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  • Overwhelmed by design patterns... where to begin?

    - by Pete
    I am writing a simple prototype code to demonstrate & profile I/O schemes (HDF4, HDF5, HDF5 using parallel IO, NetCDF, etc.) for a physics code. Since focus is on IO, the rest of the program is very simple: class Grid { public: floatArray x,y,z; }; class MyModel { public: MyModel(const int &nip1, const int &njp1, const int &nkp1, const int &numProcs); Grid grid; map<string, floatArray> plasmaVariables; }; Where floatArray is a simple class that lets me define arbitrary dimensioned arrays and do mathematical operations on them (i.e. x+y is point-wise addition). Of course, I could use better encapsulation (write accessors/setters, etc.), but that's not the concept I'm struggling with. For the I/O routines, I am envisioning applying simple inheritance: Abstract I/O class defines read & write functions to fill in the "myModel" object HDF4 derived class HDF5 HDF5 using parallel IO NetCDF etc... The code should read data in any of these formats, then write out to any of these formats. In the past, I would add an AbstractIO member to myModel and create/destroy this object depending on which I/O scheme I want. In this way, I could do something like: myModelObj.ioObj->read('input.hdf') myModelObj.ioObj->write('output.hdf') I have a bit of OOP experience but very little on the Design Patterns front, so I recently acquired the Gang of Four book "Design Patterns: Elements of Reusable Object-Oriented Software". OOP designers: Which pattern(s) would you recommend I use to integrate I/O with the myModel object? I am interested in answering this for two reasons: To learn more about design patterns in general Apply what I learn to help refactor an large old crufty/legacy physics code to be more human-readable & extensible. I am leaning towards applying the Decerator pattern to myModel, so I can attach the I/O responsibilities dynamically to myModel (i.e. whether to use HDF4, HDF5, etc.). However, I don't feel very confident that this is the best pattern to apply. Reading the Gang of Four book cover-to-cover before I start coding feels like a good way to develop an unhealthy caffeine addiction. What patterns do you recommend?

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  • Why is there no Constant keyword in Java?

    - by harigm
    I am curious learner of Java, and I was thinking about the topic of "CONSTANTS". I have learnt that Java allows us to declare constants by using final keyword. My question is why didn't Java introduce Constant (const) keyword. Since many people say it has come from C++, in C++ we have const keyword. Please share your thoughts.

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  • How can I share dynamic data between Applications?

    - by Ehsan
    Hi, I use CreateFileMapping, but this method does not useful,because only static structure can be shared by this method. for example this method is good for following structure: struct MySharedData { unsigned char Flag; int Buff[10]; }; but it's not good for : struct MySharedData { unsigned char Flag; int *Buff; }; would be thankful if somebody guide me on this, Thanks in advance!

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  • how to save poiner in C

    - by JosiP
    Hi In my app, for debugging i want to save pointer, before i do other operations on it eg: void foo(...) { /* suppose ptr1 points to one of my strcuts */ ptr1 = NULL; /* before that ptr1=NULL i want to save value of that pointer - how to do it ? */ } thx for any help

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  • Using an ampersand in scanf()

    - by Rob
    When I compile scanf("%s", &var);, gcc sends back a warning: warning: format ‘%s’ expects type ‘char *’, but argument 2 has type ‘char (*)[20]’ however when I compile scanf("%s", var);, no warning is applied. Both pieces of code work and the book I am reading specifically says to use the ampersand, but even it doesn't in some of the examples. My question is, should I continue to use the ampersand, even when the book doesn't specify?

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  • warning: returning reference to temporary

    - by Jack
    I have a function like this const string &SomeClass::Foo(int Value) { if (Value < 0 or Value > 10) return ""; else return SomeClass::StaticMember[i]; } I get warning: returning reference to temporary. Why is that? I thought the both values the function returns (reference to const char* "" and reference to a static member) cannot be temporary.

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  • Variable declarations in header files - static or not?

