#include <assert.h>
#include <stddef.h>

/* Define this to have an encoding backward from RFC.
#define ALT_ENCODING 1
*/
static const char b32_to[32] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
static const char b32_from[] = {
	['A']=1, ['a']=1,
	['B']=2, ['b']=2,
	['C']=3, ['c']=3,
	['D']=4, ['d']=4,
	['E']=5, ['e']=5,
	['F']=6, ['f']=6,
	['G']=7, ['g']=7,
	['H']=8, ['h']=8,
	['I']=9, ['i']=9,
	['J']=10, ['j']=10,
	['K']=11, ['k']=11,
	['L']=12, ['l']=12,
	['M']=13, ['m']=13,
	['N']=14, ['n']=14,
	['O']=15, ['o']=15,
	['P']=16, ['p']=16,
	['Q']=17, ['q']=17,
	['R']=18, ['r']=18,
	['S']=19, ['s']=19,
	['T']=20, ['t']=20,
	['U']=21, ['u']=21,
	['V']=22, ['v']=22,
	['W']=23, ['w']=23,
	['X']=24, ['x']=24,
	['Y']=25, ['y']=25,
	['Z']=26, ['z']=26,
	['2']=27, ['3']=28,
	['4']=29, ['5']=30,
	['6']=31, ['7']=32,
};

int b32_encode(const void *data, size_t data_len, char *s, size_t s_len) {
	const unsigned char *d=data;
	unsigned tmp, bits; /* buffer that needs to hold up to 12 bits */

	assert(data != NULL);
	assert(s != NULL);

	tmp=0;
	bits=0;
	while(data_len>0) {
		assert(bits < 5);
#if ALT_ENCODING
		tmp|=(unsigned)*d<<bits;
#else
		tmp=(tmp<<8)|*d;
#endif
		bits+=8;
		d++;
		data_len--;
		while(bits>=5) {
			if(s_len<=1) return 0; /* failure */
			bits-=5;
#if ALT_ENCODING
			*s++=b32_to[tmp&31];
			tmp>>=5;
#else
			*s++=b32_to[tmp>>bits];
			tmp&=(1<<bits)-1;
#endif
			s_len--;
		}
	}
	if(bits) {
		assert(bits <= 5);
		if(s_len<=1) return 0; /* failure */
#if ALT_ENCODING
		*s++=b32_to[tmp&31]; /* pad top with 0s. */
#else
		*s++=b32_to[tmp<<(5-bits)]; /* pad with low order 0s */
#endif
		s_len--;
	}
	if(s_len<1) return 0; /* failure */
	*s=0;
	return 1; /* success */
}

int b32_decode(const char *s, size_t s_len, void *data, size_t data_len) {
	/* TODO: implement this. */
	s=0;
	s_len=0;
	data=0;
	data_len=0;
	return 0; /* failure */
}

#include <stdlib.h>

int main()
{
	// TODO: implement a test
	abort();
}