mmalex

#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <assert.h>
#include <vector>
// arithmetic coder/decoder by @mmalex based on the wikipedia page https://en.wikipedia.org/wiki/Range_coding as of July 2022
struct encdec_state {
    typedef uint16_t artype; 
    const static int topshift = sizeof(artype)*8-8;
    artype low=0,range=~artype(0);