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

Adds fuel to this Store for Wasm to consume while executing.

For this method to work, fuel consumption must be enabled via Wasmex.EngineConfig.consume_fuel/2. By default aWasmex.Storestarts 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 asnop,drop,block, andloop, 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 viaWasmex.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.add_fuel(store, 10) :ok

@spec consume_fuel(t(), pos_integer() | 0) ::
  {:ok, pos_integer()} | {:error, binary()}

Synthetically consumes fuel from this Store.

For this method to work fuel, consumption must be enabled via Wasmex.EngineConfig.consume_fuel/2.

WebAssembly execution will automatically consume fuel but if so desired the embedder can also consume fuel manually to account for relative costs of host functions, for example.

This function will attempt to consume fuel units of fuel from within this store. If the remaining amount of fuel allows this then {:ok, N} is returned where N is the amount of remaining fuel. Otherwise an error is returned and no fuel is consumed.

errors

Errors

This function will return an error either if fuel consumption is not enabled via Wasmex.EngineConfig.consume_fuel/2 or if fuel exceeds the amount of remaining fuel within this store.

examples

Examples

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

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

Returns the amount of fuel consumed by this store's execution so far.

Note that fuel, if enabled, must be initially added via Wasmex.StoreOrCaller.add_fuel/2.

errors

Errors

If fuel consumption is not enabled via Wasmex.EngineConfig.consume_fuel/2 then this function will return an error tuple.

examples

Examples

iex> {:ok, engine} = Wasmex.Engine.new(%Wasmex.EngineConfig{consume_fuel: true})
iex> {:ok, store} = Wasmex.Store.new(nil, engine)
iex> Wasmex.StoreOrCaller.fuel_consumed(store)
{:ok, 0}
iex> Wasmex.StoreOrCaller.add_fuel(store, 10)
iex> {:ok, _fuel} = Wasmex.StoreOrCaller.consume_fuel(store, 8)
iex> Wasmex.StoreOrCaller.fuel_consumed(store)
{:ok, 8}

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

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

examples

Examples

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