refactor(l1): make improvements to public functions used by ethrex_replay (#5416)

**Motivation**

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**Description**

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introduces -->
- from_nodes doesn't decode the nodes anymore, this is useful because
when called multiple times with same set of nodes we were decoding them
more than once unnecessarily.
- `execution_witness_from_rpc_chain_config` now gets the initial state
root from the rpc_witness itself. This should ALWAYS be in the block
headers, otherwise it returns an error.

Related Replay PR: lambdaclass/ethrex-replay#50

Author: JereSalo

crates/common/trie/db.rs

@@ -1,7 +1,7 @@
 use ethereum_types::H256;
-use ethrex_rlp::{decode::RLPDecode, encode::RLPEncode, error::RLPDecodeError};
+use ethrex_rlp::encode::RLPEncode;
 
-use crate::{Nibbles, Node, NodeRLP, Trie, error::TrieError};
+use crate::{Nibbles, Node, Trie, error::TrieError};
 use std::{
     collections::BTreeMap,
     sync::{Arc, Mutex},
@@ -62,13 +62,9 @@ impl InMemoryTrieDB {
     // Do not remove or make private as we use this in ethrex-replay
     pub fn from_nodes(
         root_hash: H256,
-        state_nodes: &BTreeMap<H256, NodeRLP>,
+        state_nodes: &BTreeMap<H256, Node>,
     ) -> Result<Self, TrieError> {
-        let state_nodes: BTreeMap<_, _> = state_nodes
-            .iter()
-            .map(|(h, b)| Ok((*h, Node::decode(b)?)))
-            .collect::<Result<_, RLPDecodeError>>()?;
-        let mut embedded_root = Trie::get_embedded_root(&state_nodes, root_hash)?;
+        let mut embedded_root = Trie::get_embedded_root(state_nodes, root_hash)?;
         let mut hashed_nodes = vec![];
         embedded_root.commit(Nibbles::default(), &mut hashed_nodes);
 

crates/networking/rpc/debug/execution_witness.rs

@@ -4,7 +4,7 @@ use bytes::Bytes;
 use ethrex_common::{
     Address, H256, serde_utils,
     types::{
-        AccountState, ChainConfig,
+        AccountState, BlockHeader, ChainConfig,
         block_execution_witness::{ExecutionWitness, GuestProgramStateError},
     },
     utils::keccak,
@@ -70,8 +70,24 @@ pub fn execution_witness_from_rpc_chain_config(
     rpc_witness: RpcExecutionWitness,
     chain_config: ChainConfig,
     first_block_number: u64,
-    initial_state_root: H256,
 ) -> Result<ExecutionWitness, GuestProgramStateError> {
+    let mut initial_state_root = None;
+
+    for h in &rpc_witness.headers {
+        let header = BlockHeader::decode(h)?;
+        if header.number == first_block_number - 1 {
+            initial_state_root = Some(header.state_root);
+            break;
+        }
+    }
+
+    let initial_state_root = initial_state_root.ok_or_else(|| {
+        GuestProgramStateError::Custom(format!(
+            "header for block {} not found",
+            first_block_number - 1
+        ))
+    })?;
+
     let nodes: BTreeMap<H256, Node> = rpc_witness
         .state
         .into_iter()