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  • fastest way to crawl recursive ntfs directories in C++

    - by Peter Parker
    I have written a small crawler to scan and resort directory structures. It based on dirent(which is a small wrapper around FindNextFileA) In my first benchmarks it is surprisingy slow: around 123473ms for 4500 files(thinkpad t60p local samsung 320 GB 2.5" HD). 121481 files found in 123473 milliseconds Is this speed normal? This is my code: int testPrintDir(std::string strDir, std::string strPattern="*", bool recurse=true){ struct dirent *ent; DIR *dir; dir = opendir (strDir.c_str()); int retVal = 0; if (dir != NULL) { while ((ent = readdir (dir)) != NULL) { if (strcmp(ent->d_name, ".") !=0 && strcmp(ent->d_name, "..") !=0){ std::string strFullName = strDir +"\\"+std::string(ent->d_name); std::string strType = "N/A"; bool isDir = (ent->data.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) !=0; strType = (isDir)?"DIR":"FILE"; if ((!isDir)){ //printf ("%s <%s>\n", strFullName.c_str(),strType.c_str());//ent->d_name); retVal++; } if (isDir && recurse){ retVal += testPrintDir(strFullName, strPattern, recurse); } } } closedir (dir); return retVal; } else { /* could not open directory */ perror ("DIR NOT FOUND!"); return -1; } }

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  • std::conditional compile-time branch evaluation

    - by cmannett85
    Compiling this: template < class T, class Y, class ...Args > struct isSame { static constexpr bool value = std::conditional< sizeof...( Args ), typename std::conditional< std::is_same< T, Y >::value, isSame< Y, Args... >, // Error! std::false_type >::type, std::is_same< T, Y > >::type::value; }; int main() { qDebug() << isSame< double, int >::value; return EXIT_SUCCESS; } Gives me this compiler error: error: wrong number of template arguments (1, should be 2 or more) The issue is that isSame< double, int > has an empty Args parameter pack, so isSame< Y, Args... > effectively becomes isSame< Y > which does not match the signature. But my question is: Why is that branch being evaluated at all? sizeof...( Args ) is false, so the inner std:conditional should not be evaluated. This isn't a runtime piece of code, the compiler knows that sizeof..( Args ) will never be true with the given template types. If you're curious, it's supposed to be a variadic version of std::is_same, not that it works...

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  • Compilation errors calling find_if using a functor

    - by Jim Wong
    We are having a bit of trouble using find_if to search a vector of pairs for an entry in which the first element of the pair matches a particular value. To make this work, we have defined a trivial functor whose operator() takes a pair as input and compares the first entry against a string. Unfortunately, when we actually add a call to find_if using an instance of our functor constructed using a temporary string value, the compiler produces a raft of error messages. Oddly (to me, anyway), if we replace the temporary with a string that we've created on the stack, things seem to work. Here's what the code (including both versions) looks like: typedef std::pair<std::string, std::string> MyPair; typedef std::vector<MyPair> MyVector; struct MyFunctor: std::unary_function <const MyPair&, bool> { explicit MyFunctor(const std::string& val) : m_val(val) {} bool operator() (const MyPair& p) { return p.first == m_val; } const std::string m_val; }; bool f(const char* s) { MyFunctor f(std::string(s)); // ERROR // std::string str(s); // MyFunctor f(str); // OK MyVector vec; MyVector::const_iterator i = std::find_if(vec.begin(), vec.end(), f); return i != vec.end(); } And here's what the most interesting error message looks like: /usr/include/c++/4.2.1/bits/stl_algo.h:260: error: conversion from ‘std::pair, std::allocator , std::basic_string, std::allocator ’ to non-scalar type ‘std::string’ requested Because we have a workaround, we're mostly curious as to why the first form causes problems. I'm sure we're missing something, but we haven't been able to figure out what it is.

