1 files changed, 82 insertions, 0 deletions
diff --git a/core/java/android/util/ByteStringUtils.java b/core/java/android/util/ByteStringUtils.java
new file mode 100644
index 000000000000..7103e6da0625
--- /dev/null
+++ b/core/java/android/util/ByteStringUtils.java
@@ -0,0 +1,82 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.util;
+
+/**
+ * A utility class for common byte array to hex string operations and vise versa.
+ *
+ * @hide
+ */
+public final class ByteStringUtils {
+  private final static char[] HEX_ARRAY = "0123456789ABCDEF".toCharArray();
+
+  private ByteStringUtils() {
+    /* hide constructor */
+  }
+
+  /**
+   * Returns the hex encoded string representation of bytes.
+   * @param bytes Byte array to encode.
+   * @return Hex encoded string representation of bytes.
+   */
+  public static String toString(byte[] bytes) {
+    if (bytes == null || bytes.length == 0 || bytes.length % 2 != 0) {
+      return null;
+    }
+
+    final int byteLength = bytes.length;
+    final int charCount = 2 * byteLength;
+    final char[] chars = new char[charCount];
+
+    for (int i = 0; i < byteLength; i++) {
+      final int byteHex = bytes[i] & 0xFF;
+      chars[i * 2] = HEX_ARRAY[byteHex >>> 4];
+      chars[i * 2 + 1] = HEX_ARRAY[byteHex & 0x0F];
+    }
+    return new String(chars);
+  }
+
+  /**
+   * Returns the decoded byte array representation of str.
+   * @param str Hex encoded string to decode.
+   * @return Decoded byte array representation of str.
+   */
+  public static byte[] toByteArray(String str) {
+    if (str == null || str.length() == 0 || str.length() % 2 != 0) {
+      return null;
+    }
+
+    final char[] chars = str.toCharArray();
+    final int charLength = chars.length;
+    final byte[] bytes = new byte[charLength / 2];
+
+    for (int i = 0; i < bytes.length; i++) {
+      bytes[i] =
+          (byte)(((getIndex(chars[i * 2]) << 4) & 0xF0) | (getIndex(chars[i * 2 + 1]) & 0x0F));
+    }
+    return bytes;
+  }
+
+  private static int getIndex(char c) {
+    for (int i = 0; i < HEX_ARRAY.length; i++) {
+      if (HEX_ARRAY[i] == c) {
+        return i;
+      }
+    }
+    return -1;
+  }
+}