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• C# equivalent of recv?

  - by mlh

  Hello, I have a portion of C code that I am trying to port over to C#. In my C code, I create a socket and then issue a receive command. The receive command is void receive(mysocket, char * command_buffer) { recv(mysocket, command_buffer, COMMAND_BUFFER_SIZE, 0); } now, the command buffer is returned with new values including command_buffer[8] being a pointer to a string. I'm really confused as to how to do this in C# because C# Read() command specifically takes in bytes and not char. The important part is that I get the pointer to the string. Any ideas?

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• Adding characters to string

  - by Jamza

  I am currently trying to build a very basic serial shell with my arduino. I am able to get an output from the device using Serial.read() and can get the character it has outputted, but I cannot work out how to then add that character to a longer to form the full command. I tried the logical thing but it doesn't work: char Command[]; void loop(){ if(Serial.available() > 0){ int clinput = Serial.read(); Command = Command + char(clinput); } Can anybody help? Thank You.

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• How to split the definition of template friend funtion within template class?

  - by ~joke

  The following example compiles fine but I can't figure out how to separate declaration and definition of operator<<() is this particular case. Every time I try to split the definition friend is causing trouble and gcc complains the operator<<() definition must take exactly one argument. #include <iostream> template <typename T> class Test { public: Test(const T& value) : value_(value) {} template <typename STREAM> friend STREAM& operator<<(STREAM& os, const Test<T>& rhs) { os << rhs.value_; return os; } private: T value_; }; int main() { std::cout << Test<int>(5) << std::endl; }

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• extracting string occurrence in c

  - by David78

  I have a string from a text file that look something like this: long_str = "returns between paragraphs 20102/34.23" - 9203 1232 "test" "basic HTML" Note: Quotes are part of the string. int match(char *long_str){ char * str; if ((str = strchr(long_str, '"')) != NULL) str++; // last " ? else return 1; return 0; } Using strstr I'm trying to get the whole substring between the last two quotes: "basic HTML". I'm just not quite sure what would be a good and efficient way of getting that match. I'm open to any other ideas on how to approach this. Thanks

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• Change Wallpaper in windows mobile

  - by niks86

  Hello Friends, Hey im devloping application in that i want to set images as the wallpaper for that i written below code.when i used remote registry in registry value get updated but the wallpaper of the windows mobile does not changed.Can u plz tel me what i need to do. Here is my code. [DllImport("coredll.dll")] private static extern int SendMessage(IntPtr hWnd, uint msg, int wParam, int lParam); public const int HWND_BROADCAST = 0xffff; public const int WM_WININICHANGE = 0x001A; File.Copy(@"\My Documents\My Pictures\Album Sample_05.jpg", @"\My Documents\My Pictures\Album Sample_09.jpg", true); Registry.SetValue(@"HKEY_CURRENT_USER\Software\Microsoft\Today", "Wall", @"\My Documents\My Pictures\Album Sample_05.jpg"); SendMessage((IntPtr)HWND_BROADCAST, WM_WININICHANGE, 0xF2, 0); plz help me. Thanks.

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• typedef to store pointers in C

  - by seriouslion

  The Size of pointer depends on the arch of the machine. So sizeof(int*)=sizeof(int) or sizeof(int*)=sizeof(long int) I want to have a custom data type which is either int or long int depending on the size of pointer. I tried to use macro #if, but the condition for macros does not allow sizeof operator. Also when using if-else, typedef is limited to the scope of if. if((sizeof(int)==sizeof(int *)){ typedef int ptrtype; } else{ typedef long int ptrtype; } //ptrtype not avialble here Is there any way to define ptrtype globally?

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• Copy unmanaged data into managed array

  - by JeffRSon

  I need to copy native (i.e. unmanaged) data (byte*) to managed byte array with C++/CLI (array). I tried Marshal::Copy (data is pointed to by const void* data and is dataSize bytes) array<byte>^ _Data=gcnew array<byte>(dataSize); System::Runtime::InteropServices::Marshal::Copy((byte*)data, _Data, 0, dataSize); This gives error C2665: none of the 16 overloads can convert all parameters. Then I tried System::Runtime::InteropServices::Marshal::Copy(new IntPtr(data), _Data, 0, dataSize); which produces error C2664: parameter 1 cannot be converted from "const void*" to "__w64 int". So how can it be done and is Marshal::Copy indeed the "best" (simplest/fastest) way to do so?

