编解码
BASE64
Base64 是网络上最常见的用于传输 8Bit 字节代码的编码方式之一，大家可以查看 RFC2045～RFC2049，上面有 MIME 的详细规范。Base64 编码可用于在 HTTP 环境下传递较长的标识信息。例如，在 Java Persistence 系统 Hibernate 中，就采用了 Base64 来将一个较长的唯一 标识符 （一般为 128-bit 的 UUID）编码为一个字符串，用作 HTTP 表单和 HTTP GET URL 中的参数。在其他 应用程序 中，也常常需要把二进制数据编码为适合放在 URL（包括隐藏表单域）中的形式。此时，采用 Base64 编码不仅比较简短，同时也具有不可读性，即所编码的数据不会被人用肉眼所直接看到。
RFC2045 还规定每行位 76 个字符，每行末尾需添加一个回车换行符，即便是最后一行不够 76 个字符，也要加换行符。
实现原理
Base64 是一种用 64 个字符来表示任意二进制数据的方法。
- 每 3 个 8 位二进制码位一组，转换为 4 个 6 位二进制码为一组（不足 6 位时地位补 0）。3 个 8 位二进制码和 4 个 6 位二进制码长度都是 24 位。
- 对获得的 4 个 6 位二进制码补位，每个 6 位二进制码添加两位高位 0，组成 4 个 8 位二进制码。
- 将获得的 4 个 8 位二进制码转换为 4 个十进制码。
- 将获得的十进制码转换为 Base64 字符表中对应的字符。
案例1： 字符串 "A"，进行 Base64 编码，如下所示：
| 过程 | 数据 |
|---|---|
| 字符 | A |
| ASCII 码 | 65 |
| 二进制码 | 01000001 |
| 4 个 6 位二进制码 | 010000 010000 |
| 4 个 8 位二进制码 | 00010000 00010000 |
| 十进制码 | 16 16 |
| 字符表映射码 | Q Q = = |
字符串 A 经过 Base64 编码后得到字符串 QQ==。
结果出现了两个等号。很显然，当原文的二进制码长度不足 24 位，最终转换为十进制时也不足 4 项，这时就需要用等号补位。
将 Base64 编码后的字符串最多会有 2 个等号，这时因为：
余数 = 原文字节数 MOD 3。
案例2： 字符串 " 密 "，对其使用 UTF-8 编码等到 Byte 数组{-27，-81，-122}，
| 过程 | 数据 |
|---|---|
| 字符 | 密 |
| UTF-8 编码 | -27 -81 -122 |
| 二进制码 | 11100101 10101111 10000110 |
| 4 个 6 位二进制码 | 111001 011010 111110 000110 |
| 4 个 8 位二进制码 | 00111001 00011010 00111110 00000110 |
| 十进制码 | 57 26 62 6 |
| 字符表映射码 | 5 a + G |
| 字符串 " 密 " 经过 Base64 编码后得到字符串 | 5a+G |
案例3：
| 过程 | 数据 |
|---|---|
| 数字 1 查 ASCII 码表 | 49 |
| 1 的二进制分成 3 个 8bit： | 00110001 00000000 00000000 |
| 分成 4 个 bit: | 001100 010000 000000 000000 |
| 前面补 00： | 00001100 00010000 00000000 00000000 |
| 查 BASE64 表对应的十进制值： | 12 16 = = |
| 最终值 | MQ== |
案例4： 字符 Man
| 过程 |
|---|
| M a n |
| 77 97 110 |
| 01001101 01100001 01101110 |
| 010011 010110 000101 101110 |
| 19 22 5 46 |
| T W F u |
BASE64 码表
ACII编码表
BASE64 实现
1、com.sun.misc API
1、com.sun.misc 包是 Sun 公司提供给内部使用的专用 API，在 java API 文档中我们看不到任何有关 BASE64 影子，不建议使用。
2、Apache 的实现： （建议使用这种方式，当然，自己实现也可以）
参考 org.apache.commons.codec.binary.Base64
下载地址： http://commons.apache.org/codec/download_codec.cgi
Apache 还提供了，非标准的实现方式：
1.不再添加回车符。
2.Url Base64,也就是将 "+" 和 "" 换成了 "-" 和 "_" 符号，且不适用补位。
3、Android 提供的 Base64
4、工具类，见下
Base64 工具类
Base64Util
package com.baidu.encryptdemo;
import java.io.UnsupportedEncodingException;
/**
* A Base64 Encoder/Decoder.
