Struct MemoryFs 

pub struct MemoryFs { /* private fields */ }

In-memory filesystem.

Thread-safe via internal RwLock. All data is lost when dropped. Tracks its resident content bytes exactly (net: an overwrite charges the delta, a remove credits) and optionally draws them from a shared ByteBudget.

Implementations

impl MemoryFs

pub const DIRECTORY_MODE: u32 = 0o777

Maximum symlink follow depth (matches Linux ELOOP limit). Mode reported for a MemoryFs directory: readable, writable, and searchable by everyone.

MemoryFs has no permission model — it never refuses an operation over a mode — so these constants describe what it actually does rather than restricting anything. Reporting them (instead of None) is what lets test -w close its absent-mode default: with every writable backend reporting a mode, an absent mode means “this backend does not model permissions”, and every backend still in that position is read-only. There is no chmod builtin; these are observations.

pub const FILE_MODE: u32 = 0o666

Mode reported for a MemoryFs file: readable and writable, never executable. real_path is None for a memory-backed path, so there is nothing for exec(2) to open and the x bit would be a lie.

pub const SYMLINK_MODE: u32 = 0o777

Mode reported for a MemoryFs symlink, matching lrwxrwxrwx on Linux. Only lstat and list ever show it — stat follows the link and reports the target’s mode.

pub fn new() -> MemoryFs

Create a new empty in-memory filesystem.

pub fn with_budget(budget: Arc<ByteBudget>) -> MemoryFs

Create a filesystem whose content bytes draw on a shared budget. Writes that would exceed it fail loudly, ENOSPC-style.

Trait Implementations

impl Debug for MemoryFs

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl Default for MemoryFs

fn default() -> MemoryFs

Returns the “default value” for a type.

impl Drop for MemoryFs

Credit resident content bytes back to the shared budget when the filesystem is dropped. Without this, dropping a budgeted MemoryFs (e.g. the upper inside a dropped over_with_budget overlay, or a fork’s fresh upper) strands its charge: repeated create-then-drop cycles drain the shared ByteBudget toward spurious StorageFull with zero actual RAM held. Mirrors OverlayFs’s drop of its base-snapshot bytes.

fn drop(&mut self)

Executes the destructor for this type.

fn pin_drop(self: Pin<&mut Self>)

🔬This is a nightly-only experimental API. (pin_ergonomics)

Execute the destructor for this type, but different to Drop::drop, it requires self to be pinned.

impl Filesystem for MemoryFs

fn read<'life0, 'life1, 'async_trait>( &'life0 self, path: &'life1 Path, ) -> Pin<Box<dyn Future<Output = Result<Vec<u8>, Error>> + Send + 'async_trait>>

where 'life0: 'async_trait, 'life1: 'async_trait, MemoryFs: 'async_trait,

Read the entire contents of a file.

fn read_range<'life0, 'life1, 'async_trait>( &'life0 self, path: &'life1 Path, range: Option<ReadRange>, ) -> Pin<Box<dyn Future<Output = Result<Vec<u8>, Error>> + Send + 'async_trait>>

where 'life0: 'async_trait, 'life1: 'async_trait, MemoryFs: 'async_trait,

Read a (possibly partial) slice of a file.

fn write<'life0, 'life1, 'life2, 'async_trait>( &'life0 self, path: &'life1 Path, data: &'life2 [u8], ) -> Pin<Box<dyn Future<Output = Result<(), Error>> + Send + 'async_trait>>

where 'life0: 'async_trait, 'life1: 'async_trait, 'life2: 'async_trait, MemoryFs: 'async_trait,

Write data to a file, creating it if it doesn’t exist.

fn append<'life0, 'life1, 'life2, 'async_trait>( &'life0 self, path: &'life1 Path, data: &'life2 [u8], ) -> Pin<Box<dyn Future<Output = Result<(), Error>> + Send + 'async_trait>>

where 'life0: 'async_trait, 'life1: 'async_trait, 'life2: 'async_trait, MemoryFs: 'async_trait,

Append data to a file, creating it if it doesn’t exist.

