usb
Version:
Library to access USB devices
116 lines • 3.69 kB
JavaScript
;
const events_1 = require("events");
const device_1 = require("./device");
const usb = require("./bindings");
if (usb.INIT_ERROR) {
/* eslint-disable no-console */
console.warn('Failed to initialize libusb.');
}
Object.setPrototypeOf(usb, events_1.EventEmitter.prototype);
Object.defineProperty(usb, 'pollHotplug', {
value: false,
writable: true
});
Object.defineProperty(usb, 'pollHotplugDelay', {
value: 500,
writable: true
});
// `usb.Device` is not defined when `usb.INIT_ERROR` is true
if (usb.Device) {
Object.getOwnPropertyNames(device_1.ExtendedDevice.prototype).forEach(name => {
Object.defineProperty(usb.Device.prototype, name, Object.getOwnPropertyDescriptor(device_1.ExtendedDevice.prototype, name) || Object.create(null));
});
}
// Devices delta support for non-libusb hotplug events
let hotPlugDevices = new Set();
// This method needs to be used for attach/detach IDs (hotplugSupportType === 2) rather than a lookup because vid/pid are not unique
const emitHotplugEvents = () => {
// Collect current devices
const devices = new Set(usb.getDeviceList());
// Find attached devices
for (const device of devices) {
if (!hotPlugDevices.has(device)) {
usb.emit('attach', device);
}
}
// Find detached devices
for (const device of hotPlugDevices) {
if (!devices.has(device)) {
usb.emit('detach', device);
}
}
hotPlugDevices = devices;
};
// Polling mechanism for checking device changes where hotplug detection is not available
let pollingHotplug = false;
const pollHotplug = (start = false) => {
if (start) {
pollingHotplug = true;
}
else if (!pollingHotplug) {
return;
}
else {
emitHotplugEvents();
}
setTimeout(() => pollHotplug(), usb.pollHotplugDelay);
};
// Devices changed event handler
const devicesChanged = () => setTimeout(() => emitHotplugEvents(), usb.pollHotplugDelay);
// Hotplug control
let hotplugSupported = 0;
const startHotplug = () => {
hotplugSupported = usb.pollHotplug ? 0 : usb._supportedHotplugEvents();
if (hotplugSupported !== 1) {
// Collect initial devices when not using libusb
hotPlugDevices = new Set(usb.getDeviceList());
}
if (hotplugSupported) {
// Use hotplug event emitters
usb._enableHotplugEvents();
if (hotplugSupported === 2) {
// Use hotplug ID events to trigger a change check
usb.on('attachIds', devicesChanged);
usb.on('detachIds', devicesChanged);
}
}
else {
// Fallback to using polling to check for changes
pollHotplug(true);
}
};
const stopHotplug = () => {
if (hotplugSupported) {
// Disable hotplug events
usb._disableHotplugEvents();
if (hotplugSupported === 2) {
// Remove hotplug ID event listeners
usb.off('attachIds', devicesChanged);
usb.off('detachIds', devicesChanged);
}
}
else {
// Stop polling
pollingHotplug = false;
}
};
usb.on('newListener', event => {
if (event !== 'attach' && event !== 'detach') {
return;
}
const listenerCount = usb.listenerCount('attach') + usb.listenerCount('detach');
if (listenerCount === 0) {
startHotplug();
}
});
usb.on('removeListener', event => {
if (event !== 'attach' && event !== 'detach') {
return;
}
const listenerCount = usb.listenerCount('attach') + usb.listenerCount('detach');
if (listenerCount === 0) {
stopHotplug();
}
});
module.exports = usb;
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