* <p/>
* This class is used to encode and decode data in Base64 format as described in RFC 1521.
* <p/>
* This is "Open Source" software and released under the
* <a href="http://www.gnu.org/licenses/lgpl.html">GNU/LGPL </a>
* license. <br>
* It is provided "as is" without warranty of any kind. <br>
* Copyright 2003: Christian d'Heureuse, Inventec Informatik AG, Switzerland.
* <br>
* Home page: <a href="http://www.source-code.biz">www.source-code.biz </a> <br>
* <p/>
* Original name <b>Base64Coder.java </b>
* <p/>
* Version history: <br>
* 2003-07-22 Christian d'Heureuse (chdh): Module created. <br>
* 2005-08-11 chdh: Lincense changed from GPL to LGPL. <br>
* 2006-11-21 chdh: <br>
* Method encode(String) renamed to encodeString(String). <br>
* Method decode(String) renamed to decodeString(String). <br>
* New method encode(byte[],int) added. <br>
* New method decode(String) added. <br>
* 2007-04-30 francis.naoum: Added to sfp_lib. <br>
* byte[] encode(byte[]) changed to return a String. <br>
*
* @author Francis Naoum
* @since 1.0.0
*/
public final class Base64Util {
/**
* Mapping table from 6-bit nibbles to Base64 characters.
*/
private static final char[] MAP1 = new char[64];
static {
int i = 0;
for (char c = 'A'; c <= 'Z'; c++) {
MAP1[i++] = c;
}
for (char c = 'a'; c <= 'z'; c++) {
MAP1[i++] = c;
}
for (char c = '0'; c <= '9'; c++) {
MAP1[i++] = c;
}
MAP1[i++] = '+';
MAP1[i++] = '/';
}
/**
* Mapping table from Base64 characters to 6-bit nibbles.
*/
private static final byte[] MAP2 = new byte[128];
static {
for (int i = 0; i < MAP2.length; i++) {
MAP2[i] = -1;
}
for (int i = 0; i < 64; i++) {
MAP2[MAP1[i]] = (byte) i;
}
}
/**
* Encodes a string into Base64 format. No blanks or line breaks are inserted.
*
* @param string a String to be encoded.
* @return A String with the Base64 encoded data.
*/
public static String encodeString(final String string) {
String encodedString = null;
try {
encodedString = encodeString(string, "UTF-8");
} catch (UnsupportedEncodingException uue) {
// Should never happen, java has to support "UTF-8".
}
return encodedString;
}
/**
* Encodes a string into Base64 format. No blanks or line breaks are inserted.
*
* @param string a String to be encoded.
* @param encoding The character encoding of the string.
* @return A String with the Base64 encoded data.
* @throws UnsupportedEncodingException if the java runtime does not support <code>encoding</code>.
*/
public static String encodeString(final String string, final String encoding) throws
UnsupportedEncodingException {
byte[] stringBytes = string.getBytes(encoding);
return encode(stringBytes);
}
/**
* Encodes a byte array into Base64 format. No blanks or line breaks are inserted.
* <p/>
* This method has been modified to return a string not a char[].
*
* @param input an array containing the data bytes to be encoded.
* @return A character array with the Base64 encoded data.
*/
public static String encode(final byte[] input) {
char[] chars = encode(input, input.length);
return new String(chars);
}
/**
* Encodes a byte array into Base64 format. No blanks or line breaks are inserted.
