#include <stdio.h>

#include <stdlib.h>

#include <limits.h>

#include <string.h>

#include <stdint.h>

int Base64Decode(const char *in, char* out, int out_length)

{

    int i, v;

    static const uint8_t decodeMap[] =

    {

        0x3e, 0xff, 0xff, 0xff, 0x3f, 0x34, 0x35, 0x36,

        0x37, 0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0xff,

        0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x00, 0x01,

        0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09,

        0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x10, 0x11,

        0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19,

        0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x1a, 0x1b,

        0x1c, 0x1d, 0x1e, 0x1f, 0x20, 0x21, 0x22, 0x23,

        0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b,

        0x2c, 0x2d, 0x2e, 0x2f, 0x30, 0x31, 0x32, 0x33

    };  

    char *dst = out;

    v = ;

    for (i = ; in[i] && in[i] != '='; i++) {

        unsigned int index= in[i]-;

        if (index>= || decodeMap[index] == 0xff)

            return -;

        v = (v << ) + decodeMap[index];

        if (i & ) {

            if (dst - out < out_length) {

                *dst++ = v >> ( -  * (i & ));

            }

        }

    }