#define _POSIX_C_SOURCE 200809L

#include <stdint.h>
#include <stdlib.h>

#define WHITESPACE 64
#define EQUALS     65
#define INVALID    66

static const unsigned char d[] = {
	66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 64, 66, 66, 66, 66, 66, 66,
	    66, 66, 66, 66, 66, 66, 66, 66,
	66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66,
	    66, 62, 66, 66, 66, 63, 52, 53,
	54, 55, 56, 57, 58, 59, 60, 61, 66, 66, 66, 65, 66, 66, 66, 0, 1,
	    2, 3, 4, 5, 6, 7, 8, 9,
	10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 66,
	    66, 66, 66, 66, 66, 26, 27, 28,
	29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45,
	    46, 47, 48, 49, 50, 51, 66, 66,
	66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66,
	    66, 66, 66, 66, 66, 66, 66, 66,
	66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66,
	    66, 66, 66, 66, 66, 66, 66, 66,
	66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66,
	    66, 66, 66, 66, 66, 66, 66, 66,
	66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66,
	    66, 66, 66, 66, 66, 66, 66, 66,
	66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66, 66,
	    66, 66, 66, 66, 66, 66, 66, 66,
	66, 66, 66, 66, 66, 66
};

int base64decode(const char *in, size_t inLen, unsigned char *out,
		 size_t *outLen) {
	const char *end = in + inLen;
	char iter = 0;
	uint32_t buf = 0;
	size_t len = 0;

	while (in < end) {
		unsigned char c = d[(int)(*in++)];

		switch (c) {
		case WHITESPACE:
			continue;	/* skip whitespace */
		case INVALID:
			return 0;	/* invalid input, return error */
		case EQUALS:	/* pad character, end of data */
			in = end;
			continue;
		default:
			buf = buf << 6 | c;
			iter++;	// increment the number of iteration
			/* If the buffer is full, split it into bytes */
			if (iter == 4) {
				if ((len += 3) > *outLen)
					return 0;	/* buffer overflow */
				*(out++) = (buf >> 16) & 255;
				*(out++) = (buf >> 8) & 255;
				*(out++) = buf & 255;
				buf = 0;
				iter = 0;

			}
		}
	}

	if (iter == 3) {
		if ((len += 2) > *outLen)
			return 0;	/* buffer overflow */
		*(out++) = (buf >> 10) & 255;
		*(out++) = (buf >> 2) & 255;
	} else if (iter == 2) {
		if (++len > *outLen)
			return 0;	/* buffer overflow */
		*(out++) = (buf >> 4) & 255;
	}

	*outLen = len;		/* modify to reflect the actual output size */
	return 1;
}