Hi Andrea,
I've come up with something that... almost does what you're looking at
here. Perhaps it's useful as a guide of what one can do with the Gio
interface.
I think you may hit some awkward problems with modelling Node-style streams
with GLib ones. But perhaps it is possible and this helps. I don't really
know the Node stream semantics so I have assumed various things in my
Readable implementation as you'll see... Note that MemoryInputStream really
is just a byte stream; so there is no guarantee you'll receive the exact
block of bytes that was written -- for example, when I run this I get a
first chunk of "12", followed by "3", "4", etc.
let Gio = imports.gi.Gio;
let byteArray = imports.byteArray;
let mainloop = imports.mainloop;
class Readable {
constructor() {
this._mio = Gio.MemoryInputStream.new();
this._callbacks = {};
this._startNext();
}
_startNext() {
// Enqueue an async read; and re-enqueue when it finishes, so we're
// always waiting for data...
this._mio.read_bytes_async(4096, 1, null, (source, res) => {
this._onData(this._mio.read_bytes_finish(res));
this._startNext();
});
}
_onData(bytes) {
if (this._callbacks['data']) {
let ba = byteArray.fromGBytes(bytes);
this._callbacks['data'](ba);
this._read();
}
}
push(bytes) {
if (bytes == null) {
mainloop.quit('main');
return;
}
this._mio.add_bytes(bytes);
}
on(name, callback) {
this._callbacks[name] = callback;
if (name === 'data') {
this._read();
}
}
}
class Counter extends Readable {
constructor(opt) {
super(opt);
this._max = 1000;
this._index = 1;
}
_read() {
const i = this._index++;
if (i > this._max)
this.push(null);
else {
const str = '' + i;
const buf = byteArray.fromString(str); // Buffer.from(str, 'ascii');
this.push(buf);
}
}
}
(new Counter).on('data', (str) => {
print("data", str.toString());
});
mainloop.run('main');
On 7 November 2017 at 10:08, Andrea Giammarchi <[email protected]>
wrote:
> I am trying to implement a stream module and apparently I have everything
> I need but practically I'm unable to use streams.
>
> If I instantiate a `new Gio.InputStream` I have the following error:
> cannot create instance of abstract (non-instantiatable) type 'GInputStream'
>
> I cannot even extend it ... so I've though "ok, maybe it's like an
> interface, I implement it and that's it"
>
> But then a JS class wouldn't work as base_stream for a
> Gio.BufferedInputStream, and if I extend the JS class to be a
> GObject.Object then:
> Gjs-WARNING **: JS ERROR: TypeError: Object is of type GObject.Object -
> cannot convert to GInputStream
>
> where GInputStream is the one I cannot use in the first place.
>
> I've reached full circle then so ... I wonder if anyone has any idea how
> to use/create/extend streams in GJS (not talking about file streams but
> streams in general) or if it's even possible.
>
> In node, as example, I could do this and it will work:
>
> ```js
>
> const { Readable } = require('stream');
>
> class Counter extends Readable {
> constructor(opt) {
> super(opt);
> this._max = 1000;
> this._index = 1;
> }
>
> _read() {
> const i = this._index++;
> if (i > this._max)
> this.push(null);
> else {
> const str = '' + i;
> const buf = Buffer.from(str, 'ascii');
> this.push(buf);
> }
> }
> }
>
> (new Counter).on('data', console.log);
>
> ```
>
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>
>
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