function newStack(worker, workerImageName, stackWorker, stackImageName) {
    let p2vbuf = {
        buf: new Uint8Array(0) // proxy => vm
    };
    let v2pbuf = {
        buf: new Uint8Array(0) // vm => proxy
    };
    var proxyConn = {
        sendbuf: p2vbuf,
        recvbuf: v2pbuf
    };
    var vmConn = {
        sendbuf: v2pbuf,
        recvbuf: p2vbuf
    }
    var proxyShared = new SharedArrayBuffer(12 + 4096);
    var certbuf = {
        buf: new Uint8Array(0),
        done: false
    }
    stackWorker.onmessage = connect("proxy", proxyShared, proxyConn, certbuf);
    stackWorker.postMessage({type: "init", buf: proxyShared, imagename: stackImageName});

    var vmShared = new SharedArrayBuffer(12 + 4096);
    worker.postMessage({type: "init", buf: vmShared, imagename: workerImageName});
    return connect("vm", vmShared, vmConn, certbuf);
}

function connect(name, shared, conn, certbuf) {
    var streamCtrl = new Int32Array(shared, 0, 1);
    var streamStatus = new Int32Array(shared, 4, 1);
    var streamLen = new Int32Array(shared, 8, 1);
    var streamData = new Uint8Array(shared, 12);
    var sendbuf = conn.sendbuf;
    var recvbuf = conn.recvbuf;
    let accepted = false;
    var httpConnections = {};
    var curID = 0;
    var maxID = 0x7FFFFFFF; // storable in streamStatus(signed 32bits)
    function getID() {
        var startID = curID;
        while (true) {
            if (httpConnections[curID] == undefined) {
                return curID;
            }
            if (curID >= maxID) {
                curID = 0;
            } else {
                curID++;
            }
            if (curID == startID) {
                return -1; // exhausted
            }
        }
        return curID;
    }
    function serveData(data, len) {
        var length = len;
        if (length > streamData.byteLength)
            length = streamData.byteLength;
        if (length > data.byteLength)
            length = data.byteLength
        var buf = data.slice(0, length);
        var remain = data.slice(length, data.byteLength);
        streamLen[0] = buf.byteLength;
        streamData.set(buf, 0);
        return remain;
    }
    return function(msg){
        const req_ = msg.data;
        if (typeof req_ == "object" && req_.type) {
            switch (req_.type) {
            case "accept":
                accepted = true;
                streamData[0] = 1; // opened
                streamStatus[0] = 0;
                break;
            case "send":
                if (!accepted) {
                    console.log(name + ":" + "cannot send to unaccepted socket");
                    streamStatus[0] = -1;
                    break;
                }
                sendbuf.buf = appendData(sendbuf.buf, req_.buf);
                streamStatus[0] = 0;
                break;
            case "recv":
                if (!accepted) {
                    console.log(name + ":" + "cannot recv from unaccepted socket");
                    streamStatus[0] = -1;
                    break;
                }
                recvbuf.buf = serveData(recvbuf.buf, req_.len);
                streamStatus[0] = 0;
                break;
            case "recv-is-readable":
                var recvbufP = recvbuf.buf;
                if (recvbufP.byteLength > 0) {
                    streamData[0] = 1; // ready for reading
                } else {
                    if ((req_.timeout != undefined) && (req_.timeout > 0)) {
                        if (this.timeoutHandler) {
                            clearTimeout(this.timeoutHandler);
                            this.timeoutHandler = null;
                        }
                        this.timeoutHandler = setTimeout(() => {
                            if (this.timeoutHandler) {
                                clearTimeout(this.timeoutHandler);
                                this.timeoutHandler = null;
                            }
                            if (recvbuf.buf.byteLength > 0) {
                                streamData[0] = 1; // ready for reading
                            } else {
                                streamData[0] = 0; // timeout
                            }
                            streamStatus[0] = 0;
                            Atomics.store(streamCtrl, 0, 1);
                            Atomics.notify(streamCtrl, 0);
                        }, req_.timeout * 1000);
                        return;
                    }
                    streamData[0] = 0; // timeout
                }
                streamStatus[0] = 0;
                break;
            case "http_send":
                var reqObj = JSON.parse(new TextDecoder().decode(req_.req));
                reqObj.mode = "cors";
                reqObj.credentials = "omit";
                if (reqObj.headers && reqObj.headers["User-Agent"] != "") {
                    delete reqObj.headers["User-Agent"]; // Browser will add its own value.
                }
                var reqID = getID();
                if (reqID < 0) {
                    console.log(name + ":" + "failed to get id");
                    streamStatus[0] = -1;
                    break;
                }
                var connObj = {
                    address: new TextDecoder().decode(req_.address),
                    request: reqObj,
                    requestSent: false,