*
* @param input an array containing the data bytes to be encoded.
* @param iLen number of bytes to process in <code>in</code>.
* @return A character array with the Base64 encoded data.
*/
public static char[] encode(final byte[] input, final int iLen) {
int oDataLen = (iLen * 4 + 2) / 3; // output length without padding
int oLen = ((iLen + 2) / 3) * 4; // output length including padding
char[] out = new char[oLen];
int ip = 0;
int op = 0;
while (ip < iLen) {
int i0 = input[ip++] & 0xff;
int i1 = ip < iLen ? input[ip++] & 0xff : 0;
int i2 = ip < iLen ? input[ip++] & 0xff : 0;
int o0 = i0 >>> 2;
int o1 = ((i0 & 3) << 4) | (i1 >>> 4);
int o2 = ((i1 & 0xf) << 2) | (i2 >>> 6);
int o3 = i2 & 0x3F;
out[op++] = MAP1[o0];
out[op++] = MAP1[o1];
out[op] = op < oDataLen ? MAP1[o2] : '=';
op++;
out[op] = op < oDataLen ? MAP1[o3] : '=';
op++;
}
return out;
}
/**
* Decodes a string from Base64 format.
*
* @param string a Base64 String to be decoded.
* @return A String containing the decoded data.
* @throws IllegalArgumentException if the input is not valid Base64 encoded data.
*/
public static String decodeString(final String string) {
String decodedString = null;
try {
byte[] decodedBytes = decode(string);
decodedString = new String(decodedBytes, "UTF-8");
} catch (UnsupportedEncodingException uue) {
// Should never happen, java has to support "UTF-8".
}
return decodedString;
}
/**
* Decodes a byte array from Base64 format.
*
* @param string a Base64 String to be decoded.
* @return An array containing the decoded data bytes.
* @throws IllegalArgumentException if the input is not valid Base64 encoded data.
*/
public static byte[] decode(final String string) {
return decode(string.toCharArray());
}
/**
* Decodes a byte array from Base64 format. No blanks or line breaks are allowed within the Base64 encoded data.
*
* @param input a character array containing the Base64 encoded data.
* @return An array containing the decoded data bytes.
* @throws IllegalArgumentException if the input is not valid Base64 encoded data.
*/
public static byte[] decode(final char[] input) {
int iLen = input.length;
if (iLen % 4 != 0) {
throw new IllegalArgumentException(
"Length of Base64 encoded input string is not a multiple of 4.");
}
while (iLen > 0 && input[iLen - 1] == '=') {
iLen--;
}
int oLen = (iLen * 3) / 4;
byte[] out = new byte[oLen];
int ip = 0;
int op = 0;
while (ip < iLen) {
int i0 = input[ip++];
int i1 = input[ip++];
int i2 = ip < iLen ? input[ip++] : 'A';
int i3 = ip < iLen ? input[ip++] : 'A';
if (i0 > 127 || i1 > 127 || i2 > 127 || i3 > 127) {
throw new IllegalArgumentException("Illegal character in Base64 encoded data.");
}
int b0 = MAP2[i0];
int b1 = MAP2[i1];
int b2 = MAP2[i2];
int b3 = MAP2[i3];
if (b0 < 0 || b1 < 0 || b2 < 0 || b3 < 0) {
throw new IllegalArgumentException("Illegal character in Base64 encoded data.");
}
int o0 = (b0 << 2) | (b1 >>> 4);
int o1 = ((b1 & 0xf) << 4) | (b2 >>> 2);
int o2 = ((b2 & 3) << 6) | b3;
out[op++] = (byte) o0;
if (op < oLen) {
out[op++] = (byte) o1;
}
if (op < oLen) {
out[op++] = (byte) o2;
}
}
return out;
}
/**
* Dummy constructor.
