November 2011 - skunkworks - Skunkworks Site

Mobile - CCIE Lab in Kenya
by John Gitau 28 Nov '11

28 Nov '11

Apologies for the cross post: Is there anyone (other than guys at Safaricom) planning to sit for the CCIE lab around April next year. This means you absolutely must have done your written (R&S,Security and or SP)? or plan to do it soon. Im not interested in 'I plan to do it in xyz' for this thread. I need dates before February ie commitments to pay between now and end of January. Cisco Kenya are trying to justify having the mobile lab https://learningnetwork.cisco.com/docs/DOC-3224 here within the first half of the coming year. They do however require a minimum number of participants - +30 for it to make sense economically. If you are working on this please unicast me or the group/s so we can give an approximation of the numbers. *If you're looking to just understand the certification, please join <http://lists.my.co.ke/cgi-bin/mailman/listinfo/eanog>the East African Network Operators Group (EANOG) and start a separate thread. We'll be more than happy to answer your queries over there. Regards, JGitau

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Size of an object in memory at runtime
by James Nzomo 28 Nov '11

28 Nov '11

Has anyone here successfully (and accurately) determined the size of a C++ class instance (Object) in memory during run time? _______________________________________________ *Good judgement comes from Experience.* *Most of that comes from Bad Judgement.* _______________________________________________ * *

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Size of an object in memory at runtime
by Josh Handley 28 Nov '11

28 Nov '11

I see. You are right that sizeof won't work in this case since you need to get the size of the instance itself plus all the dynamically allocated objects (strings and pointers). Sizeof can give the size of an object but of the object and all the objects it points too. There is no simple way to do that in C++. You would have to write code to take the sizeof the object itself and then add all the sizes of the objects that it points and the sizes of the objects that they point too etc... But even if you could do that, it still wouldn't help with the problem you have. The other objects that your object points too (strings, char pointers...) will not be in the same contiguous memory block as the object itself. So even if you copy your object onto the clipboard and allocate enough space for the other objects, the other objects won't get copied onto the clipboard. Here is an example of what I mean: Say you have your drag and drop object DDObj that has a pointer to a Child object: class Child { int i; } class DDObj { Child* c; } When you create the objects, each one gets created with a call to new: DDObj dd = new DDObj(); dd.c = new Child(); // this might actually happen inside DDObj constructor So instance dd might be at memory location 100 but since dd.c was created with a different call to new it could be at totally different memory location - 200 or 1000 or 10000 - anywhere. So even though you know that the size of DDObj plus the size of c is say 16 bytes they aren't 16 bytes next to each other. You probably have 8 bytes in one place and the other 8 bytes in another. So if you try to copy 16 bytes onto the clipboard starting at the location of dd you will end picking some other values for dd.c. Even if you did get lucky and the objects were lined up in memory when the other application at the other end of the clipboard got your object the pointer to dd.c would probably no longer be valid since the object would likely have been remapped to a different virtual address space. To do this using the in memory representation of your objects you would have to either restrict the objects on the clipboard to simple value types and fixed size arrays (no std::string, no char*) or you would have to manage the memory yourself using some kind of variant of a mempool. If I were you I would look for a library that you can use to marshal/serialize your objects. Not sure if there is anything like for use with wxWidgets. Using a JSON or XML representation of the objects is one way to serialize them although you may be able to find something slightly more efficient for an in memory representation. In any case, it isn't something you want to code yourself as remapping the pointers is fairly tricky. Josh On 28/11/11 1:19 PM, skunkworks-request(a)lists.my.co.ke wrote: > Message: 3 > Date: Mon, 28 Nov 2011 13:01:49 +0300 > From: James Nzomo<kazikubwa(a)gmail.com> > To: Skunkworks Mailing List<skunkworks(a)lists.my.co.ke> > Subject: Re: [Skunkworks] Size of an object in memory at runtime > Message-ID: > <CAChuKucuy6DM5ofjp-uoOdjG-=AQjZkFwnSNZE3sohOrUrHpkA(a)mail.gmail.com> > Content-Type: text/plain; charset="iso-8859-1" > > I'm using wxWidgets. It's clipboard mechanism extends the underlying > platform's clipboard mechanism. > > The object is of a custom class. > This class contains various datatypes ranging from > ints,doubles,std::strings,char pointers to custom typedefs, structs and > other classes. > > The objects i want to D&D are of different types. I will have a clipboard > data object for each type as opposed to having an abstract implementation > which is more complex.

