Struct wasmtime_wasi::preview2::Table

pub struct Table { /* private fields */ }

The Table type is designed to map u32 handles to resources. The table is now part of the public interface to a WasiCtx - it is reference counted so that it can be shared beyond a WasiCtx with other WASI proposals (e.g. wasi-crypto and wasi-nn) to manage their resources. Elements in the Table are Any typed.

The Table type is intended to model how the Interface Types concept of Resources is shaping up. Right now it is just an approximation.

Implementations

impl Table

pub fn new() -> Self

Create an empty table

pub fn with_capacity(capacity: usize) -> Self

Create an empty table with at least the specified capacity.

pub fn push<T>(&mut self, entry: T) -> Result<Resource<T>, TableError>

where T: Send + Sync + 'static,

Inserts a new value T into this table, returning a corresponding Resource<T> which can be used to refer to it after it was inserted.

pub fn push_child<T, U>( &mut self, entry: T, parent: &Resource<U> ) -> Result<Resource<T>, TableError>

where T: Send + Sync + 'static, U: 'static,

Insert a resource at the next available index, and track that it has a parent resource.

The parent must exist to create a child. All children resources must be destroyed before a parent can be destroyed - otherwise Table::delete will fail with TableError::HasChildren.

Parent-child relationships are tracked inside the table to ensure that a parent resource is not deleted while it has live children. This allows child resources to hold “references” to a parent by table index, to avoid needing e.g. an Arc<Mutex<parent>> and the associated locking overhead and design issues, such as child existence extending lifetime of parent referent even after parent resource is destroyed, possibility for deadlocks.

Parent-child relationships may not be modified once created. There is no way to observe these relationships through the Table methods except for erroring on deletion, or the std::fmt::Debug impl.

pub fn get<T: Any + Sized>(&self, key: &Resource<T>) -> Result<&T, TableError>

Get an immutable reference to a resource of a given type at a given index.

Multiple shared references can be borrowed at any given time.

pub fn get_mut<T: Any + Sized>( &mut self, key: &Resource<T> ) -> Result<&mut T, TableError>

Get an mutable reference to a resource of a given type at a given index.

pub fn get_any_mut(&mut self, key: u32) -> Result<&mut dyn Any, TableError>

Returns the raw Any at the key index provided.

pub fn delete<T>(&mut self, resource: Resource<T>) -> Result<T, TableError>

where T: Any,

Same as delete, but typed

pub fn iter_entries<'a, T>( &'a mut self, map: HashMap<u32, T> ) -> impl Iterator<Item = (Result<&'a mut dyn Any, TableError>, T)>

Zip the values of the map with mutable references to table entries corresponding to each key. As the keys in the HashMap are unique, this iterator can give mutable references with the same lifetime as the mutable reference to the Table.

pub fn iter_children<T>( &self, parent: &Resource<T> ) -> Result<impl Iterator<Item = &(dyn Any + Send + Sync)>, TableError>

where T: 'static,

Iterate over all children belonging to the provided parent

Trait Implementations

impl Debug for Table

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

Formats the value using the given formatter.

impl Default for Table

fn default() -> Self

Returns the “default value” for a type.