*/
private Base64Util() {
}
}
BdBase64Util
package com.baidu.encryptdemo;
import java.io.UnsupportedEncodingException;
/***
* Utilities for encoding and decoding the Base64 representation of binary data. See RFCs <a
* href="http://www.ietf.org/rfc/rfc2045.txt">2045</a> and <a href="http://www.ietf.org/rfc/rfc3548.txt">3548</a>.
*/
public class BdBase64Util {
/***
* Default values for encoder/decoder flags.
*/
public static final int DEFAULT = 0;
/***
* Encoder flag bit to omit the padding '=' characters at the end of the output (if any).
*/
public static final int NO_PADDING = 1;
/***
* Encoder flag bit to omit all line terminators (i.e., the output will be on one long line).
*/
public static final int NO_WRAP = 2;
/***
* Encoder flag bit to indicate lines should be terminated with a CRLF pair instead of just an LF. Has no effect if
* {@code NO_WRAP} is specified as well.
*/
public static final int CRLF = 4;
/***
* Encoder/decoder flag bit to indicate using the "URL and filename safe" variant of Base64 (see RFC 3548 section 4)
* where {@code -} and {@code _} are used in place of {@code +} and {@code /}.
*/
public static final int URL_SAFE = 8;
/***
* Flag to pass to {@link Base64OutputStream} to indicate that it should not close the output stream it is wrapping
* when it itself is closed.
*/
public static final int NO_CLOSE = 16;
static abstract class Coder {
public byte[] output;
public int op;
/***
* Encode/decode another block of input data. this.output is provided by the caller, and must be big enough to
* hold all the coded data. On exit, this.opwill be set to the length of the coded data.
*
* @param finish true if this is the final call to process for this object. Will finalize the coder state and
* include any final bytes in the output.
* @return true if the input so far is good; false if some error has been detected in the input stream..
*/
public abstract boolean process(byte[] input, int offset, int len, boolean finish);
/***
* @return the maximum number of bytes a call to process() could produce for the given number of input bytes.
* This may be an overestimate.
*/
public abstract int maxOutputSize(int len);
}
/***
* Decode the Base64-encoded data in input and return the data in a new byte array.
* <p/>
* <p/>
* The padding '=' characters at the end are considered optional, but if any are present, there must be the correct
* number of them.
*
* @param str the input String to decode, which is converted to bytes using the default charset
* @throws IllegalArgumentException if the input contains incorrect padding
*/
public static byte[] decode(String str) {
return decode(str.getBytes(), DEFAULT);
}
/***
* Decode the Base64-encoded data in input and return the data in a new byte array.
* <p/>
* <p/>
* The padding '=' characters at the end are considered optional, but if any are present, there must be the correct
* number of them.
*
* @param str the input String to decode, which is converted to bytes using the default charset
* @param flags controls certain features of the decoded output. Pass {@code DEFAULT} to decode standard Base64.
* @throws IllegalArgumentException if the input contains incorrect padding
*/
public static byte[] decode(String str, int flags) {
return decode(str.getBytes(), flags);
}
/***
* Decode the Base64-encoded data in input and return the data in a new byte array.
* <p/>
* <p/>
* The padding '=' characters at the end are considered optional, but if any are present, there must be the correct
* number of them.
*
* @param input the input array to decode
* @throws IllegalArgumentException if the input contains incorrect padding
*/
public static byte[] decode(byte[] input) {
return decode(input, 0, input.length, DEFAULT);
}
/***
* Decode the Base64-encoded data in input and return the data in a new byte array.
* <p/>
* <p/>
* The padding '=' characters at the end are considered optional, but if any are present, there must be the correct
* number of them.
*
* @param input the input array to decode
* @param flags controls certain features of the decoded output. Pass {@code DEFAULT} to decode standard Base64.
* @throws IllegalArgumentException if the input contains incorrect padding
*/
public static byte[] decode(byte[] input, int flags) {
return decode(input, 0, input.length, flags);
}
/***
* Decode the Base64-encoded data in input and return the data in a new byte array.