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  • Vector insert() causes program to crash

    - by wrongusername
    This is the first part of a function I have that's causing my program to crash: vector<Student> sortGPA(vector<Student> student) { vector<Student> sorted; Student test = student[0]; cout << "here\n"; sorted.insert(student.begin(), student[0]); cout << "it failed.\n"; ... It crashes right at the sorted part because I can see "here" on the screen but not "it failed." The following error message comes up: Debug Assertion Failed! (a long path here...) Expression: vector emplace iterator outside range For more information on how your program can cause an assertion failure, see the Visual C++ documentation on asserts. I'm not sure what's causing the problem now, since I have a similar line of code elsewhere student.insert(student.begin() + position(temp, student), temp); that does not crash (where position returns an int and temp is another declaration of a struct Student). What can I do to resolve the problem, and how is the first insert different from the second one?

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  • How can I obtain the local TCP port and IP Address of my client program?

    - by Dr Dork
    Hello! I'm prepping for a simple work project and am trying to familiarize myself with the basics of socket programming in a Unix dev environment. At this point, I have some basic server side code and client side code setup to communicate. Currently, my client code successfully connects to the server code and the server code sends it a test message, then both quit out. Perfect! That's exactly what I wanted to accomplish. Now I'm playing around with the functions used to obtain info about the two environments (server and client). I'd like to obtain the local IP address and dynamically assigned TCP port of the client. The function I've found to do this is getsockname()... //setup the socket if ((sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1) { perror("client: socket"); continue; } //Retrieve the locally-bound name of the specified socket and store it in the sockaddr structure sa_len = sizeof(sa); getsock_check = getsockname(sockfd,(struct sockaddr *)&sa,(socklen_t *)&sa_len) ; if (getsock_check== -1) { perror("getsockname"); exit(1); } printf("Local IP address is: %s\n", inet_ntoa(sa.sin_addr)); printf("Local port is: %d\n", (int) ntohs(sa.sin_port)); but the output is always zero... Local IP address is: 0.0.0.0 Local port is: 0 does anyone see anything I might be or am definitely doing wrong? Thanks so much in advance for all your help!

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  • Inject runtime exception to pthread sometime fails. How to fix that?

    - by lionbest
    I try to inject the exception to thread using signals, but some times the exception is not get caught. For example the following code: void _sigthrow(int sig) { throw runtime_error(strsignal(sig)); } struct sigaction sigthrow = {{&_sigthrow}}; void* thread1(void*) { sigaction(SIGINT,&sigthrow,NULL); try { while(1) usleep(1); } catch(exception &e) { cerr << "Thread1 catched " << e.what() << endl; } }; void* thread2(void*) { sigaction(SIGINT,&sigthrow,NULL); try { while(1); } catch(exception &e) { cerr << "Thread2 catched " << e.what() << endl; //never goes here } }; If I try to execute like: int main() { pthread_t p1,p2; pthread_create( &p1, NULL, &thread1, NULL ); pthread_create( &p2, NULL, &thread2, NULL ); sleep(1); pthread_kill( p1, SIGINT); pthread_kill( p2, SIGINT); sleep(1); return EXIT_SUCCESS; } I get the following output: Thread1 catched Interrupt terminate called after throwing an instance of 'std::runtime_error' what(): Interrupt Aborted How can I make second threat catch exception? Is there better idea about injecting exceptions?

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  • Error_No_Token by adding printer driver (c#)

    - by user1686388
    I'm trying to add printer drivers using the windows API function AddPrinterDriver. The Win32 error 1008 (An attempt was made to reference a token that does not exist.) was always generated. My code is shown as following [DllImport("Winspool.drv")] static extern bool AddPrinterDriver(string Name, Int32 Level, [in] ref DRIVER_INFO_3 DriverInfo); [StructLayout(LayoutKind.Sequential)] public struct DRIVER_INFO_3 { public Int32 cVersion; public string Name; public string Environment; public string DriverPath; public string DataFile; public string ConfigFile; public string HelpFile; public string DependentFiles; public string MonitorName; public string DefaultDataType; } //....................... DRIVER_INFO_3 di = new DRIVER_INFO_3(); //...................... AddPrinterDriver(Environment.MachineName, 3, ref di); I have also tried to get a token by "ImpersonateSelf" before adding the printer driver. But the error 1008 insists. Does anyone have an idea? best regards.

