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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::ext::xmpfr;
use crate::ext::xmpfr::raw_round;
use crate::float::{self, Round, Special};
use crate::misc::NegAbs;
use crate::{Assign, Float};
use az::{Az, UnwrappedCast, 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;
use gmp_mpfr_sys::mpfr;
use gmp_mpfr_sys::mpfr::{exp_t, mpfr_t, prec_t};
const LIMBS_IN_SMALL: usize = (128 / gmp::LIMB_BITS) as usize;
type Limbs = [MaybeUninit<limb_t>; LIMBS_IN_SMALL];
/**
A small float that does not require any memory allocation.
This can be useful when you have a primitive number type but need a reference to
a [`Float`]. The `SmallFloat` will have a precision according to the type of the
primitive used to set its value.
* [`i8`], [`u8`]: the `SmallFloat` will have eight bits of precision.
* [`i16`], [`u16`]: the `SmallFloat` will have 16 bits of precision.
* [`i32`], [`u32`]: the `SmallFloat` will have 32 bits of precision.
* [`i64`], [`u64`]: the `SmallFloat` will have 64 bits of precision.
* [`i128`], [`u128`]: the `SmallFloat` will have 128 bits of precision.
* [`isize`], [`usize`]: the `SmallFloat` will have 32 or 64 bits of precision,
depending on the platform.
* [`f32`]: the `SmallFloat` will have 24 bits of precision.
* [`f64`]: the `SmallFloat` will have 53 bits of precision.
* [`Special`]: the `SmallFloat` will have the [minimum possible
precision][crate::float::prec_min].
The `SmallFloat` type can be coerced to a [`Float`], as it implements
<code>[Deref]\<[Target][Deref::Target] = [Float]></code>.
# Examples
```rust
use rug::float::SmallFloat;
use rug::Float;
// `a` requires a heap allocation, has 53-bit precision
let mut a = Float::with_val(53, 250);
// `b` can reside on the stack
let b = SmallFloat::from(-100f64);
a += &*b;
assert_eq!(a, 150);
// another computation:
a *= &*b;
assert_eq!(a, -15000);
```
*/
#[derive(Clone)]
pub struct SmallFloat {
inner: Mpfr,
limbs: Limbs,
}
// Safety: Mpfr has a repr equivalent to mpfr_t. The difference in the repr(C)
// types Mpfr and mpfr_t is that Mpfr uses UnsafeCell<NonNull<limb_t>> instead
// of NonNull<limb_t>, but UnsafeCell is repr(transparent).
#[repr(C)]
pub struct Mpfr {
pub prec: prec_t,
pub sign: c_int,
pub exp: exp_t,
pub d: UnsafeCell<NonNull<limb_t>>,
}
impl Clone for Mpfr {
fn clone(&self) -> Mpfr {
Mpfr {
prec: self.prec,
sign: self.sign,
exp: self.exp,
d: UnsafeCell::new(unsafe { *self.d.get() }),
}
}
}
static_assert!(mem::size_of::<Limbs>() == 16);
static_assert_same_layout!(Mpfr, mpfr_t);
// Safety: SmallFloat 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 SmallFloat can be Send because if it
// is owned, no other reference can be used to modify the UnsafeCell.
unsafe impl Send for SmallFloat {}
impl Default for SmallFloat {
#[inline]
fn default() -> Self {
SmallFloat::new()
}
}
impl SmallFloat {
/// Creates a [`SmallFloat`] with value 0 and the [minimum possible
/// precision][crate::float::prec_min].
///
/// # Examples
///
/// ```rust
/// use rug::float::SmallFloat;
/// let f = SmallFloat::new();
/// // Borrow f as if it were Float.
/// assert_eq!(*f, 0);
/// ```
#[inline]
pub const fn new() -> Self {
SmallFloat {
inner: Mpfr {
prec: float::prec_min() as prec_t,
sign: 1,
exp: xmpfr::EXP_ZERO,
d: UnsafeCell::new(NonNull::dangling()),
},
limbs: small_limbs![],
}
}
/// Returns a mutable reference to a [`Float`] for simple operations that do
/// not need to change the precision of the number.
///
/// # Safety
///
/// It is undefined behavior modify the precision of the referenced
/// [`Float`] or to swap it with another number.
