add conversion from keypath data to string

demo/src/main/java/im/status/hardwallet_lite_android/app/MainActivity.java

@@ -6,8 +6,8 @@ import android.support.v7.app.AppCompatActivity;
 import android.util.Log;
 import im.status.hardwallet_lite_android.demo.R;
 import im.status.hardwallet_lite_android.io.CardChannel;
+import im.status.hardwallet_lite_android.io.CardListener;
 import im.status.hardwallet_lite_android.io.CardManager;
-import im.status.hardwallet_lite_android.io.OnCardConnectedListener;
 import im.status.hardwallet_lite_android.wallet.*;
 import org.spongycastle.util.encoders.Hex;
 
@@ -25,7 +25,7 @@ public class MainActivity extends AppCompatActivity {
     nfcAdapter = NfcAdapter.getDefaultAdapter(this);
     cardManager = new CardManager();
 
-    cardManager.setOnCardConnectedListener(new OnCardConnectedListener() {
+    cardManager.setCardListener(new CardListener() {
       @Override
       public void onConnected(CardChannel cardChannel) {
         try {
@@ -87,11 +87,16 @@ public class MainActivity extends AppCompatActivity {
             cmdSet.generateKey();
           }
 
-          // Key derivation is needed to select the desired key. The derived key remains current until a new derive
+          // Get the current key path using GET STATUS
-          // command is sent (it is not lost on power loss). With GET STATUS one can retrieve the current path.
+          KeyPath currentPath = new KeyPath(cmdSet.getStatus(WalletAppletCommandSet.GET_STATUS_P1_KEY_PATH).checkOK().getData());
-          cmdSet.deriveKey("m/44'/0'/0'/0/0").checkOK();
+          Log.i(TAG, "Current key path: " + currentPath);
 
+          if (!currentPath.toString().equals("m/44'/0'/0'/0/0")) {
+            // Key derivation is needed to select the desired key. The derived key remains current until a new derive
+            // command is sent (it is not lost on power loss).
+            cmdSet.deriveKey("m/44'/0'/0'/0/0").checkOK();
             Log.i(TAG, "Derived m/44'/0'/0'/0/0");
+          }
 
           byte[] hash = "thiscouldbeahashintheorysoitisok".getBytes();
 
@@ -115,6 +120,11 @@ public class MainActivity extends AppCompatActivity {
         }
 
       }
+
+      @Override
+      public void onDisconnected() {
+        Log.i(TAG, "Card disconnected.");
+      }
     });
     cardManager.start();
   }

lib/src/main/java/im/status/hardwallet_lite_android/wallet/KeyPath.java

@@ -26,7 +26,6 @@ public class KeyPath {
    * @param keypath the keypath as a string
    */
   public KeyPath(String keypath) {
-    data = new byte[40];
     StringTokenizer tokenizer = new StringTokenizer(keypath, "/");
 
     String sourceOrFirstElement = tokenizer.nextToken();
@@ -52,12 +51,23 @@ public class KeyPath {
       throw new IllegalArgumentException("Too many components");
     }
 
+    data = new byte[4 * componentCount];
+
     for (int i = 0; i < componentCount; i++) {
       long component = parseComponent(tokenizer.nextToken());
       writeComponent(component, i);
     }
   }
 
+  public KeyPath(byte[] data, int source) {
+    this.data = data;
+    this.source = source;
+  }
+
+  public KeyPath(byte[] data) {
+    this(data, WalletAppletCommandSet.DERIVE_P1_SOURCE_MASTER);
+  }
+
   private long parseComponent(String num) {
     long sign;
 
@@ -99,4 +109,37 @@ public class KeyPath {
   public byte[] getData() {
     return data;
   }
+
+  @Override
+  public String toString() {
+    StringBuffer sb = new StringBuffer();
+
+    switch(source) {
+      case WalletAppletCommandSet.DERIVE_P1_SOURCE_MASTER:
+        sb.append('m');
+        break;
+      case WalletAppletCommandSet.DERIVE_P1_SOURCE_PARENT:
+        sb.append("..");
+        break;
+      case WalletAppletCommandSet.DERIVE_P1_SOURCE_CURRENT:
+        sb.append('.');
+        break;
+    }
+
+    for (int i = 0; i < this.data.length; i += 4) {
+      sb.append('/');
+      appendComponent(sb, i);
+    }
+
+    return sb.toString();
+  }
+
+  private void appendComponent(StringBuffer sb, int i) {
+    int num = ((this.data[i] & 0x7f) << 24) | ((this.data[i+1] & 0xff) << 16) | ((this.data[i+2] & 0xff) << 8) | (this.data[i+3] & 0xff);
+    sb.append(num);
+
+    if ((this.data[i] & 0x80) == 0x80) {
+      sb.append('\'');
+    }
+  }
 }

lib/src/main/java/im/status/hardwallet_lite_android/wallet/WalletAppletCommandSet.java

@@ -38,6 +38,7 @@ public class WalletAppletCommandSet {
   static final byte INS_EXPORT_KEY = (byte) 0xC2;
 
   public static final byte GET_STATUS_P1_APPLICATION = 0x00;
+  public static final byte GET_STATUS_P1_KEY_PATH = 0x01;
 
   public static final byte LOAD_KEY_P1_EC = 0x01;
   public static final byte LOAD_KEY_P1_EXT_EC = 0x02;