs: &mut Limbs) {
if self == 0 {
*size = 0;
} else if self <= 0xffff_ffff {
*size = 1;
limbs[0] = MaybeUninit::new(self.wrapping_cast());
} else if self <= 0xffff_ffff_ffff_ffff {
*size = 2;
limbs[0] = MaybeUninit::new(self.wrapping_cast());
limbs[1] = MaybeUninit::new((self >> 32).wrapping_cast());
} else if self <= 0xffff_ffff_ffff_ffff_ffff_ffff {
*size = 3;
limbs[0] = MaybeUninit::new(self.wrapping_cast());
limbs[1] = MaybeUninit::new((self >> 32).wrapping_cast());
limbs[2] = MaybeUninit::new((self >> 64).wrapping_cast());
} else {
*size = 4;
limbs[0] = MaybeUninit::new(self.wrapping_cast());
limbs[1] = MaybeUninit::new((self >> 32).wrapping_cast());
limbs[2] = MaybeUninit::new((self >> 64).wrapping_cast());
limbs[3] = MaybeUninit::new((self >> 96).wrapping_cast());
}
}
is_zero! {}
}
impl ToSmall for usize {}
impl SealedToSmall for usize {
#[cfg(target_pointer_width = "32")]
#[inline]
fn copy(self, size: &mut c_int, limbs: &mut Limbs) {
self.az::<u32>().copy(size, limbs);
}
#[cfg(target_pointer_width = "64")]
#[inline]
fn copy(self, size: &mut c_int, limbs: &mut Limbs) {
self.az::<u64>().copy(size, limbs);
}
is_zero! {}
}
impl<T: ToSmall> Assign<T> for SmallInteger {
#[inline]
fn assign(&mut self, src: T) {
src.copy(&mut self.inner.get_mut().size, &mut self.limbs);
}
}
impl<T: ToSmall> From<T> for SmallInteger {
#[inline]
fn from(src: T) -> Self {
let mut size = 0;
let mut limbs = small_limbs![0];
src.copy(&mut size, &mut limbs);
SmallInteger {
inner: UnsafeCell::new(mpz_t {
alloc: LIMBS_IN_SMALL.cast(),
size,
d: NonNull::dangling(),
}),
limbs,
}
}
}
impl Assign<&Self> for SmallInteger {
#[inline]
fn assign(&mut self, other: &Self) {
self.clone_from(other);
}
}
impl Assign for SmallInteger {
#[inline]
fn assign(&mut self, other: Self) {
drop(mem::replace(self, other));
}
}
#[cfg(test)]
mod tests {
use crate::integer::SmallInteger;
use crate::Assign;
#[test]
fn check_assign() {
let mut i = SmallInteger::from(-1i32);
assert_eq!(*i, -1);
let other = SmallInteger::from(2i32);
i.assign(&other);
assert_eq!(*i, 2);
i.assign(6u8);
assert_eq!(*i, 6);
i.assign(-6i8);
assert_eq!(*i, -6);
i.assign(other);
assert_eq!(*i, 2);
i.assign(6u16);
assert_eq!(*i, 6);
i.assign(-6i16);
assert_eq!(*i, -6);
i.assign(6u32);
assert_eq!(*i, 6);
i.assign(-6i32);
assert_eq!(*i, -6);
i.assign(0xf_0000_0006u64);
assert_eq!(*i, 0xf_0000_0006u64);
i.assign(-0xf_0000_0006i64);
assert_eq!(*i, -0xf_0000_0006i64);
i.assign(6u128 << 64 | 7u128);
assert_eq!(*i, 6u128 << 64 | 7u128);
i.assign(-6i128 << 64 | 7i128);
assert_eq!(*i, -6i128 << 64 | 7i128);
i.assign(6usize);
assert_eq!(*i, 6);
i.assign(-6isize);
assert_eq!(*i, -6);
i.assign(0u32);
assert_eq!(*i, 0);
}
}