.NET has several built in Perfmons, and I would like to know is it possible to extend one of the built in ones and add custom functionality.
More specifically, I would like to take RateOfCountsPerSecond32 and make it be something such as RateOfCountsPerMinute. Basically I would like to be able to monitor the average number of events that happen in a given time, but longer than a second.
Is extending the right idea? If so does anyone have a quick syntax example of how it can be done? I have read that it can be done but documentation is super poor on the subject. Or is there a better way to go about this entirely, very open to suggestions.
Thanks for any help,
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I have complex project without comments. The project is programed in Java but have more than one main class, use several .txt files like a template and use several .bat files. I don't know where to start and how to start discovering the project, because I need to make some changes in that project.
As with others I say this is a slow process.
However having done this in the past many times, this is my methodology:
Identify as many requirements that the code fulfils. This may give you the some reasons as to why certain things are the way they are when you look deeper. A common way of finding these is look for any tests that be available. The automated ones are best, but usually they're as missing as the comments.
Find the entry points to the code. These will give you places where you can poke the code to see how different inputs affect the flow. Common entry points are Code Loading 'Main' type functions, service interfaces, web page post backs etc..
Diagram the code. Look for tools that can build black/white box pictures of the code. For me this invaluable. I have on occasion printed out large listings and attacked then with markers and rulers. You're aim to create your own flow chart (mental or other wise) of the code flow.
Using the above (iteratively) build a set of outputs to the code that you think should occur, and add to these the outputs you may already know about such as logs, data files, database writes etc..
Finally if you have time, create some manual tests though preferably in automated test harnesses to verify the above. This where I start to involve the debugger to see detail in the code.
This methodology usually gives me confidence to make changes.
Note this is iterative process and can be done with portions of the code or overall as you see fit. I usually favour a top down approach to start with and then as I gain some insight I drill down till details become overwhelming and then I repeat. However this is just because my mind works in this way - you may be different. Good luck.
Find the main Main class. The starting point.
Start drawing a picture of the classes and the objects they own and the external entities they reference.
Follow all the branches until you can find a logical ending.
I've used UML reverse engineering tools in the past and while a visual picture is good, stepping through the code has always been the hardest and yet best methodology for me.
And, as you step through each piece you can add in your own comments..
I usually start with doxygen, turning on every extracting option (especially EXTRACT_ALL and EXTRACT_PRIVATE), and enable the SOURCE_BROWSER, HAVE_DOT, CALL_GRAPH and CALLER_GRAPH options (you also need to have dot installed). This gives good view of the software. For every function the calls are displayed and linked in a graph, also the sources are linked from there.
While doxygen is intended for C and C++, it also works with Java sources (set the OPTIMIZE_OUTPUT_JAVA option).
Auch. I'm afraid there is no speedy way to do this. Comment out a line (or two) -> test -> see what breaks. You could also put break statements here and there and run the debugger. That should give you some indication how you got there (ie. what the hierarchy between the classes is).
Hopefully the original developers used some patterns that you can recognize and make notes. Make lots of notes of everything. Start by trying to understand the high level structure and work down from there.
Be prepared to spend endless hours not understanding what the thing is doing.
Speak to the client and try to understand what the project is for, and what are all the things that it does. Someone somewhere had to put in some requirements for the stuff that's in there, if only in an email.
I would try to find the first entry point in the code closest to where you suspect you'll need to start making your changes, set a breakpoint, and start debugging. Check out the contents of local variables and work your way deeper as you get to become familiar with whats going on. Then, when you have a basic understanding of the area of code you're going to be working with, start fiddling with some small changes. Test your understanding of it. Try diagramming what you see happening. If you can do that confidently, you'll be able to decide if you need to go back and continue learning more about the code, or if you know enough to get done what you need to get done.
A start is to use an automated uml modeling tool (if you use eclipse you can use a plug-gin), and start creating UML diagrams of the various classes to see how they are related in a high level and visualize the code. This has helped many times
If there are log files being generated, have a look at it to understand the flow from the starting point (main class). Otherwise, put debug statements to understand the flow.
Ya, that sounds like a pretty bad spot to be in.
I would say that the best way is to just walk through the program line for line. Try to grasp the big picture in the code, and write alot of notes, both on paper and in comments in the code.
I would say, a good approach would be to generate documentation using javadoc or doxygen's class diagram feature, then as you run the code traverse through the class diagrams generated using doxygen and see who calls what. This works wonderfully for me everytime i am working on such a project.
I completely agree to most of the answers posted.
I can add to use a development tool that reverse engineering the code and create a class diagram, to have an overall picture of what is involved.
Then you need patience. But you will be a stronger and smarter developer when you'll get through...
Good luck!
One of the best and first things to do is to try to build and run the code. It might sound a bit simplistic but the problem when you take over undocumented code is that you can't even build it and run it. When have no clue were to start.
I have a question about best practice on how to tackle a new project, any project. When starting a new project how do you go about tackling the project, do you split it into sections, start writing code, draw up flow diagrams.
I'm asking this question because I'm looking for advice on how I can start new projects so I can get going on them quicker. I can have it planned, designed and starting coding with everything worked out.
Any advice?
Thanks
Stephen
It all really depends. Is the project for controlling a space shuttle with 200+ people working on it, or is it a hobby project with 1 person.
I'm guessing this is a small project. In that case, do whatever works for you. Write a list of things you think are required. If there are parts you know you need to learn more about or research, get reading the web, try some stuff out with prototype code to see whether it works or not. Don't turn prototype code into real code though, start again with production code and make sure you get all the appropriate error handling etc in.
