Uploaded image for project: 'Commons BCEL'
  1. Commons BCEL
  2. BCEL-160

Why using unstable sort at MethodGen.getLocalVariables() ?

    XMLWordPrintableJSON

    Details

    • Type: Improvement
    • Status: Closed
    • Priority: Blocker
    • Resolution: Fixed
    • Affects Version/s: 5.3
    • Fix Version/s: 6.0
    • Component/s: Main
    • Labels:
      None
    • Environment:

      Operating System: Linux
      Platform: PC

      Description

      I noticed that MethodGen.getLocalVariables sorts the local variables by index. However, it uses a hand written sort algorithm that is unstable. That is, it does not guarantee that variables with the same index are kept in the same order. In fact, it always swaps them.

      This does not cause a major problem apart from having a different order of variables in the local variables table when a class is simply parsed and dumped.

      A simple enhancement is to use java's own merge sort implementation (available in version 1.3, which seems to be the target platform). In getLocalVariables(), instead of calling:

      sort(lg, 0, size - 1);

      use something like (maybe remove generics):

      Arrays.sort(lg, new Comparator<LocalVariableGen>() {
      public int compare(LocalVariableGen o1, LocalVariableGen o2)

      { return o1.getIndex() - o2.getIndex(); }

      });

      The advantage, besides using a stable sort, is that this is less code to maintain, compared to the trick sort method.

        Attachments

          Activity

            People

            • Assignee:
              issues@commons.apache.org Apache Commons Developers
              Reporter:
              thiagobart@gmail.com Thiago
            • Votes:
              0 Vote for this issue
              Watchers:
              0 Start watching this issue

              Dates

              • Created:
                Updated:
                Resolved: