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273
node_modules/onoff/onoff.js
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273
node_modules/onoff/onoff.js
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"use strict";
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const fs = require('fs');
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const debounce = require('lodash.debounce');
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const Epoll = require('epoll').Epoll;
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const GPIO_ROOT_PATH = '/sys/class/gpio/';
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// fs reads and writes use Buffers
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const HIGH_BUF = Buffer.from('1');
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const LOW_BUF = Buffer.from('0');
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// lib returns numeric data and expects numeric data as arguments
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const HIGH = 1;
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const LOW = 0;
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class Gpio {
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constructor(gpio, direction, edge, options) {
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if (typeof edge === 'object' && !options) {
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options = edge;
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edge = undefined;
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}
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options = options || {};
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this._gpio = gpio;
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this._gpioPath = GPIO_ROOT_PATH + 'gpio' + this._gpio + '/';
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this._debounceTimeout = options.debounceTimeout || 0;
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this._readBuffer = Buffer.alloc(16);
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this._listeners = [];
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if (!fs.existsSync(this._gpioPath)) {
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// The pin hasn't been exported yet so export it
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fs.writeFileSync(GPIO_ROOT_PATH + 'export', this._gpio);
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// A hack to avoid the issue described here:
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// https://github.com/raspberrypi/linux/issues/553
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// I don't like this solution, but it enables compatibility with older
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// versions of onoff, i.e., the Gpio constructor was and still is
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// synchronous.
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let permissionRequiredPaths = [
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this._gpioPath + 'direction',
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this._gpioPath + 'active_low',
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this._gpioPath + 'value',
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];
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// On some systems the edge file will not exist if the GPIO does not
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// support interrupts
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// https://github.com/fivdi/onoff/issues/77#issuecomment-321980735
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if (edge && direction === 'in') {
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permissionRequiredPaths.push(this._gpioPath + 'edge');
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}
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permissionRequiredPaths.forEach((path) => {
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let tries = 0;
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while (true) {
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try {
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tries += 1;
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const fd = fs.openSync(path, 'r+');
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fs.closeSync(fd);
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break;
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} catch (e) {
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if (tries === 10000) {
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throw e;
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}
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}
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}
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});
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fs.writeFileSync(this._gpioPath + 'direction', direction);
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// On some systems writing to the edge file for an output GPIO will
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// result in an "EIO, i/o error"
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// https://github.com/fivdi/onoff/issues/87
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if (edge && direction === 'in') {
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fs.writeFileSync(this._gpioPath + 'edge', edge);
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}
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if (!!options.activeLow) {
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fs.writeFileSync(this._gpioPath + 'active_low', HIGH_BUF);
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}
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} else {
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// The pin has already been exported, perhaps by onoff itself, perhaps
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// by quick2wire gpio-admin on the Pi, perhaps by the WiringPi gpio
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// utility on the Pi, or perhaps by something else. In any case, an
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// attempt is made to set the direction and edge to the requested
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// values here. If quick2wire gpio-admin was used for the export, the
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// user should have access to both direction and edge files. This is
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// important as gpio-admin sets niether direction nor edge. If the
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// WiringPi gpio utility was used, the user should have access to edge
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// file, but not the direction file. This is also ok as the WiringPi
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// gpio utility can set both direction and edge. If there are any
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// errors while attempting to perform the modifications, just keep on
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// truckin'.
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try {
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fs.writeFileSync(this._gpioPath + 'direction', direction);
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} catch (ignore) {
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}
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try {
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// On some systems writing to the edge file for an output GPIO will
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// result in an "EIO, i/o error"
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// https://github.com/fivdi/onoff/issues/87
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if (edge && direction === 'in') {
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fs.writeFileSync(this._gpioPath + 'edge', edge);
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}
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try {
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fs.writeFileSync(this._gpioPath + 'active_low',
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!!options.activeLow ? HIGH_BUF : LOW_BUF
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);
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} catch (ignore) {
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}
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} catch (ignore) {
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}
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}
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// Cache fd for performance
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this._valueFd = fs.openSync(this._gpioPath + 'value', 'r+');
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{
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// A poller is created for both inputs and outputs. A poller isn't
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// actully needed for an output but the setDirection method can be
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// invoked to change the direction of a GPIO from output to input and
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// then a poller may be needed.
