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  • if non zero elements in same column count only once

    - by George
    I want to check the elements above the main diagonal and if I found non zero values , count one. If the non zero values are found in the same column ,then count just one ,not the number of the non zero values. For example , it should be count = 2 and not 3 in this example because 12 and 6 are in the same column. A= 1 11 12 4 5 6 0 7 0 #include <stdio.h> #include <stdlib.h> #include <math.h> int main( int argc, const char* argv[] ){ int Rows = 3 , Cols = 3; float *A = (float *) malloc ( Rows * Cols * sizeof (float) ); A[0] = 1.0; A[1] = 11.0; A[2] = 12.0; A[3] = 4.0; A[4] = 5.0; A[5] = 6.0; A[6] = 0.0; A[7] = 7.0; A[8] = 0.0; // print input matrix printf("\n Input matrix \n\n"); for ( int i = 0; i < Rows; i++ ) for ( int j = 0; j < Cols; j++ ) { printf("%f\t",A[ i * Cols + j ]); if( j == Cols-1 ) printf("\n"); } printf("\n"); int count = 0; for ( int j = 0 ; j < Cols; j++ ) { for ( int i = ( Rows - 1 ); i >= 0; i-- ) { // check the diagonal elements above the main diagonal if ( j > i ) { if ( ( A[ i * Cols + j ] != 0 ) ) { printf("\n Above nonzero Elmts = %f\n",( A[i * Cols + j] ) ); count++; } } } } printf("\ncount = %d\n",count ); return 0; }

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  • Best way to have common class shared by both C++ and Ruby?

    - by shuttle87
    I am currently working on a project where a team of us are designing a game, all of us are proficient in ruby and some (but not all) of us are proficient in c++. Initially we made the backend in ruby but we ported it to c++ for more speed. The c++ port of the backend has exactly the same features and algorithms as the original ruby code. However we still have a bunch of code in ruby that does useful things but we want it to now get the data from the c++ classes. Our first thought was that we could save some of the data structures in something like XML or redis and call that, but some of the developers don't like that idea. We don't need anything particularly complex data structures to be passed between the different parts of the code, just tuples, strings and ints. Is there any way of integrating the ruby code so that it can call the c++ stuff natively? Will we need to embed code? Will we have to make a ruby extension? If so are there any good resources/tutorials you could suggest? For example say we have this code in the c++ backend: class The_game{ private: bool printinfo; //print the player diagnostic info at the beginning if true int numplayers; std::vector<Player*> players; string current_action; int action_is_on; // the index of the player in the players array that the action is now on //more code here public: Table(std::vector<Player *> in_players, std::vector<Statistics *> player_stats ,const int in_numplayers); ~Table(); void play_game(); History actions_history; }; class History{ private: int action_sequence_number; std::vector<Action*> hand_actions; public: void print_history(); void add_action(Action* the_action_to_be_added); int get_action_sequence_number(){ return action_sequence_number;} bool history_actions_are_equal(); int last_action_size(int street,int number_of_actions_ago); History(); ~History(); }; Is there any way to natively call something in the actions_history via The_game object in ruby? (The objects in the original ruby code all had the same names and functionality) By this I mean: class MyRubyClass def method1(arg1) puts arg1 self.f() # ... but still available puts cpp_method.the_current_game.actions_history.get_action_sequence_number() end # Constructor: def initialize(arg) puts "In constructor with arg #{arg}" #get the c++ object here and call it cpp_method end end Is this possible? Any advice or suggestions are appreciated.

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  • Learning C, would appreciate input on why this solution works.

