monty_fs/
mount_mode.rs

1//! Public mount mode definitions.
2//!
3//! The public API only needs to describe the access policy for a mount. The
4//! in-memory overlay storage lives in [`super::overlay_state`] so the public
5//! enum can stay focused on behavior rather than internal data layout.
6
7use super::overlay_state::OverlayState;
8
9/// Access policy for a mount point.
10///
11/// Controls what operations sandbox code can perform on files within the mounted
12/// directory. The overlay modes provide copy-on-write semantics where reads fall
13/// through to the real directory but writes are captured separately.
14///
15/// Regardless of mode, path traversal and symlink escape protection is always enforced.
16#[derive(Debug)]
17pub enum MountMode {
18    /// Full read and write access to the host directory.
19    /// Use with caution — sandbox code can modify real files.
20    ReadWrite,
21
22    /// Read-only access. Write operations raise `PermissionError`.
23    ReadOnly,
24
25    /// Copy-on-write overlay backed by in-memory storage.
26    ///
27    /// Reads fall through to the host directory. Writes are captured in the
28    /// contained [`OverlayState`]. Deletions insert `OverlayEntry::Deleted`
29    /// tombstones that hide real files from subsequent reads. Directory listings
30    /// merge real and overlay entries, with overlay taking precedence.
31    OverlayMemory(OverlayState),
32}
33
34impl MountMode {
35    /// Parses a mode string into a [`MountMode`].
36    ///
37    /// Accepted values: `"read-only"`, `"read-write"`, `"overlay"`.
38    /// Returns a descriptive error string on invalid input.
39    pub fn from_mode_str(mode: &str) -> Result<Self, String> {
40        match mode {
41            "read-only" => Ok(Self::ReadOnly),
42            "read-write" => Ok(Self::ReadWrite),
43            "overlay" => Ok(Self::OverlayMemory(OverlayState::new())),
44            other => Err(format!(
45                "Invalid mode '{other}', expected 'read-only', 'read-write', or 'overlay'"
46            )),
47        }
48    }
49
50    /// Returns a short string label for this mode (`"read-write"`, `"read-only"`,
51    /// or `"overlay"`).
52    #[must_use]
53    pub fn as_str(&self) -> &'static str {
54        match self {
55            Self::ReadWrite => "read-write",
56            Self::ReadOnly => "read-only",
57            Self::OverlayMemory(_) => "overlay",
58        }
59    }
60}
monty_fs/mount_mode.rs

monty_fs/
mount_mode.rs
