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Wasu Iot Open API SDK for Java
package cn.iotwasu.hutool.core.codec;
import cn.iotwasu.hutool.core.util.ArrayUtil;
import cn.iotwasu.hutool.core.util.CharsetUtil;
import cn.iotwasu.hutool.core.util.StrUtil;
import java.nio.charset.Charset;
/**
* Base64解码实现
*
* @author looly
*/
public class Base64Decoder {
private static final Charset DEFAULT_CHARSET = CharsetUtil.CHARSET_UTF_8;
private static final byte PADDING = -2;
/** Base64解码表，共128位，-1表示非base64字符，-2表示padding */
// private static final byte[] DECODE_TABLE2 = {
// -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
// -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
// -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
// 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -2, -1, -1,
// -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
// 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
// -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
// 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1 };
private static final byte[] DECODE_TABLE = {
// 0 1 2 3 4 5 6 7 8 9 A B C D E F
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 00-0f
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, // 10-1f
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, 62, -1, 63, // 20-2f + - /
52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -2, -1, -1, // 30-3f 0-9
-1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, // 40-4f A-O
15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, 63, // 50-5f P-Z _
-1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, // 60-6f a-o
41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51 // 70-7a p-z
};
/**
* base64解码
*
* @param source 被解码的base64字符串
* @return 被加密后的字符串
*/
public static String decodeStr(CharSequence source) {
return decodeStr(source, DEFAULT_CHARSET);
}
/**
* base64解码
*
* @param source 被解码的base64字符串
* @param charset 字符集
* @return 被加密后的字符串
*/
public static String decodeStr(CharSequence source, Charset charset) {
return StrUtil.str(decode(source), charset);
}
/**
* base64解码
*
* @param source 被解码的base64字符串
* @return 被加密后的字符串
*/
public static byte[] decode(CharSequence source) {
return decode(StrUtil.bytes(source, DEFAULT_CHARSET));
}
/**
* 解码Base64
*
* @param in 输入
* @return 解码后的bytes
*/
public static byte[] decode(byte[] in) {
if (ArrayUtil.isEmpty(in)) {
return in;
}
return decode(in, 0, in.length);
}
/**
* 解码Base64
*
* @param in 输入
* @param pos 开始位置
* @param length 长度
* @return 解码后的bytes
*/
public static byte[] decode(byte[] in, int pos, int length) {
if (ArrayUtil.isEmpty(in)) {
return in;
}
final IntWrapper offset = new IntWrapper(pos);
byte sestet0;
byte sestet1;
byte sestet2;
byte sestet3;
int maxPos = pos + length - 1;
int octetId = 0;
byte[] octet = new byte[length * 3 / 4]; // over-estimated if non-base64 characters present
while (offset.value <= maxPos) {
sestet0 = getNextValidDecodeByte(in, offset, maxPos);
sestet1 = getNextValidDecodeByte(in, offset, maxPos);
sestet2 = getNextValidDecodeByte(in, offset, maxPos);
sestet3 = getNextValidDecodeByte(in, offset, maxPos);
if (PADDING != sestet1) {
octet[octetId++] = (byte) ((sestet0 << 2) | (sestet1 >>> 4));
}
if (PADDING != sestet2) {
octet[octetId++] = (byte) (((sestet1 & 0xf) << 4) | (sestet2 >>> 2));
}
if (PADDING != sestet3) {
octet[octetId++] = (byte) (((sestet2 & 3) << 6) | sestet3);
}
}
if (octetId == octet.length) {
return octet;
} else {
// 如果有非Base64字符混入，则实际结果比解析的要短，截取之
return (byte[]) ArrayUtil.copy(octet, new byte[octetId], octetId);
}
}
// -----------------------------------------------------------------------------------------------
// Private start
/**
* 获取下一个有效的byte字符
*
* @param in 输入
* @param pos 当前位置，调用此方法后此位置保持在有效字符的下一个位置
* @param maxPos 最大位置
* @return 有效字符，如果达到末尾返回
*/
private static byte getNextValidDecodeByte(byte[] in, IntWrapper pos, int maxPos) {
byte base64Byte;
byte decodeByte;
while (pos.value <= maxPos) {
base64Byte = in[pos.value++];
if (base64Byte > -1) {
decodeByte = DECODE_TABLE[base64Byte];
if (decodeByte > -1) {
return decodeByte;
}
}
}
// padding if reached max position
return PADDING;
}
/**
* int包装，使之可变
*
* @author looly
*/
private static class IntWrapper {
int value;
IntWrapper(int value) {
this.value = value;
}
}
// -----------------------------------------------------------------------------------------------
// Private end
}