    - by Keifer
    This is literally the first thing I've ever written in C, so please feel free to point out all it's flaws. :) My issue, however is this: if I write the program the way I feel is cleanest, I get a broken program: #include <sys/queue.h> #include <stdlib.h> #include <stdio.h> #include <string.h> /* Removed prototypes and non related code for brevity */ int main() { char *cmd = NULL; unsigned int acct = 0; int amount = 0; int done = 0; while (done==0) { scanf ("%s %u %i", cmd, &acct, &amount); if (strcmp (cmd, "exit") == 0) done = 1; else if ((strcmp (cmd, "dep") == 0) || (strcmp (cmd, "deb") == 0)) debit (acct, amount); else if ((strcmp (cmd, "wd") == 0) || (strcmp (cmd, "cred") == 0)) credit (acct, amount); else if (strcmp (cmd, "fee") == 0) service_fee(acct, amount); else printf("Invalid input!\n"); } return(0); } void credit(unsigned int acct, int amount) { } void debit(unsigned int acct, int amount) { } void service_fee(unsigned int acct, int amount) { } As it stands, the above generates no errors at compile, but gives me a segfault when ran. I can fix this by changing the program to pass cmd by reference when calling scanf and strcmp. The segfault goes away and is replaced by warnings for each use of strcmp at compile time. Despite the warnings, the affected code works. warning: passing arg 1 of 'strcmp' from incompatible pointer type As an added bonus, modifying the scanf and strcmp calls allows the program to progress far enough to execute return(0), at which point the thing crashes with an Abort trap. If I swap out return(0) for exit(0) then everything works as expected. This leaves me with two questions: why was the original program wrong? How can I fix it better than I have? The bit about needing to use exit instead of return has me especially baffled.

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  • Why does SendMailMAPI rename file attachments to shorter ones?

    - by Tom
    I use the following emailing function with Eudora. For some reason the attachment file name is renamed to be something else. How can I make sure the attachment file name remains intact? function SendMailMAPI(const Subject, Body, FileName, SenderName, SenderEMail, RecepientName, RecepientEMail: String) : Integer; var message: TMapiMessage; lpSender, lpRecepient: TMapiRecipDesc; FileAttach: TMapiFileDesc; SM: TFNMapiSendMail; MAPIModule: HModule; begin FillChar(message, SizeOf(message), 0); with message do begin if (Subject<>'') then begin lpszSubject := PChar(Subject) end; if (Body<>'') then begin lpszNoteText := PChar(Body) end; if (SenderEMail<>'') then begin lpSender.ulRecipClass := MAPI_ORIG; if (SenderName='') then begin lpSender.lpszName := PChar(SenderEMail) end else begin lpSender.lpszName := PChar(SenderName) end; lpSender.lpszAddress := PChar('SMTP:'+SenderEMail); lpSender.ulReserved := 0; lpSender.ulEIDSize := 0; lpSender.lpEntryID := nil; lpOriginator := @lpSender; end; if (RecepientEMail<>'') then begin lpRecepient.ulRecipClass := MAPI_TO; if (RecepientName='') then begin lpRecepient.lpszName := PChar(RecepientEMail) end else begin lpRecepient.lpszName := PChar(RecepientName) end; lpRecepient.lpszAddress := PChar('SMTP:'+RecepientEMail); lpRecepient.ulReserved := 0; lpRecepient.ulEIDSize := 0; lpRecepient.lpEntryID := nil; nRecipCount := 1; lpRecips := @lpRecepient; end else begin lpRecips := nil end; if (FileName='') then begin nFileCount := 0; lpFiles := nil; end else begin FillChar(FileAttach, SizeOf(FileAttach), 0); FileAttach.nPosition := Cardinal($FFFFFFFF); FileAttach.lpszPathName := PChar(FileName); nFileCount := 1; lpFiles := @FileAttach; end; end; MAPIModule := LoadLibrary(PChar(MAPIDLL)); if MAPIModule=0 then begin Result := -1 end else begin try @SM := GetProcAddress(MAPIModule, 'MAPISendMail'); if @SM<>nil then begin Result := SM(0, Application.Handle, message, MAPI_DIALOG or MAPI_LOGON_UI, 0); end else begin Result := 1 end; finally FreeLibrary(MAPIModule); end; end; if Result<>0 then begin MessageDlg('Error sending mail ('+IntToStr(Result)+').', mtError, [mbOk], 0) end;

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  • Inlining an array of non-default constructible objects in a C++ class