///
/// # Examples
///
/// ```rust
/// use rug::float::SmallFloat;
/// let mut f = SmallFloat::from(1.0f32);
/// // addition does not change the precision
/// unsafe {
/// *f.as_nonreallocating_float() += 2.0;
/// }
/// assert_eq!(*f, 3.0);
/// ```
#[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_float(&mut self) -> &mut Float {
self.update_d();
let ptr = cast_ptr_mut!(&mut self.inner, Float);
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.d.get() != d {
*self.inner.d.get() = d;
}
}
}
}
impl Deref for SmallFloat {
type Target = Float;
#[inline]
fn deref(&self) -> &Float {
self.update_d();
let ptr = cast_ptr!(&self.inner, Float);
// 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 [`SmallFloat`].
///
/// The following are implemented when `T` implements `ToSmall`:
/// * <code>[Assign]\<T> for [SmallFloat]</code>
/// * <code>[From]\<T> for [SmallFloat]</code>
///
/// This trait is sealed and cannot be implemented for more types; it is
/// implemented for the integer types [`i8`], [`i16`], [`i32`], [`i64`],
/// [`i128`], [`isize`], [`u8`], [`u16`], [`u32`], [`u64`], [`u128`] and
/// [`usize`], and for the floating-point types [`f32`] and [`f64`].
pub trait ToSmall: SealedToSmall {}
pub trait SealedToSmall: Copy {
unsafe fn copy(self, inner: *mut Mpfr, limbs: &mut Limbs);
}
macro_rules! unsafe_signed {
($($I:ty)*) => { $(
impl ToSmall for $I {}
impl SealedToSmall for $I {
#[inline]
unsafe fn copy(self, inner: *mut Mpfr, limbs: &mut Limbs) {
let (neg, abs) = self.neg_abs();
unsafe{
abs.copy(inner, limbs);
if neg {
(*inner).sign = -1;
}
}
}
}
)* };
}
macro_rules! unsafe_unsigned_32 {
($U:ty, $bits:expr) => {
impl ToSmall for $U {}
impl SealedToSmall for $U {
#[inline]
unsafe fn copy(self, inner: *mut Mpfr, limbs: &mut Limbs) {
let ptr = cast_ptr_mut!(inner, mpfr_t);
let limbs_ptr = cast_ptr_mut!(limbs.as_mut_ptr(), limb_t);
if self == 0 {
unsafe {
xmpfr::custom_zero(ptr, limbs_ptr, $bits);
}
} else {
let leading = self.leading_zeros();
let limb_leading = leading + gmp::LIMB_BITS.az::<u32>() - $bits;
limbs[0] = MaybeUninit::new(limb_t::from(self) << limb_leading);
let exp = ($bits - leading).unwrapped_cast();
unsafe {
xmpfr::custom_regular(ptr, limbs_ptr, exp, $bits);
}
}
}
}
};
}
unsafe_signed! { i8 i16 i32 i64 i128 isize }
unsafe_unsigned_32! { u8, 8 }
unsafe_unsigned_32! { u16, 16 }
unsafe_unsigned_32! { u32, 32 }
impl ToSmall for u64 {}
impl SealedToSmall for u64 {
#[inline]
unsafe fn copy(self, inner: *mut Mpfr, limbs: &mut Limbs) {
let ptr = cast_ptr_mut!(inner, mpfr_t);
let limbs_ptr = cast_ptr_mut!(limbs.as_mut_ptr(), limb_t);
if self == 0 {
unsafe {
xmpfr::custom_zero(ptr, limbs_ptr, 64);
}
} else {
let leading = self.leading_zeros();
let sval = self << leading;
#[cfg(gmp_limb_bits_64)]
{
limbs[0] = MaybeUninit::new(sval);
}
#[cfg(gmp_limb_bits_32)]
{
limbs[0] = MaybeUninit::new(sval.wrapping_cast());
limbs[1] = MaybeUninit::new((sval >> 32).wrapping_cast());
}
let exp = (64 - leading).unwrapped_cast();
unsafe {
xmpfr::custom_regular(ptr, limbs_ptr, exp, 64);