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  • Move file or folder to a different folder in google document using api problem

    - by Minh Nguyen
    In Google Document i have a struct: Folder1 +------Folder1-1 +------+------File1-1-1 +------Folder1-2 +------File1-1 Folder2 I want to move "File1-1" to "Folder2" using .Net google api library(Google Data API SDK) public static void moveFolder(string szUserName, string szPassword, string szResouceID, string szToFolderResourceID) { string szSouceUrl = "https://docs.google.com/feeds/default/private/full" + "/" + HttpContext.Current.Server.UrlEncode(szResouceID); Uri sourceUri = new Uri(szSouceUrl); //create a atom entry AtomEntry atom = new AtomEntry(); atom.Id = new AtomId(szSouceUrl); string szTargetUrl = "http://docs.google.com/feeds/default/private/full/folder%3Aroot/contents/"; if (szToFolderResourceID != "") { szTargetUrl = "https://docs.google.com/feeds/default/private/full" + "/" + HttpContext.Current.Server.UrlEncode(szToFolderResourceID) + "/contents" ; } Uri targetUri = new Uri(szTargetUrl); DocumentsService service = new DocumentsService(SERVICENAME); ((GDataRequestFactory)service.RequestFactory).KeepAlive = false; service.setUserCredentials(szUserName, szPassword); service.EntrySend(targetUri, atom, GDataRequestType.Insert); } After run this function i have: Folder1 +------Folder1-1 +------+------File1-1-1 +------Folder1-2 +------File1-1 Folder2 +------File1-1 "File1-1" display in both "Folder1" and "Folder2", and when i delete it from a folder it will be deleted in another folder. (expect: "File1-1" display only in "Folder2") What happen? How can i solve this problem?

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  • is back_insert_iterator<> safe to be passed by value?

    - by afriza
    I have a code that looks something like: struct Data { int value; }; class A { public: typedef std::deque<boost::shared_ptr<Data> > TList; std::back_insert_iterator<TList> GetInserter() { return std::back_inserter(m_List); } private: TList m_List; }; class AA { boost::scoped_ptr<A> m_a; public: AA() : m_a(new A()) {} std::back_insert_iterator<A::TList> GetDataInserter() { return m_a->GetInserter(); } }; class B { template<class OutIt> CopyInterestingDataTo(OutIt outIt) { // loop and check conditions for interesting data // for every `it` in a Container<Data*> // create a copy and store it for( ... it = ..; .. ; ..) if (...) { *outIt = OutIt::container_type::value_type(new Data(**it)); outIt++; // dummy } } void func() { AA aa; CopyInterestingDataTo(aa.GetInserter()); // aa.m_a->m_List is empty! } }; The problem is that A::m_List is always empty even after CopyInterestingDataTo() is called. However, if I debug and step into CopyInterestingDataTo(), the iterator does store the supposedly inserted data!

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  • Optimizing a shared buffer in a producer/consumer multithreaded environment

    - by Etan
    I have some project where I have a single producer thread which writes events into a buffer, and an additional single consumer thread which takes events from the buffer. My goal is to optimize this thing for a single machine to achieve maximum throughput. Currently, I am using some simple lock-free ring buffer (lock-free is possible since I have only one consumer and one producer thread and therefore the pointers are only updated by a single thread). #define BUF_SIZE 32768 struct buf_t { volatile int writepos; volatile void * buffer[BUF_SIZE]; volatile int readpos;) }; void produce (buf_t *b, void * e) { int next = (b->writepos+1) % BUF_SIZE; while (b->readpos == next); // queue is full. wait b->buffer[b->writepos] = e; b->writepos = next; } void * consume (buf_t *b) { while (b->readpos == b->writepos); // nothing to consume. wait int next = (b->readpos+1) % BUF_SIZE; void * res = b->buffer[b->readpos]; b->readpos = next; return res; } buf_t *alloc () { buf_t *b = (buf_t *)malloc(sizeof(buf_t)); b->writepos = 0; b->readpos = 0; return b; } However, this implementation is not yet fast enough and should be optimized further. I've tried with different BUF_SIZE values and got some speed-up. Additionaly, I've moved writepos before the buffer and readpos after the buffer to ensure that both variables are on different cache lines which resulted also in some speed. What I need is a speedup of about 400 %. Do you have any ideas how I could achieve this using things like padding etc?