    - by porgarmingduod
    C++ doesn't allow a class containing an array of items that are not default constructible: class Gordian { public: int member; Gordian(int must_have_variable) : member(must_have_variable) {} }; class Knot { Gordian* pointer_array[8]; // Sure, this works. Gordian inlined_array[8]; // Won't compile. Can't be initialized. }; As even beginner C++ users know, the language guarantees that all members are initialized when constructing a class. And it doesn't trust the user to initialize everything in the constructor - one has to provide valid arguments to the constructors of all members before the body of the constructor even starts. Generally, that's a great idea as far as I'm concerned, but I've come across a situation where it would be a lot easier if I could actually have an array of non-default constructible objects. The obvious solution: Have an array of pointers to the objects. This is not optimal in my case, as I am using shared memory. It would force me to do extra allocation from an already contended resource (that is, the shared memory). The entire reason I want to have the array inlined in the object is to reduce the number of allocations. This is a situation where I would be willing to use a hack, even an ugly one, provided it works. One possible hack I am thinking about would be: class Knot { public: struct dummy { char padding[sizeof(Gordian)]; }; dummy inlined_array[8]; Gordian* get(int index) { return reinterpret_cast<Gordian*>(&inlined_array[index]); } Knot() { for (int x = 0; x != 8; x++) { new (get(x)) Gordian(x*x); } } }; Sure, it compiles, but I'm not exactly an experienced C++ programmer. That is, I couldn't possibly trust my hacks less. So, the questions: 1) Does the hack I came up with seem workable? What are the issues? (I'm mainly concerned with C++0x on newer versions of GCC). 2) Is there a better way to inline an array of non-default constructible objects in a class?

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  • sqlite eatingup memory on iPhone when doing insert

    - by kviksilver
    I am having problem with inserting data to sqlite database. char *update="INSERT OR REPLACE INTO ct_subject (id,id_parent, title, description, link, address, phone, pos_lat, pos_long, no_votes, avg_vote, photo, id_comerc, id_city, placement, type, timestamp, mail) VALUES (?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?,?);"; sqlite3_stmt *stmt; if(sqlite3_prepare_v2(database, update, -1, &stmt, nil) == SQLITE_OK){ sqlite3_bind_int(stmt, 1, [[[newCategories objectAtIndex:i] valueForKey:@"id"] intValue]); sqlite3_bind_int(stmt, 2, [[[newCategories objectAtIndex:i] valueForKey:@"id_parent"] intValue]); sqlite3_bind_text(stmt, 3, [[[newCategories objectAtIndex:i] valueForKey:@"title"] UTF8String], -1, NULL); sqlite3_bind_text(stmt, 4, [[[newCategories objectAtIndex:i] valueForKey:@"description"] UTF8String], -1, NULL); sqlite3_bind_text(stmt, 5, [[[newCategories objectAtIndex:i] valueForKey:@"link"] UTF8String], -1, NULL); sqlite3_bind_text(stmt, 6, [[[newCategories objectAtIndex:i] valueForKey:@"address"] UTF8String], -1, NULL); sqlite3_bind_text(stmt, 7, [[[newCategories objectAtIndex:i] valueForKey:@"phone"] UTF8String], -1, NULL); sqlite3_bind_text(stmt, 8, [[[newCategories objectAtIndex:i] valueForKey:@"pos_lat"] UTF8String], -1, NULL); sqlite3_bind_text(stmt, 9, [[[newCategories objectAtIndex:i] valueForKey:@"pos_long"] UTF8String], -1, NULL); sqlite3_bind_int(stmt, 10, [[[newCategories objectAtIndex:i] valueForKey:@"no_votes"] intValue]); sqlite3_bind_text(stmt, 11, [[[newCategories objectAtIndex:i] valueForKey:@"avg_vote"] UTF8String], -1, NULL); if ([[[newCategories objectAtIndex:i] valueForKey:@"photo"] length]!=0) { NSMutableString *webUrl = (NSMutableString *)[[NSMutableString alloc] initWithString:@"http://www.crotune.com/public/images/subjects/"]; [webUrl appendString:[[newCategories objectAtIndex:i] valueForKey:@"photo"]]; UIImage *myImage = [self getWebImage:webUrl]; if(myImage != nil){ sqlite3_bind_blob(stmt, 12, [UIImagePNGRepresentation(myImage) bytes], [UIImagePNGRepresentation(myImage) length], NULL); } else { sqlite3_bind_blob(stmt, 12, nil, -1, NULL); } [webUrl release]; [myImage release]; } else { sqlite3_bind_blob(stmt, 12, nil, -1, NULL); //NSLog(@" ne dodajem sliku2"); } sqlite3_bind_int(stmt, 13, [[[newCategories objectAtIndex:i] valueForKey:@"id_comerc"] intValue]); sqlite3_bind_int(stmt, 14, [[[newCategories objectAtIndex:i] valueForKey:@"id_city"] intValue]); sqlite3_bind_int(stmt, 15, [[[newCategories objectAtIndex:i] valueForKey:@"placement"] intValue]); sqlite3_bind_int(stmt, 16, [[[newCategories objectAtIndex:i] valueForKey:@"type"] intValue]); sqlite3_bind_int(stmt, 17, [[[newCategories objectAtIndex:i] valueForKey:@"timestamp"] intValue]); sqlite3_bind_text(stmt, 18, [[[newCategories objectAtIndex:i] valueForKey:@"mail"] UTF8String], -1, NULL); } if (sqlite3_step(stmt) != SQLITE_DONE) { NSLog(@"%s", sqlite3_errmsg(database)); NSAssert1(0,@"nemogu updateat table %s", errorMsg); } else { NSLog(@"Ubacio %d",i); }sqlite3_finalize(stmt); What happens is that it starts to eat memory until it finaly quits... On memory warning i close and open database again, I have set cache size to 50 as mentioned in some posts here, and tried putting query into statement - same result.. it just garbles mamory and app quits after 300 inserts on iphone or somewhere around 900 inserts on iPad... Any help would be appreciated..

