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Raven Scott
233
install/secu/make/node_modules/tail/lib/tail.js
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vendored
Normal file
233
install/secu/make/node_modules/tail/lib/tail.js
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let events = require(`events`)
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let fs = require('fs')
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let path = require('path')
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// const environment = process.env['NODE_ENV'] || 'development'
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class devNull {
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info() { };
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error() { };
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};
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class Tail extends events.EventEmitter {
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constructor(filename, options = {}) {
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super();
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this.filename = filename;
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this.absPath = path.dirname(this.filename);
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this.separator = (options.separator !== undefined) ? options.separator : /[\r]{0,1}\n/;// null is a valid param
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this.fsWatchOptions = options.fsWatchOptions || {};
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this.follow = options['follow'] != undefined ? options['follow'] : true;
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this.logger = options.logger || new devNull();
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this.useWatchFile = options.useWatchFile || false;
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this.flushAtEOF = options.flushAtEOF || false;
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this.encoding = options.encoding || 'utf-8';
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const fromBeginning = options.fromBeginning || false;
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this.nLines = options.nLines || undefined;
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this.logger.info(`Tail starting...`)
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this.logger.info(`filename: ${this.filename}`);
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this.logger.info(`encoding: ${this.encoding}`);
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try {
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fs.accessSync(this.filename, fs.constants.F_OK);
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} catch (err) {
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if (err.code == 'ENOENT') {
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throw err
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}
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}
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this.buffer = '';
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this.internalDispatcher = new events.EventEmitter();
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this.queue = [];
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this.isWatching = false;
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this.pos = 0;
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// this.internalDispatcher.on('next',this.readBlock);
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this.internalDispatcher.on('next', () => {
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this.readBlock();
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});
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this.logger.info(`fromBeginning: ${fromBeginning}`);
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let startingCursor;
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if (fromBeginning) {
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startingCursor = 0;
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} else if (this.nLines !== undefined) {
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const data = fs.readFileSync(this.filename, {
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flag: 'r',
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encoding: this.encoding
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});
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const tokens = data.split(this.separator);
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const dropLastToken = (tokens[tokens.length - 1] === '') ? 1 : 0;//if the file ends with empty line ignore line NL
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if (tokens.length - this.nLines - dropLastToken <= 0) {
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//nLines is bigger than avaiable tokens: tail from the begin
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startingCursor = 0;
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} else {
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const match = data.match(new RegExp(`(?:[^\r\n]*[\r]{0,1}\n){${tokens.length - this.nLines - dropLastToken}}`));
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startingCursor = (match && match.length) ? Buffer.byteLength(match[0], this.encoding) : this.latestPosition();
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}
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} else {
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startingCursor = this.latestPosition();
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}
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if (startingCursor === undefined) throw new Error("Tail can't initialize.");
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const flush = fromBeginning || (this.nLines != undefined);
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try {
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this.watch(startingCursor, flush);
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} catch (err) {
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this.logger.error(`watch for ${this.filename} failed: ${err}`);
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this.emit("error", `watch for ${this.filename} failed: ${err}`);
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}
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}
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latestPosition() {
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try {
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return fs.statSync(this.filename).size;
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} catch (err) {
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this.logger.error(`size check for ${this.filename} failed: ${err}`);
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this.emit("error", `size check for ${this.filename} failed: ${err}`);
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throw err;
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}
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}
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readBlock() {
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if (this.queue.length >= 1) {
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const block = this.queue[0];
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if (block.end > block.start) {
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let stream = fs.createReadStream(this.filename, { start: block.start, end: block.end - 1, encoding: this.encoding });
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stream.on('error', (error) => {
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this.logger.error(`Tail error: ${error}`);
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this.emit('error', error);
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});
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stream.on('end', () => {
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let _ = this.queue.shift();
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if (this.queue.length > 0) {
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this.internalDispatcher.emit('next');
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}
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if (this.flushAtEOF && this.buffer.length > 0) {
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this.emit('line', this.buffer);
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this.buffer = "";
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}
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});
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stream.on('data', (d) => {
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if (this.separator === null) {
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this.emit("line", d);
