Iterator to inputstream

[Ayoub Benali]

Hello,

I want to convert an Iterator[String] to a java.io.InputStream but I didn't find an east way to do it.
The main challenge is I cannot store all the data in memory to say, creating the inputstream from the array of byte or something like that, it needs to be lazy.

Currently I am saving the iterator as temporary file and then opening an inputstream on the file.

Does anybody know a better way to do that ?
If the scala API can't do that kind of transformation, is there a library that would allow to do that ?

Thanks,
Ayoub.

[Dennis Haupt]

all you need to do is to delegate the read-call on inputstream to your iterator and override "marksupported" with false

anything i overlooked?

 

Gesendet: Freitag, 13. März 2015 um 10:58 Uhr
Von: "Ayoub Benali" <benali.a...@gmail.com>
An: scala...@googlegroups.com
Betreff: [scala-user] Iterator to inputstream

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[Ayoub Benali]

I am using a library that is expecting an InputStream as parameter so I cannot hack it a way.
Otherwise I guess I didn't understand what you mean.

Are you talking about implementing the InputStream Interface and using the iterator under the hood ?

[Dennis Haupt]

yes, you can just create a simple wrapper yourself. all you need is to impement 2 methods

 

Gesendet: Freitag, 13. März 2015 um 11:43 Uhr
Von: "Ayoub Benali" <benali.a...@gmail.com>
An: "Dennis Haupt" <h-s...@gmx.de>
Cc: scala...@googlegroups.com
Betreff: Re: [scala-user] Iterator to inputstream

[Oliver Ruebenacker]

     Hello,

  In your InputStream extension, you read a String from the Iterator and then convert it to a Array[Byte] using either the default encoding/charset or one of your choice (e.g. UTF-8). Then you need to remember how many Bytes you already read from the current Array[Byte] and get the next one if the previous one is exhausted. Make sure the InputStream does not block when the Iterator is exhausted.

  You can create a valid InputStream by only implementing the single-byte read method, but if you also implement the multi-byte read method, performance will be much better.

     Best, Oliver

--

Oliver Ruebenacker

Solutions Architect at Altisource Labs

Be always grateful, but never satisfied.

[Ayoub Benali]

thank you for your help, it worked :)

[Dennis Haupt]

of course it does, we're experts :D

we could even draw invisible red lines in the form of a kitten 

[Matt Fulgo]

Since this thread came up in my search, but it left me without a great answer... The best way I found to do this was to use a SequenceInputStream:

 

import scala.collection.JavaConverters._

import java.io.{ByteArrayInputStream, InputStream, SequenceInputStream}

val strings: Iterator[String] = ???

val stream: InputStream = new SequenceInputStream({

  val i = strings map { s => new ByteArrayInputStream(s.getBytes("UTF-8")) }

  i.asJavaEnumeration

})

 

 

An: scala-user@googlegroups.com

Betreff: [scala-user] Iterator to inputstream

Hello,

I want to convert an Iterator[String] to a java.io.InputStream but I didn't find an east way to do it.
The main challenge is I cannot store all the data in memory to say, creating the inputstream from the array of byte or something like that, it needs to be lazy.

Currently I am saving the iterator as temporary file and then opening an inputstream on the file.

Does anybody know a better way to do that ?
If the scala API can't do that kind of transformation, is there a library that would allow to do that ?

Thanks,
Ayoub.

 

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Oliver Ruebenacker

Solutions Architect at Altisource Labs

Be always grateful, but never satisfied.