feat(merkle_root): hash vector of leafs to get merkle_root

Signed-off-by: Johns Beharry <johns@peakshift.com>

eth2/utils/hashing/src/lib.rs

@@ -8,6 +8,31 @@ pub fn hash(input: &[u8]) -> Vec<u8> {
     result
 }
 
+pub fn merkle_root(values: &[Vec<u8>]) -> Vec<u8> {
+    let values_len = values.len();
+    let mut o: Vec<Vec<u8>> = vec![vec![0]; values_len];
+
+    o.append(&mut values.to_vec());
+
+    println!("o {:?}", o);
+
+    for i in (0..values_len).rev() {
+        let mut current_value: Vec<u8> = o[i * 2].clone();
+        current_value.append(&mut o[i * 2 + 1].clone());
+
+        o[i] = hash(&current_value[..]);
+        println!("i {:?}", i);
+        print!("   ");
+        println!("o[i * 2] {} -- {:?}", i * 2, o[i * 2]);
+        print!("   ");
+        println!("o[i * 2 + 1] {} -- {:?}", i * 2 + 1, o[i * 2 + 1]);
+    }
+
+//    println!("{:?}", o);
+
+    o[1].clone()
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -23,6 +48,56 @@ mod tests {
             0x28, 0x7b, 0x56, 0xd9, 0x51, 0x7b, 0x9c, 0x94, 0x81, 0x27, 0x31, 0x9a, 0x09, 0xa7,
             0xa3, 0x6d, 0xea, 0xc8,
         ];
+
+        println!("{:?}", expected);
+        println!("{:?}", output);
         assert_eq!(expected, output.as_slice());
     }
+
+    #[test]
+    fn test_merkle_root() {
+        let mut input = vec![
+            "a".as_bytes().to_vec(),
+            "b".as_bytes().to_vec(),
+            "c".as_bytes().to_vec(),
+            "d".as_bytes().to_vec()
+        ];
+
+        let output = merkle_root(&input[..]);
+
+        let mut leaf_1_2: Vec<u8> = input[0].clone(); // a
+        leaf_1_2.append(&mut input[1].clone()); // b
+
+        let mut leaf_3_4: Vec<u8> = input[2].clone(); // c
+        leaf_3_4.append(&mut input[3].clone()); // d
+
+        let node_1 = hash(&leaf_1_2[..]);
+        let node_2 = hash(&leaf_3_4[..]);
+
+        let mut root: Vec<u8> = node_1.clone(); // ab
+        root.append(&mut node_2.clone()); // cd
+
+        let mr = hash(&root[..]);
+
+        let expected = &[183, 91, 96, 122, 144, 174, 84, 92, 97, 156, 140, 192, 66, 221, 55, 229, 234, 48, 118, 7, 61, 207, 39, 125, 150, 32, 94, 90, 19, 88, 122, 163];
+
+        print!("    ");
+        print!("    ");
+        print!("    ");
+        print!("    ");
+        print!("    ");
+        print!("origional input");
+        println!("{:?}", input);
+        print!("NODE #1 HASH                              ");
+        println!("{:?}", node_1);
+        print!("NODE #2 HASH                              ");
+        println!("{:?}", node_2);
+        print!("ROOT HASH                              ");
+        println!("{:?}", root);
+        print!("                                                                                                                        ");
+        println!("{:?}", expected);
+
+        assert_eq!(expected, output.as_slice());
+
+    }
 }