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// This file is part of ICU4X. For terms of use, please see the file
// called LICENSE at the top level of the ICU4X source tree
use crate::ule::*;
use alloc::vec::Vec;
use core::cmp::{Ord, Ordering, PartialOrd};
use core::fmt;
use core::ops::Deref;
use super::*;
/// A zero-copy, byte-aligned vector for variable-width types.
///
/// `VarZeroVec<T>` is designed as a drop-in replacement for `Vec<T>` in situations where it is
/// desirable to borrow data from an unaligned byte slice, such as zero-copy deserialization, and
/// where `T`'s data is variable-length (e.g. `String`)
///
/// `T` must implement [`VarULE`], which is already implemented for [`str`] and `[u8]`. For storing more
/// complicated series of elements, it is implemented on `ZeroSlice<T>` as well as `VarZeroSlice<T>`
/// for nesting. [`zerovec::make_varule`](crate::make_varule) may be used to generate
/// a dynamically-sized [`VarULE`] type and conversions to and from a custom type.
///
/// For example, here are some owned types and their zero-copy equivalents:
///
/// - `Vec<String>`: `VarZeroVec<'a, str>`
/// - `Vec<Vec<u8>>>`: `VarZeroVec<'a, [u8]>`
/// - `Vec<Vec<u32>>`: `VarZeroVec<'a, ZeroSlice<u32>>`
/// - `Vec<Vec<String>>`: `VarZeroVec<'a, VarZeroSlice<str>>`
///
/// Most of the methods on `VarZeroVec<'a, T>` come from its [`Deref`] implementation to [`VarZeroSlice<T>`](VarZeroSlice).
///
/// For creating zero-copy vectors of fixed-size types, see [`ZeroVec`](crate::ZeroVec).
///
/// `VarZeroVec<T>` behaves much like [`Cow`](alloc::borrow::Cow), where it can be constructed from
/// owned data (and then mutated!) but can also borrow from some buffer.
///
/// The `F` type parameter is a [`VarZeroVecFormat`] (see its docs for more details), which can be used to select the
/// precise format of the backing buffer with various size and performance tradeoffs. It defaults to [`Index16`].
///
/// # Bytes and Equality
///
/// Two [`VarZeroVec`]s are equal if and only if their bytes are equal, as described in the trait
/// [`VarULE`]. However, we do not guarantee stability of byte equality or serialization format
/// across major SemVer releases.
///
/// To compare a [`Vec<T>`] to a [`VarZeroVec<T>`], it is generally recommended to use
/// [`Iterator::eq`], since it is somewhat expensive at runtime to convert from a [`Vec<T>`] to a
/// [`VarZeroVec<T>`] or vice-versa.
///
/// Prior to zerovec reaching 1.0, the precise byte representation of [`VarZeroVec`] is still
/// under consideration, with different options along the space-time spectrum. See
///
/// # Example
///
/// ```rust
/// # use zerovec::ule::ZeroVecError;
/// use zerovec::VarZeroVec;
///
/// // The little-endian bytes correspond to the list of strings.
/// let strings = vec!["w", "ω", "文", "𑄃"];
///
/// #[derive(serde::Serialize, serde::Deserialize)]
/// struct Data<'a> {
/// #[serde(borrow)]
/// strings: VarZeroVec<'a, str>,
/// }
///
/// let data = Data {
/// strings: VarZeroVec::from(&strings),
/// };
///
/// let bincode_bytes =
/// bincode::serialize(&data).expect("Serialization should be successful");
///
/// // Will deserialize without allocations
/// let deserialized: Data = bincode::deserialize(&bincode_bytes)
/// .expect("Deserialization should be successful");
///
/// assert_eq!(deserialized.strings.get(2), Some("文"));
/// assert_eq!(deserialized.strings, &*strings);
/// # Ok::<(), ZeroVecError>(())
/// ```
///
/// Here's another example with `ZeroSlice<T>` (similar to `[T]`):
///
/// ```rust
/// # use zerovec::ule::ZeroVecError;
/// use zerovec::VarZeroVec;
/// use zerovec::ZeroSlice;
///
/// // The structured list correspond to the list of integers.
/// let numbers: &[&[u32]] = &[
/// &[12, 25, 38],
/// &[39179, 100],
/// &[42, 55555],
/// &[12345, 54321, 9],
/// ];
///
/// #[derive(serde::Serialize, serde::Deserialize)]
/// struct Data<'a> {
/// #[serde(borrow)]
/// vecs: VarZeroVec<'a, ZeroSlice<u32>>,
/// }
///
/// let data = Data {
/// vecs: VarZeroVec::from(numbers),
/// };
///
/// let bincode_bytes =
/// bincode::serialize(&data).expect("Serialization should be successful");
///
/// let deserialized: Data = bincode::deserialize(&bincode_bytes)
/// .expect("Deserialization should be successful");
///
/// assert_eq!(deserialized.vecs[0].get(1).unwrap(), 25);
/// assert_eq!(deserialized.vecs[1], *numbers[1]);
///
/// # Ok::<(), ZeroVecError>(())
/// ```
///
/// [`VarZeroVec`]s can be nested infinitely via a similar mechanism, see the docs of [`VarZeroSlice`]
/// for more information.
