Struct CachingObjectHandle

pub struct CachingObjectHandle<S> { /* private fields */ }

A wrapper handle around a ReadObjectHandle which provides a memory cache for its contents. Contents are fetched as needed and can be evicted (for example due to memory pressure).

Implementations

impl<S: ReadObjectHandle> CachingObjectHandle<S>

pub fn new(source: S) -> Self

pub async fn read(&self, offset: usize) -> Result<CachedChunk, Error>

Returns a reference to the chunk (up to CHUNK_SIZE bytes) containing offset. If the data is already cached, this does not require reading from source. offset must be less than the size of source.

pub fn purge(&self)

Purges unused extents, freeing unused memory. This follows a second-chance algorithm: unused extents will be marked for purging the first time this is called, and if they are not used again by the next time this is called, they will be deallocated. This is intended to be run regularly, e.g. on a timer.

Trait Implementations

impl<S: ReadObjectHandle> ObjectHandle for CachingObjectHandle<S>

fn set_trace(&self, v: bool)

Sets tracing for this object.

fn object_id(&self) -> u64

Returns the object identifier for this object which will be unique for the store that the object is contained in, but not necessarily unique within the entire system.

fn allocate_buffer(&self, size: usize) -> BufferFuture<'_>

Allocates a buffer for doing I/O (read and write) for the object.

fn block_size(&self) -> u64

Returns the filesystem block size, which should be at least as big as the device block size, but not necessarily the same.

impl<S> Sync for CachingObjectHandle<S>