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  • mmap only needed pages of kernel buffer to user space

    - by axeoth
    See also this answer: http://stackoverflow.com/a/10770582/1284631 I need something similar, but without having to allocate a buffer: the buffer is large, in theory, but the user space program only needs to access some parts of it (it mocks some registers of a hardware). As I cannot allocate with vmalloc_user() such a large buffer (kernel 32 bit, in embedded environment, no swap...), I followed the same approach as in the quoted answer, trying to allocate only those pages that are really requested by the user space. So: I use a my_mmap() function for the device file (actually, is the .mmap field of a struct uio_info) to set up the fields of the vma, then, in the vm_area_struct's .fault field (also named my_fault()), I should return a page. except that: In the my_fault() method of vm_area_struct, I cannot obtain a page through: vmf->page=vmalloc_to_page(my_buf + (vmf->pgoff << PAGE_SHIFT)); since there is no allocated buffer: my_buf = vmalloc_user(MY_BUF_SIZE); fails with "allocation failed: out of vmalloc space - use vmalloc= to increase size." (and there is no room or swap to increase that vmalloc= parameter). So, I would need to get a page from the kernel and fill the vmf->page field. How to allocate a page (I assume that the offset of the page is known, as it is vm->pgoff). What base memory should I use instead of my_buf? PS: I also did set up the vma->flags |= VM_NORESERVE; (in the my_mmap()), but not sure if it helps. Is there any vmalloc_user_unreserved()-like function? (let's say, lazy allocation) Also, writing 1 to /proc/sys/vm/overcommit_memory and large values (eg 500) to /proc/sys/vm/overcommit_ratio before trying to my_buf=vmalloc_user(<large_size>) didn't work.

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  • How to create an array of buttons in C++

    - by mangoman13
    Hi, I'm using C++ in VS2005 and have an 8x8 grid of buttons on a form. I want to have these buttons in an array, so when I click on any of them it will open the same event handler (I think that is what they are called), but I will know the index of which one was clicked on. I know how to do this in VB and C#, but I can't seem to figure it out with C++ Right now I have all my buttons labelled by their location, i.e. b00, b10, b21, etc. So I think what I am looking for is a way to do something like this: Button b[8][8]; //this causes me errors (error C2728: 'System::Windows::Forms::Button' : a native array cannot contain this managed type) and (error C2227: left of '->{ctor}' must point to class/struct/union/generic type) void Assignment(){ b[0][0] = b00; b[1][0] = b10; ... } and then in form1.h: private: System::Void b_Click(System::Object^ sender, System::EventArgs^ e) { //somehow read the coordinates into variables x and y //do something based on these values } Any help would be appreciated. Also let me know if I am going in the complete wrong direction with this. Thanks!

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  • UDP sockets in ad hoc network (Ubuntu 9.10)

    - by Ekhiotz
    Hi! I am using BSD sockets in Ubuntu 9.10 to send UDP packets in broadcast with the following code: sock_fd = socket(PF_INET,SOCK_DGRAM,IPPROTO_UDP); //sock_fd=socket(AF_INET,SOCK_DGRAM,0); receiver_addr.sin_family = PF_INET; //does not send with broadcast in ad hoc receiver_addr.sin_addr.s_addr = htonl(INADDR_BROADCAST); inet_aton("169.254.255.255",&receiver_addr.sin_addr); receiver_addr.sin_port = htons(port); int broadcast = 1; // this call is what allows broadcast packets to be sent: if (setsockopt(sock_fd, SOL_SOCKET, SO_BROADCAST, &broadcast, sizeof broadcast) == -1) { perror("setsockopt (SO_BROADCAST)"); exit(1); } ret=sendto(sock_fd, packet, size, 0,(struct sockaddr*)&receiver_addr,sizeof(receiver_addr)); Note that is not all the code, it is only to have an idea. The program sends all the data with INADDR_BROADCAST if I am connected to an infrastructure wireless network. However, if my laptop is connected to an ad-hoc network, it is able to receive all the data, but not to send it. I have solved the problem using the 169.254.255.255 broadcast address, but I would like to know what is going on. Thank you in advance!

