Make regexp execution loop interruptible #1189

[blutorange]

#1189

Uses Thread.currentThread.isInterrupted() so that the interruption flag remains set to true, we only terminate the RegExp evaluation loop, but other (potentially third-party calling) code may still have to check for the interrupted flag to stop its execution as well.

I also added a test with a long-running regexp that fails without the interrupt check.

Perhaps it would have been better to throw an InterruptedException, but that would require changing the signature of many methods.

[gbrail]

Can I suggest another way to implement this that could help solve your problem, but do it without adding code for people who don't need that extra check?

The Context class has a methods called "setInstructionObserverThreshold." When set, the interpreter or the generated bytecode will call a method on the ContextFactory (which you implement using inheritance) whenever N instructions are executed. You can have this method be implemented to check for thread interruption if that's what works best for you.

The thing you'd do in this case, then, would be to add a call to ScriptRuntime.addInstructionCount on every iteration of that top-level loop in the regex. (I'd suggest just calling each trip through that loop as, I don't know, let's say 10 "instructions," but it could be a different value.)

I think this would be more general than just checking for interruption in that loop, and means that you can use the same mechanism to check for long-running regexps as what we already have for checking for long-running code in general.

[blutorange]

Thanks for the feedback. We could work with that solution as well, if you think that helps performance. Previously believe I had already tried setting an observer threshold (which did not work, as it wasn't yet implemented) I'll take a look if I can adjust it accordingly.

[blutorange]

ScriptRuntime.addInstructionCount works just as well, and yeah, that seems like a solution that integrates better into the existing mechanism. I used 5 for the instruction count. A regexp like /(.*){1,32000[bc]/.test("aaaaaaaaaaaaaaaaaaaaaaa"); takes a split second in browsers to execute (and a few seconds in rhino) and is enough to reach a quota of Integer.MAX_VALUE

[gbrail]

Thanks for that -- it seems to be fine!