fn set_mtime<'life0, 'life1, 'async_trait>( &'life0 self, path: &'life1 Path, mtime: SystemTime, ) -> Pin<Box<dyn Future<Output = Result<(), Error>> + Send + 'async_trait>>

where 'life0: 'async_trait, 'life1: 'async_trait, MemoryFs: 'async_trait,

Set the modification time of an existing path.

fn list<'life0, 'life1, 'async_trait>( &'life0 self, path: &'life1 Path, ) -> Pin<Box<dyn Future<Output = Result<Vec<DirEntry>, Error>> + Send + 'async_trait>>

where 'life0: 'async_trait, 'life1: 'async_trait, MemoryFs: 'async_trait,

List entries in a directory.

fn stat<'life0, 'life1, 'async_trait>( &'life0 self, path: &'life1 Path, ) -> Pin<Box<dyn Future<Output = Result<DirEntry, Error>> + Send + 'async_trait>>

where 'life0: 'async_trait, 'life1: 'async_trait, MemoryFs: 'async_trait,

Get metadata for a file or directory, following symlinks.

fn lstat<'life0, 'life1, 'async_trait>( &'life0 self, path: &'life1 Path, ) -> Pin<Box<dyn Future<Output = Result<DirEntry, Error>> + Send + 'async_trait>>

where 'life0: 'async_trait, 'life1: 'async_trait, MemoryFs: 'async_trait,

Get metadata for a path without following its final symlink.

fn read_link<'life0, 'life1, 'async_trait>( &'life0 self, path: &'life1 Path, ) -> Pin<Box<dyn Future<Output = Result<PathBuf, Error>> + Send + 'async_trait>>

where 'life0: 'async_trait, 'life1: 'async_trait, MemoryFs: 'async_trait,

Read the target of a symbolic link without following it.

fn symlink<'life0, 'life1, 'life2, 'async_trait>( &'life0 self, target: &'life1 Path, link: &'life2 Path, ) -> Pin<Box<dyn Future<Output = Result<(), Error>> + Send + 'async_trait>>

where 'life0: 'async_trait, 'life1: 'async_trait, 'life2: 'async_trait, MemoryFs: 'async_trait,

Create a symbolic link.

fn mkdir<'life0, 'life1, 'async_trait>( &'life0 self, path: &'life1 Path, ) -> Pin<Box<dyn Future<Output = Result<(), Error>> + Send + 'async_trait>>

where 'life0: 'async_trait, 'life1: 'async_trait, MemoryFs: 'async_trait,

Create a directory (and parent directories if needed).

fn remove<'life0, 'life1, 'async_trait>( &'life0 self, path: &'life1 Path, ) -> Pin<Box<dyn Future<Output = Result<(), Error>> + Send + 'async_trait>>

where 'life0: 'async_trait, 'life1: 'async_trait, MemoryFs: 'async_trait,

Remove a file, empty directory, or symlink.

fn rename<'life0, 'life1, 'life2, 'async_trait>( &'life0 self, from: &'life1 Path, to: &'life2 Path, ) -> Pin<Box<dyn Future<Output = Result<(), Error>> + Send + 'async_trait>>

where 'life0: 'async_trait, 'life1: 'async_trait, 'life2: 'async_trait, MemoryFs: 'async_trait,

Rename (move) a file, directory, or symlink.

fn read_only(&self) -> bool

Returns true if this filesystem is read-only.

fn resident_bytes(&self) -> Option<u64>

Memory-resident content bytes this filesystem is holding, if it tracks them.

fn path_access<'life0, 'life1, 'async_trait>( &'life0 self, path: &'life1 Path, ) -> Pin<Box<dyn Future<Output = Result<PathAccess, Error>> + Send + 'async_trait>>

where 'life0: 'async_trait, 'life1: 'async_trait, Self: 'async_trait,

What the kernel can do with one path on this filesystem.

fn exists<'life0, 'life1, 'async_trait>( &'life0 self, path: &'life1 Path, ) -> Pin<Box<dyn Future<Output = bool> + Send + 'async_trait>>

where 'life0: 'async_trait, 'life1: 'async_trait, Self: 'async_trait,

Check if a path exists, following symlinks.

fn real_path(&self, path: &Path) -> Option<PathBuf>

Get the real filesystem path for a VFS path.