Question

how’s everyone doing this morning?

I’m writing a program that will parse a(several) xml files.
This stage of the program is going to be focusing on adding/editing skills/schools/abilities/etc for a tabletop rpg (L5R). What I learn by this one example should carry me through the rest of the program.

So I’ve got the xml reading set up using XMLReader. The file I’m reading looks like…

<skills>
  <skill>
    <name>some name</name>
    <description>a skill</description>
    <type>high</type>
    <stat>perception</stat>
    <page>42</page>
    <availability>all</availability>
  </skill>
</skills>

I set up a Skill class, which holds the data, and a SkillEdit class which reads in the data, and will eventually have methods for editing and adding.

I’m currently able to read in everything right, but I had the thought that since description can vary in length, once I write the edit method the best way to ensure no data is overwritten would be to just append the edited skill to the end of the file and wipe out its previous entry.

In order for me to do that, I would need to know where skill’s file offset is, and where /skill’s file offset is. I can’t seem to find any way of getting those offsets though.

Is there a way to do that, or can you guys suggest a better implementation for editing an already existing skill?

Answer 1

If you read your XML into LINQ to XML’s XDocument (or XElement), everything could become very easy. You can read, edit, add stuff, etc. to XML files using a simple interface.

e.g.,

var xmlStr = @"<skills>
  <skill>
    <name>some name</name>
    <description>a skill</description>
    <type>high</type>
    <stat>perception</stat>
    <page>42</page>
    <availability>all</availability>
  </skill>
</skills>
";
var doc = XDocument.Parse(xmlStr);

// find the skill "some name"
var mySkill = doc
    .Descendants("skill") // out of all skills
    .Where(e => e.Element("name").Value == "some name") // that has the element name "some name"
    .SingleOrDefault(); // select it
if (mySkill != null) // if found...
{
    var skillType = mySkill.Element("type").Value; // read the type
    var skillPage = (int)mySkill.Element("page"); // read the page (as an int)
    mySkill.Element("description").Value = "an AWESOME skill"; // change the description
    // etc...
}

No need to calculate offsets, manual, step-by-step reading or maintaining other state, it is all taken care of for you.