Base64 Decoding

Decodes data encoded with MIME base64.

• C#
• VB.Net
• C
• C++
• PHP

									char CharToSixBit(char c)
{
	char lookupTable[] = {
		'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 (int x = 0; x < 64; x++)
		{
			if (lookupTable[x] == c)
				return (char)x;
		}

		return 0;
	}
}

char* Decode(char* data, unsigned int count) {
	int length, length2, length3;
	int blockCount;
	int paddingCount = 0;

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

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

	char* buffer = malloc(length);
	char* buffer2 = malloc(length2);

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

	char b, b1, b2, b3;
	char temp1, temp2, temp3, temp4;

	for (int 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 = (char)(temp1 << 2);
		b1 = (char)((temp2 & 48) >> 4);
		b1 += b;

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

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

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

	length3 = length2 - paddingCount;
	char* result = malloc(length3);

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

	free(buffer);
	free(buffer2);

	result[length3] = '\0';

	return result;
}
								

Example

									char* data = "amRmZ3NkaGZzZGZzZCA2NDQ1ZHNmc2Q3ZmcvKi8rYmZqc2RnZiUkXg==";
char* value = Decode(data, strlen(data));
								

Output

									jdfgsdhfsdfsd 6445dsfsd7fg/*/+bfjsdgf%$^