J2ME版本Base64算法实现

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，在发送电子邮件时，服务器认证的用户名和密码需要用Base64编码，附件也需要用Base64编码……

下面是以前扒来的Base64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. cat)
     * @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[i]) & 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[i]) & 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[i]) & 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;
        }
    }
}