Base64 Decoding

Decodes data encoded with MIME base64.

• C#
• VB.Net
• C
• C++
• PHP

									function CharToSixBit($c)
{
	$lookupTable = array(
		'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', '+', '/'
	);

	if ($c == '=')
	{
		return 0;
	}
	else
	{
		for ($x = 0; $x < 64; $x++)
		{
			if ($lookupTable[$x] == $c)
				return $x;
		}

		return 0;
	}
}

function Decode($data, $count) {
	$paddingCount = 0;

	$length = $count;
	$blockCount = $length / 4;
	$length2 = $blockCount * 3;

	for ($x = 0; $x < 2; $x++)
	{
		if ($data[$length - $x - 1] == '=')
			$paddingCount++;
	}

	for ($x = 0; $x < $length; $x++)
	{
		$buffer[$x] = CharToSixBit($data[$x]);
	}

	for ($x = 0; $x < $blockCount; $x++)
	{
		$temp1 = $buffer[$x * 4];
		$temp2 = $buffer[$x * 4 + 1];
		$temp3 = $buffer[$x * 4 + 2];
		$temp4 = $buffer[$x * 4 + 3];

		$b = ($temp1 << 2);
		$b1 = (($temp2 & 48) >> 4);
		$b1 += $b;

		$b = (($temp2 & 15) << 4);
		$b2 = (($temp3 & 60) >> 2);
		$b2 += $b;

		$b = (($temp3 & 3) << 6);
		$b3 = $temp4;
		$b3 += $b;

		$buffer2[$x * 3] = $b1;
		$buffer2[$x * 3 + 1] = $b2;
		$buffer2[$x * 3 + 2] = $b3;
	}

	$length3 = $length2 - $paddingCount;

	$result = array();
	
	for ($x = 0; $x < $length3; $x++)
	{
		$result[$x] = chr($buffer2[$x]);
	}

	$buffer = null;
	$buffer2 = null;

	return implode("", $result);
}
								

Example

									$data = "amRmZ3NkaGZzZGZzZCA2NDQ1ZHNmc2Q3ZmcvKi8rYmZqc2RnZiUkXg==";
$value = Decode($data, strlen($data));
								

Output

									jdfgsdhfsdfsd 6445dsfsd7fg/*/+bfjsdgf%$^