Config Lock

1// The one lock on ~/.hyperframes/config.json, for the CLI, its auto-update step and media-use. The auto-update step
2// embeds this function's source, so it must use only its arguments and globals.
3export function withFileLock(lockPath, fs, task) {
4  const token = `${process.pid}-${Date.now()}-${Math.random().toString(36).slice(2)}`;
5  const started = Date.now();
6  for (;;) {
7    let fd;
8    try {
9      fd = fs.openSync(lockPath, "wx");
10    } catch (error) {
11      if (error.code !== "EEXIST") throw error;
12      // Never taken over: a lock older than any hold was left by a process that stopped, and a person removes it.
13      let leftover = false;
14      try {
15        leftover = Date.now() - fs.statSync(lockPath).mtimeMs > 5000;
16      } catch {}
17      if (leftover || Date.now() - started > 10000)
18        throw Object.assign(
19          new Error(
20            `Settings are locked by another hyperframes process. If none is running, delete ${lockPath}`,
21          ),
22          { code: "HF_SETTINGS_LOCKED" },
23        );
24      Atomics.wait(new Int32Array(new SharedArrayBuffer(4)), 0, 0, 25);
25      continue;
26    }
27    try {
28      fs.writeSync(fd, token);
29    } catch (error) {
30      fs.rmSync(lockPath, { force: true });
31      throw error;
32    } finally {
33      fs.closeSync(fd);
34    }
35    break;
36  }
37  try {
38    return task();
39  } finally {
40    // No code removes another's lock, so release needs no check (only a person deleting a live one defeats it).
41    try {
42      fs.rmSync(lockPath);
43    } catch {}
44  }
45}