/rust/registry/src/index.crates.io-1949cf8c6b5b557f/zerovec-0.11.6/src/varzerovec/lengthless.rs

Source
// 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
// (online at: https://github.com/unicode-org/icu4x/blob/main/LICENSE ).

use super::components::VarZeroVecComponents;
use super::*;
use crate::ule::*;
use core::marker::PhantomData;

/// A slice representing the index and data tables of a [`VarZeroVec`],
/// *without* any length fields. The length field is expected to be stored elsewhere.
///
/// Without knowing the length this is of course unsafe to use directly.
#[repr(transparent)]
#[derive(PartialEq, Eq)]
pub(crate) struct VarZeroLengthlessSlice<T: ?Sized, F> {
    marker: PhantomData<(F, T)>,
    /// The original slice this was constructed from
    // Safety invariant: This field must have successfully passed through
    // VarZeroVecComponents::parse_bytes_with_length() with the length
    // associated with this value.
    entire_slice: [u8],
}

impl<T: VarULE + ?Sized, F: VarZeroVecFormat> VarZeroLengthlessSlice<T, F> {
    /// Obtain a [`VarZeroVecComponents`] borrowing from the internal buffer
    ///
    /// Safety: `len` must be the length associated with this value
    #[inline]
    pub(crate) unsafe fn as_components<'a>(&'a self, len: u32) -> VarZeroVecComponents<'a, T, F> {
        unsafe {
            // safety: VarZeroSlice is guaranteed to parse here
            VarZeroVecComponents::from_bytes_unchecked_with_length(len, &self.entire_slice)
        }
    }

    /// Parse a [`VarZeroLengthlessSlice`] from a slice of the appropriate format
    ///
    /// Slices of the right format can be obtained via [`VarZeroSlice::as_bytes()`]
    pub fn parse_bytes<'a>(len: u32, slice: &'a [u8]) -> Result<&'a Self, UleError> {
        let _ = VarZeroVecComponents::<T, F>::parse_bytes_with_length(len, slice)
            .map_err(|_| UleError::parse::<Self>())?;
        unsafe {
            // Safety: We just verified that it is of the correct format.
            Ok(Self::from_bytes_unchecked(slice))
        }
    }

    /// Uses a `&[u8]` buffer as a `VarZeroLengthlessSlice<T>` without any verification.
    ///
    /// # Safety
    ///
    /// `bytes` need to be an output from [`VarZeroLengthlessSlice::as_bytes()`], or alternatively
    /// successfully pass through `parse_bytes` (with `len`)
    ///
    /// The length associated with this value will be the length associated with the original slice.
    pub(crate) const unsafe fn from_bytes_unchecked(bytes: &[u8]) -> &Self {
        // self is really just a wrapper around a byte slice
        &*(bytes as *const [u8] as *const Self)
    }

    /// Uses a `&mut [u8]` buffer as a `VarZeroLengthlessSlice<T>` without any verification.
    ///
    /// # Safety
    ///
    /// `bytes` need to be an output from [`VarZeroLengthlessSlice::as_bytes()`], or alternatively
    /// be valid to be passed to `from_bytes_unchecked_with_length`
    ///
    /// The length associated with this value will be the length associated with the original slice.
    pub(crate) unsafe fn from_bytes_unchecked_mut(bytes: &mut [u8]) -> &mut Self {
        // self is really just a wrapper around a byte slice
        &mut *(bytes as *mut [u8] as *mut VarZeroLengthlessSlice<T, F>)
    }

    /// Get one of this slice's elements
    ///
    /// # Safety
    ///
    /// `index` must be in range, and `len` must be the length associated with this
    /// instance of [`VarZeroLengthlessSlice`].
    pub(crate) unsafe fn get_unchecked(&self, len: u32, idx: usize) -> &T {
        self.as_components(len).get_unchecked(idx)
    }