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• Getting the fractional part of a float without using modf()

  - by knight666

  Hi, I'm developing for a platform without a math library, so I need to build my own tools. My current way of getting the fraction is to convert the float to fixed point (multiply with (float)0xFFFF, cast to int), get only the lower part (mask with 0xFFFF) and convert it back to a float again. However, the imprecision is killing me. I'm using my Frac() and InvFrac() functions to draw an anti-aliased line. Using modf I get a perfectly smooth line. With my own method pixels start jumping around due to precision loss. This is my code: const float fp_amount = (float)(0xFFFF); const float fp_amount_inv = 1.f / fp_amount; inline float Frac(float a_X) { return ((int)(a_X * fp_amount) & 0xFFFF) * fp_amount_inv; } inline float Frac(float a_X) { return (0xFFFF - (int)(a_X * fp_amount) & 0xFFFF) * fp_amount_inv; } Thanks in advance!

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• Abstract class and operator!= in c++

  - by Alessandro Teruzzi

  Hi All, I have problem implementing the operator!= in a set class deriving from an abstact one. The code looks like this: class Abstract { public: //to make the syntax easier let's use a raw pointer virtual bool operator!=(const Abstract* other) = 0; }; class Implementation { SomeObject impl_; //that already implement the operator!= public: bool operator!=(const Abstract* other) { return dynamic_cast<Implementation*>(other)->impl_ != this->impl_; } }; This code works but it has the drawback to use dynamic_cast and I need to handle error in casting operation. This is a generic problem that occur when a function of a concrete class it is trying to using some internal information (not available at the abstract class level) to perform a task. Is there any better way to solve this kind of problem? Cheers

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• Visual C++ CreateThread Parameter Problem

  - by Vanwaril

  I have a class that contains a function that calls create thread, and needs to pass itself (this) as a parameter: DWORD threadId; HANDLE h = CreateThread( NULL, 0, runThread, this, 0, &threadId); My runThread definition is as follows: DWORD WINAPI runThread(LPVOID args) { Obj *t = (Obj*)args; t->funct(); return 0; } Unfortunately, the object t that I get in runThread() gets garbage. My Obj class has a function pointer attribute. Could that be the problem? class Obj{ void(*funct)(); and in the constructor: Obj(void(*f)()) { funct = f; } where is my mistake? The function pointer, the createThread itself, or type-casting? I tried whatever I could think of.

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• Program quits if pipe is closed

  - by givemelight

  I am trying to write to a pipe using C++. The following code gets called in an extra thread: void writeToPipe() { int outfifo; char buf[100]; char outfile[] = "out"; mknod(outfile, S_IFIFO | 0666, 0); if ((outfifo = open(outfile, O_WRONLY)) < 0) { perror("Opening output fifo failed"); return false; } int currentTimestamp = (int)time(0); int bufLen = sprintf(bug, "Time is %d.", currentTimestamp); write(outfifo, buf, bufLen); } The thread is called in main using: thread writeThread(writeToPipe); writeThread.detach(); If the pipe is not opened by another process, the C++ program just quits without an error. I don't know how to check if the pipe is opened.

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• Is this a valid C statement ?

  - by Philando Gullible

  Lets say I write char c[99] = {'Stack Overflow'}; in C or C++ it does compiles fine but does this valid? By valid I meant not invoking any kind of undefined or unspecified behavior. Again if I write char c[99] = 'Stack Overflow'; gcc complains about multicharacter constant which is obvious but in the above when I am enclosing within curly brackets compiler is happy! why is it so ? I also notice that puts(c); after the first statement will output 'w' precisely the last character of a general string in-place of Stack Overflow. why so ? Could somebody explain this behavior may be separately.

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• What is wrong with my loop?

  - by user3966541

  I have the following loop and don't understand why it only runs once: std::vector<sf::RectangleShape> shapes; const int res_width = 640; const int res_height = 480; for (int x = 0; x < res_width / 50; x += 50) { for (int y = 0; y < res_height / 50; y += 50) { sf::RectangleShape shape(sf::Vector2f(50, 50)); shape.setPosition(x * 50, y * 50); sf::Color color = (x % 2 == 0) ? sf::Color::Green : sf::Color::Red; shape.setFillColor(sf::Color::Green); shapes.push_back(shape); } }

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• Removing Unused (Unreferenced) Static Global Variable Constants in C++

  - by Synetech inc.

  Hi, I have a header file with a few common constants like names and stuff that are automatically included in each project (an example follows). The thing is that they are included in the compiled binary (EXE) whether they are used (referenced) or not. If I use DEFINEs instead, then naturally they are not included if they are not used, but of course consts are better than defines so… I tried Googling it, but the closest thing I could find was a question right here on SO that did not quite help. Matters of i18n aside, how can I keep the ones that are not used out of the binary, while still keeping it easy to use like this? Thanks. //COMMON.H: static const CString s_Company _T("Acme inc."); //etc. static const CString s_Digits _T("0123456789"); //TEST.CPP: #include common.h int main() { AfxMessageBox(s_Company); } //s_Company should be in the final EXE, but s_Digits should not be, but is

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• array of objects of a class

  - by anurag18294

  #include class test{ int a; char b; public: test() { cout<<"\n\nDefault constructor being called"; } test(int i,char j) { a=i; b=j; cout<<"\n\nConstructor with arguments called"; } }; int main() { test tarray[5]; test newobj(31,'z'); }; In the above code snippet can we intialize values to tarray[5].

