Audio Meta

1import { closeSync, ftruncateSync, openSync, readFileSync, writeSync } from "node:fs";
2
3// Keep the merge base and output on the same file even if its pathname changes
4// while audio generation runs. The CLI owns this handle until write or exit.
5export function openAudioMeta(path) {
6  let fd;
7  try {
8    fd = openSync(path, "r+");
9  } catch (error) {
10    if (error.code !== "ENOENT") throw error;
11  }
12  let value = {};
13  if (fd !== undefined) {
14    try {
15      value = JSON.parse(readFileSync(fd, "utf8"));
16    } catch (error) {
17      closeSync(fd);
18      throw error;
19    }
20  }
21  return {
22    value,
23    write(meta) {
24      const bytes = Buffer.from(JSON.stringify(meta, null, 2));
25      // Defer new-file creation until generation succeeds. Never overwrite a
26      // file (or follow a link) that appeared since the missing merge base.
27      if (fd === undefined) fd = openSync(path, "wx");
28      try {
29        let offset = 0;
30        while (offset < bytes.length) {
31          offset += writeSync(fd, bytes, offset, bytes.length - offset, offset);
32        }
33        ftruncateSync(fd, bytes.length);
34      } finally {
35        closeSync(fd);
36      }
37    },
38  };
39}