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-rw-r--r--third_party/rust/minimal-lexical/src/stackvec.rs308
1 files changed, 308 insertions, 0 deletions
diff --git a/third_party/rust/minimal-lexical/src/stackvec.rs b/third_party/rust/minimal-lexical/src/stackvec.rs
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+//! 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();
+ }
+}
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