Package structure: moved models and database.

Part of #963.

src/main/java/de/dennisguse/opentracks/data/UUIDUtils.java

@@ -0,0 +1,38 @@
+package de.dennisguse.opentracks.data;
+
+import androidx.annotation.NonNull;
+
+import java.nio.ByteBuffer;
+import java.util.UUID;
+
+public class UUIDUtils {
+
+    public static UUID fromBytes(byte[] bytes) {
+        ByteBuffer byteBuffer = ByteBuffer.wrap(bytes);
+        long mostSignificant = byteBuffer.getLong();
+        long lestSignificant = byteBuffer.getLong();
+        return new UUID(mostSignificant, lestSignificant);
+    }
+
+    public static byte[] toBytes(@NonNull UUID uuid) {
+        ByteBuffer byteBuffer = ByteBuffer.allocate(16);
+        byteBuffer.putLong(uuid.getMostSignificantBits());
+        byteBuffer.putLong(uuid.getLeastSignificantBits());
+        return byteBuffer.array();
+    }
+
+    private static final char[] HEX_ARRAY = "0123456789ABCDEF".toCharArray();
+
+    public static String toHex(@NonNull UUID uuid) {
+        byte[] bytes = toBytes(uuid);
+
+        char[] hexChars = new char[bytes.length * 2];
+        for (int i = 0; i < bytes.length; i++) {
+            int v = bytes[i] & 0xFF;
+
+            hexChars[i * 2] = HEX_ARRAY[v >>> 4];
+            hexChars[i * 2 + 1] = HEX_ARRAY[v & 0x0F];
+        }
+        return new String(hexChars);
+    }
+}