AsyncFileStreamer example is unclear

[paulharris]

Hi,
Getting started with uWebSockets is made more difficult because the AsyncFileStreamer.h (in particular) file seems incomplete and written by someone who doesn't know how uWebSockets works.

Example:

                // todo: I don't really know what this is supposed to mean?
                return false;

uWebSockets/examples/helpers/AsyncFileStreamer.h

Line 78 in 388e2b3

// todo: I don't really know what this is supposed to mean?

This in particular is in streamFile(), which is part of the lambda created and passed to res->onWritable().
The documentation states that You MUST return true for success, false for failure. but in this case, the lambda seems to be simply scheduling a future attempt to send some more of the file in the future.

There is more confusion in the example... can we see a complete example written with best practices please?

[uNetworkingAB]

That example is unfinished

[e3dio]

// todo: I don't really know what this is supposed to mean?

onWritable().
The documentation states that You MUST return true for success, false for failure

The return value of onWritable is not relevant, has no effect since this commit 5528e6f Could probably update the docs to clarify that

[e3dio]

If it helps here is example in JS:

import { open } from 'node:fs/promises';

const streamFile = async (res, path, headers) => {
	res.onAborted(() => res.aborted = true);
	const fh = await open(path), size = (await fh.stat()).size;
	if (res.aborted) return fh.close();
	if (headers) res.cork(() => { for (const h in headers) res.writeHeader(h, headers[h]); });
	for await (const chunk of fh.createReadStream()) {
		if (res.aborted) break;
		let ok, done;
		const lastOffset = res.getWriteOffset();
		res.cork(() => [ ok, done ] = res.tryEnd(chunk, size));
		if (!ok) done = await new Promise(resolve => {
			res.onAborted(() => resolve(true));
			res.onWritable(offset => {
				res.cork(() => [ ok, done ] = res.tryEnd(chunk.subarray(offset - lastOffset), size));
				if (ok) resolve(done); 
			});
		});
		if (done) break;
	}
	return fh.close();
};

app.get('/', r => streamFile(r, path))

[paulharris]

The comment left in that code (at the time of the commit: If write was never called, the developer should still return true so that we may drain. Yes it would be nice if documentation were updated.

…

On Tue, 3 Sept 2024, 10:21 am e3dio, ***@***.***> wrote: // todo: I don't really know what this is supposed to mean? The return value of onWritable is not relevant, has no effect since this commit 5528e6f <5528e6f> Could probably update the docs to clarify that — Reply to this email directly, view it on GitHub <#1780 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAMSASZCDOROPQZLO6J3XG3ZUUMJTAVCNFSM6AAAAABNRB2R5OVHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTANJSGYZTQMA> . You are receiving this because you authored the thread.Message ID: ***@***.*** com>

[paulharris]

Thanks, would much prefer a C++ example that was maintained with the code... The existing example doesn't even do the cork stuff?

…

On Wed, 4 Sept 2024, 2:14 am e3dio, ***@***.***> wrote: If it helps here is example in JS: import { open } from 'node:fs/promises'; const streamFile = async (res, path, headers) => { res.onAborted(() => res.aborted = true); const fh = await open(path), size = (await fh.stat()).size; if (res.aborted) return fh.close(); if (headers) res.cork(() => { for (const h in headers) res.writeHeader(h, headers[h]); }); for await (const chunk of fh.createReadStream()) { if (res.aborted) break; let ok, done; const lastOffset = res.getWriteOffset(); res.cork(() => [ ok, done ] = res.tryEnd(chunk, size)); if (!ok) done = await new Promise(resolve => res.onWritable(offset => { if (res.aborted) return resolve(true); res.cork(() => [ ok, done ] = res.tryEnd(chunk.subarray(offset - lastOffset), size)); if (ok) resolve(done); })); if (done) break; } return fh.close();}; app.get('/', r => streamFile(r, path)) — Reply to this email directly, view it on GitHub <#1780 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAMSASZ6MKDKV4JFJYYURZDZUX37FAVCNFSM6AAAAABNRB2R5OVHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTANJTGUZTOMY> . You are receiving this because you authored the thread.Message ID: ***@***.*** com>

[porsager]

Great opportunity for a PR when you figure it out 😉

[paulharris]

Because the best person to rewrite the example is someone with almost zero experience with uWebSockets?

[uNetworkingAB]

You can look at VideoStreamer.js example in uWS.js repo. Ask ChatGPT to rewrite it in C++ because uWS.js and uWS have the same interfaces

[paulharris]

I'm not much of a ChatGPT user. I gave it a try and it gave me generic C++ with traditional sockets. A second time it did it with boost/beast.
Never mind, I guess the focus for this library is to support the Node/JS world. I'll look for another library.
Good work though! Looks fantastic.

[uNetworkingAB]

sounds good