From 7c84dbaa1d06339e2ab84cd19fd6186a51c170e4 Mon Sep 17 00:00:00 2001
From: Philipp Oppermann <dev@phil-opp.com>
Date: Thu, 9 Jan 2020 15:25:37 +0100
Subject: [PATCH] Create a basic BumpAllocator type

---
 src/allocator.rs      |  2 ++
 src/allocator/bump.rs | 28 ++++++++++++++++++++++++++++
 2 files changed, 30 insertions(+)
 create mode 100644 src/allocator/bump.rs

diff --git a/src/allocator.rs b/src/allocator.rs
index f77fef9d..4b683208 100644
--- a/src/allocator.rs
+++ b/src/allocator.rs
@@ -8,6 +8,8 @@ use x86_64::{
     VirtAddr,
 };
 
+pub mod bump;
+
 pub const HEAP_START: usize = 0x_4444_4444_0000;
 pub const HEAP_SIZE: usize = 100 * 1024; // 100 KiB
 
diff --git a/src/allocator/bump.rs b/src/allocator/bump.rs
new file mode 100644
index 00000000..5644dab5
--- /dev/null
+++ b/src/allocator/bump.rs
@@ -0,0 +1,28 @@
+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 + heap_size;
+        self.next = heap_start;
+    }
+}