faces_pfm/flags.rs
1bitflags::bitflags! {
2 /// Page frame status flags.
3 ///
4 /// These flags track the state of a physical page frame, such as whether it is
5 /// locked, dirty, up-to-date, part of the LRU list, etc. They are used by the
6 /// page frame manager and compatible with the `faces::AbsFlags` trait.
7 #[derive(Debug, Copy, Default, Eq, PartialEq)]
8 pub struct PageFlags: u16 {
9 /// Page is locked and cannot be evicted or moved.
10 const LOCKED = 1 << 0;
11 /// Page has been written to (needs flushing to backing store).
12 const DIRTY = 1 << 1;
13 /// Page content is up-to-date with its backing store.
14 const UPTODATE = 1 << 2;
15 /// Page is on the LRU (least recently used) list.
16 const LRU = 1 << 3;
17 /// Page is a small (order‑0) allocation.
18 const SMALL = 1 << 4;
19 /// Page is part of a compound page (e.g., huge page).
20 const COMPOUND = 1 << 5;
21 /// Page is in the swap cache.
22 const SWAPCACHE= 1 << 6;
23 /// Page is currently being written back to disk.
24 const WRITEBACK= 1 << 7;
25 /// Page is used as a page table.
26 const PAGETABLE= 1 << 8;
27 /// Page belongs to a file mapping.
28 const FILE = 1 << 9;
29 /// Page is reserved (e.g., used by kernel or unavailable).
30 const RESERVED = 1 << 10;
31 }
32}
33
34impl const Clone for PageFlags {
35 /// Clones the page flags by copying the underlying integer.
36 fn clone(&self) -> Self {
37 Self(self.0)
38 }
39}
40
41impl From<usize> for PageFlags {
42 /// Converts a `usize` value into a `PageFlags` instance.
43 ///
44 /// # Safety
45 /// This transmutes the integer representation directly. The caller must
46 /// ensure that the `usize` contains a valid bit pattern for `PageFlags`.
47 fn from(value: usize) -> Self {
48 * unsafe {
49 core::mem::transmute::<&usize, &Self>(&value)
50 }
51 }
52}
53
54impl faces::AbsFlags for PageFlags {}