* <p/>
* <p/>
* The padding '=' characters at the end are considered optional, but if any are present, there must be the correct
* number of them.
*
* @param input the data to decode
* @param offset the position within the input array at which to start
* @param len the number of bytes of input to decode
* @param flags controls certain features of the decoded output. Pass {@code DEFAULT} to decode standard Base64.
* @throws IllegalArgumentException if the input contains incorrect padding
*/
public static byte[] decode(byte[] input, int offset, int len, int flags) {
// Allocate space for the most data the input could represent.
// (It could contain less if it contains whitespace, etc.)
Decoder decoder = new Decoder(flags, new byte[len * 3 / 4]);
if (!decoder.process(input, offset, len, true)) {
throw new IllegalArgumentException("bad base-64");
}
// Maybe we got lucky and allocated exactly enough output space.
if (decoder.op == decoder.output.length) {
return decoder.output;
}
// Need to shorten the array, so allocate a new one of the
// right size and copy.
byte[] temp = new byte[decoder.op];
System.arraycopy(decoder.output, 0, temp, 0, decoder.op);
return temp;
}
static class Decoder extends Coder {
/***
* Lookup table for turning bytes into their position in the Base64 alphabet.
*/
private static final int DECODE[] = {-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, -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, -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, -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,};
/***
* Decode lookup table for the "web safe" variant (RFC 3548 sec. 4) where - and _ replace + and /.
*/
private static final int DECODE_WEBSAFE[] = {-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, -1, -1, 62, -1, -1, 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, 63,
-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, -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, -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, -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,};
/***
* Non-data values in the DECODE arrays.
*/
private static final int SKIP = -1;
private static final int EQUALS = -2;
/***
* States 0-3 are reading through the next input tuple. State 4 is having read one '=' and expecting exactly one
* more. State 5 is expecting no more data or padding characters in the input. State 6 is the error state; an
* error has been detected in the input and no future input can "fix" it.
*/
private int state; // state number (0 to 6)
private int value;
final private int[] alphabet;
public Decoder(int flags, byte[] output) {
this.output = output;
alphabet = ((flags & URL_SAFE) == 0) ? DECODE : DECODE_WEBSAFE;
state = 0;
value = 0;
}
/***
* @return an overestimate for the number of bytes {@code len} bytes could decode to.
*/
public int maxOutputSize(int len) {
return len * 3 / 4 + 10;
}
/***
* Decode another block of input data.
*
* @return true if the state machine is still healthy. false if bad base-64 data has been detected in the input
* stream.
*/
public boolean process(byte[] input, int offset, int len, boolean finish) {
if (this.state == 6)
return false;
int p = offset;
len += offset;
// Using local variables makes the decoder about 12%
// faster than if we manipulate the member variables in
// the loop. (Even alphabet makes a measurable
// difference, which is somewhat surprising to me since
// the member variable is final.)
int state = this.state;
int value = this.value;
int op = 0;
final byte[] output = this.output;
final int[] alphabet = this.alphabet;
while (p < len) {
// Try the fast path: we're starting a new tuple and the
// next four bytes of the input stream are all data
// bytes. This corresponds to going through states
// 0-1-2-3-0. We expect to use this method for most of
// the data.
//
// If any of the next four bytes of input are non-data
// (whitespace, etc.), value will end up negative. (All
// the non-data values in decode are small negative
// numbers, so shifting any of them up and or'ing them
// together will result in a value with its top bit set.)
