Struct kismet_cache::ReadOnlyCache

pub struct ReadOnlyCache { /* fields omitted */ }

A ReadOnlyCache wraps an arbitrary number of crate::plain::Cache and crate::sharded::Cache, and attempts to satisfy ReadOnlyCache::get and ReadOnlyCache::touch requests by hitting each constituent cache in order. This interface hides the difference between plain and sharded cache directories, and should be the first resort for read-only uses.

The default cache wraps an empty set of constituent caches and performs no consistency check.

ReadOnlyCache objects are stateless and cheap to clone; don’t put an Arc on them. Avoid creating multiple ReadOnlyCaches for the same stack of directories: there is no internal state to maintain, so multiple instances simply waste memory without any benefit.

Implementations

impl ReadOnlyCache

pub fn get<'a>(&self, key: impl Into<Key<'a>>) -> Result<Option<File>>

Attempts to open a read-only file for key. The ReadOnlyCache will query each constituent cache in order of registration, and return a read-only file for the first hit.

Fails with ErrorKind::InvalidInput if key.name is invalid (empty, or starts with a dot or a forward or back slash).

Returns None if no file for key can be found in any of the constituent caches, and bubbles up the first I/O error encountered, if any.

In the worst case, each call to get attempts to open two files for each cache directory in the ReadOnlyCache stack.

pub fn touch<'a>(&self, key: impl Into<Key<'a>>) -> Result<bool>

Marks a cache entry for key as accessed (read). The ReadOnlyCache will touch the same file that would be returned by get.

Fails with ErrorKind::InvalidInput if key.name is invalid (empty, or starts with a dot or a forward or back slash).

Returns whether a file for key could be found, and bubbles up the first I/O error encountered, if any.

In the worst case, each call to touch attempts to update the access time on two files for each cache directory in the ReadOnlyCache stack.

Trait Implementations

impl Clone for ReadOnlyCache

fn clone(&self) -> ReadOnlyCache

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for ReadOnlyCache

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

Formats the value using the given formatter.

impl Default for ReadOnlyCache

fn default() -> ReadOnlyCache

Returns the “default value” for a type.