网络——Base64Encode（转：自定义Base64编码器——Base64Encode）

来源：互联网发布：江西广电网络宽带投诉编辑：程序博客网时间：2024/06/02 05:30

【0】README

0.1） 本文source code 转自 core java volume 2 ，旨在了解如何定义一个编码器，如Base64Encode ；

0.2）注意： 区别自定义的 Base64Encode 和 java.util.Base64 编码器

0.3）for souce code, please visit 自定义 Base64Encode 源代码

【1】 Base64Encode 编码器源代码如下：

package com.corejava.chapter3;import java.io.ByteArrayOutputStream;import java.io.FilterOutputStream;import java.io.IOException;import java.io.OutputStream;public class Base64Encode{/**    * Computes the Base64 encoding of a string.    * @param s a string    * @return the Base64 encoding of s    */   public static String base64Encode(String s)   {      ByteArrayOutputStream bOut = new ByteArrayOutputStream();      Base64OutputStream out = new Base64OutputStream(bOut);      try      {         out.write(s.getBytes());         out.flush();      }      catch (IOException e)      {      }      return bOut.toString();   }}/** * This stream filter converts a stream of bytes to their Base64 encoding. *  * Base64 encoding encodes 3 bytes into 4 characters. |11111122|22223333|33444444| Each set of 6 * bits is encoded according to the toBase64 map. If the number of input bytes is not a multiple of * 3, then the last group of 4 characters is padded with one or two = signs. Each output line is at * most 76 characters. */class Base64OutputStream extends FilterOutputStream{   private static char[] toBase64 = { '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', '+', '/' };   private int col = 0;   private int i = 0;   private int[] inbuf = new int[3];   /**    * Constructs the stream filter.    * @param out the stream to filter    */   public Base64OutputStream(OutputStream out)   {      super(out);   }   public void write(int c) throws IOException   {      inbuf[i] = c;      i++;      if (i == 3)      {         if (col >= 76)         {            super.write('\n');            col = 0;         }         super.write(toBase64[(inbuf[0] & 0xFC) >> 2]);         super.write(toBase64[((inbuf[0] & 0x03) << 4) | ((inbuf[1] & 0xF0) >> 4)]);         super.write(toBase64[((inbuf[1] & 0x0F) << 2) | ((inbuf[2] & 0xC0) >> 6)]);         super.write(toBase64[inbuf[2] & 0x3F]);         col += 4;         i = 0;      }   }   public void flush() throws IOException   {      if (i > 0 && col >= 76)      {         super.write('\n');         col = 0;      }      if (i == 1)      {         super.write(toBase64[(inbuf[0] & 0xFC) >> 2]);         super.write(toBase64[(inbuf[0] & 0x03) << 4]);         super.write('=');         super.write('=');      }      else if (i == 2)      {         super.write(toBase64[(inbuf[0] & 0xFC) >> 2]);         super.write(toBase64[((inbuf[0] & 0x03) << 4) | ((inbuf[1] & 0xF0) >> 4)]);         super.write(toBase64[(inbuf[1] & 0x0F) << 2]);         super.write('=');      }   }}

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