Wasmex.StoreOrCaller (wasmex v0.9.2)

Either a Wasmex.Store or "Caller" for imported functions.

A Store is a collection of Wasm instances and host-defined state, see Wasmex.Store. A Caller takes the place of a Store in imported function calls. If a Store is needed in Elixir-provided imported functions, always use the provided Caller because using the Store will cause a deadlock (the running Wasm instance locks the Stores Mutex).

When configured, a StoreOrCaller can consume fuel to halt or yield execution as desired. See Wasmex.EngineConfig.consume_fuel/2 for more information on fuel consumption.

Summary

Types

t()

Functions

get_fuel(store_or_caller)

Returns the amount of fuel available for future execution of this store.

set_fuel(store_or_caller, fuel)

Sets fuel to for Wasm to consume while executing.

Types

Link to this type

t()

@type t() :: %Wasmex.StoreOrCaller{reference: reference(), resource: binary()}

Functions

Link to this function

get_fuel(store_or_caller)

@spec get_fuel(t()) :: {:ok, pos_integer()} | {:error, binary()}

Returns the amount of fuel available for future execution of this store.

Examples 

iex> {:ok, engine} = Wasmex.Engine.new(%Wasmex.EngineConfig{consume_fuel: true})
iex> {:ok, store} = Wasmex.Store.new(nil, engine)
iex> Wasmex.StoreOrCaller.set_fuel(store, 10)
iex> Wasmex.StoreOrCaller.get_fuel(store)
{:ok, 10}
Link to this function

set_fuel(store_or_caller, fuel)

@spec set_fuel(t(), pos_integer()) :: :ok | {:error, binary()}

Sets fuel to for Wasm to consume while executing.

For this method to work, fuel consumption must be enabled via Wasmex.EngineConfig.consume_fuel/2. By default a Wasmex.Store starts with 0 fuel for Wasm to execute with (meaning it will immediately trap and halt execution). This function must be called for the store to have some fuel to allow WebAssembly to execute.

Most Wasm instructions consume 1 unit of fuel. Some instructions, such as nop, drop, block, and loop, consume 0 units, as any execution cost associated with them involves other instructions which do consume fuel.

Note that at this time when fuel is entirely consumed it will cause Wasm to trap.

Errors

This function will return an error if fuel consumption is not enabled via Wasmex.EngineConfig.consume_fuel/2.

Examples 

iex> {:ok, engine} = Wasmex.Engine.new(%Wasmex.EngineConfig{consume_fuel: true})
iex> {:ok, store} = Wasmex.Store.new(nil, engine)
iex> Wasmex.StoreOrCaller.set_fuel(store, 10)
:ok