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  • Problem with close socket

    - by zp26
    Hi, I have a problem with my socket program. I create the client program (my code is below) I have a problem when i close the socket with the disconnect method. Can i help me? Thanks and sorry for my English XP CFSocketRef s; -(void)CreaConnessione { CFSocketError errore; struct sockaddr_in sin; CFDataRef address; CFRunLoopSourceRef source; CFSocketContext context = { 0, self, NULL, NULL, NULL }; s = CFSocketCreate( NULL, PF_INET, SOCK_STREAM, IPPROTO_TCP, kCFSocketDataCallBack, AcceptDataCallback, &context); memset(&sin, 0, sizeof(sin)); int port = [fieldPorta.text intValue]; NSString *tempIp = fieldIndirizzo.text; const char *ip = [tempIp UTF8String]; sin.sin_family = AF_INET; sin.sin_port = htons(port); sin.sin_addr.s_addr = (long)inet_addr(ip); address = CFDataCreate(NULL, (UInt8 *)&sin, sizeof(sin)); errore = CFSocketConnectToAddress(s, address, 0); if(errore == 0){ buttonInvioMess.enabled = TRUE; fieldMessaggioInvio.enabled = TRUE; labelTemp.text = [NSString stringWithFormat:@"Connesso al Server"]; CFRelease(address); source = CFSocketCreateRunLoopSource(NULL, s, 0); CFRunLoopAddSource(CFRunLoopGetCurrent(), source, kCFRunLoopDefaultMode); CFRelease(source); CFRunLoopRun(); } else{ labelTemp.text = [NSString stringWithFormat:@"Errore di connessione. Verificare Ip e Porta"]; switchConnection.on = FALSE; } } //the socket doesn't disconnect -(void)Disconnetti{ CFSocketInvalidate(s); CFRelease(s); } -(IBAction)Connetti { if(switchConnection.on) [self CreaConnessione]; else [self Disconnetti]; }

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  • linux raw socket programming question

    - by user194420
    Hi all, I am trying to create a raw socket which send and receive message with ip/tcp header under linux. I can successfully binds to a port and receive tcp message(ie:syn) However, the message seems to be handled by the os, but not mine. I am just a reader of it(like wireshark). My raw socket binds to port 8888, and then i try to telnet to that port . In wireshark, it shows that the port 8888 reply a "rst ack" when it receive the "syn" request. In my program, it shows that it receive a new message and it doesnot reply with any message. Any way to actually binds to that port?(prevent os handle it) Here is part of my code, i try to cut those error checking for easy reading sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_TCP); int tmp = 1; const int *val = &tmp; setsockopt (sockfd, IPPROTO_IP, IP_HDRINCL, val, sizeof (tmp)); servaddr.sin_family = AF_INET; servaddr.sin_addr.s_addr = htonl(INADDR_ANY); servaddr.sin_port = htons(8888); bind(sockfd, (struct sockaddr*)&servaddr, sizeof(servaddr)); //call recv in loop

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  • How to implement a simple queue properly?

    - by Stephen Hsu
    The current Go library doesn't provide the queue container. To implement a simple queue, I use circle array as the underlying data structure. It follows algorithms mentioned in TAOCP: Insert Y into queue X: X[R]<-Y; R<-(R+1)%M; if R=F then OVERFLOW. Delete Y from queue X: if F=R then UNDERFLOW; Y<-X[F]; F<-(F+1) % M. F: Front, R: Rear, M: Array length. Following is the code: package main import ( "fmt" ) type Queue struct { len int head, tail int q []int } func New(n int) *Queue { return &Queue{n, 0, 0, make([]int, n)} } func (p *Queue) Enqueue(x int) bool { p.q[p.tail] = x p.tail = (p.tail + 1) % p.len return p.head != p.tail } func (p *Queue) Dequeue() (int, bool) { if p.head == p.tail { return 0, false } x := p.q[p.head] p.head = (p.head + 1) % p.len return x, true } func main() { q := New(10) for i := 1; i < 13; i++ { fmt.Println(i, q.Enqueue(i)) } fmt.Println() for i := 1; i < 13; i++ { fmt.Println(q.Dequeue()) } } But the output is obviously wrong: 1 true 2 true 3 true 4 true 5 true 6 true 7 true 8 true 9 true 10 false 11 true 12 true 11 true 12 true 0 false 0 false 0 false 0 false 0 false 0 false 0 false 0 false 0 false 0 false I think I need one more field to make the code work properly. What do you suggest?

