hashbrown/
alloc.rs

1#[cfg(test)]
2pub(crate) use self::inner::AllocError;
3pub(crate) use self::inner::{Allocator, Global, do_alloc};
4
5// Nightly-case.
6// Use unstable `allocator_api` feature.
7// This is compatible with `allocator-api2` which can be enabled or not.
8// This is used when building for `std`.
9#[cfg(feature = "nightly")]
10mod inner {
11    use core::ptr::NonNull;
12    #[cfg(test)]
13    pub(crate) use stdalloc::alloc::AllocError;
14    use stdalloc::alloc::Layout;
15    pub(crate) use stdalloc::alloc::{Allocator, Global};
16
17    pub(crate) fn do_alloc<A: Allocator>(alloc: &A, layout: Layout) -> Result<NonNull<[u8]>, ()> {
18        match alloc.allocate(layout) {
19            Ok(ptr) => Ok(ptr),
20            Err(_) => Err(()),
21        }
22    }
23}
24
25// Basic non-nightly case.
26// This uses `allocator-api2` enabled by default.
27// If any crate enables "nightly" in `allocator-api2`,
28// this will be equivalent to the nightly case,
29// since `allocator_api2::alloc::Allocator` would be re-export of
30// `core::alloc::Allocator`.
31#[cfg(all(not(feature = "nightly"), feature = "allocator-api2"))]
32mod inner {
33    #[cfg(test)]
34    pub(crate) use allocator_api2::alloc::AllocError;
35    pub(crate) use allocator_api2::alloc::{Allocator, Global};
36    use core::ptr::NonNull;
37    use stdalloc::alloc::Layout;
38
39    pub(crate) fn do_alloc<A: Allocator>(alloc: &A, layout: Layout) -> Result<NonNull<[u8]>, ()> {
40        match alloc.allocate(layout) {
41            Ok(ptr) => Ok(ptr),
42            Err(_) => Err(()),
43        }
44    }
45}
46
47// No-defaults case.
48// When building with default-features turned off and
49// neither `nightly` nor `allocator-api2` is enabled,
50// this will be used.
51// Making it impossible to use any custom allocator with collections defined
52// in this crate.
53// Any crate in build-tree can enable `allocator-api2`,
54// or `nightly` without disturbing users that don't want to use it.
55#[cfg(not(any(feature = "nightly", feature = "allocator-api2")))]
56mod inner {
57    use core::ptr::NonNull;
58    use stdalloc::alloc::{Layout, alloc, dealloc};
59
60    #[expect(clippy::missing_safety_doc)] // not exposed outside of this crate
61    pub unsafe trait Allocator {
62        fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, ()>;
63        unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout);
64    }
65
66    #[derive(Copy, Clone)]
67    pub struct Global;
68
69    unsafe impl Allocator for Global {
70        #[inline]
71        fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, ()> {
72            match unsafe { NonNull::new(alloc(layout)) } {
73                Some(data) => {
74                    // SAFETY: this is NonNull::slice_from_raw_parts.
75                    Ok(unsafe {
76                        NonNull::new_unchecked(core::ptr::slice_from_raw_parts_mut(
77                            data.as_ptr(),
78                            layout.size(),
79                        ))
80                    })
81                }
82                None => Err(()),
83            }
84        }
85        #[inline]
86        unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout) {
87            unsafe {
88                dealloc(ptr.as_ptr(), layout);
89            }
90        }
91    }
92
93    impl Default for Global {
94        #[inline]
95        fn default() -> Self {
96            Global
97        }
98    }
99
100    pub(crate) fn do_alloc<A: Allocator>(alloc: &A, layout: Layout) -> Result<NonNull<[u8]>, ()> {
101        alloc.allocate(layout)
102    }
103}
hashbrown/alloc.rs

hashbrown/
alloc.rs
