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• How to send large objects using boost::asio

  - by Max

  Good day. I'm receiving a large objects via the net using boost::asio. And I have a code: for (int i = 1; i <= num_packets; i++) boost::asio::async_read(socket_, boost::asio::buffer(Obj + packet_size * (i - 1), packet_size), boost::bind(...)); Where My_Class * Obj. I'm in doubt if that approach possible (because i have a pointer to an object here)? Or how it would be better to receive this object using packets of fixed size in bytes? Thanks in advance.

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• Does C99 guarantee that arrays are contiguous ?

  - by kriss

  Following an hot comment thread in another question, I came to debate of what is and what is not defined in C99 standard about C arrays. Basically when I define a 2D array like int a[5][5], does the standard C99 garantee or not that it will be a contiguous block of ints, can I cast it to (int *)a and be sure I will have a valid 1D array of 25 ints. As I understand the standard the above property is implicit in the sizeof definition and in pointer arithmetic, but others seems to disagree and says casting to (int*) the above structure give an undefined behavior (even if they agree that all existing implementations actually allocate contiguous values). More specifically, if we think an implementation that would instrument arrays to check array boundaries for all dimensions and return some kind of error when accessing 1D array, or does not give correct access to elements above 1st row. Could such implementation be standard compilant ? And in this case what parts of the C99 standard are relevant.

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• Python nested function scopes

  - by Thomas O

  I have code like this: def write_postcodes(self): """Write postcodes database. Write data to file pointer. Data is ordered. Initially index pages are written, grouping postcodes by the first three characters, allowing for faster searching.""" status("POSTCODE", "Preparing to sort...", 0, 1) # This function returns the key of x whilst updating the displayed # status of the sort. ctr = 0 def keyfunc(x): ctr += 1 status("POSTCODE", "Sorting postcodes", ctr, len(self.postcodes)) return x sort_res = self.postcodes[:] sort_res.sort(key=keyfunc) But ctr responds with a NameError: Traceback (most recent call last): File "PostcodeWriter.py", line 53, in <module> w.write_postcodes() File "PostcodeWriter.py", line 47, in write_postcodes sort_res.sort(key=keyfunc) File "PostcodeWriter.py", line 43, in keyfunc ctr += 1 UnboundLocalError: local variable 'ctr' referenced before assignment How can I fix this? I thought nester scopes would have allowed me to do this. I've tried with 'global', but it still doesn't work.

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• Help with Btree homework

  - by Phenom

  I need to do a preorder traversal of a Btree, and among other things, print the following information for each page (which is the same thing as a node): The B-Tree page number The value of each B-Tree page pointer (e.g., address, byte offset, RRN). My questions are: 1. How do you figure out the byte offset? What is it offset from? 2. Isn't the RRN the same as the page number? Note: A Btree is NOT A BINARY TREE. Btrees can have multiple keys in each node, and a node with n keys has n+1 child pointers.

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• Accessing WPF Template for Custom Control from Code behind

  - by Ashwani Mehlem

  Hi, i am trying to access a named grid inside a default template for a custom control from code behind. But it seems that the template for the control is null, even after calling ApplyTemplate(). Is that impossible inside the controls constuctor? Here's the code: Generic.xaml: ... <ControlTemplate TargetType="{x:Type local:TimeTableControl}"> <Grid Name="ContentGrid"> </Grid> </ControlTemplate> ... TimeTableControl.cs: public TimeTableControl() { ApplyTemplate(); contentGrid = (Grid)(Template.FindName("ContentGrid", this)); //Line above causes null-pointer-exception ... }

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• basic boost date_time input format question

  - by Chris H

  I've got a pointer to a string, (char *) as input. The date/time looks like this: Sat, 10 Apr 2010 19:30:00 I'm only interested in the date, not the time. I created an "input_facet" with the format I want: boost::date_time::date_input_facet inFmt("%a %d %b %Y"); but I'm not sure what to do with it. Ultimately I'd like to create a date object from the string. I'm pretty sure I'm on the right track with that input facet and format, but I have no idea how to use it. Thanks.

