From 7d93fa25336678b6569f119aecaa5efd7bc3095f Mon Sep 17 00:00:00 2001
From: Gav Wood <gavin@ethcore.io>
Date: Sat, 19 Mar 2016 18:37:55 +0100
Subject: [PATCH] Output stored for calls.

---
 ethcore/src/executive.rs            | 10 ++++---
 ethcore/src/externalities.rs        | 44 ++++++++++++++++++-----------
 ethcore/src/json_tests/executive.rs |  2 +-
 3 files changed, 34 insertions(+), 22 deletions(-)

diff --git a/ethcore/src/executive.rs b/ethcore/src/executive.rs
index d7c0ced0a..a45577322 100644
--- a/ethcore/src/executive.rs
+++ b/ethcore/src/executive.rs
@@ -104,7 +104,7 @@ impl<'a> Executive<'a> {
 	}
 
 	/// Creates `Externalities` from `Executive`.
-	pub fn as_externalities<'_>(&'_ mut self, origin_info: OriginInfo, substate: &'_ mut Substate, output: OutputPolicy<'_>) -> Externalities {
+	pub fn as_externalities<'_>(&'_ mut self, origin_info: OriginInfo, substate: &'_ mut Substate, output: OutputPolicy<'_, '_>) -> Externalities {
 		Externalities::new(self.state, self.info, self.engine, self.depth, origin_info, substate, output)
 	}
 
@@ -249,15 +249,17 @@ impl<'a> Executive<'a> {
 
 			// part of substate that may be reverted
 			let mut unconfirmed_substate = Substate::new(substate.subtraces.is_some());
-
 			let mut trace_info = substate.subtraces.as_ref().map(|_| (TraceAction::from_call(&params), self.depth));
+			let mut trace_output = trace_info.as_ref().map(|_| vec![]);
 
 			let res = {
-				self.exec_vm(params, &mut unconfirmed_substate, OutputPolicy::Return(output))
+				self.exec_vm(params, &mut unconfirmed_substate, OutputPolicy::Return(output, trace_output.as_mut()))
 			};
 
 			if let Some((TraceAction::Call(ref mut c), _)) = trace_info {
-				c.result = res.as_ref().ok().map(|gas_left| (c.gas - *gas_left, vec![]));
+				if let Some(output) = trace_output { 
+					c.result = res.as_ref().ok().map(|gas_left| (c.gas - *gas_left, output));
+				}
 			}
 
 			trace!("exec: sstore-clears={}\n", unconfirmed_substate.sstore_clears_count);
diff --git a/ethcore/src/externalities.rs b/ethcore/src/externalities.rs
index 6f44bb51c..b0ba67602 100644
--- a/ethcore/src/externalities.rs
+++ b/ethcore/src/externalities.rs
@@ -23,12 +23,12 @@ use evm::{self, Schedule, Ext, ContractCreateResult, MessageCallResult};
 use substate::*;
 
 /// Policy for handling output data on `RETURN` opcode.
-pub enum OutputPolicy<'a> {
+pub enum OutputPolicy<'a, 'b> {
 	/// Return reference to fixed sized output.
 	/// Used for message calls.
-	Return(BytesRef<'a>),
+	Return(BytesRef<'a>, Option<&'b mut Bytes>),
 	/// Init new contract as soon as `RETURN` is called.
-	InitContract
+	InitContract,
 }
 
 /// Transaction properties that externalities need to know about.
@@ -62,18 +62,19 @@ pub struct Externalities<'a> {
 	origin_info: OriginInfo,
 	substate: &'a mut Substate,
 	schedule: Schedule,
-	output: OutputPolicy<'a>
+	output: OutputPolicy<'a, 'a>
 }
 
 impl<'a> Externalities<'a> {
 	/// Basic `Externalities` constructor.
 	pub fn new(state: &'a mut State,
-			   env_info: &'a EnvInfo,
-			   engine: &'a Engine,
-			   depth: usize,
-			   origin_info: OriginInfo,
-			   substate: &'a mut Substate,
-			   output: OutputPolicy<'a>) -> Self {
+		env_info: &'a EnvInfo,
+		engine: &'a Engine,
+		depth: usize,
+		origin_info: OriginInfo,
+		substate: &'a mut Substate,
+		output: OutputPolicy<'a, 'a>
+	) -> Self {
 		Externalities {
 			state: state,
 			env_info: env_info,
@@ -190,20 +191,29 @@ impl<'a> Ext for Externalities<'a> {
 
 	#[cfg_attr(feature="dev", allow(match_ref_pats))]
 	fn ret(&mut self, gas: &U256, data: &[u8]) -> Result<U256, evm::Error> {
-		match &mut self.output {
-			&mut OutputPolicy::Return(BytesRef::Fixed(ref mut slice)) => unsafe {
+		let handle_copy = |to: &mut Option<&mut Bytes>| {
+			to.as_mut().map(|b| **b = data.to_owned());
+		};
+		match self.output {
+			OutputPolicy::Return(BytesRef::Fixed(ref mut slice), ref mut copy) => {
+				handle_copy(copy);
 				let len = cmp::min(slice.len(), data.len());
-				ptr::copy(data.as_ptr(), slice.as_mut_ptr(), len);
+				unsafe {
+					ptr::copy(data.as_ptr(), slice.as_mut_ptr(), len);
+				}
 				Ok(*gas)
 			},
-			&mut OutputPolicy::Return(BytesRef::Flexible(ref mut vec)) => unsafe {
+			OutputPolicy::Return(BytesRef::Flexible(ref mut vec), ref mut copy) => {
+				handle_copy(copy);
 				vec.clear();
 				vec.reserve(data.len());
-				ptr::copy(data.as_ptr(), vec.as_mut_ptr(), data.len());
-				vec.set_len(data.len());
+				unsafe {
+					ptr::copy(data.as_ptr(), vec.as_mut_ptr(), data.len());
+					vec.set_len(data.len());
+				}
 				Ok(*gas)
 			},
-			&mut OutputPolicy::InitContract => {
+			OutputPolicy::InitContract => {
 				let return_cost = U256::from(data.len()) * U256::from(self.schedule.create_data_gas);
 				if return_cost > *gas {
 					return match self.schedule.exceptional_failed_code_deposit {
diff --git a/ethcore/src/json_tests/executive.rs b/ethcore/src/json_tests/executive.rs
index c0c8b3077..7a9426ad3 100644
--- a/ethcore/src/json_tests/executive.rs
+++ b/ethcore/src/json_tests/executive.rs
@@ -239,7 +239,7 @@ fn do_json_test_for(vm: &VMType, json_data: &[u8]) -> Vec<String> {
 				0,
 				OriginInfo::from(&params),
 				&mut substate,
-				OutputPolicy::Return(BytesRef::Flexible(&mut output)),
+				OutputPolicy::Return(&mut BytesRef::Flexible(&mut output)),
 				params.address.clone()
 			);
 			let evm = engine.vm_factory().create();