//! Simple stack-allocated vector.
#![cfg(not(feature = "alloc"))]
#![doc(hidden)]
use crate::bigint;
use core::{cmp, mem, ops, ptr, slice};
/// Simple stack vector implementation.
#[derive(Clone)]
pub struct StackVec {
/// The raw buffer for the elements.
data: [mem::MaybeUninit<bigint::Limb>; bigint::BIGINT_LIMBS],
/// The number of elements in the array (we never need more than u16::MAX).
length: u16,
}
#[allow(clippy::new_without_default)]
impl StackVec {
/// Construct an empty vector.
#[inline]
pub const fn new() -> Self {
Self {
length: 0,
data: [mem::MaybeUninit::uninit(); bigint::BIGINT_LIMBS],
}
}
/// Construct a vector from an existing slice.
#[inline]
pub fn try_from(x: &[bigint::Limb]) -> Option<Self> {
let mut vec = Self::new();
vec.try_extend(x)?;
Some(vec)
}
/// Sets the length of a vector.
///
/// This will explicitly set the size of the vector, without actually
/// modifying its buffers, so it is up to the caller to ensure that the
/// vector is actually the specified size.
///
/// # Safety
///
/// Safe as long as `len` is less than `BIGINT_LIMBS`.
#[inline]
pub unsafe fn set_len(&mut self, len: usize) {
// Constant is `u16::MAX` for older Rustc versions.
debug_assert!(len <= 0xffff);
debug_assert!(len <= bigint::BIGINT_LIMBS);
self.length = len as u16;
}
/// The number of elements stored in the vector.
#[inline]
pub const fn len(&self) -> usize {
self.length as usize
}
/// If the vector is empty.
#[inline]
pub const fn is_empty(&self) -> bool {
self.len() == 0
}
/// The number of items the vector can hold.
#[inline]
pub const fn capacity(&self) -> usize {
bigint::BIGINT_LIMBS as usize
}
/// Append an item to the vector, without bounds checking.
///
/// # Safety
///
/// Safe if `self.len() < self.capacity()`.
#[inline]
pub unsafe fn push_unchecked(&mut self, value: bigint::Limb) {
debug_assert!(self.len() < self.capacity());
// SAFETY: safe, capacity is less than the current size.
unsafe {
ptr::write(self.as_mut_ptr().add(self.len()), value);
self.length += 1;
}
}
/// Append an item to the vector.
#[inline]
pub fn try_push(&mut self, value: bigint::Limb) -> Option<()> {
if self.len() < self.capacity() {
// SAFETY: safe, capacity is less than the current size.
unsafe { self.push_unchecked(value) };
Some(())
} else {
None
}
}
/// Remove an item from the end of a vector, without bounds checking.
///
/// # Safety
///
/// Safe if `self.len() > 0`.
#[inline]
pub unsafe fn pop_unchecked(&mut self) -> bigint::Limb {
debug_assert!(!self.is_empty());
// SAFETY: safe if `self.length > 0`.
// We have a trivial drop and copy, so this is safe.
self.length -= 1;
unsafe { ptr::read(self.as_mut_ptr().add(self.len())) }
}
/// Remove an item from the end of the vector and return it, or None if empty.
#[inline]
pub fn pop(&mut self) -> Option<bigint::Limb> {
if self.is_empty() {
None
} else {
// SAFETY: safe, since `self.len() > 0`.
unsafe { Some(self.pop_unchecked()) }
}
}
/// Add items from a slice to the vector, without bounds checking.
///
/// # Safety
///
/// Safe if `self.len() + slc.len() <= self.capacity()`.
#[inline]
pub unsafe fn extend_unchecked(&mut self, slc: &[bigint::Limb]) {
let index = self.len();
let new_len = index + slc.len();
debug_assert!(self.len() + slc.len() <= self.capacity());
let src = slc.as_ptr();
// SAFETY: safe if `self.len() + slc.len() <= self.capacity()`.
unsafe {
let dst = self.as_mut_ptr().add(index);
ptr::copy_nonoverlapping(src, dst, slc.len());
self.set_len(new_len);
}
}
/// Copy elements from a slice and append them to the vector.