    - by Rob
    When refactoring away some #defines I came across declarations similar to the following in a C++ header file: static const unsigned int VAL = 42; const unsigned int ANOTHER_VAL = 37; The question is, what difference, if any, will the static make? Note that multiple inclusion of the headers isn't possible due to the classic #ifndef HEADER #define HEADER #endif trick (if that matters). Does the static mean only one copy of VAL is created, in case the header is included by more than one source file?

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  • Why SQL2008 debugger would NOT step into a certain child stored procedure

    - by John Galt
    I'm encountering differences in T-SQL with SQL2008 (vs. SQL2000) that are leading me to dead-ends. I've verified that the technique of sharing #TEMP tables between a caller which CREATES the #TEMP and the child sProc which references it remain valid in SQL2008 See recent SO question. My core problem remains a critical "child" stored procedure that works fine in SQL2000 but fails in SQL2008 (i.e. a FROM clause in the child sProc is coded as: SELECT * FROM #AREAS A) despite #AREAS being created by the calling parent. Rather than post snippets of the code now, here is another symptom that may help you suggest something. I fired up the new debugger in SQL Mgmt Studio: EXEC dbo.AMS1 @S1='06',@C1='037',@StartDate='01/01/2008',@EndDate='07/31/2008',@Type=1,@ACReq = 1,@Output = 0,@NumofLines = 30,@SourceTable = 'P',@LoanPurposeCatg='P' This is a very large sProc and the key snippet that is weird is the following: **create table #Areas ( State char(2) , County char(3) , ZipCode char(5) NULL , CityName varchar(28) NULL , PData varchar(3) NULL , RData varchar(3) NULL , SMSA_CD varchar(10) NULL , TypeCounty varchar(50) , StateAbbr char(2) ) EXECUTE dbo.AMS_I_GetAreasV5 -- this child populates #Areas @SMSA = @SMSA , @S1 = @S1 , @C1 = @C1 , @Z1 = @Z1 , @SourceTable = @SourceTable , @CustomID = @CustomID , @UserName = @UserName , @CityName = @CityName , @Debug=0 EXECUTE dbo.AMS_I_GetAreas_FixAC -- this child cannot reference #Areas @StartDate = @StartDate , @EndDate = @EndDate , @SMSA_CD = @SMSA_CD , @S1 = @S1 , @C1 = @C1 , @Z1 = @Z1 , @CityName = @CityName , @CustomID = @CustomID , @Debug=0 -- continuation of the parent sProc** I can step through the execution of the parent stored procedure. When I get to the first child sproc above, I can either STEP INTO dbo.AMS_I_GetAreasV5 or STEP OVER its execution. When I arrive at the invocation of the 2nd child sProc - dbo.AMS_I_GetAreas_FixAC - I try to STEP INTO it (because that is where the problem statement is) and STEP INTO is ignored (i.e. treated like STEP OVER instead; yet I KNOW I pressed F11 not F10). It WAS executed however, because when control is returned to the statement after the EXECUTE, I click Continue to finish execution and the results windows shows the errors in the dbo.AMS_I_GetAreas_FixAC (i.e. the 2nd child) stored procedure. Is there a way to "pre-load" an sProc with the goal of setting a breakpoint on its entry so that I can pursue execution inside it? In summary, I wonder if the inability to step into a given child sproc might be related to the same inability of this particular child to reference a #temp created by its parent (caller).

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  • Struct declaration error in C

    - by Spidfire
    ive got a struct problem it returns: cd.h:15: error: two or more data types in declaration specifiers its probably something simple ... struct cd { char titel[32]; char artiest[32]; int speelduur; }; typedef struct cd CD; struct cdlijst{ CD *item; struct cdlijst *next; } typedef struct cdlijst CDLijst;

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  • Filter string in C

    - by Paul Tarjan
    How can I filter a string in c? I want to remove anything that isn't [a-z0-9_]. int main(int argc, char ** argv) { char* name = argv[1]; // remove anything that isn't [a-z0-9_] printf("%s", name); }

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  • How to have abstract and overriding constants in C# ?

