From 0f5bf89493ff9018f6be9baa6a5e22cc2678011d Mon Sep 17 00:00:00 2001
From: Jack Halford <jack@crans.org>
Date: Wed, 28 Feb 2018 20:36:29 +0100
Subject: [PATCH] -amend

---
 kernel-rs/src/memory/area_allocator.rs | 74 ++++++++++++++++++++++++++
 kernel-rs/src/memory/mod.rs            | 19 +++++++
 2 files changed, 93 insertions(+)
 create mode 100644 kernel-rs/src/memory/area_allocator.rs
 create mode 100644 kernel-rs/src/memory/mod.rs

diff --git a/kernel-rs/src/memory/area_allocator.rs b/kernel-rs/src/memory/area_allocator.rs
new file mode 100644
index 00000000..4ce96334
--- /dev/null
+++ b/kernel-rs/src/memory/area_allocator.rs
@@ -0,0 +1,74 @@
+use memory::*;
+use multiboot2::{MemoryAreaIter, MemoryArea};
+
+pub struct AreaAllocator {
+    next_free_frame: Frame,
+    current_area: Option<&'static MemoryArea>,
+    areas: MemoryAreaIter,
+    kernel_start: Frame,
+    kernel_end: Frame,
+    multiboot_start: Frame,
+    multiboot_end: Frame,
+}
+
+impl AreaFrameAllocator {
+    pub fn new(kernel_start: usize, kernel_end: usize
+               multiboot_start: usize, multiboot_end: usize
+               memory_areas: MemoryAreaIter) -> AreaAllocator {
+        let mut allocator = AreaAllocator {
+            next_free_frame: Frame::containing_address(0),
+            current_area: None,
+            areas: memory_areas,
+            kernel_start: Frame::containing_address(kernel_start),
+            kernel_end: Frame::containing_address(kernel_end),
+            multiboot_start: Frame::containing_address(multiboot_start),
+            multiboot_end: Frame::containing_address(multiboot_end),
+        }
+        allocator.choose_next_area();
+        allocator
+    }
+
+    fn choose_next_area(&mut self) {
+        // get next area with free frames
+        self.current_area = self.areas.clone().filter(|area| {
+            Frame::containing_address(area.end_address()) >= self.next_free_frame
+        }).min_by_key(|area| area.start_addr());
+
+        if let Some(area) = self.current_area {
+            let start_frame = Frame::containing_address(area.start_addr());
+            if self.next_free_frame < start_frame {
+                self.next_free_frame = start_frame;
+            }
+        }
+    }
+}
+
+impl FrameAllocator for AreaFrameAllocator {
+    fn allocate_frame(&mut self) -> Option<Frame> {
+        if let Some(area) = sef.current_area {
+            let frame = Frame { number: self.next_free_frame.number },
+            let current_area_last_frame = Frame::containing_address(area.end_address());
+            if frame > current_area_last_frame {
+                // all frames are taken in this area
+                self.choose_next_area();
+            } else if frame >= self.kernel_start && frame <= kernel_end {
+                // frame used by kernel
+                self.next_free_frame = Frame {
+                    number: self.kernel_end.number + 1;
+                }
+            } else if frame >= self.multiboot_start && frame <= multiboot_end {
+                // frame used by multiboot
+                self.next_free_frame = Frame {
+                    number: self.multiboot_end.number + 1;
+                }
+            } else {
+                self.next_free_frame_number += 1;
+                return Some(Frame);
+            }
+        } else { None }
+    }
+
+    fn deallocate_frame(&mut self, frame: Frame) {
+        unimplemented!();
+    }
+}
diff --git a/kernel-rs/src/memory/mod.rs b/kernel-rs/src/memory/mod.rs
new file mode 100644
index 00000000..667a07cf
--- /dev/null
+++ b/kernel-rs/src/memory/mod.rs
@@ -0,0 +1,19 @@
+pub const PAGE_SIZE: usize = 4096;
+
+// pub use self::area_allocator::*;
+
+#[derive(Debug, PartialEq, Eq, PartialOrd, Ord)]
+pub struct Frame {
+    number: usize,
+}
+
+impl Frame {
+    fn containing_address(address: usize) -> Frame {
+        Frame{ number: address / PAGE_SIZE }
+    }
+}
+
+pub trait FrameAllocator {
+    fn allocate_frame(&mut self) -> Option<Frame>;
+    fn deallocate_frame(&mut self, frame: Frame);
+}