From 1a2bc7f3801c565c2dab22021255a164c05a7f76 Mon Sep 17 00:00:00 2001
From: Jay Geng <jay@stellar.org>
Date: Thu, 1 Jun 2023 19:26:16 -0400
Subject: [PATCH] Access and set `FuelCosts`

---
 crates/wasmi/src/engine/config.rs   | 5 +++++
 crates/wasmi/src/engine/executor.rs | 3 ++-
 crates/wasmi/src/engine/mod.rs      | 2 +-
 crates/wasmi/src/lib.rs             | 1 +
 4 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/crates/wasmi/src/engine/config.rs b/crates/wasmi/src/engine/config.rs
index 5340b2fb57..00ec4890b4 100644
--- a/crates/wasmi/src/engine/config.rs
+++ b/crates/wasmi/src/engine/config.rs
@@ -390,6 +390,11 @@ impl Config {
         self
     }
 
+    pub fn set_fuel_costs(&mut self, costs: FuelCosts) -> &mut Self {
+        self.fuel_costs = costs;
+        self
+    }
+
     /// Returns the [`FuelConsumptionMode`] for the [`Engine`].
     ///
     /// Returns `None` if fuel metering is disabled for the [`Engine`].
diff --git a/crates/wasmi/src/engine/executor.rs b/crates/wasmi/src/engine/executor.rs
index d4006345f5..c25d7c9926 100644
--- a/crates/wasmi/src/engine/executor.rs
+++ b/crates/wasmi/src/engine/executor.rs
@@ -727,7 +727,8 @@ impl<'ctx, 'engine> Executor<'ctx, 'engine> {
         }
     }
 
-    /// Consume an amount of memory fuel specified by `delta`.
+    /// Consume an amount of memory fuel specified by `bytes`. The memory fuel cost
+    /// is always 1 per byte.
     #[inline(always)]
     fn consume_mem_fuel(&mut self, bytes: u64) -> Result<u64, TrapCode>
     {
diff --git a/crates/wasmi/src/engine/mod.rs b/crates/wasmi/src/engine/mod.rs
index 49912efef8..01577db2d9 100644
--- a/crates/wasmi/src/engine/mod.rs
+++ b/crates/wasmi/src/engine/mod.rs
@@ -19,7 +19,7 @@ mod tests;
 pub use self::{
     bytecode::DropKeep,
     code_map::CompiledFunc,
-    config::{Config, FuelConsumptionMode},
+    config::{Config, FuelConsumptionMode, FuelCosts},
     func_builder::{
         FuncBuilder,
         FuncTranslatorAllocations,
diff --git a/crates/wasmi/src/lib.rs b/crates/wasmi/src/lib.rs
index 3144bf2031..197807b5ef 100644
--- a/crates/wasmi/src/lib.rs
+++ b/crates/wasmi/src/lib.rs
@@ -123,6 +123,7 @@ pub use self::{
         Config,
         Engine,
         FuelConsumptionMode,
+        FuelCosts,
         ResumableCall,
         ResumableInvocation,
         StackLimits,