#include <stdint.h>
#include <string.h>
static const char encoding_table[] = {'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', '+', '/'};
static const char decoding_table[256] = {['A'] = 0, // using GCC initialiser style
['B'] = 1,
['C'] = 2,
['D'] = 3,
['E'] = 4,
['F'] = 5,
['G'] = 6,
['H'] = 7,
['I'] = 8,
['J'] = 9,
['K'] = 10,
['L'] = 11,
['M'] = 12,
['N'] = 13,
['O'] = 14,
['P'] = 15,
['Q'] = 16,
['R'] = 17,
['S'] = 18,
['T'] = 19,
['U'] = 20,
['V'] = 21,
['W'] = 22,
['X'] = 23,
['Y'] = 24,
['Z'] = 25,
['a'] = 26,
['b'] = 27,
['c'] = 28,
['d'] = 29,
['e'] = 30,
['f'] = 31,
['g'] = 32,
['h'] = 33,
['i'] = 34,
['j'] = 35,
['k'] = 36,
['l'] = 37,
['m'] = 38,
['n'] = 39,
['o'] = 40,
['p'] = 41,
['q'] = 42,
['r'] = 43,
['s'] = 44,
['t'] = 45,
['u'] = 46,
['v'] = 47,
['w'] = 48,
['x'] = 49,
['y'] = 50,
['z'] = 51,
['0'] = 52,
['1'] = 53,
['2'] = 54,
['3'] = 55,
['4'] = 56,
['5'] = 57,
['6'] = 58,
['7'] = 59,
['8'] = 60,
['9'] = 61,
['+'] = 62,
['/'] = 63};
static const int mod_table[] = {0, 2, 1};
unsigned char *base64_encode(const unsigned char *data,
size_t input_length,
unsigned char *encoded_data,
size_t *output_length)
{
*output_length = 4 * ((input_length + 2) / 3);
for (int i = 0, j = 0; i < input_length;)
{
uint32_t octet_a = i < input_length ? (unsigned char)data[i++] : 0;
uint32_t octet_b = i < input_length ? (unsigned char)data[i++] : 0;
uint32_t octet_c = i < input_length ? (unsigned char)data[i++] : 0;
uint32_t triple = (octet_a << 0x10) + (octet_b << 0x08) + octet_c;
encoded_data[j++] = encoding_table[(triple >> 3 * 6) & 0x3F];
encoded_data[j++] = encoding_table[(triple >> 2 * 6) & 0x3F];
encoded_data[j++] = encoding_table[(triple >> 1 * 6) & 0x3F];
encoded_data[j++] = encoding_table[(triple >> 0 * 6) & 0x3F];
}
for (int i = 0; i < mod_table[input_length % 3]; i++)
encoded_data[*output_length - 1 - i] = '=';
return encoded_data;
}
unsigned char *base64_decode(const char *data,
size_t input_length,
unsigned char *decoded_data,
size_t *output_length)
{
if (input_length % 4 != 0)
return NULL;
*output_length = input_length / 4 * 3;
if (data[input_length - 1] == '=')
(*output_length)--;
if (data[input_length - 2] == '=')
(*output_length)--;
for (int i = 0, j = 0; i < input_length;)
{
uint32_t sextet_a = data[i] == '=' ? 0 & i++ : decoding_table[(int)data[i++]];
uint32_t sextet_b = data[i] == '=' ? 0 & i++ : decoding_table[(int)data[i++]];
uint32_t sextet_c = data[i] == '=' ? 0 & i++ : decoding_table[(int)data[i++]];
uint32_t sextet_d = data[i] == '=' ? 0 & i++ : decoding_table[(int)data[i++]];
uint32_t triple = (sextet_a << 3 * 6) + (sextet_b << 2 * 6) + (sextet_c << 1 * 6) + (sextet_d << 0 * 6);
if (j < *output_length)
decoded_data[j++] = (triple >> 2 * 8) & 0xFF;
if (j < *output_length)
decoded_data[j++] = (triple >> 1 * 8) & 0xFF;
if (j < *output_length)
decoded_data[j++] = (triple >> 0 * 8) & 0xFF;
}
return decoded_data;
}