Bug 888086 - Use StringBuilder in sync/Utils.java r=rnewman

mobile/android/base/sync/CryptoRecord.java

@@ -210,7 +210,7 @@ public class CryptoRecord extends Record {
     CryptoInfo info = CryptoInfo.encrypt(cleartextBytes, keyBundle);
     String message = new String(Base64.encodeBase64(info.getMessage()));
     String iv      = new String(Base64.encodeBase64(info.getIV()));
-    String hmac    = Utils.byte2hex(info.getHMAC());
+    String hmac    = Utils.byte2Hex(info.getHMAC());
     ExtendedJSONObject ciphertext = new ExtendedJSONObject();
     ciphertext.put(KEY_CIPHERTEXT, message);
     ciphertext.put(KEY_HMAC, hmac);

mobile/android/base/sync/Utils.java

@@ -82,26 +82,20 @@ public class Utils {
   /**
    * Helper to convert a byte array to a hex-encoded string
    */
-  public static String byte2hex(byte[] b) {
-    // StringBuffer should be used instead.
-    String hs = "";
+  public static String byte2Hex(final byte[] b) {
+    final StringBuilder hs = new StringBuilder(b.length * 2);
     String stmp;
 
     for (int n = 0; n < b.length; n++) {
-      stmp = java.lang.Integer.toHexString(b[n] & 0XFF);
+      stmp = Integer.toHexString(b[n] & 0XFF);
 
       if (stmp.length() == 1) {
-        hs = hs + "0" + stmp;
-      } else {
-        hs = hs + stmp;
-      }
-
-      if (n < b.length - 1) {
-        hs = hs + "";
+        hs.append("0");
       }
+      hs.append(stmp);
     }
 
-    return hs;
+    return hs.toString();
   }
 
   public static byte[] concatAll(byte[] first, byte[]... rest) {
@@ -536,4 +530,4 @@ public class Utils {
   public static String obfuscateEmail(final String in) {
     return in.replaceAll("[^@\\.]", "X");
   }
-}
+}

mobile/android/base/sync/jpake/JPakeClient.java

@@ -308,7 +308,7 @@ public class JPakeClient {
     payload.put(Constants.JSON_KEY_CIPHERTEXT, message64);
     payload.put(Constants.JSON_KEY_IV, iv64);
     if (makeHmac) {
-      String hmacHex = Utils.byte2hex(encrypted.getHMAC());
+      String hmacHex = Utils.byte2Hex(encrypted.getHMAC());
       payload.put(Constants.JSON_KEY_HMAC, hmacHex);
     }
     return payload;