}
}
}
}
impl ToSmall for u128 {}
impl SealedToSmall for u128 {
#[inline]
unsafe fn copy(self, inner: *mut Mpfr, limbs: &mut Limbs) {
let ptr = cast_ptr_mut!(inner, mpfr_t);
let limbs_ptr = cast_ptr_mut!(limbs.as_mut_ptr(), limb_t);
if self == 0 {
unsafe {
xmpfr::custom_zero(ptr, limbs_ptr, 128);
}
} else {
let leading = self.leading_zeros();
let sval = self << leading;
#[cfg(gmp_limb_bits_64)]
{
limbs[0] = MaybeUninit::new(sval.wrapping_cast());
limbs[1] = MaybeUninit::new((sval >> 64).wrapping_cast());
}
#[cfg(gmp_limb_bits_32)]
{
limbs[0] = MaybeUninit::new(sval.wrapping_cast());
limbs[1] = MaybeUninit::new((sval >> 32).wrapping_cast());
limbs[2] = MaybeUninit::new((sval >> 64).wrapping_cast());
limbs[3] = MaybeUninit::new((sval >> 96).wrapping_cast());
}
let exp = (128 - leading).unwrapped_cast();
unsafe {
xmpfr::custom_regular(ptr, limbs_ptr, exp, 128);
}
}
}
}
impl ToSmall for usize {}
impl SealedToSmall for usize {
#[inline]
unsafe fn copy(self, inner: *mut Mpfr, limbs: &mut Limbs) {
#[cfg(target_pointer_width = "32")]
{
let val = self.az::<u32>();
unsafe {
val.copy(inner, limbs);
}
}
#[cfg(target_pointer_width = "64")]
{
let val = self.az::<u64>();
unsafe {
val.copy(inner, limbs);
}
}
}
}
impl ToSmall for f32 {}
impl SealedToSmall for f32 {
#[inline]
unsafe fn copy(self, inner: *mut Mpfr, limbs: &mut Limbs) {
let ptr = cast_ptr_mut!(inner, mpfr_t);
let limbs_ptr = cast_ptr_mut!(limbs.as_mut_ptr(), limb_t);
let val = self.into();
let rnd = raw_round(Round::Nearest);
unsafe {
xmpfr::custom_zero(ptr, limbs_ptr, 24);
mpfr::set_d(ptr, val, rnd);
}
// retain sign in case of NaN
if self.is_sign_negative() {
unsafe {
(*inner).sign = -1;
}
}
}
}
impl ToSmall for f64 {}
impl SealedToSmall for f64 {
#[inline]
unsafe fn copy(self, inner: *mut Mpfr, limbs: &mut Limbs) {
let ptr = cast_ptr_mut!(inner, mpfr_t);
let limbs_ptr = cast_ptr_mut!(limbs.as_mut_ptr(), limb_t);
let rnd = raw_round(Round::Nearest);
unsafe {
xmpfr::custom_zero(ptr, limbs_ptr, 53);
mpfr::set_d(ptr, self, rnd);
}
// retain sign in case of NaN
if self.is_sign_negative() {
unsafe {
(*inner).sign = -1;
}
}
}
}
impl ToSmall for Special {}
impl SealedToSmall for Special {
#[inline]
unsafe fn copy(self, inner: *mut Mpfr, limbs: &mut Limbs) {
let ptr = cast_ptr_mut!(inner, mpfr_t);
let limbs_ptr = cast_ptr_mut!(limbs.as_mut_ptr(), limb_t);
let prec = float::prec_min().az();
unsafe {
xmpfr::custom_special(ptr, limbs_ptr, self, prec);
}
}
}
impl<T: ToSmall> Assign<T> for SmallFloat {
#[inline]
fn assign(&mut self, src: T) {
unsafe {
src.copy(&mut self.inner, &mut self.limbs);
}
}
}
impl<T: ToSmall> From<T> for SmallFloat {
#[inline]
fn from(src: T) -> Self {
let mut inner = Mpfr {
prec: 0,
sign: 0,
exp: 0,
d: UnsafeCell::new(NonNull::dangling()),
};
let mut limbs = small_limbs![];
unsafe {
src.copy(&mut inner, &mut limbs);
}
SmallFloat { inner, limbs }
}
}
impl Assign<&Self> for SmallFloat {
#[inline]
fn assign(&mut self, other: &Self) {
self.clone_from(other);
}
}
impl Assign for SmallFloat {
#[inline]
