Range number queries

[Mike Streeton <mi...@ardentia.co.uk>]

For the recent questions about this here are a couple of methods for
encoding/decoding long values that will be sorted into order by a range
query

 

    public static String encodeLong(long num) {

      String hex = Long.toHexString(num < 0 ? Long.MAX_VALUE -
(0xffffffffffffffffL ^ num) : num);

      hex = (num < 0 ? "N" : "P")+"0000000000000000".substring(0,
16-hex.length()) + hex;

      return hex;

    }

    

    public static long decodeLong(String hex) {

      long num = Long.parseLong(hex.substring(1,17), 16);

      return hex.charAt(0) == 'N' ? (Long.MAX_VALUE - num) ^
0xffffffffffffffffL : num;

    }

    

 

 

Hope this helps

 

Mike

 

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