U256 to byts conversion

src/hash.rs

@@ -9,6 +9,7 @@ use rand::Rng;
 use rand::os::OsRng;
 use bytes::BytesConvertable;
 use math::log2;
+use uint::U256;
 
 /// types implementing FixedHash must be also BytesConvertable
 pub trait FixedHash: Sized + BytesConvertable {
@@ -307,6 +308,16 @@ macro_rules! impl_hash {
 	}
 }
 
+impl<'a> From<&'a U256> for H256 {
+    fn from(value: &'a U256) -> H256 {
+		unsafe {
+			let mut ret: H256 = ::std::mem::uninitialized();
+			value.to_bytes(&mut ret);
+			ret
+		}
+    }
+}
+
 impl_hash!(H32, 4);
 impl_hash!(H64, 8);
 impl_hash!(H128, 16);

src/uint.rs

@@ -186,6 +186,15 @@ macro_rules! construct_uint {
                 (arr[index / 8] >> ((index % 8)) * 8) as u8
             }
 
+            pub fn to_bytes(&self, bytes: &mut[u8]) {
+                assert!($n_words * 8 == bytes.len());
+                let &$name(ref arr) = self;
+                for i in 0..bytes.len() {
+                    let rev = bytes.len() - 1 - i;
+                    let pos = rev / 8;
+                    bytes[i] = (arr[pos] >> ((rev % 8) * 8)) as u8;
+                }
+            }
             /// Multiplication by u32
             fn mul_u32(self, other: u32) -> $name {
                 let $name(ref arr) = self;
@@ -514,6 +523,16 @@ mod tests {
         assert_eq!(U256([0x12f0, 1 , 0x0910203040506077, 0x8090a0b0c0d0e0f0]), U256::from_str("8090a0b0c0d0e0f00910203040506077000000000000000100000000000012f0").unwrap());
     }
 
+    #[test]
+    pub fn uint256_to() {
+		let hex = "8090a0b0c0d0e0f00910203040506077583a2cf8264910e1436bda32571012f0";
+		let uint = U256::from_str(hex).unwrap();
+		let mut bytes = [0u8; 32];
+		uint.to_bytes(&mut bytes);
+		let uint2 = U256::from(&bytes[..]);
+        assert_eq!(uint, uint2);
+    }
+
     #[test]
     pub fn uint256_bits_test() {
         assert_eq!(U256::from(0u64).bits(), 0);