#[inline]
pub fn try_extend(&mut self, slc: &[bigint::Limb]) -> Option<()> {
if self.len() + slc.len() <= self.capacity() {
// SAFETY: safe, since `self.len() + slc.len() <= self.capacity()`.
unsafe { self.extend_unchecked(slc) };
Some(())
} else {
None
}
}
/// Truncate vector to new length, dropping any items after `len`.
///
/// # Safety
///
/// Safe as long as `len <= self.capacity()`.
unsafe fn truncate_unchecked(&mut self, len: usize) {
debug_assert!(len <= self.capacity());
self.length = len as u16;
}
/// Resize the buffer, without bounds checking.
///
/// # Safety
///
/// Safe as long as `len <= self.capacity()`.
#[inline]
pub unsafe fn resize_unchecked(&mut self, len: usize, value: bigint::Limb) {
debug_assert!(len <= self.capacity());
let old_len = self.len();
if len > old_len {
// We have a trivial drop, so there's no worry here.
// Just, don't set the length until all values have been written,
// so we don't accidentally read uninitialized memory.
// SAFETY: safe if `len < self.capacity()`.
let count = len - old_len;
for index in 0..count {
unsafe {
let dst = self.as_mut_ptr().add(old_len + index);
ptr::write(dst, value);
}
}
self.length = len as u16;
} else {
// SAFETY: safe since `len < self.len()`.
unsafe { self.truncate_unchecked(len) };
}
}
/// Try to resize the buffer.
///
/// If the new length is smaller than the current length, truncate
/// the input. If it's larger, then append elements to the buffer.
#[inline]
pub fn try_resize(&mut self, len: usize, value: bigint::Limb) -> Option<()> {
if len > self.capacity() {
None
} else {
// SAFETY: safe, since `len <= self.capacity()`.
unsafe { self.resize_unchecked(len, value) };
Some(())
}
}
// HI
/// Get the high 64 bits from the vector.
#[inline(always)]
pub fn hi64(&self) -> (u64, bool) {
bigint::hi64(self)
}
// FROM
/// Create StackVec from u64 value.
#[inline(always)]
pub fn from_u64(x: u64) -> Self {
bigint::from_u64(x)
}
// MATH
/// Normalize the integer, so any leading zero values are removed.
#[inline]
pub fn normalize(&mut self) {
bigint::normalize(self)
}
/// Get if the big integer is normalized.
#[inline]
pub fn is_normalized(&self) -> bool {
bigint::is_normalized(self)
}
/// AddAssign small integer.
#[inline]
pub fn add_small(&mut self, y: bigint::Limb) -> Option<()> {
bigint::small_add(self, y)
}
/// MulAssign small integer.
#[inline]
pub fn mul_small(&mut self, y: bigint::Limb) -> Option<()> {
bigint::small_mul(self, y)
}
}
impl PartialEq for StackVec {
#[inline]
#[allow(clippy::op_ref)]
fn eq(&self, other: &Self) -> bool {
use core::ops::Deref;
self.len() == other.len() && self.deref() == other.deref()
}
}
impl Eq for StackVec {
}
impl cmp::PartialOrd for StackVec {
#[inline]
fn partial_cmp(&self, other: &Self) -> Option<cmp::Ordering> {
Some(bigint::compare(self, other))
}
}
impl cmp::Ord for StackVec {
#[inline]
fn cmp(&self, other: &Self) -> cmp::Ordering {
bigint::compare(self, other)
}
}
impl ops::Deref for StackVec {
type Target = [bigint::Limb];
#[inline]
fn deref(&self) -> &[bigint::Limb] {
// SAFETY: safe since `self.data[..self.len()]` must be initialized
// and `self.len() <= self.capacity()`.
unsafe {
let ptr = self.data.as_ptr() as *const bigint::Limb;
slice::from_raw_parts(ptr, self.len())
}
}
}
impl ops::DerefMut for StackVec {
#[inline]
fn deref_mut(&mut self) -> &mut [bigint::Limb] {
// SAFETY: safe since `self.data[..self.len()]` must be initialized
// and `self.len() <= self.capacity()`.
unsafe {
let ptr = self.data.as_mut_ptr() as *mut bigint::Limb;
slice::from_raw_parts_mut(ptr, self.len())
}
}
}
impl ops::MulAssign<&[bigint::Limb]> for StackVec {
#[inline]
fn mul_assign(&mut self, rhs: &[bigint::Limb]) {
bigint::large_mul(self, rhs).unwrap();
}
}