//
// You can remove this whole block and the output should
// be the same, just slower.
if (state == 0) {
while (p + 4 <= len
&& (value =
((alphabet[input[p] & 0xff] << 18) | (alphabet[input[p + 1] & 0xff] << 12)
| (alphabet[input[p + 2] & 0xff] << 6) | (alphabet[input[p + 3] & 0xff]))) >= 0) {
output[op + 2] = (byte) value;
output[op + 1] = (byte) (value >> 8);
output[op] = (byte) (value >> 16);
op += 3;
p += 4;
}
if (p >= len)
break;
}
// The fast path isn't available -- either we've read a
// partial tuple, or the next four input bytes aren't all
// data, or whatever. Fall back to the slower state
// machine implementation.
int d = alphabet[input[p++] & 0xff];
switch (state) {
case 0:
if (d >= 0) {
value = d;
++state;
} else if (d != SKIP) {
this.state = 6;
return false;
}
break;
case 1:
if (d >= 0) {
value = (value << 6) | d;
++state;
} else if (d != SKIP) {
this.state = 6;
return false;
}
break;
case 2:
if (d >= 0) {
value = (value << 6) | d;
++state;
} else if (d == EQUALS) {
// Emit the last (partial) output tuple;
// expect exactly one more padding character.
output[op++] = (byte) (value >> 4);
state = 4;
} else if (d != SKIP) {
this.state = 6;
return false;
}
break;
case 3:
if (d >= 0) {
// Emit the output triple and return to state 0.
value = (value << 6) | d;
output[op + 2] = (byte) value;
output[op + 1] = (byte) (value >> 8);
output[op] = (byte) (value >> 16);
op += 3;
state = 0;
} else if (d == EQUALS) {
// Emit the last (partial) output tuple;
// expect no further data or padding characters.
output[op + 1] = (byte) (value >> 2);
output[op] = (byte) (value >> 10);
op += 2;
state = 5;
} else if (d != SKIP) {
this.state = 6;
return false;
}
break;
case 4:
if (d == EQUALS) {
++state;
} else if (d != SKIP) {
this.state = 6;
return false;
}
break;
case 5:
if (d != SKIP) {
this.state = 6;
return false;
}
break;
}
}
if (!finish) {
// We're out of input, but a future call could provide
// more.
this.state = state;
this.value = value;
this.op = op;
return true;
}
// Done reading input. Now figure out where we are left in
// the state machine and finish up.
switch (state) {
case 0:
// Output length is a multiple of three. Fine.
break;
case 1:
// Read one extra input byte, which isn't enough to
// make another output byte. Illegal.
this.state = 6;
return false;
case 2:
// Read two extra input bytes, enough to emit 1 more
// output byte. Fine.
output[op++] = (byte) (value >> 4);
break;
case 3:
// Read three extra input bytes, enough to emit 2 more
// output bytes. Fine.
output[op++] = (byte) (value >> 10);
output[op++] = (byte) (value >> 2);
break;
case 4:
// Read one padding '=' when we expected 2. Illegal.
this.state = 6;
return false;
case 5:
// Read all the padding '='s we expected and no more.
// Fine.
break;
}
this.state = state;
this.op = op;
return true;
}
}
/***
* Base64-encode the given data and return a newly allocated String with the result.
*
* @param input the data to encode
*/
public static String encodeToString(byte[] input) {
try {
return new String(encode(input, DEFAULT), "US-ASCII");
} catch (UnsupportedEncodingException e) {
// US-ASCII is guaranteed to be available.
throw new AssertionError(e);
}
}
/***
* Base64-encode the given data and return a newly allocated String with the result.
*
* @param input the data to encode
* @param flags controls certain features of the encoded output. Passing {@code DEFAULT} results in output that
* adheres to RFC 2045.
*/
public static String encodeToString(byte[] input, int flags) {
try {
return new String(encode(input, flags), "US-ASCII");
} catch (UnsupportedEncodingException e) {
// US-ASCII is guaranteed to be available.
throw new AssertionError(e);
}
}
/***
* Base64-encode the given data and return a newly allocated String with the result.
*
* @param input the data to encode
* @param offset the position within the input array at which to start
* @param len the number of bytes of input to encode
* @param flags controls certain features of the encoded output. Passing {@code DEFAULT} results in output that
* adheres to RFC 2045.
