Fast indexing of PPLX data

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One of the tasks that sometimes comes up during plugin development is the need to rapidly parse and spatially index a large number of PPLX files.

Performing this task by fully hydrating each PPLX file into O-Calc proper, while relatively quick, would still take more time than desired for a large number of poles. In this post is presented a code snippet that can parse the latitude, longitude, poleID, and MCU percentage from a PPLX file very rapidly and allow for the processing of tens to hundreds of PPLX files per second depending on your system’s IO performance.

First I need to create a structure to hold the data I intend to parse form the PPLX and then instantiate a list to hold an instance of that structure for each PPLX that I parse.

  1. public struct Pole
  2. {
  3.     public double cLat;
  4.     public double cLon;
  5.     public string cName;
  6.     public string cPath;
  7.     public double cMCU;
  8. }
  9.  
  10. public List<Pole> cPoles = new List<Pole>();

Now if I create a list of file path strings of all of the PPLX files I wish to process *the construction of this list is not covered here but typically would involce one or more calls to files = Directory.GetFiles(directory, “*.pplx”);) I can process them as follows:

  1. foreach (String file in files)
  2. {
  3.     using (StreamReader sr = new StreamReader(file))
  4.     {
  5.         using (XmlTextReader xr = new System.Xml.XmlTextReader(sr))
  6.         {
  7.             String poleId = System.IO.Path.GetFileNameWithoutExtension(file);
  8.             double lat = 0;
  9.             double lon = 0;
  10.             while (xr.Read())
  11.             {
  12.                 if (xr.NodeType == System.Xml.XmlNodeType.Element && xr.Name == "VALUE")
  13.                 {
  14.                     String sname = xr.GetAttribute("NAME");
  15.                     if (sname == "Latitude")
  16.                     {
  17.                         xr.Read();
  18.                         if (!double.TryParse(xr.Value, out lat)) break;
  19.                         if (lat == 0) break;
  20.                     }
  21.                     else if (sname == "Longitude")
  22.                     {
  23.                         xr.Read();
  24.                         if (!double.TryParse(xr.Value, out lon)) break;
  25.                         if (lon == 0) break;
  26.  
  27.                         double mcu = -1;
  28.                         try
  29.                         {
  30.                             sr.DiscardBufferedData();
  31.                             sr.BaseStream.Seek(-1024, SeekOrigin.End);
  32.                             String sbuff = sr.ReadToEnd();
  33.                             int idx = sbuff.IndexOf("PercentAtMCU");
  34.                             if (idx > 0)
  35.                             {
  36.                                 mcu = Parse(sbuff.Substring(idx + 20, 100));
  37.                             }
  38.                         }
  39.                         catch
  40.                         {
  41.                             mcu = -1;
  42.                         }
  43.  
  44.                         if (lat != 0 && lon != 0)
  45.                         {
  46.                             Pole pole = new Pole();
  47.                             pole.cLat = lat;
  48.                             pole.cLon = lon;
  49.                             pole.cName = poleId;
  50.                             pole.cMCU = mcu;
  51.                             pole.cPath = file;
  52.                             cPoles.Add(pole);
  53.                         }
  54.                         break;
  55.  
  56.                     }
  57.                 }
  58.             }
  59.         }
  60.     }
  61. }

Supported by…

  1. double Parse(String pStr)
  2. {
  3.     const char gt = (char)62;
  4.     const char lt = (char)60;
  5.     int idx = pStr.IndexOf(gt);
  6.     String s = pStr.Substring(idx + 1);
  7.     idx = s.IndexOf(lt);
  8.     s = s.Substring(0, idx);
  9.     double v = 0;
  10.     if(double.TryParse(s, out v)) return v;
  11.     return 0;
  12. }

The following video shows this code in operation…

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