CODEWITHSUNDEEP
scalamergefileinputstream
ASD
ASD

Reputation: 69

Merge multiple FileInputStreams into single FileInputStream

I have situation where I need to merge multiple InputStream into single stream. I tried below code but it only return content from last file / stream. what is wrong with code? And is there a better way to merge multiple streams?

  def mergeInputStreams(l: List[File], accum: SequenceInputStream): SequenceInputStream = l match {
    case Nil => accum
    case x :: xs =>
      val is = new FileInputStream(x.pathAsString)
      mergeInputStreams(xs, new SequenceInputStream(is,  accum))
  }

Upvotes: 0

Views: 852

Answers (1)

Yawar
Yawar

Reputation: 11607

You're on the right track, but I would use SequenceInputStream's constructor that takes an Enumeration of Files and just map my input list of files into the right types to feed that:

import java.io.{File, FileInputStream, InputStream, SequenceInputStream}
import scala.collection.JavaConverters.asJavaEnumeration

def mergeInputStreams(files: Iterator[File]): InputStream =
  new SequenceInputStream(asJavaEnumeration(files.map(new FileInputStream(_))))

The other trick is to use Scala's included conversion method to convert from a Scala Iterator to a Java Enumeration. The conversion preserves the ordering and the fact that it's a traversal over a sequence of files, so it also preserves the input stream concatenation.

Upvotes: 2

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