diff rust/hg-core/src/dirstate_tree/on_disk.rs @ 48231:0524c1359bfc

dirstate-v2: Extend node flags to 16 bits

Only 7 out of 8 available bits are used right now. Reserve some more.

Future versions of Mercurial may assign meaning to some of these bits,
with the limitation that then-older versions will always reset those bits to
unset when writing nodes.
(A new node is written for any mutation in its subtree, leaving the bytes of
the old node unreachable until the data file is rewritten entirely.)

Differential Revision: https://phab.mercurial-scm.org/D11661

--- a/rust/hg-core/src/dirstate_tree/on_disk.rs	Thu Oct 14 08:58:07 2021 -0700
+++ b/rust/hg-core/src/dirstate_tree/on_disk.rs	Thu Oct 14 16:06:31 2021 +0200
@@ -33,7 +33,7 @@
 
 /// Must match constants of the same names in `mercurial/dirstateutils/v2.py`
 const TREE_METADATA_SIZE: usize = 44;
-const NODE_SIZE: usize = 43;
+const NODE_SIZE: usize = 44;
 
 /// Make sure that size-affecting changes are made knowingly
 #[allow(unused)]
@@ -94,15 +94,14 @@
     children: ChildNodes,
     pub(super) descendants_with_entry_count: Size,
     pub(super) tracked_descendants_count: Size,
-    flags: Flags,
+    flags: U16Be,
     size: U32Be,
     mtime: PackedTruncatedTimestamp,
 }
 
 bitflags! {
-    #[derive(BytesCast)]
     #[repr(C)]
-    struct Flags: u8 {
+    struct Flags: u16 {
         const WDIR_TRACKED = 1 << 0;
         const P1_TRACKED = 1 << 1;
         const P2_INFO = 1 << 2;
@@ -296,8 +295,12 @@
         })
     }
 
+    fn flags(&self) -> Flags {
+        Flags::from_bits_truncate(self.flags.get())
+    }
+
     fn has_entry(&self) -> bool {
-        self.flags.intersects(
+        self.flags().intersects(
             Flags::WDIR_TRACKED | Flags::P1_TRACKED | Flags::P2_INFO,
         )
     }
@@ -318,7 +321,7 @@
         &self,
     ) -> Result<Option<TruncatedTimestamp>, DirstateV2ParseError> {
         Ok(
-            if self.flags.contains(Flags::HAS_MTIME) && !self.has_entry() {
+            if self.flags().contains(Flags::HAS_MTIME) && !self.has_entry() {
                 Some(self.mtime.try_into()?)
             } else {
                 None
@@ -327,12 +330,12 @@
     }
 
     fn synthesize_unix_mode(&self) -> u32 {
-        let file_type = if self.flags.contains(Flags::MODE_IS_SYMLINK) {
+        let file_type = if self.flags().contains(Flags::MODE_IS_SYMLINK) {
             libc::S_IFLNK
         } else {
             libc::S_IFREG
         };
-        let permisions = if self.flags.contains(Flags::MODE_EXEC_PERM) {
+        let permisions = if self.flags().contains(Flags::MODE_EXEC_PERM) {
             0o755
         } else {
             0o644
@@ -342,15 +345,15 @@
 
     fn assume_entry(&self) -> DirstateEntry {
         // TODO: convert through raw bits instead?
-        let wdir_tracked = self.flags.contains(Flags::WDIR_TRACKED);
-        let p1_tracked = self.flags.contains(Flags::P1_TRACKED);
-        let p2_info = self.flags.contains(Flags::P2_INFO);
-        let mode_size = if self.flags.contains(Flags::HAS_MODE_AND_SIZE) {
+        let wdir_tracked = self.flags().contains(Flags::WDIR_TRACKED);
+        let p1_tracked = self.flags().contains(Flags::P1_TRACKED);
+        let p2_info = self.flags().contains(Flags::P2_INFO);
+        let mode_size = if self.flags().contains(Flags::HAS_MODE_AND_SIZE) {
             Some((self.synthesize_unix_mode(), self.size.into()))
         } else {
             None
         };
-        let mtime = if self.flags.contains(Flags::HAS_MTIME) {
+        let mtime = if self.flags().contains(Flags::HAS_MTIME) {
             Some(self.mtime.truncated_seconds.into())
         } else {
             None
@@ -600,7 +603,7 @@
                         tracked_descendants_count: node
                             .tracked_descendants_count
                             .into(),
-                        flags,
+                        flags: flags.bits().into(),
                         size,
                         mtime,
                     }