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  • Problem intialising 2D array

    - by TeeJay
    Ok, so I have a 2D Array that is initialised with values from a file (format: x y z). My file reads in the values correctly but when adding the z value to the matrix/2DArray, I run into a segfault and I have no idea why. It is possibly incorrect use of pointers? I still don't quite have the hang of them yet. This is my intialiser, works fine, even intialises all "z" values to 0. int** make2DArray(int rows, int columns) { int** newArray; newArray = (int**)malloc(rows*sizeof(int*)); if (newArray == NULL) { printf("out of memory for newArray.\n"); } for (int i = 0; i < rows; i++) { newArray[i] = (int*)malloc(columns*sizeof(int)); if (newArray[i] == NULL) { printf("out of memory for newArray[%d].\n", i); } } //intialise all values to 0 for (int i = 0; i < rows; i++) { for (int j = 0; j < columns; j++) { newArray[i][j] = 0; } } return newArray; } This is how I call the initialiser (and problem function). int** map = make2DArray(rows, columns); fillMatrix(&map, mapFile); And this is the problem code. void fillMatrix(int*** inMatrix, FILE* inFile) { int x, y, z; char line[100]; while(fgets(line, sizeof(line), inFile) != NULL) { sscanf(line, "%d %d %d", &x, &y, &z); *inMatrix[x][y] = z; } } From what I can gather through the use of ddd, the problem comes when y gets to 47. The map file has a max "x" value of 47 and a max "y" value of 63, I'm pretty sure I haven't got the order mixed up, so I don't know why the program is segfault-ing? I'm sure it's some newbie mistake...

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  • Objective C "do - while" question

    - by Rob
    The example for one of the exercises in the book I am reading shows the following code: #import <Foundation/Foundation.h> int main (int argc, const char * argv[]) { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; int input, reverse, numberOfDigits; reverse = 0; numberOfDigits = 0; NSLog (@"Please input a multi-digit number:"); scanf ("%i", &input); if ( input < 0 ) { input = -input; NSLog (@"Minus"); } do { reverse = reverse * 10 + input % 10; numberOfDigits++; } while (input /= 10); do { switch ( reverse % 10 ) { case 0: NSLog (@"Zero"); break; case 1: NSLog (@"One"); break; case 2: NSLog (@"Two"); break; case 3: NSLog (@"Three"); break; case 4: NSLog (@"Four"); break; case 5: NSLog (@"Five"); break; case 6: NSLog (@"Six"); break; case 7: NSLog (@"Seven"); break; case 8: NSLog (@"Eight"); break; case 9: NSLog (@"Nine"); break; } numberOfDigits--; } while (reverse /= 10); while (numberOfDigits--) { NSLog (@"Zero"); } [pool drain]; return 0; } My question is this, the while statement shows (input /= 10) which, if I understand this correctly basically means (input = input / 10). Now, if that is true, why doesn't the loop just run continuously? I mean, even if you were to divide 0 by 10 then that would still extract a number. If the user was to input "50607", it would first cut off the "7", then the "0", and so on and so on, but why does it exit the loop after removing the "5". Wouldn't the response after the "5" be the same as the "0" between the 5 and the 6 to the program?