fn assign(&mut self, other: Self) {
drop(mem::replace(self, other));
}
}
#[inline]
pub(crate) unsafe fn unchecked_get_unshifted_u8(small: &SmallFloat) -> u8 {
debug_assert!(small.prec() >= 8);
debug_assert!(small.is_normal());
(unsafe { small.limbs[0].assume_init() } >> (gmp::LIMB_BITS - 8)).wrapping_cast()
}
#[inline]
pub(crate) unsafe fn unchecked_get_unshifted_u16(small: &SmallFloat) -> u16 {
debug_assert!(small.prec() >= 16);
debug_assert!(small.is_normal());
(unsafe { small.limbs[0].assume_init() } >> (gmp::LIMB_BITS - 16)).wrapping_cast()
}
#[inline]
pub(crate) unsafe fn unchecked_get_unshifted_u32(small: &SmallFloat) -> u32 {
debug_assert!(small.prec() >= 32);
debug_assert!(small.is_normal());
#[cfg(gmp_limb_bits_32)]
{
unsafe { small.limbs[0].assume_init() }
}
#[cfg(gmp_limb_bits_64)]
{
(unsafe { small.limbs[0].assume_init() } >> 32).wrapping_cast()
}
}
#[inline]
pub(crate) unsafe fn unchecked_get_unshifted_u64(small: &SmallFloat) -> u64 {
debug_assert!(small.prec() >= 64);
debug_assert!(small.is_normal());
#[cfg(gmp_limb_bits_32)]
{
u64::from(unsafe { small.limbs[0].assume_init() })
| (u64::from(unsafe { small.limbs[1].assume_init() }) << 32)
}
#[cfg(gmp_limb_bits_64)]
{
unsafe { small.limbs[0].assume_init() }
}
}
#[inline]
pub(crate) unsafe fn unchecked_get_unshifted_u128(small: &SmallFloat) -> u128 {
debug_assert!(small.prec() >= 128);
debug_assert!(small.is_normal());
#[cfg(gmp_limb_bits_32)]
{
u128::from(unsafe { small.limbs[0].assume_init() })
| (u128::from(unsafe { small.limbs[1].assume_init() }) << 32)
| (u128::from(unsafe { small.limbs[2].assume_init() }) << 64)
| (u128::from(unsafe { small.limbs[3].assume_init() }) << 96)
}
#[cfg(gmp_limb_bits_64)]
{
u128::from(unsafe { small.limbs[0].assume_init() })
| (u128::from(unsafe { small.limbs[1].assume_init() }) << 64)
}
}
#[cfg(test)]
#[allow(clippy::float_cmp)]
mod tests {
use crate::float;
use crate::float::{FreeCache, SmallFloat, Special};
use crate::Assign;
#[test]
fn check_assign() {
let mut f = SmallFloat::from(-1.0f32);
assert_eq!(*f, -1.0);
f.assign(-2.0f64);
assert_eq!(*f, -2.0);
let other = SmallFloat::from(4u8);
f.assign(&other);
assert_eq!(*f, 4);
f.assign(5i8);
assert_eq!(*f, 5);
f.assign(other);
assert_eq!(*f, 4);
f.assign(6u16);
assert_eq!(*f, 6);
f.assign(-6i16);
assert_eq!(*f, -6);
f.assign(6u32);
assert_eq!(*f, 6);
f.assign(-6i32);
assert_eq!(*f, -6);
f.assign(6u64);
assert_eq!(*f, 6);
f.assign(-6i64);
assert_eq!(*f, -6);
f.assign(6u128);
assert_eq!(*f, 6);
f.assign(-6i128);
assert_eq!(*f, -6);
f.assign(6usize);
assert_eq!(*f, 6);
f.assign(-6isize);
assert_eq!(*f, -6);
f.assign(0u32);
assert_eq!(*f, 0);
f.assign(Special::Infinity);
assert!(f.is_infinite() && f.is_sign_positive());
f.assign(Special::NegZero);
assert!(f.is_zero() && f.is_sign_negative());
f.assign(Special::NegInfinity);
assert!(f.is_infinite() && f.is_sign_negative());
f.assign(Special::Zero);
assert!(f.is_zero() && f.is_sign_positive());
f.assign(Special::Nan);
assert!(f.is_nan());
float::free_cache(FreeCache::All);
}
}