ring/arithmetic/
inout.rs

1// Copyright 2025 Brian Smith.
2//
3// Permission to use, copy, modify, and/or distribute this software for any
4// purpose with or without fee is hereby granted, provided that the above
5// copyright notice and this permission notice appear in all copies.
6//
7// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
8// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
9// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
10// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
11// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
12// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
13// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
14
15pub(crate) use crate::error::LenMismatchError;
16use core::num::NonZeroUsize;
17
18pub(crate) trait AliasingSlices2<T> {
19    /// The pointers passed to `f` will be valid and non-null, and will not
20    /// be dangling, so they can be passed to C functions.
21    ///
22    /// The first pointer, `r`, may be pointing to uninitialized memory for
23    /// `expected_len` elements of type `T`, properly aligned and writable.
24    /// `f` must not read from `r` before writing to it.
25    ///
26    /// The second & third pointers, `a` and `b`, point to `expected_len`
27    /// values of type `T`, properly aligned.
28    ///
29    /// `r`, `a`, and/or `b` may alias each other only in the following ways:
30    /// `ptr::eq(r, a)`, `ptr::eq(r, b)`, and/or `ptr::eq(a, b)`; i.e. they
31    /// will not be "overlapping."
32    ///
33    /// Implementations of this trait shouldn't override this default
34    /// implementation.
35    #[inline(always)]
36    fn with_non_dangling_non_null_pointers_ra<R>(
37        self,
38        expected_len: NonZeroUsize,
39        f: impl FnOnce(*mut T, *const T) -> R,
40    ) -> Result<R, LenMismatchError>
41    where
42        Self: Sized,
43    {
44        self.with_potentially_dangling_non_null_pointers_ra(expected_len.get(), f)
45    }
46
47    /// If `expected_len == 0` then the pointers passed to `f` may be
48    /// dangling pointers, which should not be passed to C functions. In all
49    /// other respects, this works like
50    /// `Self::with_non_dangling_non_null_pointers_rab`.
51    ///
52    /// Implementations of this trait should implement this method and not
53    /// `with_non_dangling_non_null_pointers_rab`. Users of this trait should
54    /// use `with_non_dangling_non_null_pointers_rab` and not this.
55    fn with_potentially_dangling_non_null_pointers_ra<R>(
56        self,
57        expected_len: usize,
58        f: impl FnOnce(*mut T, *const T) -> R,
59    ) -> Result<R, LenMismatchError>;
60}
61
62impl<T> AliasingSlices2<T> for &mut [T] {
63    fn with_potentially_dangling_non_null_pointers_ra<R>(
64        self,
65        expected_len: usize,
66        f: impl FnOnce(*mut T, *const T) -> R,
67    ) -> Result<R, LenMismatchError> {
68        let r = self;
69        if r.len() != expected_len {
70            return Err(LenMismatchError::new(r.len()));
71        }
72        Ok(f(r.as_mut_ptr(), r.as_ptr()))
73    }
74}
75
76impl<T> AliasingSlices2<T> for (&mut [T], &[T]) {
77    fn with_potentially_dangling_non_null_pointers_ra<R>(
78        self,
79        expected_len: usize,
80        f: impl FnOnce(*mut T, *const T) -> R,
81    ) -> Result<R, LenMismatchError> {
82        let (r, a) = self;
83        if r.len() != expected_len {
84            return Err(LenMismatchError::new(r.len()));
85        }
86        if a.len() != expected_len {
87            return Err(LenMismatchError::new(a.len()));
88        }
89        Ok(f(r.as_mut_ptr(), a.as_ptr()))
90    }
91}
92
93pub(crate) trait AliasingSlices3<T> {
94    /// The pointers passed to `f` will all be non-null and properly aligned,
95    /// and will not be dangling.
96    ///
97    /// The first pointer, `r` points to potentially-uninitialized writable
98    /// space for `expected_len` elements of type `T`. Accordingly, `f` must
99    /// not read from `r` before writing to it.
100    ///
101    /// The second & third pointers, `a` and `b`, point to `expected_len`
102    /// initialized values of type `T`.
103    ///
104    /// `r`, `a`, and/or `b` may alias each other, but only in the following
105    /// ways: `ptr::eq(r, a)`, `ptr::eq(r, b)`, and/or `ptr::eq(a, b)`; they
106    /// will not be "overlapping."
107    ///
108    /// Implementations of this trait shouldn't override this default
109    /// implementation.
110    #[inline(always)]
111    fn with_non_dangling_non_null_pointers_rab<R>(
112        self,
113        expected_len: NonZeroUsize,
114        f: impl FnOnce(*mut T, *const T, *const T) -> R,
115    ) -> Result<R, LenMismatchError>
116    where
117        Self: Sized,
118    {
119        self.with_potentially_dangling_non_null_pointers_rab(expected_len.get(), f)
120    }
121
122    /// If `expected_len == 0` then the pointers passed to `f` may be
123    /// dangling pointers, which should not be passed to C functions. In all
124    /// other respects, this works like
125    /// `Self::with_non_dangling_non_null_pointers_rab`.
126    ///
127    /// Implementations of this trait should implement this method and not
128    /// `with_non_dangling_non_null_pointers_rab`. Users of this trait should
129    /// use `with_non_dangling_non_null_pointers_rab` and not this.
130    fn with_potentially_dangling_non_null_pointers_rab<R>(
131        self,
132        expected_len: usize,
133        f: impl FnOnce(*mut T, *const T, *const T) -> R,
134    ) -> Result<R, LenMismatchError>;
135}
136
137impl<T> AliasingSlices3<T> for &mut [T] {
138    fn with_potentially_dangling_non_null_pointers_rab<R>(
139        self,
140        expected_len: usize,
141        f: impl FnOnce(*mut T, *const T, *const T) -> R,
142    ) -> Result<R, LenMismatchError> {
143        <Self as AliasingSlices2<T>>::with_potentially_dangling_non_null_pointers_ra(
144            self,
145            expected_len,
146            |r, a| f(r, r, a),
147        )
148    }
149}
150
151impl<T> AliasingSlices3<T> for (&mut [T], &[T], &[T]) {
152    fn with_potentially_dangling_non_null_pointers_rab<R>(
153        self,
154        expected_len: usize,
155        f: impl FnOnce(*mut T, *const T, *const T) -> R,
156    ) -> Result<R, LenMismatchError> {
157        let (r, a, b) = self;
158        ((r, a), b).with_potentially_dangling_non_null_pointers_rab(expected_len, f)
159    }
160}
161
162impl<RA, T> AliasingSlices3<T> for (RA, &[T])
163where
164    RA: AliasingSlices2<T>,
165{
166    fn with_potentially_dangling_non_null_pointers_rab<R>(
167        self,
168        expected_len: usize,
169        f: impl FnOnce(*mut T, *const T, *const T) -> R,
170    ) -> Result<R, LenMismatchError> {
171        let (ra, b) = self;
172        if b.len() != expected_len {
173            return Err(LenMismatchError::new(b.len()));
174        }
175        ra.with_potentially_dangling_non_null_pointers_ra(expected_len, |r, a| f(r, a, b.as_ptr()))
176    }
177}
ring/arithmetic/inout.rs

ring/arithmetic/
inout.rs
