下面基于Java实现的Base64的编码和解码程序:package com.gloomyfish.smtp.util; public class Base64Coder {
public final static char[] base64_alphabet = new char[]{ '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','+','/','=' };
public static String encode(String content) {
byte[] data = content.getBytes(); int length = data.length; byte[] char_array_3 = new byte[]{0, 0, 0}; byte[] char_array_4 = new byte[]{'=','=','=','='}; String retContent = ""; int i = 0; int j = 0; int reversePos = 0; while(length > 0) { length--; char_array_3[i++] = data[reversePos++]; if(i==3) { char_array_4[0] = (byte)((char_array_3[0] & 0xfc) >> 2); // convert the char char_array_4[1] = (byte)(((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4)); char_array_4[2] = (byte)(((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6)); char_array_4[3] = (byte)(char_array_3[2] & 0x3f); for(i = 0; (i <4) ; i++) retContent += base64_alphabet[char_array_4[i]]; i = 0; } }
// handling the last input content if (i > 0 ) { for(j = i; j < 3; j++) char_array_3[j] = 0; // padding of zero
for (j = 0; (j < i + 1); j++) retContent += base64_alphabet[char_array_4[j]];
while((i++ < 3)) // padding of '=' of output string retContent += '=';
} return retContent; }
public static String decode(String enContent) { byte[] data = enContent.getBytes(); int i = 0, j = 0, enCode = 0; int mLength = data.length; byte[] char_array_4 = new byte[4]; byte[] char_array_3 = new byte[3]; String retContent = "";
// filter out the padding '=' chars while (mLength > 0 && (((char)data[enCode]) != '=') && isBase64((char)data[enCode])) { mLength--; char_array_4[i++] = data[enCode++]; if (i ==4) { for (i = 0; i <4; i++) char_array_4[i] = findChar((char)char_array_4[i]);
public class Base64Coder {
public final static char[] base64_alphabet = new char[]{
'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','+','/','='
};
public static String encode(String content) {
byte[] data = content.getBytes();
int length = data.length;
byte[] char_array_3 = new byte[]{0, 0, 0};
byte[] char_array_4 = new byte[]{'=','=','=','='};
String retContent = "";
int i = 0;
int j = 0;
int reversePos = 0;
while(length > 0) {
length--;
char_array_3[i++] = data[reversePos++];
if(i==3) {
char_array_4[0] = (byte)((char_array_3[0] & 0xfc) >> 2); // convert the char
char_array_4[1] = (byte)(((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4));
char_array_4[2] = (byte)(((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6));
char_array_4[3] = (byte)(char_array_3[2] & 0x3f);
for(i = 0; (i <4) ; i++)
retContent += base64_alphabet[char_array_4[i]];
i = 0;
}
}
// handling the last input content
if (i > 0 )
{
for(j = i; j < 3; j++)
char_array_3[j] = 0; // padding of zero
char_array_4[0] = (byte)((char_array_3[0] & 0xfc) >> 2); // right shift
char_array_4[1] = (byte)(((char_array_3[0] & 0x03) << 4) + ((char_array_3[1] & 0xf0) >> 4));
char_array_4[2] = (byte)(((char_array_3[1] & 0x0f) << 2) + ((char_array_3[2] & 0xc0) >> 6));
char_array_4[3] = (byte)(char_array_3[2] & 0x3f);
for (j = 0; (j < i + 1); j++)
retContent += base64_alphabet[char_array_4[j]];
while((i++ < 3)) // padding of '=' of output string
retContent += '=';
}
return retContent;
}
public static String decode(String enContent) {
byte[] data = enContent.getBytes();
int i = 0, j = 0, enCode = 0;
int mLength = data.length;
byte[] char_array_4 = new byte[4];
byte[] char_array_3 = new byte[3];
String retContent = "";
// filter out the padding '=' chars
while (mLength > 0 && (((char)data[enCode]) != '=') && isBase64((char)data[enCode]))
{
mLength--;
char_array_4[i++] = data[enCode++];
if (i ==4) {
for (i = 0; i <4; i++)
char_array_4[i] = findChar((char)char_array_4[i]);
char_array_3[0] = (byte)((char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4));
char_array_3[1] = (byte)(((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2));
char_array_3[2] = (byte)(((char_array_4[2] & 0x3) << 6) + char_array_4[3]);
for (i = 0; (i < 3); i++)
retContent += (char)char_array_3[i];
i = 0;
}
}
// last content handling
if (i > 0)
{
for (j = i; j <4; j++)
char_array_4[j] = 0;
for (j = 0; j <4; j++)
char_array_4[j] = findChar((char)char_array_4[j]);
char_array_3[0] = (byte)((char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4));
char_array_3[1] = (byte)(((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2));
char_array_3[2] = (byte)(((char_array_4[2] & 0x3) << 6) + char_array_4[3]);
for (j = 0; (j < i - 1); j++)
retContent += (char)char_array_3[j];
}
return retContent;
}
public static boolean isBase64(char c)
{
boolean base64 = false;
for(int i=0; i<64; i++) {
if( c == base64_alphabet[i]) {
base64 = true;
break;
}
}
return base64;
}
public static byte findChar(char x) {
byte index = 64; // 65th char '='
for(int i=0; i<64; i++) {
if( x == base64_alphabet[i]) {
index = (byte)i;
break;
}
}
return index;
}
/**
* <p> test data and result should like below output , RFC4648 Sample </p>
* BASE64("") = ""
* BASE64("f") = "Zg=="
* BASE64("fo") = "Zm8="
* BASE64("foo") = "Zm9v"
* BASE64("foob") = "Zm9vYg=="
* BASE64("fooba") = "Zm9vYmE="
* BASE64("foobar") = "Zm9vYmFy"
*
*
* @param args
*/
public static void main(String[] args) {
// BASE64Encoder coder = new BASE64Encoder();
// System.out.println(coder.encode("foobar".getBytes()));
System.out.println("#--------------encode---------------#");
System.out.println(encode(""));
System.out.println(encode("f"));
System.out.println(encode("fo"));
System.out.println(encode("foo"));
System.out.println(encode("foob"));
System.out.println(encode("fooba"));
System.out.println(encode("foobar"));
System.out.println(encode("123456789sS{1}quot;));
System.out.println("#--------------decode---------------#");
System.out.println(decode(""));
System.out.println(decode("Zg=="));
System.out.println(decode("Zm8="));
System.out.println(decode("Zm9v"));
System.out.println(decode("Zm9vYg=="));
System.out.println(decode("Zm9vYmE="));
System.out.println(decode("Zm9vYmFy"));
System.out.println(decode("MTIzNDU2Nzg5c1Mk"));
}
}