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} else {
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this.buffer += d;
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let parts = this.buffer.split(this.separator);
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this.buffer = parts.pop();
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for (const chunk of parts) {
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this.emit("line", chunk);
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}
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}
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});
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}
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}
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}
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change() {
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let p = this.latestPosition()
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if (p < this.currentCursorPos) {//scenario where text is not appended but it's actually a w+
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this.currentCursorPos = p
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} else if (p > this.currentCursorPos) {
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this.queue.push({ start: this.currentCursorPos, end: p });
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this.currentCursorPos = p
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if (this.queue.length == 1) {
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this.internalDispatcher.emit("next");
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}
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}
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}
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watch(startingCursor, flush) {
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if (this.isWatching) return;
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this.logger.info(`filesystem.watch present? ${fs.watch != undefined}`);
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this.logger.info(`useWatchFile: ${this.useWatchFile}`);
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this.isWatching = true;
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this.currentCursorPos = startingCursor;
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//force a file flush is either fromBegining or nLines flags were passed.
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if (flush) this.change();
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if (!this.useWatchFile && fs.watch) {
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this.logger.info(`watch strategy: watch`);
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this.watcher = fs.watch(this.filename, this.fsWatchOptions, (e, filename) => { this.watchEvent(e, filename); });
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} else {
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this.logger.info(`watch strategy: watchFile`);
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fs.watchFile(this.filename, this.fsWatchOptions, (curr, prev) => { this.watchFileEvent(curr, prev) });
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}
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}
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rename(filename) {
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//TODO
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//MacOS sometimes throws a rename event for no reason.
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//Different platforms might behave differently.
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//see https://nodejs.org/api/fs.html#fs_fs_watch_filename_options_listener
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//filename might not be present.
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//https://nodejs.org/api/fs.html#fs_filename_argument
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//Better solution would be check inode but it will require a timeout and
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// a sync file read.
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if (filename === undefined || filename !== this.filename) {
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this.unwatch();
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if (this.follow) {
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this.filename = path.join(this.absPath, filename);
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this.rewatchId = setTimeout((() => {
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try {
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this.watch(this.currentCursorPos);
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} catch (ex) {
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this.logger.error(`'rename' event for ${this.filename}. File not available anymore.`);
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this.emit("error", ex);
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}
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}), 1000);
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} else {
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this.logger.error(`'rename' event for ${this.filename}. File not available anymore.`);
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this.emit("error", `'rename' event for ${this.filename}. File not available anymore.`);
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}
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} else {
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// this.logger.info("rename event but same filename")
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}
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}
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watchEvent(e, evtFilename) {
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try {
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if (e === 'change') {
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this.change();
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} else if (e === 'rename') {
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this.rename(evtFilename);
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}
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} catch (err) {
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this.logger.error(`watchEvent for ${this.filename} failed: ${err}`);
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this.emit("error", `watchEvent for ${this.filename} failed: ${err}`);
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}
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}
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watchFileEvent(curr, prev) {
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if (curr.size > prev.size) {
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this.currentCursorPos = curr.size; //Update this.currentCursorPos so that a consumer can determine if entire file has been handled
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this.queue.push({ start: prev.size, end: curr.size });
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if (this.queue.length == 1) {
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this.internalDispatcher.emit("next");
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}
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}
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}
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unwatch() {
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if (this.watcher) {
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this.watcher.close();
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} else {
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fs.unwatchFile(this.filename);
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}
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if (this.rewatchId) {
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clearTimeout(this.rewatchId);
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this.rewatchId = undefined;
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}
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this.isWatching = false;
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this.queue = [];// TODO: is this correct behaviour?
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if (this.logger) {
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this.logger.info(`Unwatch ${this.filename}`);
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}
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}
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}
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exports.Tail = Tail
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