///
/// # How it Works
///
/// `VarZeroVec<T>`, when used with non-human-readable serializers (like `bincode`), will
/// serialize to a specially formatted list of bytes. The format is:
///
/// - 4 bytes for `length` (interpreted as a little-endian u32)
/// - `4 * length` bytes of `indices` (interpreted as little-endian u32)
/// - Remaining bytes for actual `data`
///
/// Each element in the `indices` array points to the starting index of its corresponding
/// data part in the `data` list. The ending index can be calculated from the starting index
/// of the next element (or the length of the slice if dealing with the last element).
///
/// See [the design doc](https://github.com/unicode-org/icu4x/blob/main/utils/zerovec/design_doc.md) for more details.
///
/// [`ule`]: crate::ule
#[non_exhaustive]
pub enum VarZeroVec<'a, T: ?Sized, F = Index16> {
/// An allocated VarZeroVec, allowing for mutations.
///
/// # Examples
///
/// ```
/// use zerovec::VarZeroVec;
///
/// let mut vzv = VarZeroVec::<str>::default();
/// vzv.make_mut().push("foo");
/// vzv.make_mut().push("bar");
/// assert!(matches!(vzv, VarZeroVec::Owned(_)));
/// ```
Owned(VarZeroVecOwned<T, F>),
/// A borrowed VarZeroVec, requiring no allocations.
///
/// If a mutating operation is invoked on VarZeroVec, the Borrowed is converted to Owned.
///
/// # Examples
///
/// ```
/// use zerovec::VarZeroVec;
///
/// let bytes = &[
/// 4, 0, 0, 0, 0, 0, 1, 0, 3, 0, 6, 0, 119, 207, 137, 230, 150, 135, 240,
/// 145, 132, 131,
/// ];
///
/// let vzv: VarZeroVec<str> = VarZeroVec::parse_byte_slice(bytes).unwrap();
/// assert!(matches!(vzv, VarZeroVec::Borrowed(_)));
/// ```
Borrowed(&'a VarZeroSlice<T, F>),
}
impl<'a, T: ?Sized, F> Clone for VarZeroVec<'a, T, F> {
fn clone(&self) -> Self {
match *self {
VarZeroVec::Owned(ref o) => o.clone().into(),
VarZeroVec::Borrowed(b) => b.into(),
}
}
}
impl<T: VarULE + ?Sized, F: VarZeroVecFormat> fmt::Debug for VarZeroVec<'_, T, F>
where
T: fmt::Debug,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
VarZeroSlice::fmt(self, f)
}
}
impl<'a, T: ?Sized, F> From<VarZeroVecOwned<T, F>> for VarZeroVec<'a, T, F> {
#[inline]
fn from(other: VarZeroVecOwned<T, F>) -> Self {
VarZeroVec::Owned(other)
}
}
impl<'a, T: ?Sized, F> From<&'a VarZeroSlice<T, F>> for VarZeroVec<'a, T, F> {
fn from(other: &'a VarZeroSlice<T, F>) -> Self {
VarZeroVec::Borrowed(other)
}
}
impl<'a, T: ?Sized + VarULE, F: VarZeroVecFormat> From<VarZeroVec<'a, T, F>>
for VarZeroVecOwned<T, F>
{
#[inline]
fn from(other: VarZeroVec<'a, T, F>) -> Self {
match other {
VarZeroVec::Owned(o) => o,
VarZeroVec::Borrowed(b) => b.into(),
}
}
}
impl<T: VarULE + ?Sized> Default for VarZeroVec<'_, T> {
#[inline]
fn default() -> Self {
Self::new()
}
}
impl<T: VarULE + ?Sized, F: VarZeroVecFormat> Deref for VarZeroVec<'_, T, F> {
type Target = VarZeroSlice<T, F>;
fn deref(&self) -> &VarZeroSlice<T, F> {
self.as_slice()
}
}
impl<'a, T: VarULE + ?Sized, F: VarZeroVecFormat> VarZeroVec<'a, T, F> {
/// Creates a new, empty `VarZeroVec<T>`.