    - by Chris
    Hi all, My code below won't compile. What am i doing wrong? I'm basically trying to have a public constant that is overridden in the base class. public abstract class MyBaseClass { public abstract const string bank = "???"; } public class SomeBankClass : MyBaseClass { public override const string bank = "Some Bank"; } Thanks as always for being so helpful!

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  • Why Constant Keyword is not introduced In Java?

    - by harigm
    I am curious learner of Java, I was thinking on one topic "CONSTANTS" I have learnt that Java allows us to declare constants by using "Final" keyword. My question is Java didnot introduce Constant(Const) Keyword. Since many people say it has come from C++, in C++ we have Const keyword Is there any strong reason behind, Please share your thoughts on this.

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  • C programming doubt!!!

    - by aks
    Hi, I am having a programming doubt? Please have a look at the below mentioned code snippet and tell me the difference? int main() { struct sockaddr_in serv_addr, cli_addr; /* Initialize socket structure */ bzero((char *) &serv_addr, sizeof(serv_addr)); } Now, what if i do something similar without typecasting (char *), then also i feel it will do the same thing? Can someone clarify? /* Initialize socket structure */ bzero( &serv_addr, sizeof(serv_addr));

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  • Reading and writing C++ vector to a file

    - by JB
    For some graphics work I need to read in a large amount of data as quickly as possible and would ideally like to directly read and write the data structures to disk. Basically I have a load of 3d models in various file formats which take too long to load so I want to write them out in their "prepared" format as a cache that will load much faster on subsequent runs of the program. Is it safe to do it like this? My worries are around directly reading into the data of the vector? I've removed error checking, hard coded 4 as the size of the int and so on so that i can give a short working example, I know it's bad code, my question really is if it is safe in c++ to read a whole array of structures directly into a vector like this? I believe it to be so, but c++ has so many traps and undefined behavour when you start going low level and dealing directly with raw memory like this. I realise that number formats and sizes may change across platforms and compilers but this will only even be read and written by the same compiler program to cache data that may be needed on a later run of the same program. #include <fstream> #include <vector> using namespace std; struct Vertex { float x, y, z; }; typedef vector<Vertex> VertexList; int main() { // Create a list for testing VertexList list; Vertex v1 = {1.0f, 2.0f, 3.0f}; list.push_back(v1); Vertex v2 = {2.0f, 100.0f, 3.0f}; list.push_back(v2); Vertex v3 = {3.0f, 200.0f, 3.0f}; list.push_back(v3); Vertex v4 = {4.0f, 300.0f, 3.0f}; list.push_back(v4); // Write out a list to a disk file ofstream os ("data.dat", ios::binary); int size1 = list.size(); os.write((const char*)&size1, 4); os.write((const char*)&list[0], size1 * sizeof(Vertex)); os.close(); // Read it back in VertexList list2; ifstream is("data.dat", ios::binary); int size2; is.read((char*)&size2, 4); list2.resize(size2); // Is it safe to read a whole array of structures directly into the vector? is.read((char*)&list2[0], size2 * sizeof(Vertex)); }

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  • What is fastest way to convert bool to byte?

    - by Amir Rezaei
    What is fastest way to convert bool to byte? I want this mapping: False=0, True=1 Note: I don't want to use any if statement. Update: I don't want to use conditional statement. I don't want the CPU to halt or guess next statement. I want to optimize this code: private static string ByteArrayToHex(byte[] barray) { char[] c = new char[barray.Length * 2]; byte k; for (int i = 0; i < barray.Length; ++i) { k = ((byte)(barray[i] >> 4)); c[i * 2] = (char)(k > 9 ? k + 0x37 : k + 0x30); k = ((byte)(barray[i] & 0xF)); c[i * 2 + 1] = (char)(k > 9 ? k + 0x37 : k + 0x30); } return new string(c); } Update: The length of the array is very large, it's in terabyte order! Therefore I need to do optimization if possible. I shouldn't need to explain my self. The question is still valid. Update: I'm working on a project and looking at others code. That's why I didn't provide with the function at first place. I didn't want to spend time on explaining for people when they have opinion about the code. I shouldn’y need to provide in my question the background of my work, and a function that is not written by me. I have started to optimize it part by part. If I needed help with the whole function I would asked that in another question. That is why I asked this very simple at the beginning. Unfortunately people couldn’t keep themselves to the question. So please if you want to help answer the question. Update: For dose who want to see the point of this question. This example shows how two if statement are reduced from the code. byte A = k > 9 ; //If it was possible (k>9) == 0 || 1 c[i * 2] = A * (k + 0x30) - (A - 1) * (k + 0x30);

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  • Ctor not allowed return type.

