--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/rust/hg-core/src/dirstate/entry.rs	Fri Sep 17 12:42:24 2021 +0200
@@ -0,0 +1,128 @@
+use crate::errors::HgError;
+use std::convert::TryFrom;
+
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+pub enum EntryState {
+    Normal,
+    Added,
+    Removed,
+    Merged,
+    Unknown,
+}
+
+/// The C implementation uses all signed types. This will be an issue
+/// either when 4GB+ source files are commonplace or in 2038, whichever
+/// comes first.
+#[derive(Debug, PartialEq, Copy, Clone)]
+pub struct DirstateEntry {
+    pub state: EntryState,
+    pub mode: i32,
+    pub mtime: i32,
+    pub size: i32,
+}
+
+pub const V1_RANGEMASK: i32 = 0x7FFFFFFF;
+
+pub const MTIME_UNSET: i32 = -1;
+
+/// A `DirstateEntry` with a size of `-2` means that it was merged from the
+/// other parent. This allows revert to pick the right status back during a
+/// merge.
+pub const SIZE_FROM_OTHER_PARENT: i32 = -2;
+/// A special value used for internal representation of special case in
+/// dirstate v1 format.
+pub const SIZE_NON_NORMAL: i32 = -1;
+
+impl DirstateEntry {
+    pub fn is_non_normal(&self) -> bool {
+        self.state != EntryState::Normal || self.mtime == MTIME_UNSET
+    }
+
+    pub fn is_from_other_parent(&self) -> bool {
+        self.state == EntryState::Normal && self.size == SIZE_FROM_OTHER_PARENT
+    }
+
+    // TODO: other platforms
+    #[cfg(unix)]
+    pub fn mode_changed(
+        &self,
+        filesystem_metadata: &std::fs::Metadata,
+    ) -> bool {
+        use std::os::unix::fs::MetadataExt;
+        const EXEC_BIT_MASK: u32 = 0o100;
+        let dirstate_exec_bit = (self.mode as u32) & EXEC_BIT_MASK;
+        let fs_exec_bit = filesystem_metadata.mode() & EXEC_BIT_MASK;
+        dirstate_exec_bit != fs_exec_bit
+    }
+
+    /// Returns a `(state, mode, size, mtime)` tuple as for
+    /// `DirstateMapMethods::debug_iter`.
+    pub fn debug_tuple(&self) -> (u8, i32, i32, i32) {
+        (self.state.into(), self.mode, self.size, self.mtime)
+    }
+
+    pub fn mtime_is_ambiguous(&self, now: i32) -> bool {
+        self.state == EntryState::Normal && self.mtime == now
+    }
+
+    pub fn clear_ambiguous_mtime(&mut self, now: i32) -> bool {
+        let ambiguous = self.mtime_is_ambiguous(now);
+        if ambiguous {
+            // The file was last modified "simultaneously" with the current
+            // write to dirstate (i.e. within the same second for file-
+            // systems with a granularity of 1 sec). This commonly happens
+            // for at least a couple of files on 'update'.
+            // The user could change the file without changing its size
+            // within the same second. Invalidate the file's mtime in
+            // dirstate, forcing future 'status' calls to compare the
+            // contents of the file if the size is the same. This prevents
+            // mistakenly treating such files as clean.
+            self.clear_mtime()
+        }
+        ambiguous
+    }
+
+    pub fn clear_mtime(&mut self) {
+        self.mtime = -1;
+    }
+}
+
+impl EntryState {
+    pub fn is_tracked(self) -> bool {
+        use EntryState::*;
+        match self {
+            Normal | Added | Merged => true,
+            Removed | Unknown => false,
+        }
+    }
+}
+
+impl TryFrom<u8> for EntryState {
+    type Error = HgError;
+
+    fn try_from(value: u8) -> Result<Self, Self::Error> {
+        match value {
+            b'n' => Ok(EntryState::Normal),
+            b'a' => Ok(EntryState::Added),
+            b'r' => Ok(EntryState::Removed),
+            b'm' => Ok(EntryState::Merged),
+            b'?' => Ok(EntryState::Unknown),
+            _ => Err(HgError::CorruptedRepository(format!(
+                "Incorrect dirstate entry state {}",
+                value
+            ))),
+        }
+    }
+}
+
+impl Into<u8> for EntryState {
+    fn into(self) -> u8 {
+        match self {
+            EntryState::Normal => b'n',
+            EntryState::Added => b'a',
+            EntryState::Removed => b'r',
+            EntryState::Merged => b'm',
+            EntryState::Unknown => b'?',
+        }
+    }
+}