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  • Getting level values from PCM raw data using Core Audio

    - by John
    I am trying to extract level data from a PCM audio file using core audio. I have gotten as far as (I believe) getting the raw data into a byte array (UInt8) but it is 16 bit PCM data and I am having trouble reading the data out. The input is from the iPhone microphone, which I have set as: [recordSetting setValue:[NSNumber numberWithInt:kAudioFormatLinearPCM] forKey:AVFormatIDKey]; [recordSetting setValue:[NSNumber numberWithFloat:44100.0] forKey:AVSampleRateKey]; [recordSetting setValue:[NSNumber numberWithInt:1] forKey:AVNumberOfChannelsKey]; [recordSetting setValue:[NSNumber numberWithInt:16] forKey:AVLinearPCMBitDepthKey]; [recordSetting setValue:[NSNumber numberWithBool:NO] forKey:AVLinearPCMIsBigEndianKey]; [recordSetting setValue:[NSNumber numberWithBool:NO] forKey:AVLinearPCMIsFloatKey]; which is obviously 16 bits. I am then trying to just print out a few values to see if they look reasonable for debug purposes below, and they do not look reasonable (many 0's). ExtAudioFileRef inputFile = NULL; ExtAudioFileOpenURL(track.location, &inputFile); AudioStreamBasicDescription inputFileFormat; UInt32 dataSize = (UInt32)sizeof(inputFileFormat); ExtAudioFileGetProperty(inputFile, kExtAudioFileProperty_FileDataFormat, &dataSize, &inputFileFormat); UInt8 *buffer = malloc(BUFFER_SIZE); AudioBufferList bufferList; bufferList.mNumberBuffers = 1; bufferList.mBuffers[0].mNumberChannels = 1; bufferList.mBuffers[0].mData = buffer; //pointer to buffer of audio data bufferList.mBuffers[0].mDataByteSize = BUFFER_SIZE; //number of bytes in the buffer while(true) { UInt32 frameCount = (bufferList.mBuffers[0].mDataByteSize / inputFileFormat.mBytesPerFrame); // Read a chunk of input OSStatus status = ExtAudioFileRead(inputFile, &frameCount, &bufferList); // If no frames were returned, conversion is finished if(0 == frameCount) break; NSLog(@"---"); int16_t *bufferl = &buffer; for(int i=0;i<100;i++){ //const int16_t *bufferl = bufferl[i]; NSLog(@"%d",bufferl[i]); } } Not sure what I am doing wrong, I think it has to do with reading the byte array. Sorry for the long code post...

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  • Long numbers. Division.

    - by user577395
    Hello, world! I have a problem. Today I tried to create a code, which finds Catalan number. But in my program can be long numbers. I found numerator and denominator. But i can't div long numbers! Also, only standard libraries was must use in this program. Help me please. This is my code #include <vector> #include <iostream> using namespace std; int main(int argc, char *argv[]) { const int base = 1000*1000*1000; vector <int> a, b; int n, carry = 0; cin>>n; a.push_back(n); for (int ii=n+2; ii!=(2*n)+1;++ii) { carry = 0; for (size_t i=0; i<a.size() || carry; ++i) { if (i == a.size()) a.push_back (0); long long cur = carry + a[i] * 1ll * ii; a[i] = int (cur % base); carry = int (cur / base); } } while (a.size() > 1 && a.back() == 0) a.pop_back(); b.push_back(n); for (int ii=1; ii!=n+1;++ii) { carry = 0; for (size_t i=0; i<b.size() || carry; ++i) { if (i == b.size()) b.push_back (0); long long cur = carry + b[i] * 1ll * ii; b[i] = int (cur % base); carry = int (cur / base); } } while (b.size() > 1 && b.back() == 0) b.pop_back(); cout<<(a.empty() ? 0 : a.back()); for (int i=(int)a.size()-2; i>=0; --i) cout<<(a[i]); cout<<" "; cout<<(b.empty() ? 0 : b.back()); for (int i=(int)b.size()-2; i>=0; --i) cout<<(b[i]); //system("PAUSE"); cout<<endl; return 0; } P.S. Sorry for my bad english =)

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  • Converting OpenGL coordinates to lower UIView (and UIImagePickerController)