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Size of an object in memory at runtime
by Josh Handley 28 Nov '11

28 Nov '11

Are you using the Windows clipboard mechanism (OpenClipboard, SetClipboardData...)? What does the object look like that you are putting on the clipboard? Is it always the same concrete type or do you have an abstract base class and you are putting different derived types on the clipboard? Is it a simple class with only value members or does it have arrays or pointers to other objects? Josh On 28/11/11 12:37 PM, skunkworks-request(a)lists.my.co.ke wrote: > Message: 3 > Date: Mon, 28 Nov 2011 12:35:08 +0300 > From: James Nzomo<kazikubwa(a)gmail.com> > To: Skunkworks Mailing List<skunkworks(a)lists.my.co.ke> > Subject: Re: [Skunkworks] Size of an object in memory at runtime > Message-ID: > <CAChuKuewWX4DQzr3foEo7KU550vAwzRrevtgVDMw2Tp6Qwz2GQ(a)mail.gmail.com> > Content-Type: text/plain; charset="iso-8859-1" > > What i'm trying to do is implement drag& drop clipboard opps for a custom > data object (a custom class/object in this case) that works accross > multiple instances of the same running application. > > In order to do this efficiently, i have to allocate the exact amount of > memory required to store the class instance as a D&D object. > > The other alternatives would be to give a generous over estimate of the > required memory or to use the objects JSON string as the D&D object. But > the latter requires alot of coding overhead. >

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Re: [Skunkworks] Gmail acting funny
by Mash 28 Nov '11

28 Nov '11

Memusi, u've set your browser to remember password Sent from My HTC ----- Reply message ----- From: "Memusi" <tonatech(a)gmail.com> To: "Skunkworks Mailing List" <skunkworks(a)lists.my.co.ke> Subject: [Skunkworks] Gmail acting funny Date: Sun, Nov 27, 2011 19:05 For me, I notice that when you log out the password and username still remains there.I.E Its still filled. FYI durin login i dont check the remember password checkbox. On Sun, Nov 27, 2011 at 7:02 PM, maina <dmaishe(a)gmail.com> wrote: Is it me or have gmail guys changed something, when i click on Sign out a new window pops, but the "original" windows remains signed in..i wonder what will happen to those pple who use public comps(cybers)..! -- David Maina. P. O. Box 8310-00200, NAIROBI, KENYA.. Cell:+254-721-950073. Registered Linux User #407239. ---------------------------------------------------------------------- "By golly, I'm beginning to think Linux really *is* the best thing since sliced bread." _______________________________________________ Skunkworks mailing list Skunkworks(a)lists.my.co.ke ------------ List info, subscribe/unsubscribe http://orion.my.co.ke/cgi-bin/mailman/listinfo/skunkworks ------------ Skunkworks Rules http://my.co.ke/phpbb/viewtopic.php?f=24&t=94 ------------ Other services @ http://my.co.ke -- Regards Memusi Communication is vital in this century....

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Size of an object in memory at runtime
by Josh Handley 28 Nov '11

28 Nov '11

Besides the situations that I pointed out it will. What are the circumstances that you are seeing in which it isn't? What is the problem exactly that you are trying to solve? There may be a better approach. Josh On 28/11/11 12:27 PM, skunkworks-request(a)lists.my.co.ke wrote: > > @Josh sizeof() doesn't give the size of the object at runtime (in memory).

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Size of an object in memory at runtime
by Josh Handley 28 Nov '11

28 Nov '11

Actually the const should be dealt with at compile time and not cost any memory. A static variable on the other hand would be stored in memory although only one copy for all instances of the class as you mentioned. In the C++ implementations I have seen the only overhead for each object instance above the memory used by the member variables is a single pointer for the vtable (virtual function table). This would not apply to the class in your example since it has no virtual functions. I don't think that this is required by the standard so different compilers will handle it differently but this is definitely what Visual C++ does. Josh On 28/11/11 11:48 AM, skunkworks-request(a)lists.my.co.ke wrote: > Message: 2 > Date: Mon, 28 Nov 2011 11:49:34 +0300 (EAT) > From: Steve Obbayi<steve(a)sobbayi.com> > To: Skunkworks Mailing List<skunkworks(a)lists.my.co.ke> > Subject: Re: [Skunkworks] Size of an object in memory at runtime > Message-ID:<97d9ac43-36ee-45f0-9699-2bbeeda8daa6@obbayi> > Content-Type: text/plain; charset="utf-8" > > In C++ to determine the size of a class in memory you look at the variables linked to the class > > so take for example: > > class myClass > { > > int x = 2; > int y = 3; > const int z = 10; > > myClass(int a, int b) > { > x = a; > y = b; > } > > int addInt() > { > return x+y; > } > > } > > The size of this class instance in memory is basically the size of the two variables x and y which would be about 8 bytes total plus some overhead which could be a single byte. > Notice the constant int z. This is not part of the instance of a C++ class. Reasoning is even if you make ten instances of the class all you will have is > 10 instances of x and 10 instances of y which is total 80 bytes. z will only be one instance. Thats why you can use z without creating an object of the class. > > The object is stored in the heap with the values and the pointer to that object is stored in the stack eg > > MyClass happy = new MyClass(10, 20); > > happy is the address of "new MyClass(10, 20)" is stored in the stack and takes up 1 byte (lets assume the underlying pointer is stored in a single byte) > "MyClass(10, 20)" is stored in the heap and takes up 10 x sizeof(int) + 20 x sizeof(int) + overhead. > > There is an argument about the memory of member functions. They behave the same way. calculate the size of the local variables in the member functions. Stuff like for loops, while, if else. those are language constructs and are handled internally by the language hence the overhead. > > It is slightly more complicate than this but I hope you get the idea behind memory management in C++ and C also (structs and unions) > > Steve

