Struct StorageHandle

pub struct StorageHandle<T> {
    instance_dir: CheckedDir,
    leafname: String,
    marker: PhantomData<fn(T) -> T>,
    flock_guard: Arc<LockFileGuard>,
}

Available on crate feature state-dir only.

A place in the state or cache directory, where we can load/store a serialisable type

Implies exclusive access.

Rust mutability-xor-sharing rules enforce proper synchronisation, unless multiple StorageHandles are created using the same InstanceStateHandle and key.

Fields

instance_dir: CheckedDir

The directory and leafname

leafname: String

KEY.json

marker: PhantomData<fn(T) -> T>

We can load and store a T.

Invariant in T. But we’re Sync and Send regardless of T. (From the Table of PhantomData patterns in the Nomicon.)

flock_guard: Arc<LockFileGuard>

Clone of the InstanceStateHandle’s lock

Implementations

impl<T: Serialize + DeserializeOwned> StorageHandle<T>

pub fn load(&self) -> Result<Option<T>>

Load this persistent state

None means the state was most recently deleteed

pub fn store(&mut self, v: &T) -> Result<()>

Store this persistent state

pub fn delete(&mut self) -> Result<()>

Delete this persistent state

fn with_load_store_target<R, F>(&self, action: Action, f: F) -> Result<R>

where F: FnOnce(Target<'_>) -> Result<R, ErrorSource>,

Operate using a load_store::Target

fn map_err(&self, action: Action) -> impl FnOnce(ErrorSource) -> Error

Helper to convert an ErrorSource to an Error, if we were performing action

fn err_resource(&self) -> Resource

Return the proper Resource for reporting errors

Trait Implementations

impl<T> ContainsInstanceStateGuard for StorageHandle<T>

fn raw_lock_guard(&self) -> Arc<LockFileGuard>

Obtain a raw clone of the underlying filesystem lock

impl<T: Debug> Debug for StorageHandle<T>

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

Formats the value using the given formatter.