///
/// # Examples
///
/// ```
/// use zerovec::VarZeroVec;
///
/// let vzv: VarZeroVec<str> = VarZeroVec::new();
/// assert!(vzv.is_empty());
/// ```
#[inline]
pub const fn new() -> Self {
Self::Borrowed(VarZeroSlice::new_empty())
}
/// Parse a VarZeroVec from a slice of the appropriate format
///
/// Slices of the right format can be obtained via [`VarZeroSlice::as_bytes()`].
///
/// # Example
///
/// ```rust
/// # use zerovec::ule::ZeroVecError;
/// # use zerovec::VarZeroVec;
///
/// let strings = vec!["foo", "bar", "baz", "quux"];
/// let vec = VarZeroVec::<str>::from(&strings);
///
/// assert_eq!(&vec[0], "foo");
/// assert_eq!(&vec[1], "bar");
/// assert_eq!(&vec[2], "baz");
/// assert_eq!(&vec[3], "quux");
/// # Ok::<(), ZeroVecError>(())
/// ```
pub fn parse_byte_slice(slice: &'a [u8]) -> Result<Self, ZeroVecError> {
let borrowed = VarZeroSlice::<T, F>::parse_byte_slice(slice)?;
Ok(VarZeroVec::Borrowed(borrowed))
}
/// Uses a `&[u8]` buffer as a `VarZeroVec<T>` without any verification.
///
/// # Safety
///
/// `bytes` need to be an output from [`VarZeroSlice::as_bytes()`].
pub const unsafe fn from_bytes_unchecked(bytes: &'a [u8]) -> Self {
Self::Borrowed(core::mem::transmute::<&[u8], &VarZeroSlice<T, F>>(bytes))
}
/// Convert this into a mutable vector of the owned `T` type, cloning if necessary.
///
///
/// # Example
///
/// ```rust,ignore
/// # use zerovec::ule::ZeroVecError;
/// # use zerovec::VarZeroVec;
///
/// let strings = vec!["foo", "bar", "baz", "quux"];
/// let mut vec = VarZeroVec::<str>::from(&strings);
///
/// assert_eq!(vec.len(), 4);
/// let mutvec = vec.make_mut();
/// mutvec.push("lorem ipsum".into());
/// mutvec[2] = "dolor sit".into();
/// assert_eq!(&vec[0], "foo");
/// assert_eq!(&vec[1], "bar");
/// assert_eq!(&vec[2], "dolor sit");
/// assert_eq!(&vec[3], "quux");
/// assert_eq!(&vec[4], "lorem ipsum");
/// # Ok::<(), ZeroVecError>(())
/// ```
//
// This function is crate-public for now since we don't yet want to stabilize
// the internal implementation details
pub fn make_mut(&mut self) -> &mut VarZeroVecOwned<T, F> {
match self {
VarZeroVec::Owned(ref mut vec) => vec,
VarZeroVec::Borrowed(slice) => {
let new_self = VarZeroVecOwned::from_slice(slice);
*self = new_self.into();
// recursion is limited since we are guaranteed to hit the Owned branch
self.make_mut()
}
}
}
/// Converts a borrowed ZeroVec to an owned ZeroVec. No-op if already owned.
///
/// # Example
///
/// ```
/// # use zerovec::ule::ZeroVecError;
/// # use zerovec::VarZeroVec;
///
/// let strings = vec!["foo", "bar", "baz", "quux"];
/// let vec = VarZeroVec::<str>::from(&strings);
///
/// assert_eq!(vec.len(), 4);
/// // has 'static lifetime
/// let owned = vec.into_owned();
/// # Ok::<(), ZeroVecError>(())
/// ```
pub fn into_owned(mut self) -> VarZeroVec<'static, T, F> {
self.make_mut();
match self {
VarZeroVec::Owned(vec) => vec.into(),
_ => unreachable!(),
}
}
/// Obtain this `VarZeroVec` as a [`VarZeroSlice`]
pub fn as_slice(&self) -> &VarZeroSlice<T, F> {
match *self {
VarZeroVec::Owned(ref owned) => owned,
VarZeroVec::Borrowed(b) => b,
}
}
/// Takes the byte vector representing the encoded data of this VarZeroVec. If borrowed,
/// this function allocates a byte vector and copies the borrowed bytes into it.
///
/// The bytes can be passed back to [`Self::parse_byte_slice()`].
///
/// To get a reference to the bytes without moving, see [`VarZeroSlice::as_bytes()`].
