SHA-256 Merkle tree: Difference between revisions
Added Java Solution
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fmt.Printf("%x", hashes[0])
fmt.Println()
}</lang>
{{out}}
<pre>
a4f902cf9d51fe51eda156a6792e1445dff65edf3a217a1f3334cc9cf1495c2c
</pre>
=={{header|Java}}==
<lang java>import java.io.*;
import java.security.*;
import java.util.*;
public class SHA256MerkleTree {
public static void main(String[] args) {
try {
if (args.length != 1) {
System.err.println("missing file argument");
System.exit(1);
}
try (InputStream in = new BufferedInputStream(new FileInputStream(args[0]))) {
byte[] digest = sha256MerkleTree(in, 1024);
if (digest != null)
System.out.println(digestToString(digest));
}
} catch (Exception e) {
e.printStackTrace();
}
}
private static String digestToString(byte[] digest) {
StringBuilder result = new StringBuilder();
for (int i = 0; i < digest.length; ++i)
result.append(String.format("%02x", (int)digest[i] & 0xFF));
return result.toString();
}
private static byte[] sha256MerkleTree(InputStream in, int blockSize) throws Exception {
byte[] buffer = new byte[blockSize];
int bytes;
MessageDigest md = MessageDigest.getInstance("SHA-256");
List<byte[]> digests = new ArrayList<>();
while ((bytes = in.read(buffer)) > 0) {
md.reset();
md.update(buffer, 0, bytes);
digests.add(md.digest());
}
int length = digests.size();
if (length == 0)
return null;
while (length > 1) {
int j = 0;
for (int i = 0; i < length; i += 2, ++j) {
byte[] digest1 = digests.get(i);
if (i + 1 < length) {
byte[] digest2 = digests.get(i + 1);
md.reset();
md.update(digest1);
md.update(digest2);
digests.set(j, md.digest());
} else {
digests.set(j, digest1);
}
}
length = j;
}
return digests.get(0);
}
}</lang>
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