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Base64 Encode & Decode By Javascript [펌] 본문

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Base64 Encode & Decode By Javascript [펌]

Michael 이현민 (지후지율아빠) 2008.11.28 11:08
<html>
<head>
<title>JavaScript Base64 Encoder/Decoder</title>
<script type="text/javascript">
// First things first, set up our array that we are going to use.
var keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" + //all caps
   "abcdefghijklmnopqrstuvwxyz" + //all lowercase
   "0123456789+/="; // all numbers plus +/=
//Heres the encode function
function encode64(inp)
{
 var out = ""; //This is the output
 var chr1, chr2, chr3 = ""; //These are the 3 bytes to be encoded
 var enc1, enc2, enc3, enc4 = ""; //These are the 4 encoded bytes
 var i = 0; //Position counter
 do //Set up the loop here
 {
  chr1 = inp.charCodeAt(i++); //Grab the first byte
  chr2 = inp.charCodeAt(i++); //Grab the second byte
  chr3 = inp.charCodeAt(i++); //Grab the third byte
  //Here is the actual base64 encode part.
  //There really is only one way to do it.
  enc1 = chr1 >> 2;
  enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);
  enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);
  enc4 = chr3 & 63;
  if (isNaN(chr2))
  {
   enc3 = enc4 = 64;
  }
  else if (isNaN(chr3))
  {
   enc4 = 64;
  }
  //Lets spit out the 4 encoded bytes
  out = out + keyStr.charAt(enc1) + keyStr.charAt(enc2) + keyStr.charAt(enc3) +
  keyStr.charAt(enc4);
  // OK, now clean out the variables used.
  chr1 = chr2 = chr3 = "";
  enc1 = enc2 = enc3 = enc4 = "";
 } while (i < inp.length);
 //And finish off the loop
 //Now return the encoded values.
 return out;
}
//Heres the decode function
function decode64(inp)
{
 var out = ""; //This is the output
 var chr1, chr2, chr3 = ""; //These are the 3 decoded bytes
 var enc1, enc2, enc3, enc4 = ""; //These are the 4 bytes to be decoded
 var i = 0; //Position counter
 // remove all characters that are not A-Z, a-z, 0-9, +, /, or =
 var base64test = /[^A-Za-z0-9+/=]/g;
 if (base64test.exec(inp)) //Do some error checking
 {
  alert("There were invalid base64 characters in the input text.n" +
  "Valid base64 characters are A-Z, a-z, 0-9, ?+?, ?/?, and ?=?n" +
  "Expect errors in decoding.");
 }
 inp = inp.replace(/[^A-Za-z0-9+/=]/g, "");
 do //Here’s the decode loop.
 {
  //Grab 4 bytes of encoded content.
  enc1 = keyStr.indexOf(inp.charAt(i++));
  enc2 = keyStr.indexOf(inp.charAt(i++));
  enc3 = keyStr.indexOf(inp.charAt(i++));
  enc4 = keyStr.indexOf(inp.charAt(i++));
  //Heres the decode part. There’s really only one way to do it.
  chr1 = (enc1 << 2) | (enc2 >> 4);
  chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);
  chr3 = ((enc3 & 3) << 6) | enc4;
  //Start to output decoded content
  out = out + String.fromCharCode(chr1);
  if (enc3 != 64)
  {
   out = out + String.fromCharCode(chr2);
  }
  if (enc4 != 64)
  {
   out = out + String.fromCharCode(chr3);
  }
  //now clean out the variables used
  chr1 = chr2 = chr3 = "";
  enc1 = enc2 = enc3 = enc4 = "";
 } while (i < inp.length); //finish off the loop
 //Now return the decoded values.
 return out;
}
</script>
</head>
<body>
<form name="Base64">
Enter what you want encoded or decoded and push the Encode or Decode buttons<br>
<textarea name="Test" cols="40" rows="6"></textarea><br>
<input type="button" name="encode" value="Encode" onClick="document.Base64.Test.value=encode64(document.Base64.Test.value);">
<input type="button" name="decode" value="Decode" onClick="document.Base64.Test.value=decode64(document.Base64.Test.value);">
</form>
</body>
</html>
 

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