1 /* 2 * Copyright (C) 2021 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.android.libraries.entitlement.utils; 18 19 import androidx.annotation.Nullable; 20 21 import java.nio.ByteBuffer; 22 23 public class BytesConverter { 24 private static final int INTEGER_SIZE = 4; // 4 bytes 25 26 // A table mapping from a number to a hex character for fast encoding hex strings. 27 private static final char[] HEX_CHARS = { 28 '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F' 29 }; 30 31 /** 32 * Converts a byte array into a String of hexadecimal characters. 33 * 34 * @param bytes an array of bytes 35 * @return hex string representation of bytes array 36 */ 37 @Nullable convertBytesToHexString(byte[] bytes)38 public static String convertBytesToHexString(byte[] bytes) { 39 if (bytes == null) { 40 return null; 41 } 42 43 StringBuilder ret = new StringBuilder(2 * bytes.length); 44 45 for (int i = 0; i < bytes.length; i++) { 46 int b; 47 b = 0x0f & (bytes[i] >> 4); 48 ret.append(HEX_CHARS[b]); 49 b = 0x0f & bytes[i]; 50 ret.append(HEX_CHARS[b]); 51 } 52 53 return ret.toString(); 54 } 55 56 /** 57 * Converts integer to 4 bytes. 58 */ convertIntegerTo4Bytes(int value)59 public static byte[] convertIntegerTo4Bytes(int value) { 60 return ByteBuffer.allocate(INTEGER_SIZE).putInt(value).array(); 61 } 62 } 63