MVar.ts

import { Mutex } from "async-mutex";

export type MVar<T> = {
  take: () => Promise<T>;
  read: () => Promise<T>;
  put: (newVal: T) => Promise<void>;
};

export const newMVar = function <T>(initial: T): MVar<T> {
  const val = { current: initial };
  const mutex = new Mutex();
  let release = () => {};
  return {
    take: async () => {
      release = await mutex.acquire();
      return val.current;
    },
    read: async () => {
      const releaseLocal = await mutex.acquire();
      const res = val.current;
      releaseLocal();
      return res;
    },
    put: async (newVal: T) => {
      release();
      const releaseLocal = await mutex.acquire();
      val.current = newVal;
      releaseLocal();
    },
  };
};


import { Mutex } from "async-mutex";

export const newMVarSimple = function <T>(initial: T) {
  const val = { current: initial };
  const mutex = new Mutex();
  return {
    over: async (f: (value: T) => Promise<T>) =>
      mutex.runExclusive(() =>
        f(val.current).then((newVal) => {
          val.current = newVal;
        })
      ),
  };
};