*/
public static String encodeToString(byte[] input, int offset, int len, int flags) {
try {
return new String(encode(input, offset, len, flags), "US-ASCII");
} catch (UnsupportedEncodingException e) {
// US-ASCII is guaranteed to be available.
throw new AssertionError(e);
}
}
/***
* Base64-encode the given data and return a newly allocated byte[] with the result.
*
* @param input the data to encode
*/
public static byte[] encode(byte[] input) {
return encode(input, 0, input.length, DEFAULT);
}
/***
* Base64-encode the given data and return a newly allocated byte[] with the result.
*
* @param input the data to encode
* @param flags controls certain features of the encoded output. Passing {@code DEFAULT} results in output that
* adheres to RFC 2045.
*/
public static byte[] encode(byte[] input, int flags) {
return encode(input, 0, input.length, flags);
}
/***
* Base64-encode the given data and return a newly allocated byte[] with the result.
*
* @param input the data to encode
* @param offset the position within the input array at which to start
* @param len the number of bytes of input to encode
* @param flags controls certain features of the encoded output. Passing {@code DEFAULT} results in output that
* adheres to RFC 2045.
*/
public static byte[] encode(byte[] input, int offset, int len, int flags) {
Encoder encoder = new Encoder(flags, null);
// Compute the exact length of the array we will produce.
int output_len = len / 3 * 4;
// Account for the tail of the data and the padding bytes, if any.
if (encoder.do_padding) {
if (len % 3 > 0) {
output_len += 4;
}
} else {
switch (len % 3) {
case 0:
break;
case 1:
output_len += 2;
break;
case 2:
output_len += 3;
break;
}
}
// Account for the newlines, if any.
if (encoder.do_newline && len > 0) {
output_len += (((len - 1) / (3 * Encoder.LINE_GROUPS)) + 1) * (encoder.do_cr ? 2 : 1);
}
encoder.output = new byte[output_len];
encoder.process(input, offset, len, true);
assert encoder.op == output_len;
return encoder.output;
}
static class Encoder extends Coder {
/***
* Emit a new line every this many output tuples. Corresponds to a 76-character line length (the maximum
* allowable according to <a href="http://www.ietf.org/rfc/rfc2045.txt">RFC 2045</a>).
*/
public static final int LINE_GROUPS = 19;
/***
* Lookup table for turning Base64 alphabet positions (6 bits) into output bytes.
*/
private static final byte ENCODE[] = {'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', '+', '/',};
/***
* Lookup table for turning Base64 alphabet positions (6 bits) into output bytes.
*/
private static final byte ENCODE_WEBSAFE[] = {'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', '-', '_',};
final private byte[] tail;
int tailLen;
private int count;
final public boolean do_padding;
final public boolean do_newline;
final public boolean do_cr;
final private byte[] alphabet;
public Encoder(int flags, byte[] output) {
this.output = output;
do_padding = (flags & NO_PADDING) == 0;
do_newline = (flags & NO_WRAP) == 0;
do_cr = (flags & CRLF) != 0;
alphabet = ((flags & URL_SAFE) == 0) ? ENCODE : ENCODE_WEBSAFE;
tail = new byte[2];
tailLen = 0;
count = do_newline ? LINE_GROUPS : -1;
}
/***
* @return an overestimate for the number of bytes {@code len} bytes could encode to.
*/
public int maxOutputSize(int len) {
return len * 8 / 5 + 10;
}
public boolean process(byte[] input, int offset, int len, boolean finish) {
// Using local variables makes the encoder about 9% faster.
final byte[] alphabet = this.alphabet;
final byte[] output = this.output;
int op = 0;
int count = this.count;
int p = offset;
len += offset;
int v = -1;
// First we need to concatenate the tail of the previous call
// with any input bytes available now and see if we can empty
// the tail.
switch (tailLen) {
case 0:
// There was no tail.
break;
case 1:
if (p + 2 <= len) {
// A 1-byte tail with at least 2 bytes of
// input available now.
