From 6a3c64ff606a287f1a645ebf0c84c14d8f91a01e Mon Sep 17 00:00:00 2001
From: Nikolay Volf <nikvolf@gmail.com>
Date: Sun, 10 Jul 2016 20:18:23 +0200
Subject: [PATCH] Some obvious evm & uint optimizations  (#1576)

* fix name and tests for endians

* using renamed func

* zero and sign opt
---
 src/uint.rs | 57 ++++++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 52 insertions(+), 5 deletions(-)

diff --git a/src/uint.rs b/src/uint.rs
index 2f58061..8e08e59 100644
--- a/src/uint.rs
+++ b/src/uint.rs
@@ -524,9 +524,8 @@ pub trait Uint: Sized + Default + FromStr + From<u64> + fmt::Debug + fmt::Displa
 	fn bit(&self, index: usize) -> bool;
 	/// Return single byte
 	fn byte(&self, index: usize) -> u8;
-	/// Get this Uint as slice of bytes
-	fn to_raw_bytes(&self, bytes: &mut[u8]);
-
+	/// Convert U256 to the sequence of bytes with a big endian
+	fn to_big_endian(&self, bytes: &mut[u8]);
 	/// Create `Uint(10**n)`
 	fn exp10(n: usize) -> Self;
 	/// Return eponentation `self**other`. Panic on overflow.
@@ -551,6 +550,9 @@ pub trait Uint: Sized + Default + FromStr + From<u64> + fmt::Debug + fmt::Displa
 
 	/// Returns negation of this `Uint` and overflow (always true)
 	fn overflowing_neg(self) -> (Self, bool);
+
+	/// Returns
+	fn is_zero(&self) -> bool;
 }
 
 macro_rules! construct_uint {
@@ -616,6 +618,13 @@ macro_rules! construct_uint {
 				arr[0]
 			}
 
+			#[inline]
+			fn is_zero(&self) -> bool {
+				let &$name(ref arr) = self;
+				for i in 0..$n_words { if arr[i] != 0 { return false; } }
+				return true;
+			}
+
 			/// Return the least number of bits needed to represent the number
 			#[inline]
 			fn bits(&self) -> usize {
@@ -638,7 +647,7 @@ macro_rules! construct_uint {
 				(arr[index / 8] >> (((index % 8)) * 8)) as u8
 			}
 
-			fn to_raw_bytes(&self, bytes: &mut[u8]) {
+			fn to_big_endian(&self, bytes: &mut[u8]) {
 				assert!($n_words * 8 == bytes.len());
 				let &$name(ref arr) = self;
 				for i in 0..bytes.len() {
@@ -1454,7 +1463,7 @@ mod tests {
 		let hex = "8090a0b0c0d0e0f00910203040506077583a2cf8264910e1436bda32571012f0";
 		let uint = U256::from_str(hex).unwrap();
 		let mut bytes = [0u8; 32];
-		uint.to_raw_bytes(&mut bytes);
+		uint.to_big_endian(&mut bytes);
 		let uint2 = U256::from(&bytes[..]);
 		assert_eq!(uint, uint2);
 	}
@@ -2021,6 +2030,44 @@ mod tests {
 		assert!(overflow);
     }
 
+	#[test]
+	fn big_endian() {
+		let source = U256([1, 0, 0, 0]);
+		let mut target = vec![0u8; 32];
+
+		assert_eq!(source, U256::from(1));
+
+		source.to_big_endian(&mut target);
+		assert_eq!(
+			vec![0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8,
+				0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 1u8],
+			target);
+
+		let source = U256([512, 0, 0, 0]);
+		let mut target = vec![0u8; 32];
+
+		source.to_big_endian(&mut target);
+		assert_eq!(
+			vec![0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8,
+				0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 2u8, 0u8],
+			target);
+
+		let source = U256([0, 512, 0, 0]);
+		let mut target = vec![0u8; 32];
+
+		source.to_big_endian(&mut target);
+		assert_eq!(
+			vec![0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8,
+				0u8, 0u8, 0u8, 0u8, 0u8, 2u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8, 0u8],
+			target);
+
+		let source = U256::from_str("0102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f20").unwrap();
+		source.to_big_endian(&mut target);
+		assert_eq!(
+			vec![0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x10, 0x11,
+				0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20],
+			target);
+	}
 
 	#[test]
 	#[cfg_attr(feature="dev", allow(cyclomatic_complexity))]