Need the best way to iterate a file returning batches of lines as XML

Question

I'm looking for the best way to process a file in which, based on the contents, i combine certain lines into XML and return the XML.

e.g. Given

line 1
line 2
line 3
line 4
line 5

I may want the first call to return

<msg>line 1, line 2</msg>

and a subsequent call to return

<msg>line 5, line 4</msg>

skipping line 3 for uninteresting content and exhausting the input stream. (Note: the <msg> tags will always contain contiguous lines but the number and organization of those lines in the XML will vary.) If you'd like some criteria for choosing lines to include in a message, assume odd line #s combine with the following four lines, even line #s combine with the following two lines, mod(10) line #s combine with the following five lines, skip lines that start with '#'.

I was thinking I should implement this as an iterator so i can just do

<root>{ for (m <- messages(inputstream)) yield m }</root>

Is that reasonable? If so, how best to implement it? If not, how best to implement it? :)

Thanks

Not enough information. What criteria is used to decide what order these lines come in, what should be included, and should not? I note the lines are inverted too -- 1, 2 and then 5, 4. What's the criteria here? — Daniel C. Sobral, May 23 '11 at 20:38
@daniel-c-sobral The conditions are too complicated to include. I'd think it'd be enough to know the file is read start to end and there are multiple conditions to determine when lines are combined and multiple conditions indicate when combined lines are returned as a Node. Let's say if the line# is even, it is combined with the four following lines. If the line# is odd, it is combined with the two follow lines. If the line is a mod(10), it is combined with the five following lines. — nix, May 23 '11 at 21:11

score 0 · Accepted Answer · edited May 23 '17 at 11:47

This answer provided my solution: How do you return an Iterator in Scala?

I tried the following but there appears to be some sort of buffer issue and lines are skipped between calls to Log.next.

class Log(filename:String) {

  val src = io.Source.fromFile(filename)
  var node:Node = null

  def iterator = new Iterator[Node] {
    def hasNext:Boolean = {
      for (line <- src.getLines()) {
        // ... do stuff ...
        if (null != node) return true
      }
      src.close()
      false
    }

  def next = node
}

There might be a more Scala-way to do it and i'd like to see it but this is my solution to move forward for now.

Need the best way to iterate a file returning batches of lines as XML

1 Answers1