github.com/gopherjs/gopherjs@v1.19.0-beta1.0.20240506212314-27071a8796e4/compiler/prelude/goroutines.js

var $stackDepthOffset = 0;
var $getStackDepth = () => {
    var err = new Error();
    if (err.stack === undefined) {
        return undefined;
    }
    return $stackDepthOffset + err.stack.split("\n").length;
};

var $panicStackDepth = null, $panicValue;
var $callDeferred = (deferred, jsErr, fromPanic) => {
    if (!fromPanic && deferred !== null && $curGoroutine.deferStack.indexOf(deferred) == -1) {
        throw jsErr;
    }
    if (jsErr !== null) {
        var newErr = null;
        try {
            $panic(new $jsErrorPtr(jsErr));
        } catch (err) {
            newErr = err;
        }
        $callDeferred(deferred, newErr);
        return;
    }
    if ($curGoroutine.asleep) {
        return;
    }

    $stackDepthOffset--;
    var outerPanicStackDepth = $panicStackDepth;
    var outerPanicValue = $panicValue;

    var localPanicValue = $curGoroutine.panicStack.pop();
    if (localPanicValue !== undefined) {
        $panicStackDepth = $getStackDepth();
        $panicValue = localPanicValue;
    }

    try {
        while (true) {
            if (deferred === null) {
                deferred = $curGoroutine.deferStack[$curGoroutine.deferStack.length - 1];
                if (deferred === undefined) {
                    /* The panic reached the top of the stack. Clear it and throw it as a JavaScript error. */
                    $panicStackDepth = null;
                    if (localPanicValue.Object instanceof Error) {
                        throw localPanicValue.Object;
                    }
                    var msg;
                    if (localPanicValue.constructor === $String) {
                        msg = localPanicValue.$val;
                    } else if (localPanicValue.Error !== undefined) {
                        msg = localPanicValue.Error();
                    } else if (localPanicValue.String !== undefined) {
                        msg = localPanicValue.String();
                    } else {
                        msg = localPanicValue;
                    }
                    throw new Error(msg);
                }
            }
            var call = deferred.pop();
            if (call === undefined) {
                $curGoroutine.deferStack.pop();
                if (localPanicValue !== undefined) {
                    deferred = null;
                    continue;
                }
                return;
            }
            var r = call[0].apply(call[2], call[1]);
            if (r && r.$blk !== undefined) {
                deferred.push([r.$blk, [], r]);
                if (fromPanic) {
                    throw null;
                }
                return;
            }

            if (localPanicValue !== undefined && $panicStackDepth === null) {
                /* error was recovered */
                if (fromPanic) {
                    throw null;
                }
                return;
            }
        }
    } catch (e) {
        // Deferred function threw a JavaScript exception or tries to unwind stack
        // to the point where a panic was handled.
        if (fromPanic) {
            // Re-throw the exception to reach deferral execution call at the end
            // of the function.
            throw e;
        }
        // We are at the end of the function, handle the error or re-throw to
        // continue unwinding if necessary, or simply stop unwinding if we got far
        // enough.
        $callDeferred(deferred, e, fromPanic);
    } finally {
        if (localPanicValue !== undefined) {
            if ($panicStackDepth !== null) {
                $curGoroutine.panicStack.push(localPanicValue);
            }
            $panicStackDepth = outerPanicStackDepth;
            $panicValue = outerPanicValue;
        }
        $stackDepthOffset++;
    }
};

var $panic = value => {
    $curGoroutine.panicStack.push(value);
    $callDeferred(null, null, true);
};
var $recover = () => {
    if ($panicStackDepth === null || ($panicStackDepth !== undefined && $panicStackDepth !== $getStackDepth() - 2)) {
        return $ifaceNil;
    }
    $panicStackDepth = null;
    return $panicValue;
};
var $throw = err => { throw err; };

var $noGoroutine = { asleep: false, exit: false, deferStack: [], panicStack: [] };
var $curGoroutine = $noGoroutine, $totalGoroutines = 0, $awakeGoroutines = 0, $checkForDeadlock = true, $exportedFunctions = 0;
var $mainFinished = false;
var $go = (fun, args) => {
    $totalGoroutines++;
    $awakeGoroutines++;
    var $goroutine = () => {
        try {
            $curGoroutine = $goroutine;
            var r = fun(...args);
            if (r && r.$blk !== undefined) {
                fun = () => { return r.$blk(); };
                args = [];
                return;
            }
            $goroutine.exit = true;
        } catch (err) {
            if (!$goroutine.exit) {
                throw err;
            }
        } finally {
            $curGoroutine = $noGoroutine;
            if ($goroutine.exit) { /* also set by runtime.Goexit() */
                $totalGoroutines--;
                $goroutine.asleep = true;
            }
            if ($goroutine.asleep) {
                $awakeGoroutines--;
                if (!$mainFinished && $awakeGoroutines === 0 && $checkForDeadlock && $exportedFunctions === 0) {
                    console.error("fatal error: all goroutines are asleep - deadlock!");
                    if ($global.process !== undefined) {
                        $global.process.exit(2);
                    }
                }
            }
        }
    };
    $goroutine.asleep = false;
    $goroutine.exit = false;
    $goroutine.deferStack = [];
    $goroutine.panicStack = [];
    $schedule($goroutine);
};

