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
5use crate::ule::*;
6use core::str;
7
8// Safety (based on the safety checklist on the ULE trait):
9// 1. [T; N] does not include any uninitialized or padding bytes since T is ULE
10// 2. [T; N] is aligned to 1 byte since T is ULE
11// 3. The impl of validate_byte_slice() returns an error if any byte is not valid.
12// 4. The impl of validate_byte_slice() returns an error if there are leftover bytes.
13// 5. The other ULE methods use the default impl.
14// 6. [T; N] byte equality is semantic equality since T is ULE
15unsafe impl<T: ULE, const N: usize> ULE for [T; N] {
16 #[inline]
17 fn validate_byte_slice(bytes: &[u8]) -> Result<(), ZeroVecError> {
18 // a slice of multiple Selfs is equivalent to just a larger slice of Ts
19 T::validate_byte_slice(bytes)
20 }
21}
22
23impl<T: AsULE, const N: usize> AsULE for [T; N] {
24 type ULE = [T::ULE; N];
25 #[inline]
26 fn to_unaligned(self) -> Self::ULE {
27 self.map(T::to_unaligned)
28 }
29 #[inline]
30 fn from_unaligned(unaligned: Self::ULE) -> Self {
31 unaligned.map(T::from_unaligned)
32 }
33}
34
35unsafe impl<T: EqULE, const N: usize> EqULE for [T; N] {}
36
37// Safety (based on the safety checklist on the VarULE trait):
38// 1. str does not include any uninitialized or padding bytes.
39// 2. str is aligned to 1 byte.
40// 3. The impl of `validate_byte_slice()` returns an error if any byte is not valid.
41// 4. The impl of `validate_byte_slice()` returns an error if the slice cannot be used in its entirety
42// 5. The impl of `from_byte_slice_unchecked()` returns a reference to the same data.
43// 6. `parse_byte_slice()` is equivalent to `validate_byte_slice()` followed by `from_byte_slice_unchecked()`
44// 7. str byte equality is semantic equality
45unsafe impl VarULE for str {
46 #[inline]
47 fn validate_byte_slice(bytes: &[u8]) -> Result<(), ZeroVecError> {
48 str::from_utf8(bytes).map_err(|_| ZeroVecError::parse::<Self>())?;
49 Ok(())
50 }
51
52 #[inline]
53 fn parse_byte_slice(bytes: &[u8]) -> Result<&Self, ZeroVecError> {
54 str::from_utf8(bytes).map_err(|_| ZeroVecError::parse::<Self>())
55 }
56 /// Invariant: must be safe to call when called on a slice that previously
57 /// succeeded with `parse_byte_slice`
58 #[inline]
59 unsafe fn from_byte_slice_unchecked(bytes: &[u8]) -> &Self {
60 str::from_utf8_unchecked(bytes)
61 }
62}
63
64/// Note: VarULE is well-defined for all `[T]` where `T: ULE`, but [`ZeroSlice`] is more ergonomic
65/// when `T` is a low-level ULE type. For example:
66///
67/// ```no_run
68/// # use zerovec::ZeroSlice;
69/// # use zerovec::VarZeroVec;
70/// # use zerovec::ule::AsULE;
71/// // OK: [u8] is a useful type
72/// let _: VarZeroVec<[u8]> = unimplemented!();
73///
74/// // Technically works, but [u32::ULE] is not very useful
75/// let _: VarZeroVec<[<u32 as AsULE>::ULE]> = unimplemented!();
76///
77/// // Better: ZeroSlice<u32>
78/// let _: VarZeroVec<ZeroSlice<u32>> = unimplemented!();
79/// ```
80///
81/// [`ZeroSlice`]: crate::ZeroSlice
82// Safety (based on the safety checklist on the VarULE trait):
83// 1. [T] does not include any uninitialized or padding bytes (achieved by being a slice of a ULE type)
84// 2. [T] is aligned to 1 byte (achieved by being a slice of a ULE type)
85// 3. The impl of `validate_byte_slice()` returns an error if any byte is not valid.
86// 4. The impl of `validate_byte_slice()` returns an error if the slice cannot be used in its entirety
87// 5. The impl of `from_byte_slice_unchecked()` returns a reference to the same data.
88// 6. All other methods are defaulted
89// 7. `[T]` byte equality is semantic equality (achieved by being a slice of a ULE type)
90unsafe impl<T> VarULE for [T]
91where
92 T: ULE,
93{
94 #[inline]
95 fn validate_byte_slice(slice: &[u8]) -> Result<(), ZeroVecError> {
96 T::validate_byte_slice(bytes:slice)
97 }
98
99 #[inline]
100 unsafe fn from_byte_slice_unchecked(bytes: &[u8]) -> &Self {
101 T::from_byte_slice_unchecked(bytes)
102 }
103}
104