Attachment 219135 Details for Bug 385891 – improved base64 decoder

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improved base64 decoder

decode.txt (text/plain), 1.63 KB, created by Mike Wilson

on 2012-07-24 16:36:12 EDT

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Description:

Filename:

MIME Type:

Creator: Mike Wilson

Created: 2012-07-24 16:36:12 EDT

Size: 1.63 KB

patch

obsolete

>function decodeBase64(input) {
>	 
>	var seg1, seg2, seg3, seg4;
>	var output = "";
>
>	/* equivalent to 
>		"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/="
>			.indexOf(input.charAt(index))
>	*/
>	function decodeChar (input, index) {
>		var code = input.charCodeAt(index);
>		if (code === 43 /* '+' */) { return 62; }
>		if (code === 47 /* '/' */) { return 63; }
>		if (code === 61 /* '=' */) { return 64; }
>		if (code > 96 /* lowercase */) { return code - 71; }
>		if (code > 64 /* uppercase */) { return code - 65; }
>		return code + 4; /* numbers */
>	}
>	
>	/* Emit 0..3 characters based on the encoded value. */
>	function emitChars (c) {
>		if (c < 128) {
>			if (c === 10) {
>				return;  /* Strip CR chars */
>			}
>			output += String.fromCharCode(c);
>		}
>		else if(c < 2048) {
>			output += String.fromCharCode((c >> 6) | 192);
>			output += String.fromCharCode((c & 63) | 128);
>		}
>		else {
>			output += String.fromCharCode((c >> 12) | 224);
>			output += String.fromCharCode(((c >> 6) & 63) | 128);
>			output += String.fromCharCode((c & 63) | 128);
>		}
>	}
>
>	/* Strip line breaks and any other bogus characters. */
>	input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");
>	if (input.length % 4 !== 0) {
>		throw "malformed base64";
>	}
>	
>	for (var i = 0; i < input.length; ) {
>		seg1 = decodeChar(input, i++);
>		seg2 = decodeChar(input, i++);
>		seg3 = decodeChar(input, i++);
>		seg4 = decodeChar(input, i++);
>		
>		emitChars((seg1 << 2) | (seg2 >> 4));
>		if (seg3 !== 64) {
>			emitChars(((seg2 & 15) << 4) | (seg3 >> 2));
>		}
>		if (seg4 !== 64) {
>			emitChars(((seg3 & 3) << 6) | seg4);
>		}
>	}
>
>	return output;
>}

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Attachments on bug 385891: 219135 | 219154