    - by atch
    Having code: struct B { int* a; B(int value):a(new int(value)) { } B():a(nullptr){} B(const B&); } B::B(const B& pattern) { } I'm getting err msg: 'Error 1 error C2533: 'B::{ctor}' : constructors not allowed a return type' Any idea why? P.S. I'm using VS 2010RC

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  • How to create a simple Proxy to access web servers in C

    - by jesusiniesta
    Hi. I’m trying to create an small Web Proxy in C. First, I’m trying to get a webpage, sending a GET frame to the server. I don’t know what I have missed, but I am not receiving any response. I would really appreciate if you can help me to find what is missing in this code. int main (int argc, char** argv) { int cache_size, //size of the cache in KiB port, port_google = 80, dir, mySocket, socket_google; char google[] = "www.google.es", ip[16]; struct sockaddr_in socketAddr; char buffer[10000000]; if (GetParameters(argc,argv,&cache_size,&port) != 0) return -1; GetIP (google, ip); printf("ip2 = %s\n",ip); dir = inet_addr (ip); printf("ip3 = %i\n",dir); /* Creation of a socket with Google */ socket_google = conectClient (port_google, dir, &socketAddr); if (socket_google < 0) return -1; else printf("Socket created\n"); sprintf(buffer,"GET /index.html HTTP/1.1\r\n\r\n"); if (write(socket_google, (void*)buffer, LONGITUD_MSJ+1) < 0 ) return 1; else printf("GET frame sent\n"); strcpy(buffer,"\n"); read(socket_google, buffer, sizeof(buffer)); // strcpy(message,buffer); printf("%s\n", buffer); return 0; } And this is the code I use to create the socket. I think this part is OK, but I copy it just in case. int conectClient (int puerto, int direccion, struct sockaddr_in *socketAddr) { int mySocket; char error[1000]; if ( (mySocket = socket(AF_INET, SOCK_STREAM, 0)) == -1) { printf("Error when creating the socket\n"); return -2; } socketAddr->sin_family = AF_INET; socketAddr->sin_addr.s_addr = direccion; socketAddr->sin_port = htons(puerto); if (connect (mySocket, (struct sockaddr *)socketAddr,sizeof (*socketAddr)) == -1) { snprintf(error, sizeof(error), "Error in %s:%d\n", __FILE__, __LINE__); perror(error); printf("%s\n",error); printf ("-- Error when stablishing a connection\n"); return -1; } return mySocket; } Thanks!

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  • Can't insert a number into a C++ custom streambuf/ostream

    - by 0xbe5077ed
    I have written a custom std::basic_streambuf and std::basic_ostream because I want an output stream that I can get a JNI string from in a manner similar to how you can call std::ostringstream::str(). These classes are quite simple. namespace myns { class jni_utf16_streambuf : public std::basic_streambuf<char16_t> { JNIEnv * d_env; std::vector<char16_t> d_buf; virtual int_type overflow(int_type); public: jni_utf16_streambuf(JNIEnv *); jstring jstr() const; }; typedef std::basic_ostream<char16_t, std::char_traits<char16_t>> utf16_ostream; class jni_utf16_ostream : public utf16_ostream { jni_utf16_streambuf d_buf; public: jni_utf16_ostream(JNIEnv *); jstring jstr() const; }; // ... } // namespace myns In addition, I have made four overloads of operator<<, all in the same namespace: namespace myns { // ... utf16_ostream& operator<<(utf16_ostream&, jstring) throw(std::bad_cast); utf16_ostream& operator<<(utf16_ostream&, const char *); utf16_ostream& operator<<(utf16_ostream&, const jni_utf16_string_region&); jni_utf16_ostream& operator<<(jni_utf16_ostream&, jstring); // ... } // namespace myns The implementation of jni_utf16_streambuf::overflow(int_type) is trivial. It just doubles the buffer width, puts the requested character, and sets the base, put, and end pointers correctly. It is tested and I am quite sure it works. The jni_utf16_ostream works fine inserting unicode characters. For example, this works fine and results in the stream containing "hello, world": myns::jni_utf16_ostream o(env); o << u"hello, wor" << u'l' << u'd'; My problem is as soon as I try to insert an integer value, the stream's bad bit gets set, for example: myns::jni_utf16_ostream o(env); if (o.badbit()) throw "bad bit before"; // does not throw int32_t x(5); o << x; if (o.badbit()) throw "bad bit after"; // throws :( I don't understand why this is happening! Is there some other method on std::basic_streambuf I need to be implementing????