When you think you've got a good feel for what's needed, get coding. If you hit a point where you think it's not working, go back to the design and rethink it and sketch some more diagrams, and then go back to the code again.
It is extremely doubtful that you can work everything out in your plan and that's how things will actually work out. So, there's little point in trying to plan too far ahead because you'll be wasting time. Just plan out far enough ahead to keep yourself focused on working on the right things and so that you've given yourself a reasonable chance that the code you're working on will fit the big picture and solve the problem you're trying to solve.
Start by writing a simple functional spec, a few paragraphs from the user's perspective: what they see, how they perform actions, what they expect to happen if they click widget X. This will glue the logic together in your head, and on paper.
From there you can work on the technical spec, which details the gritty things like database structure, special controls and components you need, SDK's if any, and all other developer-type details that you need to implement.
I definitely appreciate a good interface and as a developer, I try to create them for my users. But appreciating a good interface and designing one are a different thing. I'm looking for good interfaces (such as IMHO StackOverflow, Gmail) as examples of good UI from which I can model my own UI's.
I personally think that Netflix has an excellent web UI. Responsive, easy to navigate. Not mutch CRUD going on, but I find it very comfortable.
Pretty much anything by google, really. They're all very simple and to the point, focusing on usability.
You should get yourself a copy of both Don't Make Me Think and The Non-Designer's Design Book for your base knowledge/insight.
From there, it's much easier for you to dissect and analyze the layouts you already know and like, and recreate them for your own amusement.
edit: To mitigate misunderstanding, the point I'm trying to make is that you probably don't need as many good examples of nice layouts, if you know what to look for. For example, I can be shown a thousand haute couture dresses, and I still couldn't make one myself, because I don't know what to look for.
My favorites
Stack Overflow: This is a WIKI so it's not a rep point grab. I just really love the interface on this site. Been to too many crappy Q/A sites
Google Reader
MSDN: It's gotten a ton better in recent years and is a great way to grab little esoteric details about various APIs
iStockPhoto.com it's simple, effective and handles a large amount of information and data without getting bogged down. It also doesn't get in the way of the info you are looking for.
A good user interface fulfills a specific need of its users effectively.
As an example, here is a site (translation) that I have created for finding out what food is available in the cafeterias of the University of Helsinki. The typical use case is that when a student is hungry, he needs to know what food is available in the neighborhood student cafeterias (which are cheap for students), so that he can choose where to eat and what. He knows where each of those cafeterias is, but does not know what food they have today.
That site shows all the needed information at once. Because the students typically have a couple of cafeterias where they go, they can either bookmark the page with those cafeterias selected, or save the selection as a cookie. After that they can reach their goal without any navigation on the web site.
I don't use it on a day-to-day basis, but I'm very impressed with the Perseus Project digital library.
Here's a link to a poem from Catullus' Carmina in Latin as an example of the interface. Some features that I really like:
Click on the bar near the top to jump to any poem in the work. Larger chunks of the bar represent larger sections of the work (poems, chapters, however that particular work is logically broken up by the author).
Click on a Latin word in the poem to bring up a window (be patient; it seems to take a while) with lexicon entries, user voting and statistics on the word form (i.e. what the inflection means in the context of the sentence; it can be ambiguous in Latin) and so forth.
There are a number of resources down the right column, including various English translations, notes, references, etc. Any of them can be either shown in the right column, or swapped out with whatever is in the main content area in the center.
One of my personal favs: newspond.com
Does midiOutPrepareHeader, midiInPrepareHeader just setup some data fields, or does it do something that is more time intensive?
I am trying to decide whether to build and destroy the MIDIHDR's as needed, or to maintain a pool of them.
You really have only two ways to tell (without the Windows source):
1) Profile it. Depending on your findings for how long it takes, have a debug-only scoped timer that logs when it suddenly takes longer than what you think is acceptable for your application, or do your pool solution. Though the docs say not to modify the buffer once you call the prepare function, and it seems if you wanted to re-use it you may have to modify it. I'm not familiar enough with the docs to say one way or the other if your proposed solution would work.
2) Step through the assembly and see. Don't be afraid. Get the MSFT public symbols and see if it looks like it's just filling out fields or if it's doing something complicated.
I've read about systems which use the Flickr database of photos to fill in gaps in photos (http://blogs.zdnet.com/emergingtech/?p=629).
How feasible is a system like this? I was toying with the idea (not just a way of killing time but as a good addition to something I am coding) of using Flickr to get photos of a certain entity (in this case, race tracks) and reconstruct a model. My biggest concern is that there aren't enough photos of a particular track and even then, it would be difficult to tell if two photos are of the same part of the racetrack, in which case one of them may be irrelevant.
How feasible is something like this? Is it worth attempting by a sole developer?
Sounds like you're wanting to build a Photosynth style system - check out Blaise Aguera y Arcas' demo at TED back in 2007. There's a section about 4 minutes in where he builds a model of the Sagrada FamÃlia from photographs.
I say +1 for photosynth answer, its a great tool. Not sure how well you could incorporate it into your own app though.
Its definately feasable. Anything is possible. And yes, doable for a single developer, just depends how much free time you have. It would be great to see something like this integrated into Virtual Earth or Google Maps Street View. Someone who could nail some software like this could help 3D model the entire world based purely on photographs. That would be a great product and make any single developer rich and famous.
So get coding. :)
I have plenty of free time, as I am in between jobs.
One way to do it is to get an overhead view of the track layout, make a blueprint based on this model, and then get one photo of the track and mimic the track's road colour. That would be a start.
LINQ to Flickr on codeplex has a great API and would be helpful for your task.