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/*
* Copyright 2018, OpenCensus Authors
*
* 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 io.opencensus.trace;
import io.opencensus.internal.Utils;
import java.util.Arrays;
/** Internal copy of the Guava implementation of the {@code BaseEncoding.base16().lowerCase()}. */
final class LowerCaseBase16Encoding {
private static final String ALPHABET = "0123456789abcdef";
private static final int ASCII_CHARACTERS = 128;
private static final char[] ENCODING = buildEncodingArray();
private static final byte[] DECODING = buildDecodingArray();
private static char[] buildEncodingArray() {
char[] encoding = new char[512];
for (int i = 0; i < 256; ++i) {
encoding[i] = ALPHABET.charAt(i >>> 4);
encoding[i | 0x100] = ALPHABET.charAt(i & 0xF);
}
return encoding;
}
private static byte[] buildDecodingArray() {
byte[] decoding = new byte[ASCII_CHARACTERS];
Arrays.fill(decoding, (byte) -1);
for (int i = 0; i < ALPHABET.length(); i++) {
char c = ALPHABET.charAt(i);
decoding[c] = (byte) i;
}
return decoding;
}
/**
* Encodes the specified byte array, and returns the encoded {@code String}.
*
* @param bytes byte array to be encoded.
* @return the encoded {@code String}.
*/
static String encodeToString(byte[] bytes) {
StringBuilder stringBuilder = new StringBuilder(bytes.length * 2);
for (byte byteVal : bytes) {
int b = byteVal & 0xFF;
stringBuilder.append(ENCODING[b]);
stringBuilder.append(ENCODING[b | 0x100]);
}
return stringBuilder.toString();
}
/**
* Decodes the specified character sequence, and returns the resulting {@code byte[]}.
*
* @param chars the character sequence to be decoded.
* @return the resulting {@code byte[]}
* @throws IllegalArgumentException if the input is not a valid encoded string according to this
* encoding.
*/
static byte[] decodeToBytes(CharSequence chars) {
Utils.checkArgument(chars.length() % 2 == 0, "Invalid input length " + chars.length());
int bytesWritten = 0;
byte[] bytes = new byte[chars.length() / 2];
for (int i = 0; i < chars.length(); i += 2) {
bytes[bytesWritten++] = decodeByte(chars.charAt(i), chars.charAt(i + 1));
}
return bytes;
}
private static byte decodeByte(char hi, char lo) {
Utils.checkArgument(lo < ASCII_CHARACTERS && DECODING[lo] != -1, "Invalid character " + lo);
Utils.checkArgument(hi < ASCII_CHARACTERS && DECODING[hi] != -1, "Invalid character " + hi);
int decoded = DECODING[hi] << 4 | DECODING[lo];
return (byte) decoded;
}
// Private constructor to disallow instances.
private LowerCaseBase16Encoding() {}
}
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