implemented a bump allocator

1 files changed, 61 insertions, 0 deletions

diff --git a/StrixKernel/src/allocator/bump.rs b/StrixKernel/src/allocator/bump.rs
new file mode 100644
index 0000000..d6d2885
--- /dev/null
+++ b/StrixKernel/src/allocator/bump.rs
@@ -0,0 +1,61 @@
+use super::{Locked, align_up};
+use alloc::alloc::{GlobalAlloc, Layout};
+use core::ptr;
+
+pub struct BumpAllocator {
+    heap_start: usize,
+    heap_end: usize,
+    next: usize,
+    allocations: usize,
+}
+
+impl BumpAllocator {
+    /// Creates a new empty bump allocator.
+    pub const fn new() -> Self {
+        BumpAllocator {
+            heap_start: 0,
+            heap_end: 0,
+            next: 0,
+            allocations: 0,
+        }
+    }
+
+    /// Initializes the bump allocator with the given heap bounds.
+    ///
+    /// This method is unsafe because the caller must ensure that the given
+    /// memory range is unused. Also, this method must be called only once.
+    pub unsafe fn init(&mut self, heap_start: usize, heap_size: usize) {
+        self.heap_start = heap_start;
+        self.heap_end = heap_start.saturating_add(heap_size);
+        self.next = heap_start;
+    }
+}
+
+unsafe impl GlobalAlloc for Locked<BumpAllocator> {
+    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+        let mut bump = self.lock(); // get a mutable reference
+
+        let alloc_start = align_up(bump.next, layout.align());
+        let alloc_end = match alloc_start.checked_add(layout.size()) {
+            Some(end) => end,
+            None => return ptr::null_mut(),
+        };
+
+        if alloc_end > bump.heap_end {
+            ptr::null_mut() // out of memory
+        } else {
+            bump.next = alloc_end;
+            bump.allocations += 1;
+            alloc_start as *mut u8
+        }
+    }
+
+    unsafe fn dealloc(&self, _ptr: *mut u8, _layout: Layout) {
+        let mut bump = self.lock(); // get a mutable reference
+
+        bump.allocations -= 1;
+        if bump.allocations == 0 {
+            bump.next = bump.heap_start;
+        }
+    }
+}
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