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• comlen function in Java

  - by davit-datuashvili

  in c or c++ the function comlen is defined such int comlen(char *p,char *q){ int i=0; while *p && (*p++==*q++) i++; return i; } Is this code equivalent of this function? int comlen(String s,String m){ int i=0; while (i<s.length() && s.charAt(i)==m.charAt(i)){ i++; } return i; }

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• referencing struct fields in c with square brackets and an index instead of . and ->?

  - by lsiebert

  Assuming I have a structure such as: typedef struct { char * string1; char * string2; } TWO_WORDS; such that all the fields are of the same type, and my main has TWO_WORDS tw; can I reference string1 with tw[0] and string2 with two[1]? If so: is this part of the c standard? do i have to cast the struct to an array first? what about fields which are different sizes in memory what about fields which are different types but the same size? can you do pointer arithmetic within a structure? -

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• Redundant naming in C/C++ typedefs/structs

  - by bloomy

  #include <stdio.h> #include <string.h> const int NAMELEN=30; const int MAXCLASSSIZE=10; typedef struct StudentRec { char lastname[NAMELEN]; char firstname[NAMELEN]; long int ID; int finalmark; }Student; I'm new to coding..and I have a question about why there is Student; after the bracket.. is it a format that we have to follow.

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• Level Order Successor of node in BST

  - by dsiap

  How can we find level order successor of a node in bst if parent pointer is given(with out using Queue ) ?

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• C++ convert formatted string to a stream

  - by Roey

  Hi All, I'm using VS2008 C++. As I understand it there is no way to pass something like this in a C++ stream : (without using external libraries) "number " << i <------ when i is an integer. So I was looking for a better way to do this, and I all I could come up with is create a string using : char fullstring = new char[10]; sprintf(fullString, "number %d", i); .... pass fullstring to the stream ..... delete[] fullString; I know it's stupid, but is there a better way of doing this?

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• C++: Checking for non-numeric input and assigning to a double

  - by Brundle

  Here is the code I have at the moment: char ch; int sum = 0; double values[10]; int i = 0; cin >> ch; while (!isalpha(ch)) { values[i] = ch; sum += values[i]; i++; cin >> ch; } What is happening is that if I enter the value 1, that gets assigned to ch as a char. Now ch is assigning it's value to a double and doing an implicit cast. So it is assigning the ASCII value of '1' to values[i]. I want it to just assign 1 to values[i]. Is there a better way to do this? Or is there something that I'm missing?

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• Debugging metaprograms [C++]

  - by atch

  Hi, Is there any way to check step by step what's going on in let's say template? I mean how it is instantiated step by step and so on? In book I've mentioned here , I found (2 minutes ago) quite interesting example of how binary could be implemented as a metafunction. template <unsigned long N> struct binary { static unsigned const value = binary<N/10>::value << 1 // prepend higher bits | N%10; // to lowest bit }; template <> // specialization struct binary<0> // terminates recursion { static unsigned const value = 0; }; and I think it could be quite useful to be able to see step by step what's been done during the instantiation of this template. Thanks for your replies.

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• including a std::map within a struct? Is it ok?

  - by user553514

  class X_class{ public: struct extra {int extra1; int extra2; int extra3; }; enum a { n,m}; struct x_struct{ char b; char c; int d; int e; std::map <int, extra> myExtraMap; }; }; in my code I define : x_struct myStruct; why do I get compile errors compiling the above class? The error either says: 1) expected ; before < on the line --- where I defined the map (above) if I eliminate std:: or 2) error: invalid use of ::; error: expected ; before < token

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• why does it use the movl instead of push ?!

  - by user554403

  hi all. pay attention to this code : #include <stdio.h> void a(int a, int b, int c) { char buffer1[5]; char buffer2[10]; } int main() { a(1,2,3); } after that : gcc -S a.c that command shows our source code in assembly. now we can see in the main function, we never use "push" command to push the arguments of the a function into the stack. and it used "movel" instead of that main: pushl %ebp movl %esp, %ebp andl $-16, %esp subl $16, %esp movl $3, 8(%esp) movl $2, 4(%esp) movl $1, (%esp) call a leave why does it happen? what's difference between them?

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• How to efficiently render different things at different times in a game?

  - by Baqjohanson

  Sorry for the ambiguous title. What I am wondering is what is an efficient way to alternate rendering between lets say a main menu, options menu, and "in the game." The only two ways I've come up with so far are to have 1 render function, with code for each part (menu, ...) and a variable to control what gets drawn, or to have multiple render functions, and use a function pointer to point to the appropriate one, and then just call the function pointer. I always wonder how more professional games do it.

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