                    reqBodybuf: new Uint8Array(0),
                    reqBodyEOF: false,
                };
                httpConnections[reqID] = connObj;
                streamStatus[0] = reqID;
                break;
            case "http_writebody":
                httpConnections[req_.id].reqBodybuf = appendData(httpConnections[req_.id].reqBodybuf, req_.body)
                httpConnections[req_.id].reqBodyEOF = req_.isEOF;
                streamStatus[0] = 0;
                if (req_.isEOF && !httpConnections[req_.id].requestSent) {
                    httpConnections[req_.id].requestSent = true;
                    var connObj = httpConnections[req_.id];
                    if ((connObj.request.method != "HEAD") && (connObj.request.method != "GET")) {
                        connObj.request.body = connObj.reqBodybuf;
                    }
                    fetch(connObj.address, connObj.request).then((resp) => {
                        connObj.response = new TextEncoder().encode(JSON.stringify({
                            bodyUsed: resp.bodyUsed,
                            headers: resp.headers,
                            redirected: resp.redirected,
                            status: resp.status,
                            statusText: resp.statusText,
                            type: resp.type,
                            url: resp.url
                        })),
                        connObj.done = false;
                        connObj.respBodybuf = new Uint8Array(0);
                        if (resp.ok) {
                            resp.arrayBuffer().then((data) => {
                                connObj.respBodybuf = new Uint8Array(data);
                                connObj.done = true;
                            }).catch((error) => {
                                connObj.respBodybuf = new Uint8Array(0);
                                connObj.done = true;
                                console.log("failed to fetch body: " + error);
                            });
                        } else {
                            connObj.done = true;
                        }
                    }).catch((error) => {
                        connObj.response = new TextEncoder().encode(JSON.stringify({
                            status: 503,
                            statusText: "Service Unavailable",
                        }))
                        connObj.respBodybuf = new Uint8Array(0);
                        connObj.done = true;
                    });
                }
                break;
            case "http_isreadable":
                if ((httpConnections[req_.id] != undefined) && (httpConnections[req_.id].response != undefined)) {
                    streamData[0] = 1; // ready for reading
                } else {
                    streamData[0] = 0; // nothing to read
                }
                streamStatus[0] = 0;
                break;
            case "http_recv":
                if ((httpConnections[req_.id] == undefined) || (httpConnections[req_.id].response == undefined)) {
                    console.log(name + ":" + "response is not available");
                    streamStatus[0] = -1;
                    break;
                }
                httpConnections[req_.id].response = serveData(httpConnections[req_.id].response, req_.len);
                streamStatus[0] = 0;
                if (httpConnections[req_.id].response.byteLength == 0) {
                    streamStatus[0] = 1; // isEOF
                }
                break;
            case "http_readbody":
                if ((httpConnections[req_.id] == undefined) || (httpConnections[req_.id].response == undefined)) {
                    console.log(name + ":" + "response body is not available");
                    streamStatus[0] = -1;
                    break;
                }
                httpConnections[req_.id].respBodybuf = serveData(httpConnections[req_.id].respBodybuf, req_.len);
                streamStatus[0] = 0;
                if ((httpConnections[req_.id].done) && (httpConnections[req_.id].respBodybuf.byteLength == 0)) {
                    streamStatus[0] = 1;
                    delete httpConnections[req_.id]; // connection done
                }
                break;
            case "send_cert":
                certbuf.buf = appendData(certbuf.buf, req_.buf);
                certbuf.done = true;
                streamStatus[0] = 0;
                break;
            case "recv_cert":
                if (!certbuf.done) {
                    streamStatus[0] = -1;
                    break;
                }
                certbuf.buf = serveData(certbuf.buf, req_.len);
                streamStatus[0] = 0;
                if (certbuf.buf.byteLength == 0) {
                    streamStatus[0] = 1; // isEOF
                }
                break;
            default:
                console.log(name + ":" + "unknown request: " +  req_.type)
                return;
            }
            Atomics.store(streamCtrl, 0, 1);
            Atomics.notify(streamCtrl, 0);
        } else {
            console.log("UNKNOWN MSG " + msg);
        }
    }
}

function appendData(data1, data2) {
    buf2 = new Uint8Array(data1.byteLength + data2.byteLength);
    buf2.set(new Uint8Array(data1), 0);
    buf2.set(new Uint8Array(data2), data1.byteLength);
    return buf2;
}