v = ((tail[0] & 0xff) << 16) | ((input[p++] & 0xff) << 8) | (input[p++] & 0xff);
tailLen = 0;
}
;
break;
case 2:
if (p + 1 <= len) {
// A 2-byte tail with at least 1 byte of input.
v = ((tail[0] & 0xff) << 16) | ((tail[1] & 0xff) << 8) | (input[p++] & 0xff);
tailLen = 0;
}
break;
}
if (v != -1) {
output[op++] = alphabet[(v >> 18) & 0x3f];
output[op++] = alphabet[(v >> 12) & 0x3f];
output[op++] = alphabet[(v >> 6) & 0x3f];
output[op++] = alphabet[v & 0x3f];
if (--count == 0) {
if (do_cr)
output[op++] = '\r';
output[op++] = '\n';
count = LINE_GROUPS;
}
}
// At this point either there is no tail, or there are fewer
// than 3 bytes of input available.
// The main loop, turning 3 input bytes into 4 output bytes on
// each iteration.
while (p + 3 <= len) {
v = ((input[p] & 0xff) << 16) | ((input[p + 1] & 0xff) << 8) | (input[p + 2] & 0xff);
output[op] = alphabet[(v >> 18) & 0x3f];
output[op + 1] = alphabet[(v >> 12) & 0x3f];
output[op + 2] = alphabet[(v >> 6) & 0x3f];
output[op + 3] = alphabet[v & 0x3f];
p += 3;
op += 4;
if (--count == 0) {
if (do_cr)
output[op++] = '\r';
output[op++] = '\n';
count = LINE_GROUPS;
}
}
if (finish) {
// Finish up the tail of the input. Note that we need to
// consume any bytes in tail before any bytes
// remaining in input; there should be at most two bytes
// total.
if (p - tailLen == len - 1) {
int t = 0;
v = ((tailLen > 0 ? tail[t++] : input[p++]) & 0xff) << 4;
tailLen -= t;
output[op++] = alphabet[(v >> 6) & 0x3f];
output[op++] = alphabet[v & 0x3f];
if (do_padding) {
output[op++] = '=';
output[op++] = '=';
}
if (do_newline) {
if (do_cr)
output[op++] = '\r';
output[op++] = '\n';
}
} else if (p - tailLen == len - 2) {
int t = 0;
v =
(((tailLen > 1 ? tail[t++] : input[p++]) & 0xff) << 10)
| (((tailLen > 0 ? tail[t++] : input[p++]) & 0xff) << 2);
tailLen -= t;
output[op++] = alphabet[(v >> 12) & 0x3f];
output[op++] = alphabet[(v >> 6) & 0x3f];
output[op++] = alphabet[v & 0x3f];
if (do_padding) {
output[op++] = '=';
}
if (do_newline) {
if (do_cr)
output[op++] = '\r';
output[op++] = '\n';
}
} else if (do_newline && op > 0 && count != LINE_GROUPS) {
if (do_cr)
output[op++] = '\r';
output[op++] = '\n';
}
assert tailLen == 0;
assert p == len;
} else {
// Save the leftovers in tail to be consumed on the next
// call to encodeInternal.
if (p == len - 1) {
tail[tailLen++] = input[p];
} else if (p == len - 2) {
tail[tailLen++] = input[p];
tail[tailLen++] = input[p + 1];
}
}
this.op = op;
this.count = count;
return true;
}
}
private BdBase64Util() {
} // don't instantiate
}
JDK8.x 和 common codec 中对 Base64 算法的实现
public class Base64Util {
public static String jdkBase64Encode(String src) {
return Base64.getEncoder().encodeToString(src.getBytes());
}
public static String jdkBase64Decode(String src) {
return new String(Base64.getDecoder().decode(src));
}
public static String codecBase64Encode(String src) {
return org.apache.commons.codec.binary.Base64.encodeBase64String(src.getBytes());
}
public static String codecBase64Decode(String src) {
return new String(org.apache.commons.codec.binary.Base64.decodeBase64(src));
}
}