autoinstallers/install/secu/make/node_modules/tail/lib/tail.js

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2022-05-31 19:28:17 -04:00
let events = require(`events`)
let fs = require('fs')
let path = require('path')
// const environment = process.env['NODE_ENV'] || 'development'
class devNull {
info() { };
error() { };
};
class Tail extends events.EventEmitter {
constructor(filename, options = {}) {
super();
this.filename = filename;
this.absPath = path.dirname(this.filename);
this.separator = (options.separator !== undefined) ? options.separator : /[\r]{0,1}\n/;// null is a valid param
this.fsWatchOptions = options.fsWatchOptions || {};
this.follow = options['follow'] != undefined ? options['follow'] : true;
this.logger = options.logger || new devNull();
this.useWatchFile = options.useWatchFile || false;
this.flushAtEOF = options.flushAtEOF || false;
this.encoding = options.encoding || 'utf-8';
const fromBeginning = options.fromBeginning || false;
this.nLines = options.nLines || undefined;
this.logger.info(`Tail starting...`)
this.logger.info(`filename: ${this.filename}`);
this.logger.info(`encoding: ${this.encoding}`);
try {
fs.accessSync(this.filename, fs.constants.F_OK);
} catch (err) {
if (err.code == 'ENOENT') {
throw err
}
}
this.buffer = '';
this.internalDispatcher = new events.EventEmitter();
this.queue = [];
this.isWatching = false;
this.pos = 0;
// this.internalDispatcher.on('next',this.readBlock);
this.internalDispatcher.on('next', () => {
this.readBlock();
});
this.logger.info(`fromBeginning: ${fromBeginning}`);
let startingCursor;
if (fromBeginning) {
startingCursor = 0;
} else if (this.nLines !== undefined) {
const data = fs.readFileSync(this.filename, {
flag: 'r',
encoding: this.encoding
});
const tokens = data.split(this.separator);
const dropLastToken = (tokens[tokens.length - 1] === '') ? 1 : 0;//if the file ends with empty line ignore line NL
if (tokens.length - this.nLines - dropLastToken <= 0) {
//nLines is bigger than avaiable tokens: tail from the begin
startingCursor = 0;
} else {
const match = data.match(new RegExp(`(?:[^\r\n]*[\r]{0,1}\n){${tokens.length - this.nLines - dropLastToken}}`));
startingCursor = (match && match.length) ? Buffer.byteLength(match[0], this.encoding) : this.latestPosition();
}
} else {
startingCursor = this.latestPosition();
}
if (startingCursor === undefined) throw new Error("Tail can't initialize.");
const flush = fromBeginning || (this.nLines != undefined);
try {
this.watch(startingCursor, flush);
} catch (err) {
this.logger.error(`watch for ${this.filename} failed: ${err}`);
this.emit("error", `watch for ${this.filename} failed: ${err}`);
}
}
latestPosition() {
try {
return fs.statSync(this.filename).size;
} catch (err) {
this.logger.error(`size check for ${this.filename} failed: ${err}`);
this.emit("error", `size check for ${this.filename} failed: ${err}`);
throw err;
}
}
readBlock() {
if (this.queue.length >= 1) {
const block = this.queue[0];
if (block.end > block.start) {
let stream = fs.createReadStream(this.filename, { start: block.start, end: block.end - 1, encoding: this.encoding });
stream.on('error', (error) => {
this.logger.error(`Tail error: ${error}`);
this.emit('error', error);
});
stream.on('end', () => {
let _ = this.queue.shift();
if (this.queue.length > 0) {
this.internalDispatcher.emit('next');
}
if (this.flushAtEOF && this.buffer.length > 0) {
this.emit('line', this.buffer);
this.buffer = "";
}
});
stream.on('data', (d) => {
if (this.separator === null) {
this.emit("line", d);
} else {
this.buffer += d;
let parts = this.buffer.split(this.separator);
this.buffer = parts.pop();
for (const chunk of parts) {
this.emit("line", chunk);
}
}
});
}
}
}
change() {
let p = this.latestPosition()
if (p < this.currentCursorPos) {//scenario where text is not appended but it's actually a w+
this.currentCursorPos = p
} else if (p > this.currentCursorPos) {
this.queue.push({ start: this.currentCursorPos, end: p });
this.currentCursorPos = p
if (this.queue.length == 1) {
this.internalDispatcher.emit("next");
}
}
}
watch(startingCursor, flush) {
if (this.isWatching) return;
this.logger.info(`filesystem.watch present? ${fs.watch != undefined}`);
this.logger.info(`useWatchFile: ${this.useWatchFile}`);
this.isWatching = true;
this.currentCursorPos = startingCursor;
//force a file flush is either fromBegining or nLines flags were passed.
if (flush) this.change();
if (!this.useWatchFile && fs.watch) {
this.logger.info(`watch strategy: watch`);
this.watcher = fs.watch(this.filename, this.fsWatchOptions, (e, filename) => { this.watchEvent(e, filename); });
} else {
this.logger.info(`watch strategy: watchFile`);
fs.watchFile(this.filename, this.fsWatchOptions, (curr, prev) => { this.watchFileEvent(curr, prev) });
}
}
rename(filename) {
//TODO
//MacOS sometimes throws a rename event for no reason.
//Different platforms might behave differently.
//see https://nodejs.org/api/fs.html#fs_fs_watch_filename_options_listener
//filename might not be present.
//https://nodejs.org/api/fs.html#fs_filename_argument
//Better solution would be check inode but it will require a timeout and
// a sync file read.
if (filename === undefined || filename !== this.filename) {
this.unwatch();
if (this.follow) {
this.filename = path.join(this.absPath, filename);
this.rewatchId = setTimeout((() => {
try {
this.watch(this.currentCursorPos);
} catch (ex) {
this.logger.error(`'rename' event for ${this.filename}. File not available anymore.`);
this.emit("error", ex);
}
}), 1000);
} else {
this.logger.error(`'rename' event for ${this.filename}. File not available anymore.`);
this.emit("error", `'rename' event for ${this.filename}. File not available anymore.`);
}
} else {
// this.logger.info("rename event but same filename")
}
}
watchEvent(e, evtFilename) {
try {
if (e === 'change') {
this.change();
} else if (e === 'rename') {
this.rename(evtFilename);
}
} catch (err) {
this.logger.error(`watchEvent for ${this.filename} failed: ${err}`);
this.emit("error", `watchEvent for ${this.filename} failed: ${err}`);
}
}
watchFileEvent(curr, prev) {
if (curr.size > prev.size) {
this.currentCursorPos = curr.size; //Update this.currentCursorPos so that a consumer can determine if entire file has been handled
this.queue.push({ start: prev.size, end: curr.size });
if (this.queue.length == 1) {
this.internalDispatcher.emit("next");
}
}
}
unwatch() {
if (this.watcher) {
this.watcher.close();
} else {
fs.unwatchFile(this.filename);
}
if (this.rewatchId) {
clearTimeout(this.rewatchId);
this.rewatchId = undefined;
}
this.isWatching = false;
this.queue = [];// TODO: is this correct behaviour?
if (this.logger) {
this.logger.info(`Unwatch ${this.filename}`);
}
}
}
exports.Tail = Tail