Fix OOM on malformed input

[shimamoto]

Hi.

I tried in the latest master version since the bug (#35) have been merged.
But the survey found that there are still cases that OOM occur.
Specifically, CDATA sections, comment, DTD.

// broken CDATA
val r = new XMLEventReader(Source.fromString("<broken><![CDATA[A"))

// broken comment
val r = new XMLEventReader(Source.fromString("<!-- broken "))

// broken DTD
val r = new XMLEventReader(Source.fromString(
    """<?xml version="1.0" encoding="utf-8"?>
      |<!DOCTYPE broken [
      |  <!ELE
    """.stripMargin))

All of the above cases occur OOM.

[error] (XMLEventReader) java.lang.OutOfMemoryError: Java heap space

I am in trouble since OOM have a large impact on the production.

This PR is going to avoid the OOM caused by the above-mentioned.
This commit make up for the lack of #35. Specifically,
CDATA sections, comment, DTD.

[biswanaths]

Hey @shimamoto ,

Thank you for taking the time report and submit a PR. Please give me some time to let me go through this issue and also some others to respond back. We are on the verge of a release. If everything works fine, I will merge this PR and do the release.

Thanks again.

[shimamoto]

@biswanaths I am grateful for your prompt response. Then, I am looking forward to a good reply from you!

[ashawley]

It doesn't seem like adding the eof here triggers an OOM for any of your tests. I couldn't find an example that triggered the OOM for an XML processing instruction (PI) or a CDATA section -- they're the only ones that use xTakeUntil . I guess it's ok to cargo-cult an eof check everywhere, but it seems you were trying to avoid that.

[shimamoto]

@ashawley Thank you for the review and comment! It is significant to add this eof. This is necessary in test of CDATA section <broken><![CDATA[A. Without it, the following OOM occur:

Exception in thread "XMLEventReader" java.lang.OutOfMemoryError: Java heap space
        at java.util.Arrays.copyOf(Arrays.java:3332)
        at java.lang.AbstractStringBuilder.expandCapacity(AbstractStringBuilder.java:137)
        at java.lang.AbstractStringBuilder.ensureCapacityInternal(AbstractStringBuilder.java:121)
        at java.lang.AbstractStringBuilder.append(AbstractStringBuilder.java:622)
        at java.lang.StringBuilder.append(StringBuilder.java:202)
        at scala.collection.mutable.StringBuilder.append(StringBuilder.scala:267)
        at scala.xml.parsing.MarkupParserCommon$class.xTakeUntil(MarkupParserCommon.scala:253)
        at scala.xml.pull.XMLEventReader$Parser.xTakeUntil(XMLEventReader.scala:60)
        at scala.xml.parsing.MarkupParser$class.xCharData(MarkupParser.scala:379)
        at scala.xml.pull.XMLEventReader$Parser.xCharData(XMLEventReader.scala:60)
        at scala.xml.parsing.MarkupParser$class.content1(MarkupParser.scala:424)
        at scala.xml.pull.XMLEventReader$Parser.content1(XMLEventReader.scala:60)
        at scala.xml.parsing.MarkupParser$class.content(MarkupParser.scala:459)
        at scala.xml.pull.XMLEventReader$Parser.content(XMLEventReader.scala:60)
        at scala.xml.parsing.MarkupParser$class.element1(MarkupParser.scala:588)
        at scala.xml.pull.XMLEventReader$Parser.element1(XMLEventReader.scala:60)
        at scala.xml.parsing.MarkupParser$class.content1(MarkupParser.scala:433)
        at scala.xml.pull.XMLEventReader$Parser.content1(XMLEventReader.scala:60)
        at scala.xml.parsing.MarkupParser$class.document(MarkupParser.scala:247)
        at scala.xml.pull.XMLEventReader$Parser.document(XMLEventReader.scala:60)
        at scala.xml.pull.XMLEventReader$Parser$$anonfun$run$1.apply(XMLEventReader.scala:96)
        at scala.xml.pull.XMLEventReader$Parser$$anonfun$run$1.apply(XMLEventReader.scala:96)
        at scala.xml.pull.ProducerConsumerIterator$class.interruptibly(XMLEventReader.scala:125)
        at scala.xml.pull.XMLEventReader.interruptibly(XMLEventReader.scala:27)
        at scala.xml.pull.XMLEventReader$Parser.run(XMLEventReader.scala:96)
        at java.lang.Thread.run(Thread.java:745)

It turned out that error checking is rudimentary, however, you are quite right. I fix some tests.

[ashawley]

@shimamoto Ok, cool! I thought that was odd. Thanks for fixing up the unit tests!

[ashawley]

Changes look good to me! Thanks for cleaning up and refactoring the tests while you were at it.

[shimamoto]

Fix unit tests of a broken CDATA section and comment since not enough the verification. Without this time fix, I confirmed that OOM occur in these cases.

[biswanaths]

This looks good to me. If there is nothing else I will merge this tomorrow.