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  • help needed on libcurl programming in sending HTTP HEAD Request.

    - by Mani
    Hi all, I need clarifications on using libcurl for the following: I need to send an http HEAD request shown as below :: HEAD /mshare/3/30002:12:primary/stream_xNKNVH.mpeg HTTP/1.1 Host: 192.168.70.1:8080 Accept: */* User-Agent: Kreatel_IP-STB getcontentFeatures.dlna.org: 1 The code I wrote (shown below) , sends the HEAD Request in slightly different way: curl_global_init(CURL_GLOBAL_ALL); CURL* ctx = NULL; const char *url = "http://192.168.70.1:8080/mshare/3/30002:12:primary/stream_xNKNVH.mpeg" ; char *returnString; struct curl_slist *headers = NULL; ctx = curl_easy_init(); headers = curl_slist_append(headers,"Accept: */*"); headers = curl_slist_append(headers,"User-Agent: Kreatel_IP-STB");\ headers = curl_slist_append(headers,"getcontentFeatures.dlna.org: 1"); headers = curl_slist_append(headers,"Pragma:"); headers = curl_slist_append(headers,"Proxy-Connection:"); curl_easy_setopt(ctx,CURLOPT_HTTPHEADER , headers ); curl_easy_setopt(ctx,CURLOPT_NOBODY ,1 ); curl_easy_setopt(ctx,CURLOPT_VERBOSE, 1); curl_easy_setopt(ctx,CURLOPT_URL,url ); curl_easy_setopt(ctx,CURLOPT_NOPROGRESS ,1 ); curl_easy_perform(ctx); curl_easy_cleanup(ctx); curl_global_cleanup(); The code shown above sends the HEAD Request in slightly different form (shown below) HEAD http://192.168.70.1:8080/mshare/3/30002:12:primary/stream_xNKNVH.mpeg HTTP/1.1 Host: 192.168.70.1:8080 Proxy-Connection: Keep-Alive Accept: */* User-Agent: Kreatel_IP-STB getcontentFeatures.dlna.org: 1 Can any one , share the appropriate code ?

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  • Get an array of structures from native dll to c# application

    - by PaulH
    I have a C# .NET 2.0 CF project where I need to invoke a method in a native C++ DLL. This native method returns an array of type TableEntry. At the time the native method is called, I do not know how large the array will be. How can I get the table from the native DLL to the C# project? Below is effectively what I have now. // in C# .NET 2.0 CF project [StructLayout(LayoutKind.Sequential)] public struct TableEntry { [MarshalAs(UnmanagedType.LPWStr)] public string description; public int item; public int another_item; public IntPtr some_data; } [DllImport("MyDll.dll", CallingConvention = CallingConvention.Winapi, CharSet = CharSet.Auto)] public static extern bool GetTable(ref TableEntry[] table); SomeFunction() { TableEntry[] table = null; bool success = GetTable( ref table ); // at this point, the table is empty } // In Native C++ DLL std::vector< TABLE_ENTRY > global_dll_table; extern "C" __declspec(dllexport) bool GetTable( TABLE_ENTRY* table ) { table = &global_dll_table.front(); return true; } Thanks, PaulH

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  • Type errors when using same name