    - by John Qualis
    I am new to OpenGL on the iPhone. I am developing an iPhone app similar to a barcode reader but with an extra OpenGL layer. The bottommost layer is UIImagePickerController, then I use UIView on top and draw a rectangle at certain coordinates on the iPhone screen. So far everything is OK. Then I am trying to draw an OpenGL 3-D model in that rectangle. I am able to load a 3-D model in the iPhone based on this code here - http://iphonedevelopment.blogspot.com/2008/12/start-of-wavefront-obj-file-loader.html I am not able to transform the coordinates of the rectangle into OpenGL coordinates. Appreciate any help. Do I need to use a matrix to translate the currentPosition of the 3-D model so it is drawn within myRect? The code is given below. -(void)setupView:(GLView*)view { const GLfloat zNear = 0.01, zFar = 1000.0, fieldOfView = 45.0; GLfloat size; glEnable(GL_DEPTH_TEST); glMatrixMode(GL_PROJECTION); size = zNear * tanf(DEGREES_TO_RADIANS(fieldOfView) / 2.0); CGRect rect = view.bounds; glFrustumf(-size, size, -size / (rect.size.width / rect.size.height), size / (rect.size.width / rect.size.height), zNear, zFar); glViewport(0, 0, rect.size.width, rect.size.height); glMatrixMode(GL_MODELVIEW); glLoadIdentity(); glClearColor(0.0f, 0.0f, 0.0f, 0.0f); NSString *path = [[NSBundle mainBundle] pathForResource:@"plane" ofType:@"obj"]; OpenGLWaveFrontObject *theObject = [[OpenGLWaveFrontObject alloc] initWithPath:path]; Vertex3D position; position.z = -8.0; position.y = 3.0; position.x = 2.0; theObject.currentPosition = position; self.plane = theObject; [theObject release]; } - (void)drawView:(GLView*)view; { static GLfloat rotation = 0.0; glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glLoadIdentity(); glColor4f(0.0, 0.5, 1.0, 1.0); // the coordinates of the rectangle are // myRect.x, myRect.y, myRect.width, myRect.height // Do I need to use a matrix to translate the currentPosition of the // 3-D model so it is drawn within myRect? //glOrthof(-160.0f, 160.0f, -240.0f, 240.0f, -1.0f, 1.0f); [plane drawSelf]; }

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  • [C#] How to do a search from a list with non-prefix keywords

    - by aNui
    First of all, sorry if my english or my post got any mistakes. I am programming a program to search the name from the list and I need to find them if the keyword is not in front of the names (that's what I mean non-prefix) e.g. if I my list is the music instruments and I type "guit" to the search textbox. It should find the names "Guitar, Guitarrón, Acoustic Guitar, Bass Guitar, ..." or something like this Longdo Dictionary's search suggestion. here is my simple and stupid algorithm (that's all I can do) const int SEARCHROWLIMIT = 30; private string[] DoSearch(string Input, string[] ListToSearch) { List<string> FoundNames = new List<string>(); int max = 0; bool over = false; for (int k = 0; !over; k++) { foreach (string item in ListToSearch) { max = (max > item.Length) ? max : item.Length; if (k > item.Length) continue; if (k >= max) { over = true; break; } if (!Input.Equals("Search") && item.Substring(k, item.Length - k).StartsWith(Input, StringComparison.OrdinalIgnoreCase)) { bool exist = false; int i = 0; while (!exist && i < FoundNames.Count) { if (item.Equals(FoundNames[i])) { exist = true; break; } i++; } if (!exist && FoundNames.Count < SEARCHROWLIMIT) FoundNames.Add(item); else if (FoundNames.Count >= SEARCHROWLIMIT) over = true; } } } return FoundNames.ToArray(); } I think this algorithm is too slow for a large number of names and after several trial-and-error, I decided to add SEARCHROWLIMIT to breaks the operation And I also think there're some readymade methods that can do that. And another problem is I need to search music instruments by a category like strings, percussions, ... and by the country of origins. So I need to search them with filter by type and country. please help me. P.S. Me and my friends are just student from Thailand and developing the project to compete in Microsoft Imagine Cup 2010 and please become fan on our facebook page [KRATIB][3]. And we're so sorry we don't have much information in English but you can talk to us in English.

