walrus-meter 0.1.0

Instrumentation-based gas metering built on `walrus`
Documentation 
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// Copyright (c) Zefchain Labs, Inc.
// SPDX-License-Identifier: Apache-2.0

/*!
Various prebuilt cost strategies.
*/

mod wasmtime;
pub use wasmtime::Costs as Wasmtime;

/// A trait that encodes the costs of different Wasm operations.
pub trait Costs {
    fn instruction(&self, instruction: &walrus::ir::Instr) -> i32;

    // TODO: add an implicit_return cost that can be used to instrument the
    // module to achieve Wasmtime equivalence.

    // TODO: achieve feature parity with `wasm-instrument`, with memory-grow
    // costs and per-local costs.
}

/// Costs that never consume fuel.
pub struct Free;
impl Costs for Free {
    fn instruction(&self, _instruction: &walrus::ir::Instr) -> i32 {
        0
    }
}