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• Storing member function pointers of derived classes in map

  - by Kiran Mohan

  Hello, I am trying to implement a factory for two classes Circle, Square both of which inherits from Shape. class Shape { public: virtual static Shape * getInstance() = 0; }; class Circle : public Shape { public: static const std::string type; Shape * getInstance() { return new Circle; } }; const std::string Circle::type = "Circle"; class Square : public Shape { public: static const std::string type; Shape * getInstance() { return new Square; } }; const std::string Square::type = "Square"; I want to now create a map with key as shape type (string) and value as a function pointer to getInstance() of the corresponding derived class. Is it possible? Thanks, Kiran

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• VB.NET function that takes other functions as a parameter, and executes them

  - by rob

  Hello, Is there a way in vb.net to create a sub/function that will take as an argument some kind of pointer to another function, and allow this new sub/function to execute the passed function? What I have are 10-12 xml-rpc functions I am calling against a remote server. Each of these functions has different argument lists (one takes 1 string, another might take 3 strings and one int, etc). All of them return an object. As I am calling these, it seems like it should be able to be factored better. For instance, everytime I call any of these functions, I want to test the return value for a session drop, and do something to try and reconnect to the remote system, etc. Using .net 3.5 Thanks! -R

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• Passing big multi-dimensional array to function in C

  - by kirbuchi

  Hi, I'm having trouble passing a big array to a function in C. I declare: int image[height][width][3]={}; where height and width can be as big as 1500. And when I call: foo((void *)image,height,width); which is declared as follows: int *foo(const int *inputImage, int h, int w); I get segmentation fault error. What's strange is that if my values are: height=1200; width=290; theres no problem, but when they're: height=1200; width=291; i get the mentioned error. At 4 bytes per integer with both height and width of 1500 (absolute worst case) the array size would be of 27MB which imo isn't that big and shouldn't really matter because I'm only passing a pointer to the first element of the array. Any advice?

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• How to stop toggle event from being fired multiple times on mouseenter/mouseleave?

  - by Clean

  Hi, I'm using jQuery to toggle the visibility of a using the jQuery toggle method. The toggle is fired on the mouseenter and mouseleave event, thus creating the effect of the div to fold out on mouseenter and fold in on mouseleave. Problem is, if the user drags the mouse over the a few times and then leaves the , the div will toggle in and out several times. This can happen if the user accidentally moves around the mouse pointer in the are. Do anyone have any idea on how I can avoid this behavior? Thanx!

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• identifying the type

  - by Gokul

  Hi, In my application, there is a inheritance hierarchy in which only the classes that are at the end of the inheritance chain are non-abstract classes. Also there is some usage of boost::variant. I want to write a function which takes a pointer and a Type and says whether the object belongs to that type. For example template< typename Type, bool TypeisAbstract, typename ptrType > bool checkType( ptrType* t) { return ( typeid(*t) == typeid(Type) ); } template< typename Type, typename ptrType > bool checkType<Type, true, ptrType>( ptrType* t) { return ( dynamic_cast<Type*>(t) != NULL ); } Now if there is a boost variant, i want to find out whether the boost variant stores that particular type. Can someone help me with that? Thanks, Gokul.

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• Finding the closest grid coordinate to the mouse onclick with javascript/jQuery

  - by Acorn

  What I'm trying to do is make a grid of invisible coordinates on the page equally spaced. I then want a <div> to be placed at whatever grid coordinate is closest to the pointer when onclick is triggered. Here's the rough idea: I have the tracking of the mouse coordinates and the placing of the <div> worked out fine. What I'm stuck with is how to approach the problem of the grid of coordinates. First of all, should I have all my coordinates in an array which I then compare my onclick coordinate to? Or seeing as my grid coordinates follow a rule, could I do something like finding out which coordinate that is a multiple of whatever my spacing is is closest to the onclick coordinate? And then, where do I start with working out which grid point coordinate is closest? What's the best way of going about it? Thanks!

