Home | History | Annotate | Download | only in trace 
      1 /*
      2  * Copyright 2018, OpenCensus Authors
      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 io.opencensus.trace;
     18 
     19 import io.opencensus.internal.Utils;
     20 import java.util.Arrays;
     21 
     22 /** Internal copy of the Guava implementation of the {@code BaseEncoding.base16().lowerCase()}. */
     23 final class LowerCaseBase16Encoding {
     24   private static final String ALPHABET = "0123456789abcdef";
     25   private static final int ASCII_CHARACTERS = 128;
     26   private static final char[] ENCODING = buildEncodingArray();
     27   private static final byte[] DECODING = buildDecodingArray();
     28 
     29   private static char[] buildEncodingArray() {
     30     char[] encoding = new char[512];
     31     for (int i = 0; i < 256; ++i) {
     32       encoding[i] = ALPHABET.charAt(i >>> 4);
     33       encoding[i | 0x100] = ALPHABET.charAt(i & 0xF);
     34     }
     35     return encoding;
     36   }
     37 
     38   private static byte[] buildDecodingArray() {
     39     byte[] decoding = new byte[ASCII_CHARACTERS];
     40     Arrays.fill(decoding, (byte) -1);
     41     for (int i = 0; i < ALPHABET.length(); i++) {
     42       char c = ALPHABET.charAt(i);
     43       decoding[c] = (byte) i;
     44     }
     45     return decoding;
     46   }
     47 
     48   /**
     49    * Encodes the specified byte array, and returns the encoded {@code String}.
     50    *
     51    * @param bytes byte array to be encoded.
     52    * @return the encoded {@code String}.
     53    */
     54   static String encodeToString(byte[] bytes) {
     55     StringBuilder stringBuilder = new StringBuilder(bytes.length * 2);
     56     for (byte byteVal : bytes) {
     57       int b = byteVal & 0xFF;
     58       stringBuilder.append(ENCODING[b]);
     59       stringBuilder.append(ENCODING[b | 0x100]);
     60     }
     61     return stringBuilder.toString();
     62   }
     63 
     64   /**
     65    * Decodes the specified character sequence, and returns the resulting {@code byte[]}.
     66    *
     67    * @param chars the character sequence to be decoded.
     68    * @return the resulting {@code byte[]}
     69    * @throws IllegalArgumentException if the input is not a valid encoded string according to this
     70    *     encoding.
     71    */
     72   static byte[] decodeToBytes(CharSequence chars) {
     73     Utils.checkArgument(chars.length() % 2 == 0, "Invalid input length " + chars.length());
     74     int bytesWritten = 0;
     75     byte[] bytes = new byte[chars.length() / 2];
     76     for (int i = 0; i < chars.length(); i += 2) {
     77       bytes[bytesWritten++] = decodeByte(chars.charAt(i), chars.charAt(i + 1));
     78     }
     79     return bytes;
     80   }
     81 
     82   private static byte decodeByte(char hi, char lo) {
     83     Utils.checkArgument(lo < ASCII_CHARACTERS && DECODING[lo] != -1, "Invalid character " + lo);
     84     Utils.checkArgument(hi < ASCII_CHARACTERS && DECODING[hi] != -1, "Invalid character " + hi);
     85     int decoded = DECODING[hi] << 4 | DECODING[lo];
     86     return (byte) decoded;
     87   }
     88 
     89   // Private constructor to disallow instances.
     90   private LowerCaseBase16Encoding() {}
     91 }
     92