https://www.v2ex.com/t/888186

buffer.cpp

#define m 16
char buffer[m] = {0};
int index = 0;

void fillBuffer(const char *buf, int n)
{
    if(index + n <= m)
    {
        memcpy(buffer + index, buf, n);
        index += n;
    }
    else
    {
        memcpy(buffer + index, buf, m - index);
        //print here
        index = 0;
        fillBuffer(buffer, n - (m - index));
    }
}