Event "end" in a ReadStream object seems not working if properties "start" and "end" properties are used in the object specified as second parameter in fs.createReadStream()

[Oscar Torrente Artero]

I mean...this code works perfectly:

    var fs = require("fs")
    var readable = fs.createReadStream("file.txt")
    readable.on("end", function ()          { console.log("End") })
    readable.on("error", function (err)     { console.log(err)   })
    readable.on("readable", function ()     { var chunk = readable.read(); console.log(chunk.toString()) })

But this not:

    var fs = require("fs")
    var readable = fs.createReadStream("file.txt", {start:0, end:1})
    readable.on("end", function ()          { console.log("End") })
    readable.on("error", function (err)     { console.log(err)   })
    readable.on("readable", function ()     { var chunk = readable.read(); console.log(chunk.toString()) })

I see two related problems:
       -It seems "readable" event is emitted twice (why??!!)
       -As a consequenca, the second time "readable" event is emitted, chunk is null because there's nothing to read, so method toString() crashes. I thought that just after the first time "readable" event is emitted, then the "end" event would be emitted too, but it doesn't.

I'm sure I am doing something wrong, but I really can't see it.

Thanks a lot

[greelgorke]

1. if you check chunk for null before printing, everything is working fine.

readable.on("readable", function ()     { var chunk = readable.read(); console.log(chunk != null ? chunk.toString() : 'null') })

2. you could read on a single event till null.

readable.on("readable", function ()     { var chunk; while ( (chunk = readable.read()) != null) console.log(chunk.toString()) })

chunk == null tells you, that the buffer of the stream is empty now and you should wait till the next 'readable' or the 'end'

[Oscar Torrente Artero]

Yes, it's true what you say, but I think it a little more tricky it should be.

*Why there are two "readable" events emitted?

*Why "end" event isn't emitted when there aren't more data to read?

*Why is there such an inconsistence between the two codes I've exposed?

Thanks a lot for your patiente.

[Oscar Torrente Artero]

Well, I insist.
If you try this code:

    var fs = require("fs")
    var readable = fs.createReadStream("file.txt")
    readable.on("end", function ()            { console.log("End") })

    readable.on("readable", function ()     { var chunk = readable.read(1); console.log(chunk.toString()) })  

you will see "readable" event is emitted twice (!!??) when I think  it should be emitted many times as until buffer is drained (namely, many times as bytes are inside "file.txt"),  shouldn't??!!

[greelgorke]

may be you should place an issue on github?

[Isaac Schlueter]

Working as designed.

The 'end' event doesn't happen until you read PAST the last chunk. If
there's no data in the buffer, then that read() returns null, and then
'end' is emitted.

The reason for this is to prevent 'end' being emitted before you have
a chance to attach a listener, on zero-length readable streams (ie,
streams that end without *ever* having any data).

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[Oscar Torrente Artero]

Ooh, thanks a lot !!! And sorry for this so silly question...

Maybe a explanation like this in online documentation could help to understand these details and could avoid you to repeat these things.

Thanks!!

[greelgorke]

ah that was my missing puzzle piece