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/*
* 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.
*/
/**
* @author Alexander Y. Kleymenov
*/
package libcore.io;
import java.nio.charset.StandardCharsets;
import libcore.util.EmptyArray;
/**
* <a href="http://www.ietf.org/rfc/rfc2045.txt">Base64</a> encoder/decoder.
* In violation of the RFC, this encoder doesn't wrap lines at 76 columns.
*/
public final class Base64 {
private Base64() {
}
public static byte[] decode(byte[] in) {
return decode(in, in.length);
}
public static byte[] decode(byte[] in, int len) {
// approximate output length
int length = len / 4 * 3;
// return an empty array on empty or short input without padding
if (length == 0) {
return EmptyArray.BYTE;
}
// temporary array
byte[] out = new byte[length];
// number of padding characters ('=')
int pad = 0;
byte chr;
// compute the number of the padding characters
// and adjust the length of the input
for (;;len--) {
chr = in[len-1];
// skip the neutral characters
if ((chr == '\n') || (chr == '\r') ||
(chr == ' ') || (chr == '\t')) {
continue;
}
if (chr == '=') {
pad++;
} else {
break;
}
}
// index in the output array
int outIndex = 0;
// index in the input array
int inIndex = 0;
// holds the value of the input character
int bits = 0;
// holds the value of the input quantum
int quantum = 0;
for (int i=0; i<len; i++) {
chr = in[i];
// skip the neutral characters
if ((chr == '\n') || (chr == '\r') ||
(chr == ' ') || (chr == '\t')) {
continue;
}
if ((chr >= 'A') && (chr <= 'Z')) {
// char ASCII value
// A 65 0
// Z 90 25 (ASCII - 65)
bits = chr - 65;
} else if ((chr >= 'a') && (chr <= 'z')) {
// char ASCII value
// a 97 26
// z 122 51 (ASCII - 71)
bits = chr - 71;
} else if ((chr >= '0') && (chr <= '9')) {
// char ASCII value
// 0 48 52
// 9 57 61 (ASCII + 4)
bits = chr + 4;
} else if (chr == '+') {
bits = 62;
} else if (chr == '/') {
bits = 63;
} else {
return null;
}
// append the value to the quantum
quantum = (quantum << 6) | (byte) bits;
if (inIndex%4 == 3) {
// 4 characters were read, so make the output:
out[outIndex++] = (byte) (quantum >> 16);
out[outIndex++] = (byte) (quantum >> 8);
out[outIndex++] = (byte) quantum;
}
inIndex++;
}
if (pad > 0) {
// adjust the quantum value according to the padding
quantum = quantum << (6*pad);
// make output
out[outIndex++] = (byte) (quantum >> 16);
if (pad == 1) {
out[outIndex++] = (byte) (quantum >> 8);
}
}
// create the resulting array
byte[] result = new byte[outIndex];
System.arraycopy(out, 0, result, 0, outIndex);
return result;
}
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', '+', '/'};
public static String encode(byte[] in) {
int length = (in.length + 2) * 4 / 3;
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];
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)];
out[index++] = '=';
break;
}
return new String(out, 0, index, StandardCharsets.US_ASCII);
}
}
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