Base64內容傳送編碼被設計用來把任意序列的8位字節描述為一種不易被人直接識別的形式。（The Base64 Content-Transfer-Encoding is designed to represent arbitrary sequences of octets in a form that need not be humanly readable.）
Base64是網絡上最常見的用於傳輸8Bit字節代碼的編碼方式之一，在發送電子郵件時，服務器認證的用戶名和密碼需要用Base64編碼，附件也需要用Base64編碼……
下面是以前扒來的MD5算法的Java版本，J2ME可以放心使用。
package hlib;
import Java.io.ByteArrayOutputStream;
import Java.io.IOException;
import Java.io.OutputStream;
import Java.util.Vector;
public class HBase64 {
private static final char[] legalChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
.toCharArray();
private static Vector nodes = new Vector();
/**
* Split string into multiple strings
*
* @param original
* Original string
* @param separator
* Separator string in original string
* @return Splitted string array
*/
public static String[] split(String original, String separator) {
nodes.removeAllElements();
// Parse nodes into vector
int index = original.indexOf(separator);
while (index >= 0) {
nodes.addElement(original.substring(0, index));
original = original.substring(index + separator.length());
index = original.indexOf(separator);
}
// Get the last node
nodes.addElement(original);
// Create splitted string array
String[] result = new String[nodes.size()];
if (nodes.size() > 0) {
for (int loop = 0; loop < nodes.size(); loop++)
result[loop] = (String) nodes.elementAt(loop);
}
return result;
}
/*
* Replace all instances of a String in a String. @param s String to alter.
* @param f String to look for. @param r String to replace it with, or null
* to just remove it.
*/
public static String replace(String s, String f, String r) {
if (s == null)
return s;
if (f == null)
return s;
if (r == null)
r = "";
int index01 = s.indexOf(f);
while (index01 != -1) {
s = s.substring(0, index01) + r + s.substring(index01 + f.length());
index01 += r.length();
index01 = s.indexOf(f, index01);
}
return s;
}
/**
* Method removes Html tags from given string.
*
* @param text
* Input parameter containing Html tags (eg. <b>cat</b>)
* @return String without Html tags (eg. cat)
*/
public static String removeHtml(String text) {
try {
int idx = text.indexOf("<");
if (idx == -1)
return text;
String plainText = "";
String HtmlText = text;
int htmlStartIndex = HtmlText.indexOf("<", 0);
if (HtmlStartIndex == -1) {
return text;
}
while (HtmlStartIndex >= 0) {
plainText += htmlText.substring(0, HtmlStartIndex);
int htmlEndIndex = htmlText.indexOf(">", HtmlStartIndex);
htmlText = htmlText.substring(HtmlEndIndex + 1);
htmlStartIndex = HtmlText.indexOf("<", 0);
}
plainText = plainText.trim();
return plainText;
} catch (Exception e) {
System.err.println("Error while removing Html: " + e.toString());
return text;
}
}
/** Base64 encode the given data */
public static String encode(byte[] data) {
int start = 0;
int len = data.length;
StringBuffer buf = new StringBuffer(data.length * 3 / 2);
int end = len - 3;
int i = start;
int n = 0;
while (i <= end) {
int d = ((((int) data) & 0x0ff) << 16)
| ((((int) data[i + 1]) & 0x0ff) << 8)
| (((int) data[i + 2]) & 0x0ff);
buf.append(legalChars[(d >> 18) & 63]);
buf.append(legalChars[(d >> 12) & 63]);
buf.append(legalChars[(d >> 6) & 63]);
buf.append(legalChars[d & 63]);
i += 3;
if (n++ >= 14) {
n = 0;
buf.append(" ");
}
}
if (i == start + len - 2) {
int d = ((((int) data) & 0x0ff) << 16)
| ((((int) data[i + 1]) & 255) << 8);
buf.append(legalChars[(d >> 18) & 63]);
buf.append(legalChars[(d >> 12) & 63]);
buf.append(legalChars[(d >> 6) & 63]);
buf.append("=");
} else if (i == start + len - 1) {
int d = (((int) data) & 0x0ff) << 16;
buf.append(legalChars[(d >> 18) & 63]);
buf.append(legalChars[(d >> 12) & 63]);
buf.append("==");
}
return buf.toString();
}
private static int decode(char c) {
if (c >= 'A' && c <= 'Z')
return ((int) c) - 65;
else if (c >= 'a' && c <= 'z')
return ((int) c) - 97 + 26;
else if (c >= '0' && c <= '9')
return ((int) c) - 48 + 26 + 26;
else
switch (c) {
case '+':
return 62;
case '/':
return 63;
case '=':
return 0;
default:
throw new RuntimeException("unexpected code: " + c);
}
}
/**
* Decodes the given Base64 encoded String to a new byte array. The byte
* array holding the decoded data is returned.
*/
public static byte[] decode(String s) {
ByteArrayOutputStream bos = new ByteArrayOutputStream();
try {
decode(s, bos);
} catch (IOException e) {
throw new RuntimeException();
}
byte[] decodedBytes = bos.toByteArray();
try {
bos.close();
bos = null;
} catch (IOException ex) {
System.err.println("Error while decoding BASE64: " + ex.toString());
}
return decodedBytes;
}
private static void decode(String s, OutputStream os) throws IOException {
int i = 0;
int len = s.length();
while (true) {
while (i < len && s.charAt(i) <= ' ')
i++;
if (i == len)
break;
int tri = (decode(s.charAt(i)) << 18)
+ (decode(s.charAt(i + 1)) << 12)
+ (decode(s.charAt(i + 2)) << 6)
+ (decode(s.charAt(i + 3)));
os.write((tri >> 16) & 255);
if (s.charAt(i + 2) == '=')
break;
os.write((tri >> 8) & 255);
if (s.charAt(i + 3) == '=')
break;
os.write(tri & 255);
i += 4;
}
}
}
