[tor-bugs] #14859 [Onionoo]: Adapt Onionoo's parsing code for MaxMind's GeoLite2 City files to their new format

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#14859: Adapt Onionoo's parsing code for MaxMind's GeoLite2 City files to their new
format
-------------------------+-----------------
     Reporter:  karsten  |      Owner:
         Type:  defect   |     Status:  new
     Priority:  normal   |  Milestone:
    Component:  Onionoo  |    Version:
   Resolution:           |   Keywords:
Actual Points:           |  Parent ID:
       Points:           |
-------------------------+-----------------

Comment (by iwakeh):

 Actually the implementations of the two InputStreamReader constructors
 differ:
 * the current code will internally use a decoder with
 {{{CodingErrorAction.REPLACE}}}, i.e. drop erroneous input. (see
 {{{java.io.InputStreamReader.java}}} and {{{sun.nio.cs.StreamDecoder}}})
 * whereas, the constructor with the decoder parameter reports a
 {{{java.nio.charset.MalformedInputException}}} (one subclass of
 CharacterCodingException).

 I couldn't make up an invalid utf-8 file. So, the code below demonstrates
 the difference
 using US-ASCII.

 {{{
 public class CharsetDecTest{

     public static void main(String[] args)throws Exception{
         String geo = "GeoLite2-City-Locations-en.csv";
         try{
             BufferedReader br1 =
                 new BufferedReader(new InputStreamReader(new
 FileInputStream(new File(geo)), "US-ASCII"));
             while(br1.readLine()!=null){}
         }catch(Throwable t){
             System.out.println("e1: " + t);
         }
         try{
             BufferedReader br2 = new BufferedReader(
                 new InputStreamReader(new FileInputStream(new File(geo)),
                       StandardCharsets.US_ASCII.newDecoder()));
             while(br2.readLine()!=null){}
         }catch(Throwable t){
             System.out.println("e2: " + t);
         }


     }
 }

 }}}

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/14859#comment:8>
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