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const pollerEventHandler = (err, fd, events) => {
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const value = this.readSync();
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if ((value === LOW && this._fallingEnabled) ||
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(value === HIGH && this._risingEnabled)) {
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this._listeners.slice(0).forEach((callback) => {
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callback(err, value);
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});
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}
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};
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this._risingEnabled = edge === 'both' || edge == 'rising';
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this._fallingEnabled = edge === 'both' || edge == 'falling';
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// Read GPIO value before polling to prevent an initial unauthentic
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// interrupt
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this.readSync();
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if (this._debounceTimeout > 0) {
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const db = debounce(pollerEventHandler, this._debounceTimeout);
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this._poller = new Epoll((err, fd, events) => {
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this.readSync(); // Clear interrupt
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db(err, fd, events);
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});
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} else {
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this._poller = new Epoll(pollerEventHandler);
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}
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}
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}
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read(callback) {
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fs.read(this._valueFd, this._readBuffer, 0, 1, 0, (err, bytes, buf) => {
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if (typeof callback === 'function') {
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if (err) {
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return callback(err);
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}
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callback(null, buf[0] === HIGH_BUF[0] ? HIGH : LOW);
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}
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});
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}
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readSync() {
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fs.readSync(this._valueFd, this._readBuffer, 0, 1, 0);
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return this._readBuffer[0] === HIGH_BUF[0] ? HIGH : LOW;
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}
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write(value, callback) {
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const writeBuffer = value === HIGH ? HIGH_BUF : LOW_BUF;
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fs.write(this._valueFd, writeBuffer, 0, writeBuffer.length, 0, callback);
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}
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writeSync(value) {
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const writeBuffer = value === HIGH ? HIGH_BUF : LOW_BUF;
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fs.writeSync(this._valueFd, writeBuffer, 0, writeBuffer.length, 0);
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}
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watch(callback) {
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this._listeners.push(callback);
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if (this._listeners.length === 1) {
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this._poller.add(this._valueFd, Epoll.EPOLLPRI);
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}
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}
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unwatch(callback) {
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if (this._listeners.length > 0) {
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if (typeof callback !== 'function') {
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this._listeners = [];
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} else {
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this._listeners = this._listeners.filter((listener) => {
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return callback !== listener;
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});
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}
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if (this._listeners.length === 0) {
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this._poller.remove(this._valueFd);
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}
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}
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}
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unwatchAll() {
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this.unwatch();
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}
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direction() {
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return fs.readFileSync(this._gpioPath + 'direction').toString().trim();
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}
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setDirection(direction) {
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fs.writeFileSync(this._gpioPath + 'direction', direction);
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}
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edge() {
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return fs.readFileSync(this._gpioPath + 'edge').toString().trim();
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}
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setEdge(edge) {
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fs.writeFileSync(this._gpioPath + 'edge', edge);
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this._risingEnabled = edge === 'both' || edge == 'rising';
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this._fallingEnabled = edge === 'both' || edge == 'falling';
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}
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activeLow() {
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return fs.readFileSync(
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this._gpioPath + 'active_low')[0] === HIGH_BUF[0] ? true : false;
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}
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setActiveLow(invert) {
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fs.writeFileSync(this._gpioPath + 'active_low', !!invert ? HIGH_BUF : LOW_BUF);
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}
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unexport() {
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this.unwatchAll();
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fs.closeSync(this._valueFd);
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try {
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fs.writeFileSync(GPIO_ROOT_PATH + 'unexport', this._gpio);
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} catch (ignore) {
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// Flow of control always arrives here when cape_universal is enabled on
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// the bbb.
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}
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}
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static get accessible() {
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let fd;
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try {
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fd = fs.openSync(GPIO_ROOT_PATH + 'export', 'w');
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} catch(e) {
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// e.code === 'ENOENT' / 'EACCES' are most common
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// though any failure to open will also result in a gpio
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// failure to export.
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return false;
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} finally {
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if (fd) {
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fs.closeSync(fd);
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}
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}
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return true;
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}
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}
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Gpio.HIGH = HIGH;
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Gpio.LOW = LOW;
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exports.Gpio = Gpio;
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