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/*
* 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 toHexString(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[] fromHexToByteArray(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;
}
}
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