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This is why airtel will continue making losses: worst network
by Jared Koyier 28 Nov '11

28 Nov '11

After heavy usage,I exceeded my limit by 1/- on Safaricom line and without a blink got disconnected. Am not complaining about that, kinda gotten used to it now. Since I still had lots of calls to make I bought a zain/airtel line. Loaded it with 500 airtime and sat pretty to make calls, this was just about when arsenal vs fulham match was about to start. Shock on me I couldn't make calls,frantic calls to 111 airtel customer care disconnected just like any other call I tried to make. 10min later aft reading the Mwaks that come with the line I called 222. By this time it was halftime btn arsenal-fulham,score line 0-0,I hadn't scored either past the a zillion AVRs. Why would i want to know how much it cost to call India anyway,I don't give a hoot. When I finally did, just as the teams were getting back on the pitch the gentleman on the zain side told me they are having a network issue around my area...promising answer,until I asked him how it was that I was able to call airtel and whether the channel was different. He calmly told me to switch off my phone and thanked me just before I shouted bullshit. Problem always come in twos and as the zain guy hung up, and so,vermalean scored an own goal. Frustrated at the two issues, I decided to call zain again, did another round of filanga free musicals and 20minutes later I was talking to a lady. My charge was dying too so I kinda wanted the conversation crisp. She calmly told me I calling using an orange line! How the F&$( is that even possible to call222 from another provider sim. Before I could digest that load of fart,she told me the line belongs to francis wanjala....hehehe. "so now you have access to Orange databases?", I asked. As if doubting myself,I took the plastic that hold the sim and looked at it hoping to see orange but all I saw was zain. The conversation was crisp indeed coz mysteriously I got a prompt to leave a message...I ended up hanging up Tried calling the number a few more times after the arsenal draw but couldn't get through to customer care. Watched Juventus match all through while trying to get past the 222 avrs but couldn't. Then like a stroke of genius it hit me that the people I wanted call had slept anyway. I gave up , 500/- lost, lost opportunity,frustrated and convinced that better the devils(read safaricom) than the Indian you don't. Sent from my iPad

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Size of an object in memory at runtime
by Josh Handley 28 Nov '11

28 Nov '11

The C++ sizeof operator can give you the object size at compile time: int size = sizeof(MyClass) For most classes this shouldn't differ from the run time size unless you are doing some weird stuff with memory. Only gotcha is that sizeof needs to have the correct type so if you do sizeof on the base class but at runtime what you have is a derived class with additional data then it won't be accurate. You could work around this by adding a virtual size method to your class hierarchy where each derived class returns the result of the sizeof operator on itself. Also if your class has other objects that it allocates dynamically and points to then those sizes are not taken into account. You would have to write code to traverse all of them and sum up the sizes. If you share more details about what you are trying to accomplish I'm happy to offer other ideas. Josh On 28/11/11 11:12 AM, skunkworks-request(a)lists.my.co.ke wrote: > Message: 1 > Date: Mon, 28 Nov 2011 10:56:23 +0300 > From: James Nzomo<kazikubwa(a)gmail.com> > To: Skunkworks Mailing List<skunkworks(a)lists.my.co.ke> > Subject: [Skunkworks] Size of an object in memory at runtime > Message-ID: > <CAChuKueA0LoOZKGhyKmQUrd6OrOGUgJTKoTrRMiOQUOvfHpz6A(a)mail.gmail.com> > Content-Type: text/plain; charset="iso-8859-1" > > Has anyone here successfully (and accurately) determined the size of a C++ > class instance (Object) in memory during run time?

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<Ad> Looking for Used Laptop
by Garr Patronas 28 Nov '11

28 Nov '11

Hola Skunks, I'm looking for a used laptop. Specs: 2.0GHz and above Ram: min 1GB HDD: 80GB DVD-RW Ethernet port & WiFi Preferably older model Dell (Latitude or Inspiron) or HP d530. Anyone with any of the above and willing to sell, lemme know offlist. Thanks, and good day all. GP

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