feat: trait for inspectors that accumulate output (#120)

* feat: trait for inspectors that accumulate output

* feat: add impl for 4 byte

Author: prestwich

Cargo.toml

@@ -45,6 +45,7 @@ alloy = { version = "1.0.25", default-features = false, features = [
 ] }
 
 revm = { version = "27.1", default-features = false }
+revm-inspectors = { version = "0.27.1", optional = true }
 
 dashmap = { version = "6.1.0", optional = true }
 tracing = { version = "0.1.41", optional = true }
@@ -69,6 +70,7 @@ default = [
     "call",
     "concurrent-db",
     "estimate_gas",
+    "tracing-inspectors",
     "revm/std",
     "revm/c-kzg",
     "revm/blst",
@@ -111,3 +113,4 @@ full_env_cfg = [
     "optional_eip3607",
     "optional_no_base_fee",
 ]
+tracing-inspectors = ["dep:revm-inspectors", "alloy/rpc-types-trace"]

src/inspectors/mod.rs

@@ -4,12 +4,18 @@ pub use layer::Layered;
 mod timeout;
 pub use timeout::TimeLimit;
 
+#[cfg(feature = "tracing-inspectors")]
+mod tracing;
+
 mod set;
 pub use set::InspectorSet;
 
 mod spanning;
 pub use spanning::SpanningInspector;
 
+mod with_output;
+pub use with_output::InspectorWithOutput;
+
 #[cfg(test)]
 mod test {
     use super::*;

src/inspectors/tracing.rs

@@ -0,0 +1,20 @@
+use crate::{helpers::Ctx, inspectors::InspectorWithOutput};
+use alloy::rpc::types::trace::geth::FourByteFrame;
+use revm::Database;
+use revm_inspectors::tracing::FourByteInspector;
+
+impl<Db: Database> InspectorWithOutput<Ctx<Db>> for FourByteInspector {
+    type Output = FourByteFrame;
+
+    fn has_output(&self) -> bool {
+        !self.inner().is_empty()
+    }
+
+    fn reset_output(&mut self) {
+        *self = Self::default();
+    }
+
+    fn take_output(&mut self) -> Self::Output {
+        std::mem::take(self).into()
+    }
+}

src/inspectors/with_output.rs

@@ -0,0 +1,49 @@
+use crate::{helpers::Ctx, Trevm};
+use revm::{inspector::CountInspector, Database};
+
+/// An inspector that can produce an output value after EVM execution.
+pub trait InspectorWithOutput<CTX>: revm::inspector::Inspector<CTX> {
+    /// The type of output produced by the inspector.
+    type Output;
+
+    /// Returns `true` if the inspector has a valid output value.
+    fn has_output(&self) -> bool;
+
+    /// Reset the output value to the default state, discarding any current
+    /// value.
+    fn reset_output(&mut self) {
+        self.take_output();
+    }
+
+    /// Take the output value from the inspector, resetting it to the default
+    /// state.
+    fn take_output(&mut self) -> Self::Output;
+}
+
+impl<Db: Database, Insp> Trevm<Db, Insp>
+where
+    Insp: InspectorWithOutput<Ctx<Db>>,
+{
+    /// Take the output value from the inspector.
+    ///
+    /// This will also reset the output value in the inspector.
+    pub fn take_output(&mut self) -> Insp::Output {
+        self.inspector_mut().take_output()
+    }
+}
+
+impl<Ctx> InspectorWithOutput<Ctx> for CountInspector {
+    type Output = Self;
+
+    fn has_output(&self) -> bool {
+        self.total_opcodes() > 0
+    }
+
+    fn reset_output(&mut self) {
+        self.clear();
+    }
+
+    fn take_output(&mut self) -> Self::Output {
+        std::mem::take(self)
+    }
+}