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#[cfg(any(feature = "nightly", feature = "allocator-api"))]
pub mod proxy {
#[cfg(feature = "nightly")]
#[allow(unused_imports)]
pub use alloc::alloc::{Global, handle_alloc_error}; // Global lives in the alloc crate!
#[cfg(feature = "nightly")]
#[allow(unused_imports)]
pub use core::alloc::{AllocError, Allocator, Layout};
#[cfg(all(not(feature = "nightly"), feature = "allocator-api"))]
#[allow(unused_imports)]
pub use allocator_api2::alloc::{AllocError, Allocator, Global, Layout, handle_alloc_error};
}
#[cfg(all(not(feature = "nightly"), not(feature = "allocator-api")))]
pub mod proxy {
pub use core::alloc::Layout;
/// A trait for custom memory allocators.
///
/// # Safety
///
/// Implementors must ensure that the `allocate` and `deallocate` methods are safe to call and that they correctly manage memory.
/// The `allocate` method must return a valid pointer to a block of memory of the requested size and alignment, or an `AllocError` if allocation fails.
/// The `deallocate` method must free the memory pointed to by the given pointer, which must have been previously allocated by the same allocator.
/// Implementors must also ensure that the allocator is thread-safe if it will be used in a multi-threaded context.
///
pub unsafe trait Allocator {
/// Allocates a block of memory with the given layout.
/// # Result
///
/// The `allocate` method returns a `Result` containing a non-null pointer to the allocated memory block on success, or an `AllocError` on failure. The `deallocate`
///
/// # Errors
///
/// The `allocate` method may return an `AllocError` if the allocation fails, for example, due to insufficient memory. The caller must handle this error appropriately.
///
fn allocate(&self, layout: Layout) -> Result<core::ptr::NonNull<[u8]>, AllocError>;
/// Deallocates a previously allocated block of memory.
///
/// # Safety
/// The caller must ensure that the pointer was allocated by this allocator and that the layout matches the original allocation.
unsafe fn deallocate(&self, ptr: core::ptr::NonNull<u8>, layout: Layout);
}
/// A simple global allocator that uses the built-in global allocator.
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
pub struct AllocError;
/// This is the default global allocator that uses the built-in global allocator.
/// It is used when no custom allocator is provided.
#[derive(Copy, Clone, Default, Debug)]
pub struct Global;
unsafe impl Allocator for Global {
#[inline]
#[allow(unused_variables)]
fn allocate(&self, layout: Layout) -> Result<core::ptr::NonNull<[u8]>, AllocError> {
#[cfg(feature = "alloc")]
unsafe {
// 1. Call the built-in global allocator function directly
let raw_ptr = alloc::alloc::alloc(layout);
if raw_ptr.is_null() {
return Err(AllocError);
}
// 2. Turn the raw pointer into a slice pointer tracking the size
let slice_ptr = core::ptr::slice_from_raw_parts_mut(raw_ptr, layout.size());
Ok(core::ptr::NonNull::new_unchecked(slice_ptr))
}
// Fallback for environments compiling with absolutely zero heap features
#[cfg(not(feature = "alloc"))]
{
Err(AllocError)
}
}
#[inline]
#[allow(unused_variables)]
unsafe fn deallocate(&self, ptr: core::ptr::NonNull<u8>, layout: Layout) {
#[cfg(feature = "alloc")]
unsafe {
alloc::alloc::dealloc(ptr.as_ptr(), layout);
}
}
}
#[inline]
pub fn handle_alloc_error(layout: Layout) -> ! {
// If the 'alloc' feature is active, forward to the official alloc error handler
#[cfg(feature = "alloc")]
{
alloc::alloc::handle_alloc_error(layout);
}
// If 'alloc' is completely compiled out, panic directly
#[cfg(not(feature = "alloc"))]
{
panic!("OOM: Allocation of {} bytes failed", layout.size());
}
}
}