/*
* Copyright 2017 Patrick Favre-Bulle
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 at.favre.lib.bytes;
import java.util.Arrays;
/**
* From https://github.com/square/okio/blob/okio-parent-1.15.0/okio/src/main/java/okio/Base64.java
* under Apache 2 license.
*
* @author Alexander Y. Kleymenov
*/
final class Base64 {
private Base64() {
}
private static final byte[] MAP = new byte[]{
'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S',
'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l',
'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4',
'5', '6', '7', '8', '9', '+', '/'
};
private static final byte[] URL_MAP = new byte[]{
'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S',
'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l',
'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4',
'5', '6', '7', '8', '9', '-', '_'
};
static byte[] decode(CharSequence in) {
// Ignore trailing '=' padding and whitespace from the input.
int limit = in.length();
for (; limit > 0; limit--) {
char c = in.charAt(limit - 1);
if (c != '=' && c != '\n' && c != '\r' && c != ' ' && c != '\t') {
break;
}
}
// If the input includes whitespace, this output array will be longer than necessary.
byte[] out = new byte[(int) (limit * 6L / 8L)];
int outCount = 0;
int inCount = 0;
int word = 0;
for (int pos = 0; pos < limit; pos++) {
char c = in.charAt(pos);
int bits;
if (c >= 'A' && c <= 'Z') {
// char ASCII value
// A 65 0
// Z 90 25 (ASCII - 65)
bits = c - 65;
} else if (c >= 'a' && c <= 'z') {
// char ASCII value
// a 97 26
// z 122 51 (ASCII - 71)
bits = c - 71;
} else if (c >= '0' && c <= '9') {
// char ASCII value
// 0 48 52
// 9 57 61 (ASCII + 4)
bits = c + 4;
} else if (c == '+' || c == '-') {
bits = 62;
} else if (c == '/' || c == '_') {
bits = 63;
} else if (c == '\n' || c == '\r' || c == ' ' || c == '\t') {
continue;
} else {
throw new IllegalArgumentException("invalid character to decode: " + c);
}
// Append this char's 6 bits to the word.
word = (word << 6) | (byte) bits;
// For every 4 chars of input, we accumulate 24 bits of output. Emit 3 bytes.
inCount++;
if (inCount % 4 == 0) {
out[outCount++] = (byte) (word >> 16);
out[outCount++] = (byte) (word >> 8);
out[outCount++] = (byte) word;
}
}
int lastWordChars = inCount % 4;
if (lastWordChars == 1) {
// We read 1 char followed by "===". But 6 bits is a truncated byte! Fail.
return null;
} else if (lastWordChars == 2) {
// We read 2 chars followed by "==". Emit 1 byte with 8 of those 12 bits.
word = word << 12;
out[outCount++] = (byte) (word >> 16);
} else if (lastWordChars == 3) {
// We read 3 chars, followed by "=". Emit 2 bytes for 16 of those 18 bits.
word = word << 6;
out[outCount++] = (byte) (word >> 16);
out[outCount++] = (byte) (word >> 8);
}
// If we sized our out array perfectly, we're done.
if (outCount == out.length) return out;
// Copy the decoded bytes to a new, right-sized array.
return Arrays.copyOfRange(out, 0, outCount);
}
static byte[] encode(byte[] in) {
return encode(in, false, true);
}
static byte[] encode(byte[] in, boolean urlSafe, boolean usePadding) {
return encode(in, urlSafe ? URL_MAP : MAP, usePadding);
}
private static byte[] encode(byte[] in, byte[] map, boolean usePadding) {
int length = outLength(in.length, usePadding);
byte[] out = new byte[length];
int index = 0, end = in.length - in.length % 3;
for (int i = 0; i < end; i += 3) {
out[index++] = map[(in[i] & 0xff) >> 2];
out[index++] = map[((in[i] & 0x03) << 4) | ((in[i + 1] & 0xff) >> 4)];
out[index++] = map[((in[i + 1] & 0x0f) << 2) | ((in[i + 2] & 0xff) >> 6)];
out[index++] = map[(in[i + 2] & 0x3f)];
}
switch (in.length % 3) {
case 1:
out[index++] = map[(in[end] & 0xff) >> 2];
out[index++] = map[(in[end] & 0x03) << 4];
if (usePadding) {
out[index++] = '=';
out[index] = '=';
}
break;
case 2:
out[index++] = map[(in[end] & 0xff) >> 2];
out[index++] = map[((in[end] & 0x03) << 4) | ((in[end + 1] & 0xff) >> 4)];
out[index++] = map[((in[end + 1] & 0x0f) << 2)];
if (usePadding) {
out[index] = '=';
}
break;
}
return out;
}
private static int outLength(int srclen, boolean doPadding) {
int len;
if (doPadding) {
len = 4 * ((srclen + 2) / 3);
} else {
int n = srclen % 3;
len = 4 * (srclen / 3) + (n == 0 ? 0 : n + 1);
}
return len;
}
}
