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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,30 @@ | ||
| import {SyncMessenger} from "../../src/fsa-to-node/worker/SyncMessenger"; | ||
| import {encode, decode} from 'json-joy/es6/json-pack/msgpack/util'; | ||
| import {IFileSystemDirectoryHandle} from "../../src/fsa/types"; | ||
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| const sab: SharedArrayBuffer = new SharedArrayBuffer(1024 * 32); | ||
| const messenger = new SyncMessenger(sab); | ||
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| onmessage = (e) => { | ||
| const data = e.data; | ||
| console.log('>', data); | ||
| if (data && typeof data === 'object') { | ||
| switch (data.type) { | ||
| case 'set-root': { | ||
| postMessage({type: 'root-set', id: data.id}); | ||
| const dir = data.dir as IFileSystemDirectoryHandle; | ||
| messenger.serveAsync(async (request) => { | ||
| const message = decode(request as any); | ||
| const list: string[] = []; | ||
| for await (const key of dir.keys()) { | ||
| list.push(key); | ||
| } | ||
| return encode(list); | ||
| }); | ||
| break; | ||
| } | ||
| } | ||
| } | ||
| }; | ||
|
|
||
| postMessage({type: 'init', sab}); |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,65 @@ | ||
| type AsyncCallback = (request: Uint8Array) => Promise<Uint8Array>; | ||
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| const microSleepSync = () => { | ||
| /** @todo Replace this by synchronous XHR call. */ | ||
| Math.random(); | ||
| }; | ||
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| const sleepUntilSync = (condition: () => boolean) => { | ||
| while (!condition()) microSleepSync(); | ||
| }; | ||
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| /** | ||
| * `SyncMessenger` allows to execute asynchronous code synchronously. The | ||
| * asynchronous code is executed in a Worker, while the main thread is blocked | ||
| * until the asynchronous code is finished. | ||
| * | ||
| * First, four 4-byte works is header, where the first word is used for Atomics | ||
| * notifications. The second word is used for spin-locking the main thread until | ||
| * the asynchronous code is finished. The third word is used to specify payload | ||
| * length. The fourth word is currently unused. | ||
| * | ||
| * The maximum payload size is the size of the SharedArrayBuffer minus the | ||
| * header size. | ||
| */ | ||
| export class SyncMessenger { | ||
| protected readonly int32: Int32Array; | ||
| protected readonly uint8: Uint8Array; | ||
| protected readonly headerSize; | ||
| protected readonly dataSize; | ||
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| public constructor(protected readonly sab: SharedArrayBuffer) { | ||
| this.int32 = new Int32Array(sab); | ||
| this.uint8 = new Uint8Array(sab); | ||
| this.headerSize = 4 * 4; | ||
| this.dataSize = sab.byteLength - this.headerSize; | ||
| } | ||
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| public callSync(data: Uint8Array): Uint8Array { | ||
| const requestLength = data.length; | ||
| this.int32[1] = 0; | ||
| this.int32[2] = requestLength; | ||
| this.uint8.set(data, this.headerSize); | ||
| Atomics.notify(this.int32, 0); | ||
| sleepUntilSync(() => this.int32[1] === 1); | ||
| const responseLength = this.int32[2]; | ||
| const response = this.uint8.slice(this.headerSize, this.headerSize + responseLength); | ||
| return response; | ||
| } | ||
|
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| public serveAsync(callback: AsyncCallback): void { | ||
| (async () => { | ||
| try { | ||
| const res = Atomics.wait(this.int32, 0, 0); | ||
| if (res !== 'ok') throw new Error(`Unexpected Atomics.wait result: ${res}`); | ||
| const requestLength = this.int32[2]; | ||
| const request = this.uint8.slice(this.headerSize, this.headerSize + requestLength); | ||
| const response = await callback(request); | ||
| const responseLength = response.length; | ||
| this.int32[2] = responseLength; | ||
| this.uint8.set(response, this.headerSize); | ||
| this.int32[1] = 1; | ||
| } catch {} | ||
| })().catch(() => {}); | ||
| } | ||
| } |
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