/*
* Copyright 2014-2017 MongoDB, Inc.
* Copyright 1999,2005 The Apache Software Foundation.
*
* 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 org.bson.internal;
/**
* <p>Provides Base64 encoding and decoding.</p>
* <p>This class implements Base64 encoding</p>
* <p>Thanks to Apache Commons project. This class refactored from org.apache.commons.codec.binary</p>
* <p>Original Thanks to <a href="http://svn.apache.org/repos/asf/webservices/commons/trunk/modules/util/">commons</a> project in
* ws.apache.org for this code. </p>
*
* @since 3.5
*/
public final class Base64 {
private static final int BYTES_PER_UNENCODED_BLOCK = 3;
private static final int BYTES_PER_ENCODED_BLOCK = 4;
/**
* Mask used to extract 6 bits, used when encoding
*/
private static final int SIX_BIT_MASK = 0x3f;
/**
* padding char
*/
private static final byte PAD = '=';
/**
* This array is a lookup table that translates 6-bit positive integer index values into their "Base64 Alphabet"
* equivalents as specified in Table 1 of RFC 2045.
*/
private static final byte[] ENCODE_TABLE = {'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 int[] DECODE_TABLE = new int[128];
static {
for (int i = 0; i < ENCODE_TABLE.length; i++) {
DECODE_TABLE[ENCODE_TABLE[i]] = i;
}
}
/**
* Decodes the given Base64-encoded string.
*
* @param s the Base64-encoded string
* @return the decoded byte array
*/
public static byte[] decode(final String s) {
int delta = s.endsWith("==") ? 2 : s.endsWith("=") ? 1 : 0;
byte[] buffer = new byte[s.length() * BYTES_PER_UNENCODED_BLOCK / BYTES_PER_ENCODED_BLOCK - delta];
int mask = 0xFF;
int pos = 0;
for (int i = 0; i < s.length(); i += BYTES_PER_ENCODED_BLOCK) {
int c0 = DECODE_TABLE[s.charAt(i)];
int c1 = DECODE_TABLE[s.charAt(i + 1)];
buffer[pos++] = (byte) (((c0 << 2) | (c1 >> 4)) & mask);
if (pos >= buffer.length) {
return buffer;
}
int c2 = DECODE_TABLE[s.charAt(i + 2)];
buffer[pos++] = (byte) (((c1 << 4) | (c2 >> 2)) & mask);
if (pos >= buffer.length) {
return buffer;
}
int c3 = DECODE_TABLE[s.charAt(i + 3)];
buffer[pos++] = (byte) (((c2 << 6) | c3) & mask);
}
return buffer;
}
/**
* Encodes the given byte array into a Base64-encoded string.
*
*
* @param in the byte array
* @return the Base64-encoded string
*/
public static String encode(final byte[] in) {
int modulus = 0;
int bitWorkArea = 0;
int numEncodedBytes = (in.length / BYTES_PER_UNENCODED_BLOCK) * BYTES_PER_ENCODED_BLOCK
+ ((in.length % BYTES_PER_UNENCODED_BLOCK == 0) ? 0 : 4);
byte[] buffer = new byte[numEncodedBytes];
int pos = 0;
for (int b : in) {
modulus = (modulus + 1) % BYTES_PER_UNENCODED_BLOCK;
if (b < 0) {
b += 256;
}
bitWorkArea = (bitWorkArea << 8) + b; // BITS_PER_BYTE
if (0 == modulus) { // 3 bytes = 24 bits = 4 * 6 bits to extract
buffer[pos++] = ENCODE_TABLE[(bitWorkArea >> 18) & SIX_BIT_MASK];
buffer[pos++] = ENCODE_TABLE[(bitWorkArea >> 12) & SIX_BIT_MASK];
buffer[pos++] = ENCODE_TABLE[(bitWorkArea >> 6) & SIX_BIT_MASK];
buffer[pos++] = ENCODE_TABLE[bitWorkArea & SIX_BIT_MASK];
}
}
switch (modulus) { // 0-2
case 1: // 8 bits = 6 + 2
buffer[pos++] = ENCODE_TABLE[(bitWorkArea >> 2) & SIX_BIT_MASK]; // top 6 bits
buffer[pos++] = ENCODE_TABLE[(bitWorkArea << 4) & SIX_BIT_MASK]; // remaining 2
buffer[pos++] = PAD;
buffer[pos] = PAD; // Last entry no need to ++
break;
case 2: // 16 bits = 6 + 6 + 4
buffer[pos++] = ENCODE_TABLE[(bitWorkArea >> 10) & SIX_BIT_MASK];
buffer[pos++] = ENCODE_TABLE[(bitWorkArea >> 4) & SIX_BIT_MASK];
buffer[pos++] = ENCODE_TABLE[(bitWorkArea << 2) & SIX_BIT_MASK];
buffer[pos] = PAD; // Last entry no need to ++
break;
default:
break;
}
return byteArrayToString(buffer);
}
@SuppressWarnings("deprecation")
private static String byteArrayToString(final byte[] buffer) {
return new String(buffer, 0, 0, buffer.length);
}
private Base64() {
}
}