///
/// # Example
///
/// ```rust
/// # use zerovec::ule::ZeroVecError;
/// # use zerovec::VarZeroVec;
///
/// let strings = vec!["foo", "bar", "baz"];
/// let bytes = VarZeroVec::<str>::from(&strings).into_bytes();
///
/// let mut borrowed: VarZeroVec<str> = VarZeroVec::parse_byte_slice(&bytes)?;
/// assert_eq!(borrowed, &*strings);
///
/// # Ok::<(), ZeroVecError>(())
/// ```
pub fn into_bytes(self) -> Vec<u8> {
match self {
VarZeroVec::Owned(vec) => vec.into_bytes(),
VarZeroVec::Borrowed(vec) => vec.as_bytes().to_vec(),
}
}
/// Return whether the [`VarZeroVec`] is operating on owned or borrowed
/// data. [`VarZeroVec::into_owned()`] and [`VarZeroVec::make_mut()`] can
/// be used to force it into an owned type
pub fn is_owned(&self) -> bool {
match self {
VarZeroVec::Owned(..) => true,
VarZeroVec::Borrowed(..) => false,
}
}
#[cfg(feature = "bench")]
#[doc(hidden)]
pub fn as_components<'b>(&'b self) -> VarZeroVecComponents<'b, T, F> {
self.as_slice().as_components()
}
}
impl<A, T, F> From<&Vec<A>> for VarZeroVec<'static, T, F>
where
T: VarULE + ?Sized,
A: EncodeAsVarULE<T>,
F: VarZeroVecFormat,
{
#[inline]
fn from(elements: &Vec<A>) -> Self {
Self::from(elements.as_slice())
}
}
impl<A, T, F> From<&[A]> for VarZeroVec<'static, T, F>
where
T: VarULE + ?Sized,
A: EncodeAsVarULE<T>,
F: VarZeroVecFormat,
{
#[inline]
fn from(elements: &[A]) -> Self {
if elements.is_empty() {
VarZeroSlice::new_empty().into()
} else {
#[allow(clippy::unwrap_used)] // TODO(#1410) Better story for fallibility
VarZeroVecOwned::try_from_elements(elements).unwrap().into()
}
}
}
impl<A, T, F, const N: usize> From<&[A; N]> for VarZeroVec<'static, T, F>
where
T: VarULE + ?Sized,
A: EncodeAsVarULE<T>,
F: VarZeroVecFormat,
{
#[inline]
fn from(elements: &[A; N]) -> Self {
Self::from(elements.as_slice())
}
}
impl<'a, 'b, T, F> PartialEq<VarZeroVec<'b, T, F>> for VarZeroVec<'a, T, F>
where
T: VarULE,
T: ?Sized,
T: PartialEq,
F: VarZeroVecFormat,
{
#[inline]
fn eq(&self, other: &VarZeroVec<'b, T, F>) -> bool {
// VZV::from_elements used to produce a non-canonical representation of the
// empty VZV, so we cannot use byte equality for empty vecs.
if self.is_empty() || other.is_empty() {
return self.is_empty() && other.is_empty();
}
// VarULE has an API guarantee that byte equality is semantic equality.
// For non-empty VZVs, there's only a single metadata representation,
// so this guarantee extends to the whole VZV representation.
self.as_bytes().eq(other.as_bytes())
}
}
impl<'a, T, F> Eq for VarZeroVec<'a, T, F>
where
T: VarULE,
T: ?Sized,
T: Eq,
F: VarZeroVecFormat,
{
}
impl<T, A, F> PartialEq<&'_ [A]> for VarZeroVec<'_, T, F>
where
T: VarULE + ?Sized,
T: PartialEq,
A: AsRef<T>,
F: VarZeroVecFormat,
{
#[inline]
fn eq(&self, other: &&[A]) -> bool {
self.iter().eq(other.iter().map(|t| t.as_ref()))
}
}
impl<T, A, F, const N: usize> PartialEq<[A; N]> for VarZeroVec<'_, T, F>
where
T: VarULE + ?Sized,
T: PartialEq,
A: AsRef<T>,
F: VarZeroVecFormat,
{
#[inline]
fn eq(&self, other: &[A; N]) -> bool {
self.iter().eq(other.iter().map(|t| t.as_ref()))
}
}
impl<'a, T: VarULE + ?Sized + PartialOrd, F: VarZeroVecFormat> PartialOrd for VarZeroVec<'a, T, F> {
fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
self.iter().partial_cmp(other.iter())
}
}
impl<'a, T: VarULE + ?Sized + Ord, F: VarZeroVecFormat> Ord for VarZeroVec<'a, T, F> {
fn cmp(&self, other: &Self) -> Ordering {
self.iter().cmp(other.iter())
}
}
#[test]
fn assert_single_empty_representation() {
assert_eq!(
VarZeroVec::<str>::new().as_bytes(),
VarZeroVec::<str>::from(&[] as &[&str]).as_bytes()
);
}
#[test]
fn weird_empty_representation_equality() {
assert_eq!(
VarZeroVec::<str>::parse_byte_slice(&[0, 0, 0, 0]).unwrap(),
VarZeroVec::<str>::parse_byte_slice(&[]).unwrap()
);
}