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  • sendmessage mouseevent not working

    - by kevin
    I have this code: Private Const MOUSEEVENTF_LEFTDOWN = &H2 Private Const MOUSEEVENTF_LEFTUP = &H4 Dim WindowHandle As Long = FindWindow(vbNullString, "Ultima Online") SendMessage(WindowHandle, MOUSEEVENTF_LEFTDOWN, 0, 0) SendMessage(WindowHandle, MOUSEEVENTF_LEFTUP, 0, 0) I know it is getting the windowhandle fine, because I made a conditional statment that pops up a messagebox if windowhandle = 0 The problem is that it is not sending the mouse click to the window.

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  • iphone problem receiving UDP packets

    - by SooDesuNe
    I'm using sendto() and recvfrom() to send some simple packets via UDP over WiFI. I've tried using two phones, and a simulator, the results I'm getting are: Packets sent from phones - recieved by simulator Packets sent from simulator - simulator recvfrom remains blocking. Packets sent from phones - other phone recvfrom remains blocking. I'm not sure how to start debugging this one, since the simulator/mac is able to receive the the packets, but the phones don't appear to be getting the message. A slight aside, do I need to keep my packets below the MTU for my network? Or is fragmentation handled by the OS or some other lower level software? UPDATE: I forgot to include the packet size and structure. I'm transmitting: typedef struct PacketForTransmission { int32_t packetTypeIdentifier; char data[64]; // size to fit my biggest struct } PacketForTransmission; of which the char data[64] is: typedef struct PacketHeader{ uint32_t identifier; uint32_t datatype; } PacketHeader; typedef struct BasePacket{ PacketHeader header; int32_t cardValue; char sendingDeviceID[41]; //dont forget to save room for the NULL terminator! } BasePacket; typedef struct PositionPacket{ BasePacket basePacket; int32_t x; int32_t y; } PositionPacket; sending packet is like: PositionPacket packet; bzero(&packet, sizeof(packet)); //fill packet with it's associated data PacketForTransmission transmissionPacket; transmissionPacket.packetTypeIdentifier = kPositionPacketType; memcpy(&transmissionPacket.data, (void*)&packet, sizeof(packet)); //put the PositionPacket into data[64] size_t sendResult = sendto(_socket, &transmissionPacket, sizeof(transmissionPacket), 0, [address bytes], [address length]); NSLog(@"packet sent of size: %i", sendResult); and recieving packets is like: while(1){ char dataBuffer[8192]; struct sockaddr addr; socklen_t socklen = sizeof(addr); ssize_t len = recvfrom(_socket, dataBuffer, sizeof(dataBuffer), 0, &addr, &socklen); //continues blocking here NSLog(@"packet recieved of length: %i", len); //do some more stuff }

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  • Variable popen calls in C

    - by Bushman
    I'm trying to execute MS-DOS DEL commands inside a Win32 C program, and I already know that system and popen can be used for this. However, the problem is that both require string literals (type const char) for the commands, and I need something like the DOS equivalent of dir ~ | grep -P '/\d{7,8}\.exe$/' | rm, which obviously can't use string literals. Is there some other subprocess function in C that allows for char arrays as arguments for process names?

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