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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 core::str;
// Safety (based on the safety checklist on the ULE trait):
// 1. [T; N] does not include any uninitialized or padding bytes since T is ULE
// 2. [T; N] is aligned to 1 byte since T is ULE
// 3. The impl of validate_byte_slice() returns an error if any byte is not valid.
// 4. The impl of validate_byte_slice() returns an error if there are leftover bytes.
// 5. The other ULE methods use the default impl.
// 6. [T; N] byte equality is semantic equality since T is ULE
unsafe impl<T: ULE, const N: usize> ULE for [T; N] {
#[inline]
fn validate_byte_slice(bytes: &[u8]) -> Result<(), ZeroVecError> {
// a slice of multiple Selfs is equivalent to just a larger slice of Ts
T::validate_byte_slice(bytes)
}
}
impl<T: AsULE, const N: usize> AsULE for [T; N] {
type ULE = [T::ULE; N];
#[inline]
fn to_unaligned(self) -> Self::ULE {
self.map(T::to_unaligned)
}
#[inline]
fn from_unaligned(unaligned: Self::ULE) -> Self {
unaligned.map(T::from_unaligned)
}
}
unsafe impl<T: EqULE, const N: usize> EqULE for [T; N] {}
// Safety (based on the safety checklist on the VarULE trait):
// 1. str does not include any uninitialized or padding bytes.
// 2. str is aligned to 1 byte.
// 3. The impl of `validate_byte_slice()` returns an error if any byte is not valid.
// 4. The impl of `validate_byte_slice()` returns an error if the slice cannot be used in its entirety
// 5. The impl of `from_byte_slice_unchecked()` returns a reference to the same data.
// 6. `parse_byte_slice()` is equivalent to `validate_byte_slice()` followed by `from_byte_slice_unchecked()`
// 7. str byte equality is semantic equality
unsafe impl VarULE for str {
#[inline]
fn validate_byte_slice(bytes: &[u8]) -> Result<(), ZeroVecError> {
str::from_utf8(bytes).map_err(|_| ZeroVecError::parse::<Self>())?;
Ok(())
}
#[inline]
fn parse_byte_slice(bytes: &[u8]) -> Result<&Self, ZeroVecError> {
str::from_utf8(bytes).map_err(|_| ZeroVecError::parse::<Self>())
}
/// Invariant: must be safe to call when called on a slice that previously
/// succeeded with `parse_byte_slice`
#[inline]
unsafe fn from_byte_slice_unchecked(bytes: &[u8]) -> &Self {
str::from_utf8_unchecked(bytes)
}
}
/// Note: VarULE is well-defined for all `[T]` where `T: ULE`, but [`ZeroSlice`] is more ergonomic
/// when `T` is a low-level ULE type. For example:
///
/// ```no_run
/// # use zerovec::ZeroSlice;
/// # use zerovec::VarZeroVec;
/// # use zerovec::ule::AsULE;
/// // OK: [u8] is a useful type
/// let _: VarZeroVec<[u8]> = unimplemented!();
///
/// // Technically works, but [u32::ULE] is not very useful
/// let _: VarZeroVec<[<u32 as AsULE>::ULE]> = unimplemented!();
///
/// // Better: ZeroSlice<u32>
/// let _: VarZeroVec<ZeroSlice<u32>> = unimplemented!();
/// ```
///
/// [`ZeroSlice`]: crate::ZeroSlice
// Safety (based on the safety checklist on the VarULE trait):
// 1. [T] does not include any uninitialized or padding bytes (achieved by being a slice of a ULE type)
// 2. [T] is aligned to 1 byte (achieved by being a slice of a ULE type)
// 3. The impl of `validate_byte_slice()` returns an error if any byte is not valid.
// 4. The impl of `validate_byte_slice()` returns an error if the slice cannot be used in its entirety
// 5. The impl of `from_byte_slice_unchecked()` returns a reference to the same data.
// 6. All other methods are defaulted
// 7. `[T]` byte equality is semantic equality (achieved by being a slice of a ULE type)
unsafe impl<T> VarULE for [T]
where
T: ULE,
{
#[inline]
fn validate_byte_slice(slice: &[u8]) -> Result<(), ZeroVecError> {
T::validate_byte_slice(slice)
}
#[inline]
unsafe fn from_byte_slice_unchecked(bytes: &[u8]) -> &Self {
T::from_byte_slice_unchecked(bytes)
}
}