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com.alibaba.nls.client.util.Base64Encoder Maven / Gradle / Ivy
/*
* Copyright 2015 Alibaba Group Holding Limited
*
* 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 com.alibaba.nls.client.util;
import java.nio.charset.Charset;
import java.util.Arrays;
/**
* @author zhishen.ml
* A simple encoder from Java 1.8, since we are using 1.6.
*/
public class Base64Encoder {
private static final char[] TO_BASE_64 = {
'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 LINE_MAX = -1;
private static final boolean DO_PADDING = true;
private static final byte[] NEW_LINE = null;
private static int outLength(int srclen) {
int len = 0;
if (DO_PADDING) {
len = 4 * ((srclen + 2) / 3);
} else {
int n = srclen % 3;
len = 4 * (srclen / 3) + (n == 0 ? 0 : n + 1);
}
if (LINE_MAX > 0) {
len += (len - 1) / LINE_MAX * NEW_LINE.length;
}
return len;
}
private static int encode0(byte[] src, int off, int end, byte[] dst) {
char[] base64 = TO_BASE_64;
int sp = off;
int slen = (end - off) / 3 * 3;
int sl = off + slen;
if (LINE_MAX > 0 && slen > LINE_MAX / 4 * 3) { slen = LINE_MAX / 4 * 3; }
int dp = 0;
while (sp < sl) {
int sl0 = Math.min(sp + slen, sl);
for (int sp0 = sp, dp0 = dp; sp0 < sl0; ) {
int bits = (src[sp0++] & 0xff) << 16 |
(src[sp0++] & 0xff) << 8 |
(src[sp0++] & 0xff);
dst[dp0++] = (byte)base64[(bits >>> 18) & 0x3f];
dst[dp0++] = (byte)base64[(bits >>> 12) & 0x3f];
dst[dp0++] = (byte)base64[(bits >>> 6) & 0x3f];
dst[dp0++] = (byte)base64[bits & 0x3f];
}
int dlen = (sl0 - sp) / 3 * 4;
dp += dlen;
sp = sl0;
if (dlen == LINE_MAX && sp < end) {
for (byte b : NEW_LINE) {
dst[dp++] = b;
}
}
}
if (sp < end) {
int b0 = src[sp++] & 0xff;
dst[dp++] = (byte)base64[b0 >> 2];
if (sp == end) {
dst[dp++] = (byte)base64[(b0 << 4) & 0x3f];
if (DO_PADDING) {
dst[dp++] = '=';
dst[dp++] = '=';
}
} else {
int b1 = src[sp++] & 0xff;
dst[dp++] = (byte)base64[(b0 << 4) & 0x3f | (b1 >> 4)];
dst[dp++] = (byte)base64[(b1 << 2) & 0x3f];
if (DO_PADDING) {
dst[dp++] = '=';
}
}
}
return dp;
}
public static String encode(byte[] src) {
int len = outLength(src.length);
byte[] dst = new byte[len];
int ret = encode0(src, 0, src.length, dst);
if (ret != dst.length) {
dst = Arrays.copyOf(dst, ret);
}
return new String(dst, 0, dst.length, Charset.defaultCharset());
}
}
