Enum wasmi::FuelConsumptionMode

pub enum FuelConsumptionMode {
    Lazy,
    Eager,
}

The fuel consumption mode of the wasmi Engine.

This mode affects when fuel is charged for Wasm bulk-operations. Affected Wasm instructions are:

• memory.{grow, copy, fill}
• data.init
• table.{grow, copy, fill}
• element.init

The default fuel consumption mode is FuelConsumptionMode::Lazy.

Variants

Lazy

Fuel consumption for bulk-operations is lazy.

Lazy fuel consumption means that fuel for bulk-operations is checked before executing the instruction but only consumed if the executed instruction suceeded. The reason for this is that bulk-operations fail fast and therefore do not cost a lot of compute power in case of failure.

Note

Lazy fuel consumption makes sense as default mode since the affected bulk-operations usually are very costly if they are successful. Therefore users generally want to avoid having to using more fuel than what was actually used, especially if there is an underlying cost model associated to the used fuel.

Eager

Fuel consumption for bulk-operations is eager.

Eager fuel consumption means that fuel for bulk-operations is always consumed before executing the instruction independent of it suceeding or failing.

Note

A use case for when a user might prefer eager fuel consumption is when the fuel required to perform an execution should be identical to the actual fuel consumed by an execution. Otherwise it can be confusing that the execution consumed x gas while it needs x + gas_for_bulk_op to not run out of fuel.

Trait Implementations

impl Clone for FuelConsumptionMode

fn clone(&self) -> FuelConsumptionMode

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for FuelConsumptionMode

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

Formats the value using the given formatter.

impl Default for FuelConsumptionMode

fn default() -> FuelConsumptionMode

Returns the “default value” for a type.

impl Copy for FuelConsumptionMode