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sw.js
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sw.js
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const WRITE = 0
const PULL = 0
const ERROR = 1
const ABORT = 1
const CLOSE = 2
const PING = 3
/** @implements {UnderlyingSource} */
class MessagePortSource {
/** @type {ReadableStreamController<any>} controller */
controller
/** @param {MessagePort} port */
constructor (port) {
this.port = port;
this.port.onmessage = evt => this.onMessage(evt.data)
}
/**
* @param {ReadableStreamController<any>} controller
*/
start (controller) {
this.controller = controller
this.port.postMessage({ type: PULL })
}
/** @param {Error} reason */
cancel (reason) {
// Firefox can notify a cancel event, chrome can't
// https://bugs.chromium.org/p/chromium/issues/detail?id=638494
this.port.postMessage({ type: ERROR, reason: reason.message })
this.port.close()
}
/** @param {{ type: number; chunk: Uint8Array; reason: any; }} message */
onMessage (message) {
// enqueue() will call pull() if needed when there's no backpressure
if (message.type === WRITE) {
this.controller.enqueue(message.chunk)
this.port.postMessage({ type: PULL })
}
if (message.type === ABORT) {
this.controller.error(message.reason)
this.port.close()
}
if (message.type === CLOSE) {
this.controller.close()
this.port.close()
}
}
}
self.addEventListener('install', () => {
self.skipWaiting()
})
self.addEventListener('activate', event => {
event.waitUntil(self.clients.claim())
})
const map = new Map()
// This should be called once per download
// Each event has a dataChannel that the data will be piped through
globalThis.addEventListener('message', evt => {
const data = evt.data
if (data.url && data.readablePort) {
data.rs = new ReadableStream(
new MessagePortSource(evt.data.readablePort),
new CountQueuingStrategy({ highWaterMark: 4 })
)
map.set(data.url, data)
}
})
globalThis.addEventListener('fetch', evt => {
const url = evt.request.url
const data = map.get(url)
if (!data) return null
map.delete(url)
evt.respondWith(new Response(data.rs, {
headers: data.headers
}))
})