Add Groestl hash support

build.gradle

@@ -60,6 +60,7 @@ dependencies {
         exclude group: 'org.hamcrest', module: 'hamcrest-core'
     }
     testImplementation group: 'org.hamcrest', name: 'hamcrest-core', version: '2.2'
+    implementation 'de.sfuhrm:saphir-hash-core:3.0.5'
 }
 
 task(runDrongo, dependsOn: 'classes', type: JavaExec) {

src/main/java/com/sparrowwallet/drongo/crypto/Groestl.java

@@ -0,0 +1,70 @@
+package com.sparrowwallet.drongo.crypto;
+
+import fr.cryptohash.Groestl512;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.security.MessageDigest;
+import java.security.NoSuchAlgorithmException;
+
+/**
+ * Created by Hash Engineering on 12/24/14 for the Groestl algorithm
+ */
+public class Groestl {
+
+    private static final Logger log = LoggerFactory.getLogger(Groestl.class);
+    private static boolean native_library_loaded = false;
+    private static final Groestl512 digestGroestl = new Groestl512();
+
+    static {
+        try {
+            System.loadLibrary("groestld");
+            native_library_loaded = true;
+        } catch(UnsatisfiedLinkError x) {
+            native_library_loaded = false;
+        } catch(Exception e) {
+            native_library_loaded = false;
+        }
+    }
+
+    public static byte[] digest(byte[] input, int offset, int length) {
+        try {
+            return native_library_loaded ? groestld_native(input, offset, length) : groestl(input, offset, length);
+        } catch (Exception e) {
+            return null;
+        }
+    }
+
+    public static byte[] digest(byte[] input) {
+        try {
+            return native_library_loaded ? groestld_native(input, 0, input.length) : groestl(input);
+        } catch (Exception e) {
+            return null;
+        }
+    }
+
+    static native byte [] groestld_native(byte [] input, int offset, int len);
+
+    static byte [] groestl(byte header[]) {
+        Groestl512 hasher1 = new Groestl512();
+        Groestl512 hasher2 = new Groestl512();
+
+        byte [] hash1 = hasher1.digest(header);
+        byte [] hash2 = hasher2.digest(hash1);
+
+        byte [] hash = new byte [32];
+        System.arraycopy(hash2, 0, hash, 0, 32);
+        return hash;
+    }
+
+    static byte [] groestl(byte header[], int offset, int length) {
+        digestGroestl.reset();
+        digestGroestl.update(header, offset, length);
+        byte [] hash1 = digestGroestl.digest();
+        byte [] hash2 = digestGroestl.digest(hash1);
+
+        byte [] hash = new byte [32];
+        System.arraycopy(hash2, 0, hash, 0, 32);
+        return hash;
+    }
+}