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  • glReadPixels() returning non-accurate value

    - by max
    I'm trying to implement the flood fill algorithm. But glReadPixels() is returning float RGB values of a pixel which are slightly different from the actual value set by me, causing the algorithm to fail. Why is this happening? Outputting returned RGB values to check. #include<iostream> #include<GL/glut.h> using namespace std; float boundaryColor[3]={0,0,0}, interiorColor[3]={0,0,0.5}, fillColor[3]={1,0,0}; float readPixel[3]; void init(void) { glClearColor(0,0,0.5,0); glMatrixMode(GL_PROJECTION); gluOrtho2D(0,500,0,500); } void setPixel(int x,int y) { glColor3fv(fillColor); glBegin(GL_POINTS); glVertex2f(x,y); glEnd(); } void getPixel(int x, int y, float *color) { glReadPixels(x,y,1,1,GL_RGB,GL_FLOAT,color); } void floodFill(int x,int y) { getPixel(x,y,readPixel); //outputting values here to check cout<<readPixel[0]<<endl; cout<<readPixel[1]<<endl; cout<<readPixel[2]<<endl; if( readPixel[0]==interiorColor[0] && readPixel[1]==interiorColor[1] && readPixel[2]==interiorColor[2] ) { setPixel(x,y); floodFill(x+1,y); floodFill(x,y+1); floodFill(x-1,y); floodFill(x,y-1); } } void display() { glClear(GL_COLOR_BUFFER_BIT); glColor3fv(boundaryColor); glLineWidth(3); glBegin(GL_LINE_STRIP); glVertex2i(150,150); glVertex2i(150,350); glVertex2i(350,350); glVertex2i(350,150); glVertex2i(150,150); glEnd(); floodFill(200,200); glFlush(); } int main(int argc,char** argv) { glutInit(&argc,argv); glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB); glutInitWindowPosition(100,100); glutInitWindowSize(500,500); glutCreateWindow("Flood fill"); init(); glutDisplayFunc(display); glutMainLoop(); }

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  • C++ Regarding cin.ignore()

    - by user1578897
    i would hope someone can modify my code as its so buggy. sometime its work, sometime it dont.. so let me explain more.. Text file data is as below Line3D, [70, -120, -3], [-29, 1, 268] Line3D, [25, -69, -33], [-2, -41, 58] To read the above line.. i use the following char buffer[30]; cout << "Please enter filename: "; cin.ignore(); getline(cin,filename); readFile.open(filename.c_str()); //if successfully open if(readFile.is_open()) { //record counter set to 0 numberOfRecords = 0; while(readFile.good()) { //input stream get line by line readFile.getline(buffer,20,','); if(strstr(buffer,"Point3D")) { Point3D point3d_tmp; readFile>>point3d_tmp; // and so on... Then i did a overload on the ifstream for Line3d ifstream& operator>>(ifstream &input,Line3D &line3d) { int x1,y1,z1,x2,y2,z2; //get x1 input.ignore(2); input>>x1; //get y1 input.ignore(); input>>y1; //get z1 input.ignore(); input>>z1; //get x2 input.ignore(4); input>>x2; //get y2 input.ignore(); input>>y2; //get z2 input.ignore(); input>>z2; input.ignore(2); Point3D pt1(x1,y1,z1); Point3D pt2(x2,y2,z2); line3d.setPt1(pt1); line3d.setPt2(pt2); line3d.setLength(); } But the issue is the record work sometime and sometime it dont.. what i mean is if at this point //i add a cout cout << x1 << y1 << z1; cout << x2 << y2 << z2; //its works! Point3D pt1(x1,y1,z1); Point3D pt2(x2,y2,z2); line3d.setPt1(pt1); line3d.setPt2(pt2); line3d.setLength(); but if i take away the cout it dont work. how do i change my cin.ignore() so the data can be handle properly , consider number range is -999 to 999

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  • stringindexoutofbounds with currency converter java program

