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    Fast indexing of PPLX data

    by Admin

    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.

    < View plain text >
    C#

    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:

    < View plain text >
    C#

    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…

    < View plain text >
    C#

    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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