fun.fengwk.commons.codec.Base64 Maven / Gradle / Ivy
The newest version!
package fun.fengwk.commons.codec;
/**
* Base64编码解码器。
*
* @author fengwk
*/
public class Base64 {
private static final byte EQ = '=';
private static final char[] 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', '+', '/',
};
/**
* 索引为编码的ASCII值，值为其在BASE_64中的索引，也就是BASE_64码值
*/
private static final byte[] BASE_64_REVERSE;
static {
int maxIndex = -1;
for (int i = 0; i < BASE_64.length; i++) {
int c = BASE_64[i];
if (c > maxIndex) {
maxIndex = c;
}
}
byte[] reverse = new byte[maxIndex + 1];
for (int i = 0; i < BASE_64.length; i++) {
reverse[BASE_64[i]] = (byte) i;
}
BASE_64_REVERSE = reverse;
}
/**
* 将输入字节数组进行Base64编码。
*
* @param src
* @return
*/
public byte[] encode(byte[] src) {
int len = src.length;
if (len % 3 != 0) {
len += 3 - (len % 3);
}
byte[] dest = new byte[len * 8 / 6];
for (int i = 0, j = 0; j < dest.length; i += 3, j += 4) {
byte t1 = src[i];
byte t2 = i + 1 < src.length ? src[i + 1] : -1;
byte t3 = i + 2 < src.length ? src[i + 2] : -1;
if (t2 != -1 && t3 != -1) {
dest[j] = (byte) BASE_64[((t1 >>> 2) & 0b111111)];
dest[j + 1] = (byte) BASE_64[((t1 << 4) & 0b110000) | (t2 >>> 4) & 0b001111];
dest[j + 2] = (byte) BASE_64[((t2 << 2) & 0b111100) | (t3 >>> 6) & 0b000011];
dest[j + 3] = (byte) BASE_64[t3 & 0b111111];
} else if (t2 == -1) {
dest[j] = (byte) BASE_64[((t1 >>> 2) & 0b111111)];
dest[j + 1] = (byte) BASE_64[(t1 << 4) & 0b110000];
dest[j + 2] = EQ;
dest[j + 3] = EQ;
} else {
dest[j] = (byte) BASE_64[((t1 >>> 2) & 0b111111)];
dest[j + 1] = (byte) BASE_64[((t1 << 4) & 0b110000) | (t2 >>> 4) & 0b001111];
dest[j + 2] = (byte) BASE_64[((t2 << 2) & 0b111100)];
dest[j + 3] = EQ;
}
}
return dest;
}
/**
* 将输入的Base64编码数组进行解码。
*
* @param src
* @return
*/
public byte[] decode(byte[] src) {
if (src.length % 4 != 0) {
throw new IllegalArgumentException();
}
int len = src.length * 6 / 8;
if (src.length - 2 >= 0 && src[src.length - 2] == EQ) {
len -= 2;
} else if (src.length - 1 >= 0 && src[src.length - 1] == EQ) {
len -= 1;
}
byte[] dest = new byte[len];
for (int i = 0, j = 0; i < src.length; i += 4, j += 3) {
byte t1 = BASE_64_REVERSE[src[i]];
byte t2 = BASE_64_REVERSE[src[i + 1]];
byte t3 = src[i + 2] == EQ ? -1 : BASE_64_REVERSE[src[i + 2]];
byte t4 = src[i + 3] == EQ ? -1 : BASE_64_REVERSE[src[i + 3]];
if (t3 == -1) {
dest[j] = (byte) (((t1 & 0b00111111) << 2) | ((t2 >>> 4) & 0b00000011));
} else if (t4 == -1) {
dest[j] = (byte) (((t1 & 0b00111111) << 2) | ((t2 >>> 4) & 0b00000011));
dest[j + 1] = (byte) (((t2 & 0b00001111) << 4) | ((t3 >>> 2) & 0b00001111));
} else {
dest[j] = (byte) (((t1 & 0b00111111) << 2) | ((t2 >>> 4) & 0b00000011));
dest[j + 1] = (byte) (((t2 & 0b00001111) << 4) | ((t3 >>> 2) & 0b00001111));
dest[j + 2] = (byte) (((t3 & 0b00000011) << 6) | (t4 & 0b00111111));
}
}
return dest;
}
}