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'use strict';
const {
Array,
FunctionPrototypeBind,
} = primordials;
const {
// For easy access to the nextTick state in the C++ land,
// and to avoid unnecessary calls into JS land.
tickInfo,
// Used to run V8's micro task queue.
runMicrotasks,
setTickCallback,
enqueueMicrotask
} = internalBinding('task_queue');
const {
triggerUncaughtException
} = internalBinding('errors');
const {
setHasRejectionToWarn,
hasRejectionToWarn,
listenForRejections,
processPromiseRejections
} = require('internal/process/promises');
const {
getDefaultTriggerAsyncId,
newAsyncId,
initHooksExist,
destroyHooksExist,
emitInit,
emitBefore,
emitAfter,
emitDestroy,
symbols: { async_id_symbol, trigger_async_id_symbol }
} = require('internal/async_hooks');
const {
ERR_INVALID_CALLBACK,
ERR_INVALID_ARG_TYPE
} = require('internal/errors').codes;
const FixedQueue = require('internal/fixed_queue');
// *Must* match Environment::TickInfo::Fields in src/env.h.
const kHasTickScheduled = 0;
function hasTickScheduled() {
return tickInfo[kHasTickScheduled] === 1;
}
function setHasTickScheduled(value) {
tickInfo[kHasTickScheduled] = value ? 1 : 0;
}
const queue = new FixedQueue();
// Should be in sync with RunNextTicksNative in node_task_queue.cc
function runNextTicks() {
if (!hasTickScheduled() && !hasRejectionToWarn())
runMicrotasks();
if (!hasTickScheduled() && !hasRejectionToWarn())
return;
processTicksAndRejections();
}
function processTicksAndRejections() {
let tock;
do {
while (tock = queue.shift()) {
const asyncId = tock[async_id_symbol];
emitBefore(asyncId, tock[trigger_async_id_symbol]);
try {
const callback = tock.callback;
if (tock.args === undefined) {
callback();
} else {
const args = tock.args;
switch (args.length) {
case 1: callback(args[0]); break;
case 2: callback(args[0], args[1]); break;
case 3: callback(args[0], args[1], args[2]); break;
case 4: callback(args[0], args[1], args[2], args[3]); break;
default: callback(...args);
}
}
} finally {
if (destroyHooksExist())
emitDestroy(asyncId);
}
emitAfter(asyncId);
}
runMicrotasks();
} while (!queue.isEmpty() || processPromiseRejections());
setHasTickScheduled(false);
setHasRejectionToWarn(false);
}
// `nextTick()` will not enqueue any callback when the process is about to
// exit since the callback would not have a chance to be executed.
function nextTick(callback) {
if (typeof callback !== 'function')
throw new ERR_INVALID_CALLBACK(callback);
if (process._exiting)
return;
let args;
switch (arguments.length) {
case 1: break;
case 2: args = [arguments[1]]; break;
case 3: args = [arguments[1], arguments[2]]; break;
case 4: args = [arguments[1], arguments[2], arguments[3]]; break;
default:
args = new Array(arguments.length - 1);
for (let i = 1; i < arguments.length; i++)
args[i - 1] = arguments[i];
}
if (queue.isEmpty())
setHasTickScheduled(true);
const asyncId = newAsyncId();
const triggerAsyncId = getDefaultTriggerAsyncId();
const tickObject = {
[async_id_symbol]: asyncId,
[trigger_async_id_symbol]: triggerAsyncId,
callback,
args
};
if (initHooksExist())
emitInit(asyncId, 'TickObject', triggerAsyncId, tickObject);
queue.push(tickObject);
}
let AsyncResource;
const defaultMicrotaskResourceOpts = { requireManualDestroy: true };
function createMicrotaskResource() {
// Lazy load the async_hooks module
if (AsyncResource === undefined) {
AsyncResource = require('async_hooks').AsyncResource;
}
return new AsyncResource('Microtask', defaultMicrotaskResourceOpts);
}
function runMicrotask() {
this.runInAsyncScope(() => {
const callback = this.callback;
try {
callback();
} catch (error) {
// runInAsyncScope() swallows the error so we need to catch
// it and handle it here.
triggerUncaughtException(error, false /* fromPromise */);
} finally {
this.emitDestroy();
}
});
}
function queueMicrotask(callback) {
if (typeof callback !== 'function') {
throw new ERR_INVALID_ARG_TYPE('callback', 'function', callback);
}
const asyncResource = createMicrotaskResource();
asyncResource.callback = callback;
enqueueMicrotask(FunctionPrototypeBind(runMicrotask, asyncResource));
}
module.exports = {
setupTaskQueue() {
// Sets the per-isolate promise rejection callback
listenForRejections();
// Sets the callback to be run in every tick.
setTickCallback(processTicksAndRejections);
return {
nextTick,
runNextTicks
};
},
queueMicrotask
};
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