Enhance XML Parsing complexity - c# XML Looping

问题:

I am writing my own c# custom map navigation program. I am using OpenStreetMaps for the map data. It's a large XML file that contains Nodes and ways. I wrote a convertor that strips the XML file from useless junk (like timestamp, user etc) so the file will become smaller.

Now while I attempt to loop through the XML and convert the data to C# object Ways and Nodes I came across a problem. I need to do so much looping that the loading time is way too long.

XML Example (w = way, n = node, rf = reference to a node ):

      <n id="2638006578" l="5.9295547" b="52.5619519" />
      <n id="2638006579" l="5.9301973" b="52.5619526" />
      <n id="2638006581" l="5.9303625" b="52.5619565" />
      <n id="2638006583" l="5.9389539" b="52.5619577" />
      <n id="2638006589" l="5.9386643" b="52.5619733" />
      <n id="2638006590" l="5.9296231" b="52.5619760" />
      <n id="2638006595" l="5.9358987" b="52.5619864" />
      <n id="2638006596" l="5.9335913" b="52.5619865" />
      <w id="453071384">
        <nd rf="2638006581" />
        <nd rf="2638006590" />
        <nd rf="2638006596" />
        <nd rf="2638006583" />
        <nd rf="2638006578" />
      </w>
      <w id="453071385">
        <nd rf="2638006596" />
        <nd rf="2638006578" />
        <nd rf="2638006581" />
        <nd rf="2638006583" />
      </w>

• The Way nodes contain references to nodes, so a node can be existent in multiple ways (the nodes connect the ways).

• nodes contain a longitude and latitude (l = lon, b = lat).

• These XML files contain a lot of nodes and ways, so it's not just a small file. The XML file in the code example below has 500K lines.

My Code

class Program {

        static List<Way> ways = new List<Way>();
        static List<Node> nodes = new List<Node>();

        static void Main(String[] args) {
            read();
        }
        public static void read() {
            String xmlLoc = @"C:\Users\MyName\Desktop\result.xml";
            long time = DateTime.Now.Ticks;
            Parse(xmlLoc);
            long time2 = DateTime.Now.Ticks;
            Console.WriteLine("Done: {0} ms", (time2 - time) / 10000);
            Console.WriteLine(" - Nodes Amount:" + nodes.Count());
            Console.WriteLine(" - Ways Amount: " + ways.Count());
        }

        private static Node GetByRef(long reference) {
            return nodes.First(x => x.ID == reference);
        }

        private static void Parse(string path) {
            using (XmlReader reader = XmlReader.Create(path)) {
                reader.MoveToContent();
                while (reader.Read()) {
                    if (reader.NodeType == XmlNodeType.Element) {
                        XElement element = XElement.ReadFrom(reader) as XElement;
                        if ( element.Name.ToString().Equals("w")) {
                            Way w = new Way();
                            var name = element.Attribute("nm");
                            if (name != null) w.Name = name.Value;
                            var children = element.Descendants("nd");
                            foreach (XElement child in children) w.References.Add(long.Parse(child.Attribute("rf").Value));
                            ways.Add(w);
                        }else if (element.Name.ToString().Equals("n")) {
                            Node n = new Node();
                            n.ID = long.Parse(element.Attribute("id").Value);
                            n.Lon = double.Parse(element.Attribute("l").Value);
                            n.Lat = double.Parse(element.Attribute("b").Value);
                            nodes.Add(n);
                        }
                    }
                }
            }
        }
    }

    class Way {

        public List<long> References { get; private set; }
        public long ID { get; set; }
        public String Name { get; set; }
        public bool OneWay { get; set; }

        public Way() {
            this.References = new List<long>();
        }
    }

    class Node {
        public long ID { get; set; }
        public double Lat { get; set; }
        public double Lon { get; set; }
    }

Currently there's no actual relation between the class Way and the class Node. There's only a list with long values. I somehow need to add a list with Nodes to the class Way, but that'll require me to work with another (two?) for/while loops. That would mean O(N4) I believe, which is slow.

Technically I am looking for both a solution and ways to build this better, if you have advise I'd like to hear it!

Thanks in advance!

PS: If I should update/edit my question, please tell me instead of downvoting immediately.

回答1:

Use xml linq

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data;
using System.Xml;
using System.Xml.Linq;
using System.IO;


namespace ConsoleApplication31
{
    class Program
    {
        const string FILENAME = @"c:\temp\test.xml";
        static void Main(string[] args)
        {

            XDocument xdoc = XDocument.Load(FILENAME);

            var results = xdoc.Elements("root").Select(x => new
            {
                ns = x.Descendants("n").Select(y => new {
                    id = (long)y.Attribute("id"),
                    l = (double)y.Attribute("l"),
                    b = (double)y.Attribute("b")
                }).ToList(),
                ws = x.Descendants("w").Select(y => new {
                    id = (long)y.Attribute("id"),
                    rfs= y.Descendants("nd").Select(z => (long)z.Attribute("rf")).ToList()
                }).ToList()
            }).FirstOrDefault();

        }
    }

}