Save and load index from file

[jlarmstrongiv]

I’m glad to see that hnswlib-wasm supports saving and loading indexes via IndexedDB (IDBFS) 😄

I also noticed plans for future NodeJS support in this comment

I’m curious though—is it possible to save and load indexes to and from a file? That would help a lot to avoid rebuilding the index on different machines or browsers. Plus, sharing indexes with the upcoming node version would be awesome.

For example, sql.js lets users save and load a database via:

/* loading */
dbFileElm.onchange = () => {
  const f = dbFileElm.files[0];
  const r = new FileReader();
  r.onload = function() {
    const Uints = new Uint8Array(r.result);
    db = new SQL.Database(Uints);
  }
  r.readAsArrayBuffer(f);
}

const sqlPromise = initSqlJs({
  locateFile: file => `https://path/to/your/dist/folder/dist/${file}`
});
const dataPromise = fetch("/path/to/database.sqlite").then(res => res.arrayBuffer());
const [SQL, buf] = await Promise.all([sqlPromise, dataPromise])
const db = new SQL.Database(new Uint8Array(buf));

/* saving */
const fs = require("fs");
// [...] (create the database)
const data = db.export();
const buffer = Buffer.from(data);
fs.writeFileSync("filename.sqlite", buffer);

and I’m implementing an example for wa-sqlite to save and load sqlite.db files to and from IndexedDB with the Web Streams API.

Would you be open to adding save and load file functions to your package? Do you have suggestions on the best way for me to implement those?