Question

I’m developing a REST service, so a request could be something like this:

/Data/Main/Table=Customers/

I need to get the segments one by one, and for each segment I will decide wich object I’m going to use, after I’ll pass to that object the rest of the query so it can decide what to do next. Basically, the REST query is a path on a tree 😛

This imply lots String operations (depending on the query complexity), but StringBuilder is useful just for concatenations and remove, you cannot perform a search with IndexOf or similar.

I’ve developed this class that fulfill my requirement, but the problem is that is manipulating Strings, so every time I get one segment … I’ll create extra Strings because String is an inmutable data type:

public class RESTQueryParser
{
    String _query;

    public RESTQueryParser(String query)
    {
        _query = query;
    }

    public String GetNext()
    {
        String result = String.Empty;
        Int32 startPosition = _query.StartsWith("/", StringComparison.InvariantCultureIgnoreCase) ? 1 : 0;

        Int32 i = _query.IndexOf("/", startPosition, StringComparison.InvariantCultureIgnoreCase) - 1;

        if (!String.IsNullOrEmpty(_query))
        {
            if (i < 0)
            {
                result = _query.Substring(startPosition, _query.Length - 1);
                _query = String.Empty;
            }
            else
            {
                result = _query.Substring(startPosition, i);
                _query = _query.Remove(0, i + 1);
            }
        }

        return result;
    }
}

The server should support a lot of calls, and the queries could be huge, so this is gonna be a very repetitive task. I don’t really know how big is the impact on the memory and the performance, I’ve just readed about it in some books.

Should I implement a class that manage a Char[] instead Strings and implement the methods that I want? Or should be ok with this one? Regular expressions maybe?

UPDATE:

The above class is just a small aproximation, I’m still working on it and I have to parse more complex patterns.

I cannot use WCF REST or predefined paths (like map a regular expression to a specific method) because the query format can be changed by the user at runtime. So it has to be parsed step by step.

I cannot use String.Split, because for example a query could be : “Data/Search=’01/01/2008’/Whatever”.

Answer 1

You might try a regular expression like this:

var input = "/Data/Main/Table=Customers/";
var regex = new Regex(@"\w+?/");
var matches = regex.Matches(input);
foreach (var match in matches)
{
    Console.WriteLine(match.ToString());
}
Console.ReadKey();

Also, you might look into the System.Web.Routing namespace…