/**
|
* tail-file.js: TODO: add file header description.
|
*
|
* (C) 2010 Charlie Robbins
|
* MIT LICENCE
|
*/
|
|
'use strict';
|
|
const fs = require('fs');
|
const { StringDecoder } = require('string_decoder');
|
const { Stream } = require('readable-stream');
|
|
/**
|
* Simple no-op function.
|
* @returns {undefined}
|
*/
|
function noop() {}
|
|
/**
|
* TODO: add function description.
|
* @param {Object} options - Options for tail.
|
* @param {function} iter - Iterator function to execute on every line.
|
* `tail -f` a file. Options must include file.
|
* @returns {mixed} - TODO: add return description.
|
*/
|
module.exports = (options, iter) => {
|
const buffer = Buffer.alloc(64 * 1024);
|
const decode = new StringDecoder('utf8');
|
const stream = new Stream();
|
let buff = '';
|
let pos = 0;
|
let row = 0;
|
|
if (options.start === -1) {
|
delete options.start;
|
}
|
|
stream.readable = true;
|
stream.destroy = () => {
|
stream.destroyed = true;
|
stream.emit('end');
|
stream.emit('close');
|
};
|
|
fs.open(options.file, 'a+', '0644', (err, fd) => {
|
if (err) {
|
if (!iter) {
|
stream.emit('error', err);
|
} else {
|
iter(err);
|
}
|
stream.destroy();
|
return;
|
}
|
|
(function read() {
|
if (stream.destroyed) {
|
fs.close(fd, noop);
|
return;
|
}
|
|
return fs.read(fd, buffer, 0, buffer.length, pos, (error, bytes) => {
|
if (error) {
|
if (!iter) {
|
stream.emit('error', error);
|
} else {
|
iter(error);
|
}
|
stream.destroy();
|
return;
|
}
|
|
if (!bytes) {
|
if (buff) {
|
// eslint-disable-next-line eqeqeq
|
if (options.start == null || row > options.start) {
|
if (!iter) {
|
stream.emit('line', buff);
|
} else {
|
iter(null, buff);
|
}
|
}
|
row++;
|
buff = '';
|
}
|
return setTimeout(read, 1000);
|
}
|
|
let data = decode.write(buffer.slice(0, bytes));
|
if (!iter) {
|
stream.emit('data', data);
|
}
|
|
data = (buff + data).split(/\n+/);
|
|
const l = data.length - 1;
|
let i = 0;
|
|
for (; i < l; i++) {
|
// eslint-disable-next-line eqeqeq
|
if (options.start == null || row > options.start) {
|
if (!iter) {
|
stream.emit('line', data[i]);
|
} else {
|
iter(null, data[i]);
|
}
|
}
|
row++;
|
}
|
|
buff = data[l];
|
pos += bytes;
|
return read();
|
});
|
}());
|
});
|
|
if (!iter) {
|
return stream;
|
}
|
|
return stream.destroy;
|
};
|
