puppeteer/lib/Tracing.js

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/**
* Copyright 2017 Google Inc. All rights reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
const fs = require('fs');
const helper = require('./helper');
class Tracing {
/**
* @param {!Session} client
*/
constructor(client) {
this._client = client;
this._recording = false;
this._path = '';
}
/**
* @param {!Object} options
* @return {!Promise}
*/
async start(options) {
console.assert(!this._recording, 'Cannot start recording trace while already recording trace.');
console.assert(options.path, 'Must specify a path to write trace file to.');
const categoriesArray = [
'-*', 'devtools.timeline', 'v8.execute', 'disabled-by-default-devtools.timeline',
'disabled-by-default-devtools.timeline.frame', 'toplevel',
'blink.console', 'blink.user_timing', 'latencyInfo', 'disabled-by-default-devtools.timeline.stack',
'disabled-by-default-v8.cpu_profiler'
];
if (options.screenshots)
categoriesArray.push('disabled-by-default-devtools.screenshot');
this._path = options.path;
this._recording = true;
await this._client.send('Tracing.start', {
transferMode: 'ReturnAsStream',
categories: categoriesArray.join(',')
});
}
/**
* @return {!Promise}
*/
async stop() {
let fulfill;
let contentPromise = new Promise(x => fulfill = x);
this._client.once('Tracing.tracingComplete', event => {
this._readStream(event.stream, this._path).then(fulfill);
});
await this._client.send('Tracing.end');
this._recording = false;
return contentPromise;
}
/**
* @param {string} handle
* @param {string} path
* @return {!Promise}
*/
async _readStream(handle, path) {
let eof = false;
let file = fs.openSync(path, 'w');
while (!eof) {
let response = await this._client.send('IO.read', {handle});
eof = response.eof;
if (path)
fs.writeSync(file, response.data);
}
fs.closeSync(file);
await this._client.send('IO.close', {handle});
}
}
helper.tracePublicAPI(Tracing);
module.exports = Tracing;