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Add basic description for frame allocator methods

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Philipp Oppermann
2015-11-14 20:03:03 +01:00
parent 8304439c82
commit 16078431db
2 changed files with 89 additions and 66 deletions
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44
src/memory/area_frame_allocator.rs
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@@ -43,27 +43,33 @@ impl AreaFrameAllocator {
impl FrameAllocator for AreaFrameAllocator {
fn allocate_frame(&mut self) -> Option<Frame> {
match self.current_area {
None => None,
Some(area) => {
let frame = self.next_free_frame;
let current_area_last_frame = {
let address = area.base_addr + area.length - 1;
Frame::containing_address(address as usize)
};
if let Some(area) = self.current_area {
let frame = self.next_free_frame;
if frame > current_area_last_frame {
self.choose_next_area()
} else if frame >= self.kernel_start && frame <= self.kernel_end {
self.next_free_frame = Frame{ number: self.kernel_end.number + 1 }
} else if frame >= self.multiboot_start && frame <= self.multiboot_end {
self.next_free_frame = Frame{ number: self.multiboot_end.number + 1 }
} else {
self.next_free_frame.number += 1;
return Some(frame);
}
self.allocate_frame()
// the last frame of the current area
let current_area_last_frame = {
let address = area.base_addr + area.length - 1;
Frame::containing_address(address as usize)
};
if frame > current_area_last_frame {
// all frames of current area are used, switch to next area
self.choose_next_area();
} else if frame >= self.kernel_start && frame <= self.kernel_end {
// `frame` is used by the kernel
self.next_free_frame = Frame{ number: self.kernel_end.number + 1 };
} else if frame >= self.multiboot_start && frame <= self.multiboot_end {
// `frame` is used by the multiboot information structure
self.next_free_frame = Frame{ number: self.multiboot_end.number + 1 };
} else {
// frame is unused, increment `next_free_frame` and return it
self.next_free_frame.number += 1;
return Some(frame);
}
// `frame` was not valid, try it again with the updated `next_free_frame`
self.allocate_frame()
} else {
None // no free frames left
}
}