var $scheduled = [];
var $runScheduled = () => {
    // For nested setTimeout calls browsers enforce 4ms minimum delay. We minimize
    // the effect of this penalty by queueing the timer preemptively before we run
    // the goroutines, and later cancelling it if it turns out unneeded. See:
    // https://developer.mozilla.org/en-US/docs/Web/API/setTimeout#nested_timeouts
    var nextRun = setTimeout($runScheduled);
    try {
        var start = Date.now();
        var r;
        while ((r = $scheduled.shift()) !== undefined) {
            r();
            // We need to interrupt this loop in order to allow the event loop to
            // process timers, IO, etc. However, invoking scheduling through
            // setTimeout is ~1000 times more expensive, so we amortize this cost by
            // looping until the 4ms minimal delay has elapsed (assuming there are
            // scheduled goroutines to run), and then yield to the event loop.
            var elapsed = Date.now() - start;
            if (elapsed > 4 || elapsed < 0) { break; }
        }
    } finally {
        if ($scheduled.length == 0) {
            // Cancel scheduling pass if there's nothing to run.
            clearTimeout(nextRun);
        }
    }
};

var $schedule = goroutine => {
    if (goroutine.asleep) {
        goroutine.asleep = false;
        $awakeGoroutines++;
    }
    $scheduled.push(goroutine);
    if ($curGoroutine === $noGoroutine) {
        $runScheduled();
    }
};

var $setTimeout = (f, t) => {
    $awakeGoroutines++;
    return setTimeout(() => {
        $awakeGoroutines--;
        f();
    }, t);
};

var $block = () => {
    if ($curGoroutine === $noGoroutine) {
        $throwRuntimeError("cannot block in JavaScript callback, fix by wrapping code in goroutine");
    }
    $curGoroutine.asleep = true;
};

var $restore = (context, params) => {
    if (context !== undefined && context.$blk !== undefined) {
        return context;
    }
    return params;
}

var $send = (chan, value) => {
    if (chan.$closed) {
        $throwRuntimeError("send on closed channel");
    }
    var queuedRecv = chan.$recvQueue.shift();
    if (queuedRecv !== undefined) {
        queuedRecv([value, true]);
        return;
    }
    if (chan.$buffer.length < chan.$capacity) {
        chan.$buffer.push(value);
        return;
    }

    var thisGoroutine = $curGoroutine;
    var closedDuringSend;
    chan.$sendQueue.push(closed => {
        closedDuringSend = closed;
        $schedule(thisGoroutine);
        return value;
    });
    $block();
    return {
        $blk() {
            if (closedDuringSend) {
                $throwRuntimeError("send on closed channel");
            }
        }
    };
};
var $recv = chan => {
    var queuedSend = chan.$sendQueue.shift();
    if (queuedSend !== undefined) {
        chan.$buffer.push(queuedSend(false));
    }
    var bufferedValue = chan.$buffer.shift();
    if (bufferedValue !== undefined) {
        return [bufferedValue, true];
    }
    if (chan.$closed) {
        return [chan.$elem.zero(), false];
    }

    var thisGoroutine = $curGoroutine;
    var f = { $blk() { return this.value; } };
    var queueEntry = v => {
        f.value = v;
        $schedule(thisGoroutine);
    };
    chan.$recvQueue.push(queueEntry);
    $block();
    return f;
};
var $close = chan => {
    if (chan.$closed) {
        $throwRuntimeError("close of closed channel");
    }
    chan.$closed = true;
    while (true) {
        var queuedSend = chan.$sendQueue.shift();
        if (queuedSend === undefined) {
            break;
        }
        queuedSend(true); /* will panic */
    }
    while (true) {
        var queuedRecv = chan.$recvQueue.shift();
        if (queuedRecv === undefined) {
            break;
        }
        queuedRecv([chan.$elem.zero(), false]);
    }
};
var $select = comms => {
    var ready = [];
    var selection = -1;
    for (var i = 0; i < comms.length; i++) {
        var comm = comms[i];
        var chan = comm[0];
        switch (comm.length) {
            case 0: /* default */
                selection = i;
                break;
            case 1: /* recv */
                if (chan.$sendQueue.length !== 0 || chan.$buffer.length !== 0 || chan.$closed) {
                    ready.push(i);
                }
                break;
            case 2: /* send */
                if (chan.$closed) {
                    $throwRuntimeError("send on closed channel");
                }
                if (chan.$recvQueue.length !== 0 || chan.$buffer.length < chan.$capacity) {
                    ready.push(i);
                }
                break;
        }
    }

    if (ready.length !== 0) {
        selection = ready[Math.floor(Math.random() * ready.length)];
    }
    if (selection !== -1) {
        var comm = comms[selection];
        switch (comm.length) {
            case 0: /* default */
                return [selection];
            case 1: /* recv */
                return [selection, $recv(comm[0])];
            case 2: /* send */
                $send(comm[0], comm[1]);
                return [selection];
        }
    }

    var entries = [];
    var thisGoroutine = $curGoroutine;
    var f = { $blk() { return this.selection; } };
    var removeFromQueues = () => {
        for (var i = 0; i < entries.length; i++) {
            var entry = entries[i];
            var queue = entry[0];
            var index = queue.indexOf(entry[1]);
            if (index !== -1) {
                queue.splice(index, 1);
            }
        }
    };
    for (var i = 0; i < comms.length; i++) {
        (i => {
            var comm = comms[i];
            switch (comm.length) {
                case 1: /* recv */
                    var queueEntry = value => {
                        f.selection = [i, value];
                        removeFromQueues();
                        $schedule(thisGoroutine);
                    };
                    entries.push([comm[0].$recvQueue, queueEntry]);
                    comm[0].$recvQueue.push(queueEntry);
                    break;
                case 2: /* send */
                    var queueEntry = () => {
                        if (comm[0].$closed) {
                            $throwRuntimeError("send on closed channel");
                        }
                        f.selection = [i];
                        removeFromQueues();
                        $schedule(thisGoroutine);
                        return comm[1];
                    };
                    entries.push([comm[0].$sendQueue, queueEntry]);
                    comm[0].$sendQueue.push(queueEntry);
                    break;
            }
        })(i);
    }
    $block();
    return f;
};