zoukankan      html  css  js  c++  java
  • base64 编解码

    http://www.eoeandroid.com/thread-26961-1-1.html

    private static final char[] legalChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".toCharArray();

    /** 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) & 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;
    }
    }

  • 相关阅读:
    一文了解Python中的判断语句
    想成为Python全栈开发工程师必须掌握的技能
    Python中变量的命名
    Python中变量的基本使用
    Java使用IO流读取TXT文件
    怎样用 I/O流读取txt文件?
    ORACLE数据库数据被修改或者删除恢复数据(闪回)
    字节流,读取 a.txt 文件内容,并打印出来
    使用js设置input标签只读 readonly 属性
    MyEclipse 选中属性或方法后 相同的不变色
  • 原文地址:https://www.cnblogs.com/ttssrs/p/2869904.html
Copyright © 2011-2022 走看看