halfbit/mm/
nop_alloc.rs

1use crate::num::NonZeroUsize;
2use crate::num::Pow2Usize;
3use super::NonNull;
4use super::AllocError;
5use super::Allocator;
6
7pub struct NopAllocator { }
8
9pub const NOP_ALLOCATOR: NopAllocator = NopAllocator { };
10
11unsafe impl Allocator for NopAllocator {
12    unsafe fn alloc(
13        &self,
14        _size: NonZeroUsize,
15        _align: Pow2Usize
16    ) -> Result<NonNull<u8>, AllocError> {
17        Err(AllocError::UnsupportedOperation)
18    }
19    unsafe fn free(
20        &self,
21        _ptr: NonNull<u8>,
22        _current_size: NonZeroUsize,
23        _align: Pow2Usize) {
24    }
25    unsafe fn grow(
26        &self,
27        _ptr: NonNull<u8>,
28        _current_size: NonZeroUsize,
29        _new_larger_size: NonZeroUsize,
30        _align: Pow2Usize
31    ) -> Result<NonNull<u8>, AllocError> {
32        Err(AllocError::UnsupportedOperation)
33    }
34    unsafe fn shrink(
35        &self,
36        _ptr: NonNull<u8>,
37        _current_size: NonZeroUsize,
38        _new_smaller_size: NonZeroUsize,
39        _align: Pow2Usize
40    ) -> Result<NonNull<u8>, AllocError> {
41        Err(AllocError::UnsupportedOperation)
42    }
43    fn supports_contains(&self) -> bool { false }
44    fn contains(&self, _ptr: NonNull<u8>) -> bool {
45        panic!("contains not supported!");
46    }
47    fn name(&self) -> &'static str { "nop-allocator" }
48}
49
50#[cfg(test)]
51mod tests {
52    use super::*;
53
54    #[test]
55    fn specific_name() {
56        assert!(NOP_ALLOCATOR.name().contains("nop"));
57    }
58
59    #[test]
60    fn alloc_not_supported() {
61        assert_eq!(unsafe { NOP_ALLOCATOR.alloc(NonZeroUsize::new(1).unwrap(), Pow2Usize::one()) }.unwrap_err(), AllocError::UnsupportedOperation);
62    }
63
64    #[test]
65    fn free_silently_completes() {
66        unsafe { NOP_ALLOCATOR.free(NonNull::dangling(), NonZeroUsize::new(1).unwrap(), Pow2Usize::one()) };
67    }
68
69    #[test]
70    fn grow_not_supported() {
71        assert_eq!(unsafe { NOP_ALLOCATOR.grow(NonNull::dangling(), NonZeroUsize::new(1).unwrap(), NonZeroUsize::new(2).unwrap(), Pow2Usize::one()) }.unwrap_err(), AllocError::UnsupportedOperation);
72    }
73
74    #[test]
75    fn shrink_not_supported() {
76        assert_eq!(unsafe { NOP_ALLOCATOR.shrink(NonNull::dangling(), NonZeroUsize::new(2).unwrap(), NonZeroUsize::new(1).unwrap(), Pow2Usize::one()) }.unwrap_err(), AllocError::UnsupportedOperation);
77    }
78
79    #[test]
80    fn contains_not_supported() {
81        assert!(!NOP_ALLOCATOR.supports_contains());
82    }
83
84    #[test]
85    #[should_panic]
86    fn calling_contains_panics() {
87        NOP_ALLOCATOR.contains(NonNull::dangling());
88    }
89}
halfbit/mm/nop_alloc.rs

halfbit/mm/
nop_alloc.rs
