package com.jcomeau;
public class Base64 {
 public static String base64code = 
  "ABCDEFGHIJKLMNOPQRSTUVWXYZ" +
  "abcdefghijklmnopqrstuvwxyz" + "0123456789" + "+/";
 public static int splitLinesAt = 76;
 public static String encode(String string) {
  String encoded = "";
  byte[] stringArray;
  try {
   stringArray = string.getBytes("UTF-8");  // necessary for wchars
  } catch (Exception ignored) {
   stringArray = string.getBytes(); // use default locale
  }
  // determine how many padding bytes to add to the output
  int paddingCount = (3 - (stringArray.length % 3)) % 3;
  // add any necessary padding to the input
  stringArray = zeroPad(stringArray.length + paddingCount, stringArray);
  // process 3 bytes at a time, churning out 4 output bytes
  // worry about CRLF insertions later
  for (int i = 0; i < stringArray.length; i += 3) {
   int j = (stringArray[i] << 16) + (stringArray[i + 1] << 8) +
    stringArray[i + 2];
   encoded = encoded + base64code.charAt((j >> 18) & 0x3f) +
    base64code.charAt((j >> 12) & 0x3f) +
    base64code.charAt((j >> 6) & 0x3f) + 
    base64code.charAt(j & 0x3f);
  }
  // replace encoded padding nulls with "="
  return splitLines(encoded.substring(0, encoded.length() - paddingCount) +
   "==".substring(0, paddingCount));
 }
 public static byte[] zeroPad(int length, byte[] bytes) {
  byte[] padded = new byte[length]; // initialized to zero by JVM
  System.arraycopy(bytes, 0, padded, 0, bytes.length);
  return padded;
 }
 public static byte[] appendBytes(byte[] byteArray1, byte[] byteArray2) {
  byte[] arraySum = new byte[byteArray1.length + byteArray2.length];
  System.arraycopy(byteArray1, 0, arraySum, 0, byteArray1.length);
  System.arraycopy(byteArray2, 0, arraySum, byteArray1.length,
   byteArray2.length);
  return arraySum;
 }
 public static String splitLines(String string) {
  String lines = "";
  for (int i = 0; i < string.length(); i += splitLinesAt) {
   lines += string.substring(i, Math.min(string.length(), i + splitLinesAt));
   lines += "\r\n";
  }
  return lines;
 }
 public static String filterOut(String chars, String target) {
  int index;
  for (int i = 0; i < chars.length(); i++) {
   while ((index = target.indexOf(chars.charAt(i))) >= 0) {
    target = target.substring(0, index) + target.substring(index + 1);
   }
  }
  return target;
 } 
 public static String decode(String encoded) {
  int paddingCount = 0, extra = 0;
  String decoded = "";
  encoded = filterOut(" \r\n", encoded);
  while(encoded.endsWith("=")) {
   encoded = encoded.substring(0, encoded.length() - 1);
   paddingCount++;
  }
  encoded = encoded + "AA".substring(0, paddingCount);  // add nulls
  if ((extra = encoded.length() % 4) > 0) {
   System.err.println("Code string \"" + encoded +
    "\" length not a multiple of 4, chopping " + extra + " extra bytes");
   encoded = encoded.substring(0, encoded.length() - extra);
  }
  for (int i = 0, k = 0; i < encoded.length(); i += 4, k = 0) {
   for (int j = 0, c = 0; j < 4; j++) {
    c = encoded.charAt(i + j);
    if (base64code.indexOf(c) >= 0) c = base64code.indexOf(c);
    else c = 0;
    k = (k << 6) | c;
   }
   decoded = decoded + (char)(k >> 16) + (char)((k >> 8) & 0xff) + 
    (char)(k & 0xff);
  }
  return decoded.substring(0, decoded.length() - paddingCount);
 }
 public static void encodeFilter() {
  Common.debug("Base64 encoding stdin");
  byte[] text = new byte[3];
  try {
   while (System.in.read(text, 0, 3) == 3)
    System.out.print(encode(new String(text)));
  } catch (Exception exception) {
   System.err.println("aborted: " + exception);
  }
 }
 public static void decodeFilter() {
  Common.debug("Base64 decoding stdin");
  byte[] code = new byte[76];
  try {
   for (int found = code.length + 1, soFar = 0; found > -1;) {
    found = System.in.read(code, soFar, 1);
    if (found > 0 && code[soFar] >= ' ') soFar += found;
    if (found <= 0 || soFar == code.length) {
     Common.debug("decoding: " + new String(code));
     System.out.print(decode(new String(code).substring(0, soFar)));
     soFar = 0;
    }
   }
  } catch (Exception exception) {
   System.err.println("aborted: " + exception);
  }
 }
 public static void main(String args[]) {
  if (args.length == 1 && args[0].startsWith("base64") &&
   args[0].endsWith("codeFilter")) {
   Common.debug("filter invoked");
   if (args[0].equals("encodeFilter")) encodeFilter();
   else if (args[0].equals("decodeFilter")) decodeFilter();
   else System.err.println("no such filter " + args[0]);
  } else {
   String encoded;
   for (int i = 0; i < args.length; i++) {
    System.err.println("encoding \"" + args[i] + "\"");
    encoded = encode(args[i]);
    System.out.println("encoded: " + encoded);
    System.out.println("decoded: " + decode(encoded));
   }
  }
 }
}