Question

In Java it’s written like this.. when I was porting this code… realizied there is no such thing as
break <label> and continue <label>.

I know those commands were not included because there HAS to be a cleaner way of doing this when using a goto with a command..

But I ended up using.. the C# code below any way to rewrite it cleaner?

Java Code

for(JClass c : classes) {
    for(JMethod m : c.getMethods()) {
        JCode code = m.getCode();
        if(code == null)
            continue;
        label: for(int index = 0; index < code.getExceptionLookupTable().length; index++) {
            JException e = code.getExceptionTable().get(index);
            for(int index2 = e.getStartIndex(); index2 < e.getEndIndex(); index2++)
                if(code.getInstruction(index2).getOpcode() == NEW && ((NEW) code.getInstruction(index2)).getType().equals("java/lang/RuntimeException"))
                    continue label;
                if(e.getCatchTypeClassName().equals("java/lang/RuntimeException")) {
                    for(int index = e.getHandlerIndex(); index < code.getInstrLength(); index++) {
                        JInstruction instr = code.getInstruction(index);
                        if(instr.getOpcode() == ATHROW)
                            break;
                        else if(instr instanceof ReturnInstruction)
                            break label;
                    }
                    removeStuff(code, ei--);
                }
            }
    }
}

C# Code.

foreach(JClass c in classes) {
    foreach(JMethod m in c.getMethods()) {
        JCode code = m.getCode();
        if(code == null)
            continue;

        for(int index = 0; index < code.getExceptionTable().Length; index++) {
            bool continueELoop = false;
            bool breakELoop = false;
            JException e = code.getExceptionTable().get(index);
            for(int index2 = e.getStartIndex(); index2 < e.getEndIndex(); index2++) {
                if(code.getInstruction(index2).getOpcode() == JInstructions.NEW && ((NEW) code.getInstruction(index2)).getType().Equals("java/lang/RuntimeException")) {
                    continueELoop = true;
                    break;
                }
            }
            if(continueELoop) continue;

            if(e.getCatchTypeClassName().Equals("java/lang/RuntimeException")) {
                for(int index = e.getHandlerIndex(); index < code.getInstrLength(); index++) {
                    JInstruction instr = code.getInstruction(index);
                    if (instr.getOpcode() == JInstructions.ATHROW) {
                        break;
                    } else if (isReturnInstruction(instr)) {
                        breakELoop = true;
                        break;
                    }
                }
                removeStuff(code, ei--);
            }
            if (breakELoop) break;
        }
    }
}

You can see when looking at the Java version then looking at the ported C# version.. the clean feeling goes away. Did I make some mistakes that can make the code shorter? or nicer looking? thanks for the help.

Answer 1

I guess, in C# you would never write such ugly code in the first place.

Here’s your code refactored into multiple methods and to use LINQ with a fictional class hierarchy:

IEnumerable<JCode> GetCodes(IEnumerable<JClass> classes)
{
    return from @class in classes
           from method in @class.Methods
           where method.Code != null
           select method.Code;
}

IEnumerable<Tuple<JCode, JException>> GetCandidates(IEnumerable<JCode> codes)
{
    return from code in codes
           from ex in code.ExceptionTable
           where !code.Instructions
                      .Skip(ex.Start)
                      .Take(ex.End - ex.Start + 1)
                      .Any(i => i.OpCode == New && ...)
           select Tuple.Create(code, ex);
}

and then

void RewriteMethods(IEnumerable<JClass> classes)
{
    var codes = GetCodes(classes);

    var candidates = GetCandidates(codes);

    foreach (var candidate in candidates)
    {
        var code = candidate.Item1;
        var ex = candidate.Item2;

        var instructionsToRemove = code.Instructions
                                       .Skip(ex.HandlerStart)
                                       .TakeWhile(i => i.OpCode != Return)
                                       .Where(i => i.OpCode == AThrow);

        code.RemoveAll(instructionsToRemove);
    }
}