    /// Get a reference to the entire encoded backing buffer of this slice
    ///
    /// The bytes can be passed back to [`Self::parse_bytes()`].
    ///
    /// To take the bytes as a vector, see [`VarZeroVec::into_bytes()`].
    #[inline]
    pub(crate) const fn as_bytes(&self) -> &[u8] {
        &self.entire_slice
    }

    /// Get the bytes behind this as a mutable slice
    ///
    /// # Safety
    ///
    ///  - `len` is the length associated with this [`VarZeroLengthlessSlice`]
    ///  - The resultant slice is only mutated in a way such that it remains a valid `T`
    ///
    /// # Panics
    ///
    ///  Panics when idx is not in bounds for this slice
    pub(crate) unsafe fn get_bytes_at_mut(&mut self, len: u32, idx: usize) -> &mut [u8] {
        let components = self.as_components(len);
        let range = components.get_things_range(idx);
        let offset = components.get_indices_size();

        // get_indices_size() returns the start of the things slice, and get_things_range()
        // returns a range in-bounds of the things slice
        #[expect(clippy::indexing_slicing)]
        &mut self.entire_slice[offset..][range]
    }
}

Line	Count	Source
1		// This file is part of ICU4X. For terms of use, please see the file
2		// called LICENSE at the top level of the ICU4X source tree
3		// (online at: https://github.com/unicode-org/icu4x/blob/main/LICENSE ).
4
5		use super::components::VarZeroVecComponents;
6		use super::*;
7		use crate::ule::*;
8		use core::marker::PhantomData;
9
10		/// A slice representing the index and data tables of a [`VarZeroVec`],
11		/// without any length fields. The length field is expected to be stored elsewhere.
12		///
13		/// Without knowing the length this is of course unsafe to use directly.
14		#[repr(transparent)]
15		#[derive(PartialEq, Eq)]
16		pub(crate) struct VarZeroLengthlessSlice<T: ?Sized, F> {
17		marker: PhantomData<(F, T)>,
18		/// The original slice this was constructed from
19		// Safety invariant: This field must have successfully passed through
20		// VarZeroVecComponents::parse_bytes_with_length() with the length
21		// associated with this value.
22		entire_slice: [u8],
23		}
24
25		impl<T: VarULE + ?Sized, F: VarZeroVecFormat> VarZeroLengthlessSlice<T, F> {
26		/// Obtain a [`VarZeroVecComponents`] borrowing from the internal buffer
27		///
28		/// Safety: `len` must be the length associated with this value
29		#[inline]
30	0	pub(crate) unsafe fn as_components<'a>(&'a self, len: u32) -> VarZeroVecComponents<'a, T, F> {
31		unsafe {
32		// safety: VarZeroSlice is guaranteed to parse here
33	0	VarZeroVecComponents::from_bytes_unchecked_with_length(len, &self.entire_slice)
34		}
35	0	} Unexecuted instantiation: <zerovec::varzerovec::lengthless::VarZeroLengthlessSlice<[u8], zerovec::varzerovec::components::Index16>>::as_components Unexecuted instantiation: <zerovec::varzerovec::lengthless::VarZeroLengthlessSlice<_, _>>::as_components
36
37		/// Parse a [`VarZeroLengthlessSlice`] from a slice of the appropriate format
38		///
39		/// Slices of the right format can be obtained via [`VarZeroSlice::as_bytes()`]
40	0	pub fn parse_bytes<'a>(len: u32, slice: &'a [u8]) -> Result<&'a Self, UleError> {
41	0	let _ = VarZeroVecComponents::<T, F>::parse_bytes_with_length(len, slice)
42	0	.map_err(\|_\| UleError::parse::<Self>())?;
43		unsafe {
44		// Safety: We just verified that it is of the correct format.
45	0	Ok(Self::from_bytes_unchecked(slice))
46		}
47	0	}
48
49		/// Uses a `&[u8]` buffer as a `VarZeroLengthlessSlice<T>` without any verification.
50		///
51		/// # Safety
52		///
53		/// `bytes` need to be an output from [`VarZeroLengthlessSlice::as_bytes()`], or alternatively
54		/// successfully pass through `parse_bytes` (with `len`)
55		///
56		/// The length associated with this value will be the length associated with the original slice.
57	0	pub(crate) const unsafe fn from_bytes_unchecked(bytes: &[u8]) -> &Self {
58		// self is really just a wrapper around a byte slice
59	0	&(bytes as const [u8] as *const Self)
60	0	}
61
62		/// Uses a `&mut [u8]` buffer as a `VarZeroLengthlessSlice<T>` without any verification.
63		///
64		/// # Safety
65		///
66		/// `bytes` need to be an output from [`VarZeroLengthlessSlice::as_bytes()`], or alternatively
67		/// be valid to be passed to `from_bytes_unchecked_with_length`
68		///
69		/// The length associated with this value will be the length associated with the original slice.
70	0	pub(crate) unsafe fn from_bytes_unchecked_mut(bytes: &mut [u8]) -> &mut Self {
71		// self is really just a wrapper around a byte slice
72	0	&mut (bytes as mut [u8] as *mut VarZeroLengthlessSlice<T, F>)
73	0	} Unexecuted instantiation: <zerovec::varzerovec::lengthless::VarZeroLengthlessSlice<[u8], zerovec::varzerovec::components::Index16>>::from_bytes_unchecked_mut Unexecuted instantiation: <zerovec::varzerovec::lengthless::VarZeroLengthlessSlice<_, _>>::from_bytes_unchecked_mut
74
75		/// Get one of this slice's elements
76		///
77		/// # Safety
78		///
79		/// `index` must be in range, and `len` must be the length associated with this
80		/// instance of [`VarZeroLengthlessSlice`].
81	0	pub(crate) unsafe fn get_unchecked(&self, len: u32, idx: usize) -> &T {
82	0	self.as_components(len).get_unchecked(idx)
83	0	} Unexecuted instantiation: <zerovec::varzerovec::lengthless::VarZeroLengthlessSlice<[u8], zerovec::varzerovec::components::Index16>>::get_unchecked Unexecuted instantiation: <zerovec::varzerovec::lengthless::VarZeroLengthlessSlice<_, _>>::get_unchecked
84
85		/// Get a reference to the entire encoded backing buffer of this slice
86		///
87		/// The bytes can be passed back to [`Self::parse_bytes()`].
88		///
89		/// To take the bytes as a vector, see [`VarZeroVec::into_bytes()`].
90		#[inline]
91	0	pub(crate) const fn as_bytes(&self) -> &[u8] {
92	0	&self.entire_slice
93	0	}
94
95		/// Get the bytes behind this as a mutable slice
96		///
97		/// # Safety
98		///
99		/// - `len` is the length associated with this [`VarZeroLengthlessSlice`]
100		/// - The resultant slice is only mutated in a way such that it remains a valid `T`
101		///
102		/// # Panics
103		///
104		/// Panics when idx is not in bounds for this slice
105	0	pub(crate) unsafe fn get_bytes_at_mut(&mut self, len: u32, idx: usize) -> &mut [u8] {
106	0	let components = self.as_components(len);
107	0	let range = components.get_things_range(idx);
108	0	let offset = components.get_indices_size();
109
110		// get_indices_size() returns the start of the things slice, and get_things_range()
111		// returns a range in-bounds of the things slice
112		#[expect(clippy::indexing_slicing)]
113	0	&mut self.entire_slice[offset..][range]
114	0	} Unexecuted instantiation: <zerovec::varzerovec::lengthless::VarZeroLengthlessSlice<[u8], zerovec::varzerovec::components::Index16>>::get_bytes_at_mut Unexecuted instantiation: <zerovec::varzerovec::lengthless::VarZeroLengthlessSlice<_, _>>::get_bytes_at_mut
115		}

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Created: 2026-08-13 07:14