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• Hide select option Cross Browser

  - by Tapas Bose

  Isn't there any way to do it? I have made jsFiddle which is not working in IE. The piece of code is given below: The HTML <select id="testing"> <option value="1">Option 1</option> <option value="2">Option 2</option> <option value="3">Option 3</option> </select> The jQuery $(document).ready(function() { $('select#testing option').eq(1).attr({ disabled: 'disabled' }); }); The CSS select option[disabled] {display: none;} Any pointer would be helpful. Note: I cannot use .remove() method.

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• How to GetGuiResources for all system processes?

  - by Krzysztof

  Hello, I need to measure all used GDI objects in a Windows xp system. I found a GetGuiResources(__in HANDLE hProcess, __in DWORD uiFlags) method (with the GR_GDIOBJECTS flag). I call it for the process which I get from the method GetCurrentProcess() defined in WinBase.h. I don't know how to call it for other system processes, which I get by System::Diagnostics::Process::GetProcesses(), because that function returns an array of Process pointers, and GetGuiResources takes a HANDLE. Does anybody know a solution for that? How can I transform Process pointer to a Handle or get HANDLEs for all running system processes? thanks for help in advance!

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• [Objective-C] Primitive question, (void) init method.

  - by user354289

  Hi, I have a question in Objective-C. I'm using init method Apple recommended style. - (id)initMyClass: (int)a { if (self = [super init]) { // a... } return self; } Init method returns own object pointer. Then, if the object will not be refered from any objects, can empty return method(void) be better? - (void)initMyClass: (int)a { if ([super init] != nil) { // a... } } I want to know about that, if init method doesn't return self, what problem will occur?

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• Accessing structure through pointers [c]

  - by Blackbinary

  I've got a structure which holds names and ages. I've made a linked-list of these structures, using this as a pointer: aNode *rootA; in my main. Now i send **rootA to a function like so addElement(5,"Drew",**rootA); Because i need to pass rootA by reference so that I can edit it in other functions (in my actual program i have two roots, so return will not work) The problem is, in my program, i can't say access the structure members. *rootA->age = 4; for example doesnt work. Hopefully you guys can help me out. Thanks!

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• What's the big difference between those two binary files?

  - by Lela Dax

  These are two files (contained in the tar.bz2) that were generated using a just-in-time compiler for a game engine. The generated code from ui-linux.bin is from a x86_64 gcc compiler and the ui-windows.bin from the same brand of compiler but targetting win x86_64 (mingw-w64). I've attempted to debug a problem that occurs only on the windows version and i stumbled upon what it seems to be different end-binary code. However, the input assembly code was virtually identical (only difference being pointer representations as int). (there's theoretically no winabi/unixabi conflict since that's taken care of by an attribute flag on certain declarations involved). Any idea what it might be that makes these two binary codes different? The C for the mini-compiler and base assembly producing it appears compatible at first glance. http://www0.org/vm/bins.tar.bz2

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• Is it possible to call a user-space callback function from kernel space in Linux (ioctl)?

  - by Makis

  Is it possible to expand the ioctl interface in Linux so that the user-space application can send a pointer to a function to the kernel space driver? I'm in particular thinking of ways to handle the stream in user-controllable way but doing it in the kernel. Those operations could be attached to the kernel module but this would make development a lot easier as I wouldn't need to mess with the kernel during development. More specifically, this would be the process: Data is read by the driver to a buffer. Data is handled by these user-defined functions in place. Some more handling is done, possibly with some HW blocks. Data is used by a user-space application.

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• Windows Server 2008 and com objects

  - by Marthin

  Hi, im moving a Dll (built in c++) from windows 2000 server to a 2008 server but im have some trouble to register it. In 2000 all you normaly have to do is a "regsrv32 name.dll" but this will not work in 2008 because you get a pointer error, iv also tried to use "gacutil /i name.dll" because someone told me this might work, but it didnt. So, im kind of desperate, is there anyone that have some solution to how i can get this c++ dll to work in 2000 server so that i can access it from an old classic asp page. EDIT: This is the error when running regsrv: " The module "name.dll" was loaded but the entry-point DllRegisterServer was not found. Make sure that "name.dll" is a valid DLL or OCX file and then try again. " Note that i cant edit the dll file in anyway =( Best Regards Marthin

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• Does JavaME and/or Proguard reorder assignments?