    - by lykimq
    I have 3 files: 1) cpf0.ml type string = char list type url = string type var = string type name = string type symbol = | Symbol_name of name 2) problem.ml: type symbol = | Ident of string 3) test.ml open Problem;; open Cpf0;; let symbol b = function | Symbol_name n -> Ident n When I combine test.ml: ocamlc -c test.ml. I received an error: This expression has type Cpf0.name = char list but an expression was expected of type string Could you please help me to correct it? Thank you very much EDIT: Thank you for your answer. I want to explain more about these 3 files: Because I am working with extraction in Coq to Ocaml type: cpf0.ml is generated from cpf.v : Require Import String. Definition string := string. Definition name := string. Inductive symbol := | Symbol_name : name -> symbol. The code extraction.v: Set Extraction Optimize. Extraction Language Ocaml. Require ExtrOcamlBasic ExtrOcamlString. Extraction Blacklist cpf list. where ExtrOcamlString I opened: open Cpf0;; in problem.ml, and I got a new problem because in problem.ml they have another definition for type string This expression has type Cpf0.string = char list but an expression was expected of type Util.StrSet.elt = string Here is a definition in util.ml defined type string: module Str = struct type t = string end;; module StrOrd = Ord.Make (Str);; module StrSet = Set.Make (StrOrd);; module StrMap = Map.Make (StrOrd);; let set_add_chk x s = if StrSet.mem x s then failwith (x ^ " already declared") else StrSet.add x s;; I was trying to change t = string to t = char list, but if I do that I have to change a lot of function it depend on (for example: set_add_chk above). Could you please give me a good idea? how I would do in this case.

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  • How to send Event signal through Processes - C

    - by Jamie Keeling
    Hello all! I have an application consisting of two windows, one communicates to the other and sends it a struct constaining two integers (In this case two rolls of a dice). I will be using events for the following circumstances: Process a sends data to process b, process b displays data Process a closes, in turn closing process b Process b closes a, in turn closing process a I have noticed that if the second process is constantly waiting for the first process to send data then the program will be just sat waiting, which is where the idea of implementing threads on each process occurred and I have started to implement this already. The problem i'm having is that I don't exactly have a lot of experience with threads and events so I'm not sure of the best way to actually implement what I want to do. I'm trying to work out how the other process will know of the event being fired so it can do the tasks it needs to do, I don't understand how one process that is separate from another can tell what the states the events are in especially as it needs to act as soon as the event has changed state. Thanks for any help Edit: I can only use the Create/Set/Open methods for events, sorry for not mentioning it earlier.

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  • Modifying C# dictionary value

    - by minjang
    I'm a C++ expert, but not at all for C#. I created a Dictionary<string, STATS>, where STATS is a simple struct. Once I built the dictionary with initial string and STATS pairs, I want to modify the dictionary's STATS value. In C++, it's very clear: Dictionary<string, STATS*> benchmarks; Initialize it... STATS* stats = benchmarks[item.Key]; // Touch stats directly However, I tried like this in C#: Dictionary<string, STATS> benchmarks = new Dictionary<string, STATS>(); // Initialize benchmarks with a bunch of STATS foreach (var item in _data) benchmarks.Add(item.app_name, item); foreach (KeyValuePair<string, STATS> item in benchmarks) { // I want to modify STATS value inside of benchmarks dictionary. STATS stat_item = benchmarks[item.Key]; ParseOutputFile("foo", ref stat_item); // But, not modified in benchmarks... stat_item is just a copy. } This is a really novice problem, but wasn't easy to find an answer. EDIT: I also tried like the following: STATS stat_item = benchmarks[item.Key]; ParseOutputFile(file_name, ref stat_item); benchmarks[item.Key] = stat_item; However, I got the exception since such action invalidates Dictionary: Unhandled Exception: System.InvalidOperationException: Collection was modified; enumeration operation may not execute. at System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource) at System.Collections.Generic.Dictionary`2.Enumerator.MoveNext() at helper.Program.Main(String[] args) in D:\dev\\helper\Program.cs:line 75

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  • C socket programming: client send() but server select() doesn't see it

