package DNA.Cryptography;

import java.util.Arrays;

import DNA.UInt256;

/**

* 哈希树

*/

public class MerkleTree {

/**

* 计算根节点的值

* <param name="hashes">子节点列表</param>

* <returns>返回计算的结果</returns>

*/

public static UInt256 computeRoot(UInt256[] hashes) {

if (hashes.length == 0) {

throw new IllegalArgumentException();

}

if (hashes.length == 1) {

return hashes[0];

}

return new UInt256(computeRoot(Arrays.stream(hashes).map(p -> p.toArray()).toArray(byte[][]::new)));

}

private static byte[] computeRoot(byte[][] hashes) {

if (hashes.length == 0) {

throw new IllegalArgumentException();

}

if (hashes.length == 1) {

return hashes[0];

}

if (hashes.length % 2 == 1) {

byte[][] temp = new byte[hashes.length + 1][];

System.arraycopy(hashes, 0, temp, 0, hashes.length);

temp[temp.length - 1] = hashes[hashes.length - 1];

hashes = temp;

}

byte[][] hashes_new = new byte[hashes.length / 2][];

for (int i = 0; i < hashes_new.length; i++) {

byte[] buffer = new byte[hashes[i * 2].length + hashes[i * 2 + 1].length];

System.arraycopy(hashes[i * 2], 0, buffer, 0, hashes[i * 2].length);

System.arraycopy(hashes[i * 2 + 1], 0, buffer, hashes[i * 2].length, hashes[i * 2 + 1].length);

hashes_new[i] = Digest.hash256(buffer);

}

return computeRoot(hashes_new);

}

}