From 4df096fed3d68e0f44283e30352d5c543ddf95be Mon Sep 17 00:00:00 2001
From: debris <marek.kotewicz@gmail.com>
Date: Wed, 10 Feb 2016 00:12:09 +0100
Subject: [PATCH] optimize blockchains transaction_at

---
 ethcore/src/blockchain.rs |  2 +-
 ethcore/src/views.rs      | 20 +++++++++++++++++++-
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/ethcore/src/blockchain.rs b/ethcore/src/blockchain.rs
index af7800870..c88a375a8 100644
--- a/ethcore/src/blockchain.rs
+++ b/ethcore/src/blockchain.rs
@@ -117,7 +117,7 @@ pub trait BlockProvider {
 
 	/// Get transaction at given address.
 	fn transaction_at(&self, address: &TransactionAddress) -> Option<LocalizedTransaction> {
-		self.block(&address.block_hash).map(|bytes| BlockView::new(&bytes).localized_transactions()).and_then(|t| t.into_iter().nth(address.index))
+		self.block(&address.block_hash).and_then(|bytes| BlockView::new(&bytes).localized_transaction_at(address.index))
 	}
 
 	/// Get a list of transactions for a given block.
diff --git a/ethcore/src/views.rs b/ethcore/src/views.rs
index 3cfe5f183..4a7ff054d 100644
--- a/ethcore/src/views.rs
+++ b/ethcore/src/views.rs
@@ -160,7 +160,7 @@ impl<'a> BlockView<'a> {
 		let header = self.header_view();
 		let block_hash = header.sha3();
 		let block_number = header.number();
-		self.rlp.val_at::<Vec<SignedTransaction>>(1)
+		self.transactions()
 			.into_iter()
 			.enumerate()
 			.map(|(i, t)| LocalizedTransaction {
@@ -186,6 +186,24 @@ impl<'a> BlockView<'a> {
 		self.rlp.at(1).iter().map(|rlp| rlp.as_raw().sha3()).collect()
 	}
 
+	/// Returns transaction at given index without deserializing unnecessary data.
+	pub fn transaction_at(&self, index: usize) -> Option<SignedTransaction> {
+		self.rlp.at(1).iter().nth(index).map(|rlp| rlp.as_val())
+	}
+
+	/// Returns localized transaction at given index.
+	pub fn localized_transaction_at(&self, index: usize) -> Option<LocalizedTransaction> {
+		let header = self.header_view();
+		let block_hash = header.sha3();
+		let block_number = header.number();
+		self.transaction_at(index).map(|t| LocalizedTransaction {
+			signed: t,
+			block_hash: block_hash,
+			block_number: block_number,
+			transaction_index: index
+		})
+	}
+
 	/// Return list of uncles of given block.
 	pub fn uncles(&self) -> Vec<Header> {
 		self.rlp.val_at(2)