    - by Fantastic Fourier
    Hey all, I have a server and a client running on two different machines where the client send()s but the server doesn't seem to receive the message. The server employs select() to monitor sockets for any incoming connections/messages. I can see that when the server accepts a new connection, it updates the fd_set array but always returns 0 despite the client send() messages. The connection is TCP and the machines are separated by like one router so dropping packets are highly unlikely. I have a feeling that it's not select() but perhaps send()/sendto() from client that may be the problem but I'm not sure how to go about localizing the problem area. while(1) { readset = info->read_set; ready = select(info->max_fd+1, &readset, NULL, NULL, &timeout); } above is the server side code where the server has a thread that runs select() indefinitely. rv = connect(sockfd, (struct sockaddr *) &server_address, sizeof(server_address)); printf("rv = %i\n", rv); if (rv < 0) { printf("MAIN: ERROR connect() %i: %s\n", errno, strerror(errno)); exit(1); } else printf("connected\n"); sleep(3); char * somemsg = "is this working yet?\0"; rv = send(sockfd, somemsg, sizeof(somemsg), NULL); if (rv < 0) printf("MAIN: ERROR send() %i: %s\n", errno, strerror(errno)); printf("MAIN: rv is %i\n", rv); rv = sendto(sockfd, somemsg, sizeof(somemsg), NULL, &server_address, sizeof(server_address)); if (rv < 0) printf("MAIN: ERROR sendto() %i: %s\n", errno, strerror(errno)); printf("MAIN: rv is %i\n", rv); and this is the client side where it connects and sends messages and returns connected MAIN: rv is 4 MAIN: rv is 4 any comments or insightful insights are appreciated.

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  • How to specialize template for type derived from particular type

    - by relaxxx
    I have class World which manages creation of object... After creation it calls afterCreation method and I the created object is user-defined type derived from Entity (eg. MyEntity), I want to call addEntity. I the object was something else, I want to do nothing. addEntity must be called with appropriate T, because it generates unique IDs for every derived class etc. Here is my solution: template <int v> struct ToType { enum { value = v }; }; template <typename T> void World::afterCreation(T * t) { afterCreation(t, ToType<std::is_base_of<Entity, T>::value>()); } template <typename T> void World::afterCreation(T * t, ToType<true>) { addEntity(t); //here I cant pass Entity *, I need the real type, eg. MyEntity } template <typename T> void World::afterCreation(T * t, ToType<false>) { } My question is - Can in be done better way? How can I simulate following code without ToType or similar? template <typename T> void afterCreation(){/*generic impl*/} template <typename T where T is derived from Entity> void afterCreation(){/*some specific stuff*/} "specialize" in the title is only to describe my intention, no need to solve problem with template specialization

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  • Indices instead of pointers in STL containers?

    - by zvrba
    Due to specific requirements [*], I need a singly-linked list implementation that uses integer indices instead of pointers to link nodes. The indices are always interpreted with respect to a vector containing the list nodes. I thought I might achieve this by defining my own allocator, but looking into the gcc's implementation of , they explicitly use pointers for the link fields in the list nodes (i.e., they do not use the pointer type provided by the allocator): struct _List_node_base { _List_node_base* _M_next; ///< Self-explanatory _List_node_base* _M_prev; ///< Self-explanatory ... } (For this purpose, the allocator interface is also deficient in that it does not define a dereference function; "dereferencing" an integer index always needs a pointer to the underlying storage.) Do you know a library of STL-like data structures (i am mostly in need of singly- and doubly-linked list) that use indices (wrt. a base vector) instead of pointers to link nodes? [*] Saving space: the lists will contain many 32-bit integers. With two pointers per node (STL list is doubly-linked), the overhead is 200%, or 400% on 64-bit platform, not counting the overhead of the default allocator.

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  • safe placement new & explicit destructor call

    - by uray
    this is an example of my codes: ` template <typename T> struct MyStruct { T object; } template <typename T> class MyClass { MyStruct<T>* structPool; size_t structCount; MyClass(size_t count) { this->structCount = count; this->structPool = new MyStruct<T>[count]; for( size_t i=0 ; i<count ; i++ ) { //placement new to call constructor new (&this->structPool[i].object) T(); } } ~MyClass() { for( size_t i=0 ; i<this->structCount ; i++ ) { //explicit destructor call this->structPool[i].object.~T(); } delete[] this->structPool; } } ` my question is, is this a safe way to do? do I make some hidden mistake at some condition? will it work for every type of object (POD and non-POD) ?

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