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//! Buddy memory allocation.
//!
//! TODO: more efficient

use buddy_system_allocator::Heap;
use core::alloc::Layout;
use core::ptr::NonNull;

use crate::{AllocError, AllocResult, BaseAllocator, ByteAllocator};

/// A byte-granularity memory allocator based on the [buddy_system_allocator].
///
/// [buddy_system_allocator]: https://docs.rs/buddy_system_allocator/latest/buddy_system_allocator/
pub struct BuddyByteAllocator {
    inner: Heap<32>,
}

impl BuddyByteAllocator {
    /// Creates a new empty `BuddyByteAllocator`.
    pub const fn new() -> Self {
        Self {
            inner: Heap::<32>::new(),
        }
    }
}

impl BaseAllocator for BuddyByteAllocator {
    fn init(&mut self, start: usize, size: usize) {
        unsafe { self.inner.init(start, size) };
    }

    fn add_memory(&mut self, start: usize, size: usize) -> AllocResult {
        unsafe { self.inner.add_to_heap(start, start + size) };
        Ok(())
    }
}

impl ByteAllocator for BuddyByteAllocator {
    fn alloc(&mut self, layout: Layout) -> AllocResult<NonNull<u8>> {
        self.inner.alloc(layout).map_err(|_| AllocError::NoMemory)
    }

    fn dealloc(&mut self, pos: NonNull<u8>, layout: Layout) {
        self.inner.dealloc(pos, layout)
    }

    fn total_bytes(&self) -> usize {
        self.inner.stats_total_bytes()
    }

    fn used_bytes(&self) -> usize {
        self.inner.stats_alloc_actual()
    }

    fn available_bytes(&self) -> usize {
        self.inner.stats_total_bytes() - self.inner.stats_alloc_actual()
    }
}