  - by chrisdew

  This is a simplified example - I have two threads: Can JavaME and/Proguard ever reorder the obX = ... statements, such that thread_B will have a null pointer exception at ob2.someMethod? thread_A: Object ob1 = null; Object ob2 = null; ... ob1 = something1; ob2 = something2; thread_B: if (ob2 != null) { ob1.someMethod(); ... } P.S. I do realise that synchronising these will avoid the issue. Synchronisation has both a performance overhead, and more importantly, a chance to introduce deadlock.

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• 0 not a valid FILE* when provided as a template argument

  - by Seva Alekseyev

  The following code #include <stdio.h> template <typename T, T v> class Tem { T t; Tem() { t = v; } }; typedef Tem<FILE*,NULL> TemFile; when compiled in a .mm file (Objective C++) by Xcode on MacOS X, throws the following error: error: could not convert template argument '0' to 'FILE*'. What's going on, please? The code in question compiled fine under MSVC. Since when is the 0 constant not a valid pointer to anything? Is this an artifact of Objective C++ (as opposed to vanilla C++)?

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• variable names in function definition, call and declaration

  - by yCalleecharan

  Hi, I see C books that use the same variable names in the function definition, calling function and declaration. Others use the same variable names in the calling function and in the declaration/prototype but a different one in the definition as in: void blabla(int something); //prototype blabla(something) // calling function inside main after something has been initialized to int void blabla(int something_else) //definition I have two questions: What convention is best to use in C?; Does the convention apply regardless whether a value is being passed "by-value" or if it's being passed by a pointer? Thanks a lot...

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• How to dynamically replace a method implementation in ObjC2?

  - by Abhi

  I am trying to learn how to write plugins using SIMBL. I got my plugin to load with the target application, and also know the method that I wish to override. However, I am not able to use class_getInstanceMethod correctly based on snippets on the Internet. Have things changed in OSX 10.6 and/or ObjC2? The following code from culater.net gives "Dereferencing pointer to incomplete type" on the second-last statement: BOOL DTRenameSelector(Class _class, SEL _oldSelector, SEL _newSelector) { Method method = nil; // First, look for the methods method = class_getInstanceMethod(_class, _oldSelector); if (method == nil) return NO; method->method_name = _newSelector; return YES; } Is there a complete example of how to override a method using SIMBL plugins? Thanks!

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• Navigating cursor rows in SQLite

  - by Alan Harris-Reid

  Hi there, I am trying to understand how the following builtin functions work when sequentially processing cursor rows. The descriptions come from the Python 3.1 manual (using SQLite3) Cursor.fetchone() Fetches the next row of a query result set, returning a single sequence. Cursor.fetchmany() Fetches the next set of rows of a query result, returning a list. Cursor.fetchall() Fetches all (remaining) rows of a query result, returning a list. So if I have a loop in which I am processing one row at a time using cursor.fetchone(), and some later code requires that I return to the first row, or fetch all rows using fetchall(), how do I do it? The concept is a bit strange to me, especially coming from a Foxpro background which has the concept of a record pointer which can be moved to the 1st or last row in a cursor (go top/bottom), or go to the nth row (go n) Any help would be appreciated. Alan

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• How can I find the places of system calls of my program?

  - by Lucky Man

  From strace manual: -i Print the instruction pointer at the time of the system call. I straced my programm: strace -i prog As a result I got a lot of system calls. One of them: [000da49c] open("./rabbit.o", O_RDONLY) = 3 But disassembled instruction at this address of prog doesn't call any syscall (hte editor): da49c ! mov r7, ip What is wrong? How can I find the places of system calls of my program? P.S. Architecture of my device doesn't support GDB-command catch syscall.

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