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jlongster · Jun 28, 2021 · 6510646 · 6510646
commit 6510646
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diff --git a/.gitignore b/.gitignore
@@ -0,0 +1 @@
+node_modules
diff --git a/babel.config.js b/babel.config.js
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+module.exports = {presets: ['@babel/preset-env']}
diff --git a/backend.js b/backend.js
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+let syncifyWorker = new Worker('syncify.js');
+
+function get_string(buf) {
+  return String.fromCharCode
+    .apply(null, new Uint16Array(buf))
+    .replace(/\u0000/g, '');
+}
+
+function put_string(buf, str) {
+  var bufView = new Uint16Array(buf);
+  for (var i = 0, strLen = str.length; i < strLen; i++) {
+    Atomics.store(bufView, i, str.charCodeAt(i));
+  }
+  return buf;
+}
+
+function loadURL(sab, urlSab, url) {
+  sab[0] = 0;
+
+  let view = new Int32Array(sab);
+  let urlView = new Int32Array(urlSab);
+
+  put_string(urlSab, url);
+  Atomics.notify(urlView, 0, 1);
+  Atomics.wait(view, 0, 0);
+
+  return JSON.parse(get_string(sab));
+}
+
+function run() {
+  // SYNCHRONOUS!!
+  console.log(
+    loadURL(sab, urlSab, 'https://jsonplaceholder.typicode.com/todos/1')
+  );
+}
+
+let sab = new SharedArrayBuffer(10000);
+let urlSab = new SharedArrayBuffer(10000);
+syncifyWorker.postMessage([sab, urlSab]);
+
+syncifyWorker.onmessage = msg => {
+  switch (msg.data.type) {
+    case 'syncify-ready':
+      // run();
+      let f = self.webkitRequestFileSystemSync(self.PERSISTENT, 1000);
+      console.log(f);
+  }
+};
diff --git a/favicon.ico b/favicon.ico
diff --git a/index.html b/index.html
@@ -0,0 +1,5 @@
+<!DOCTYPE html>
+
+<body>
+  <script src="main.js"></script>
+</body>
diff --git a/main.js b/main.js
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+let worker = new Worker('backend.js');
+
+// alert(window.PERSISTENT)
diff --git a/package.json b/package.json
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+{
+  "dependencies": {
+    "@babel/preset-env": "^7.14.7",
+    "babel": "^6.23.0",
+    "jest": "^27.0.5"
+  }
+}
diff --git a/syncify.js b/syncify.js
@@ -0,0 +1,42 @@
+function get_string(buf) {
+  return String.fromCharCode
+    .apply(null, new Uint16Array(buf))
+    .replace(/\u0000/g, '');
+}
+
+function put_string(buf, str) {
+  var bufView = new Uint16Array(buf);
+  for (var i = 0, strLen = str.length; i < strLen; i++) {
+    bufView[i] = str.charCodeAt(i);
+  }
+  return buf;
+}
+
+async function run(url, sab) {
+  let res = await fetch(url);
+  let json = await res.json();
+
+  put_string(sab, JSON.stringify(json));
+
+  let view = new Int32Array(sab);
+  Atomics.notify(view, 0, 1);
+}
+
+async function listen(sab, urlSab) {
+  let view = new Int32Array(urlSab);
+
+  while (1) {
+    Atomics.wait(view, 0, 0);
+
+    let url = get_string(urlSab);
+    view[0] = 0;
+    await run(url, sab);
+  }
+}
+
+self.onmessage = msg => {
+  postMessage({ type: 'syncify-ready' });
+
+  let [sab, urlSab] = msg.data;
+  listen(sab, urlSab);
+};
diff --git a/virtual-file.js b/virtual-file.js
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+function range(start, end, step) {
+  let r = [];
+  for (let i = start; i <= end; i += step) {
+    r.push(i);
+  }
+  return r;
+}
+
+export function concatChunks(chunks, start, end) {
+  let buffer = new Buffer(end - start);
+  let view = new Uint8Array(buffer);
+
+  let cursor = 0;
+  for (let i = 0; i < chunks.length; i++) {
+    console.log(chunks[i]);
+    let cstart = 0;
+    let cend = chunks[i].byteLength;
+    if (start > chunks[i].pos) {
+      cstart = start - chunks[i].pos;
+    }
+    if (end < chunks[i].pos + chunks[i].data.byteLength) {
+      cend = end - chunks[i].pos;
+    }
+
+    console.log(cstart, cend);
+    view.set(new Uint8Array(chunks[i], cstart, cend), cursor);
+    cursor += cend - cstart;
+  }
+  return buffer;
+}
+
+class File {
+  constructor(chunkSize) {
+    this.chunkSize = chunkSize;
+    // TODO: make LRU cache
+    this.cache = new Map();
+  }
+
+  loadMissing(boundaries) {}
+
+  updateCache(chunks) {
+    for (let i = 0; i < chunks.length; i++) {
+      this.cache.set(chunks[i].pos, chunks[i]);
+    }
+  }
+
+  getBoundaryIndexes(start, end) {
+    let startC = start - (start % this.chunkSize);
+    let endC = end - 1 - ((end - 1) % this.chunkSize);
+
+    return range(startC, endC, this.chunkSize);
+  }
+
+  load(start, end) {
+    let indexes = this.getBoundaryIndexes(start, end);
+    let status = boundaries.reduce(
+      (acc, b) => {
+        let cached = this.chunks.get(b);
+        if (cached) {
+          acc.cached.push(cached);
+        } else {
+          acc.missing.push(cached);
+        }
+        return acc;
+      },
+      { cached: [], missing: [] }
+    );
+
+    let missingChunks = this.loadMissing(status.missing);
+
+    let allChunks = status.cached.concat(missingChunks);
+    allChunks.sort((c1, c2) => {
+      return c1.pos - c2.pos;
+    });
+
+    this.updateCache(allChunks);
+    return concatChunks(allChunks, start, end);
+  }
+
+  read(buffer, offset, length, position) {
+    let readBuffer = this.load(position, position + length);
+    let view = new Uint8Array(buffer);
+    toView.set(new Uint8Array(readBuffer), offset);
+    // TODO: need to check end of file
+    return length;
+  }
+
+  write(buffer, offset, length, position) {}
+}
diff --git a/virtual-file.test.js b/virtual-file.test.js
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+import { concatChunks } from './virtual-file';
+
+function makeChunks(chunkSize, data) {
+  let arr = [];
+  for (let i = 0; i < data.length; i += chunkSize) {
+    arr.push({ pos: i, data: Int8Array.from(data.slice(i, i + chunkSize)) });
+  }
+  return arr;
+}
+
+describe('concatChunks', () => {
+  test('works', () => {
+    let chunks = makeChunks(3, [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]);
+    expect(Array.from(concatChunks(chunks, 1, 7))).toBe([]);
+  });
+});