- (NSString *)encodeBase64:(const uint8_t *)input length:(NSInteger)length{
    static char table[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
    NSMutableData* data = [NSMutableData dataWithLength:((length + 2) / 3) * 4];
    uint8_t* output = (uint8_t*)data.mutableBytes;
    for (NSInteger i = 0; i < length; i += 3) {
        NSInteger value = 0;
        for (NSInteger j = i; j < (i + 3); j++) {
            value <<= 8;
            if (j < length) {
                value |= (0xFF & input[j]);
            }
        }
        NSInteger index = (i / 3) * 4;
        output[index + 0] =                    table[(value >> 18) & 0x3F];
        output[index + 1] =                    table[(value >> 12) & 0x3F];
        output[index + 2] = (i + 1) < length ? table[(value >> 6)  & 0x3F] : '=';
        output[index + 3] = (i + 2) < length ? table[(value >> 0)  & 0x3F] : '=';
    }
    return [[[NSString alloc] initWithData:data    encoding:NSASCIIStringEncoding] autorelease];
}

// Exact code above @end is : 

/*
- (NSString *)encodeBase64:(const uint8_t *)input length:(NSInteger)length
{ 
#warning Replace this method.
return nil;
}


- (NSString *)decodeBase64:(NSString *)input length:(NSInteger *)length
{
#warning Replace this method.
return nil;
}

#warning Implement this function.
char* base64_encode(const void* buf,size_t size)
{ return NULL; }

#warning Implement this function.
void * base64_decode(const char* s,size_t * data_len)
{ return NULL; }

*/
@end