    - by user1795926
    I am have trouble with a summary not showing up. I am supposed to modify a previous Java assignment by by adding an array of objects. Within the loop, instantiate each individual object. Make sure the user cannot keep adding another Foreign conversion beyond your array size. After the user selects quit from the menu, prompt if the user want to display a summary report. If they select ‘Y’ then, using your array of objects, display the following report: Item Conversion Dollars Amount 1 Japanese Yen 100.00 32,000.00 2 Mexican Peso 400.00 56,000.00 3 Canadian Dollar 100.00 156.00 etc. Number of Conversions = 3 There are no errors when I compile..but when I run the program it is fine until I hit 0 to end the conversion and have it ask if i want to see a summary. This error displays: Exception in thread "main" java.lang.StringIndexOutOfBoundsException: String index out of range: 0 at java.lang.String.charAt(String.java:658) at Lab8.main(Lab8.java:43) my code: import java.util.Scanner; import java.text.DecimalFormat; public class Lab8 { public static void main(String[] args) { final int Max = 10; String a; char summary; int c = 0; Foreign[] Exchange = new Foreign[Max]; Scanner Keyboard = new Scanner(System.in); Foreign.opening(); do { Exchange[c] = new Foreign(); Exchange[c].getchoice(); Exchange[c].dollars(); Exchange[c].amount(); Exchange[c].vertical(); System.out.println("\n" + Exchange[c]); c++; System.out.println("\n" + "Please select 1 through 4, or 0 to quit" + >"\n"); c= Keyboard.nextInt(); } while (c != 0); System.out.print("\nWould you like a summary of your conversions? (Y/N): "); a = Keyboard.nextLine(); summary = a.charAt(0); summary = Character.toUpperCase(summary); if (summary == 'Y') { System.out.println("\nCountry\t\tRate\t\tDollars\t\tAmount"); System.out.println("========\t\t=======\t\t=======\t\t========="); for (int i=0; i < Exchange.length; i++) System.out.println(Exchange[i]); Foreign.counter(); } } } I looked at line 43 and its this line: summary = a.charAt(0); But I am not sure what's wrong with it, can anyone point it out? Thank you.

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  • Why can't I reserve 1,000,000,000 in my vector ?

    - by vipersnake005
    When I type in the foll. code, I get the output as 1073741823. #include <iostream> #include <vector> using namespace std; int main() { vector <int> v; cout<<v.max_size(); return 0; } However when I try to resize the vector to 1,000,000,000, by v.resize(1000000000); the program stops executing. How can I enable the program to allocate the required memory, when it seems that it should be able to? I am using MinGW in Windows 7. I have 2 GB RAM. Should it not be possible? In case it is not possible, can't I declare it as an array of integers and get away? BUt even that doesn't work. Another thing is that, suppose I would use a file(which can easily handle so much data ). How can I let it read and write and the same time. Using fstream file("file.txt', ios::out | ios::in ); doesn't create a file, in the first place. But supposing the file exists, I am unable to use to do reading and writing simultaneously. WHat I mean is this : Let the contents of the file be 111111 Then if I run : - #include <fstream> #include <iostream> using namespace std; int main() { fstream file("file.txt",ios:in|ios::out); char x; while( file>>x) { file<<'0'; } return 0; } Shouldn't the file's contents now be 101010 ? Read one character and then overwrite the next one with 0 ? Or incase the entire contents were read at once into some buffer, should there not be atleast one 0 in the file ? 1111110 ? But the contents remain unaltered. Please explain. Thank you.

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  • Can I Have Polymorphic Containers With Value Semantics in C++11?

    - by John Dibling
    This is a sequel to a related post which asked the eternal question: Can I have polymorphic containers with value semantics in C++? The question was asked slightly incorrectly. It should have been more like: Can I have STL containers of a base type stored by-value in which the elements exhibit polymorphic behavior? If you are asking the question in terms of C++, the answer is "no." At some point, you will slice objects stored by-value. Now I ask the question again, but strictly in terms of C++11. With the changes to the language and the standard libraries, is it now possible to store polymorphic objects by value in an STL container? I'm well aware of the possibility of storing a smart pointer to the base class in the container -- this is not what I'm looking for, as I'm trying to construct objects on the stack without using new. Consider if you will (from the linked post) as basic C++ example: #include <iostream> using namespace std; class Parent { public: Parent() : parent_mem(1) {} virtual void write() { cout << "Parent: " << parent_mem << endl; } int parent_mem; }; class Child : public Parent { public: Child() : child_mem(2) { parent_mem = 2; } void write() { cout << "Child: " << parent_mem << ", " << child_mem << endl; } int child_mem; }; int main(int, char**) { // I can have a polymorphic container with pointer semantics vector<Parent*> pointerVec; pointerVec.push_back(new Parent()); pointerVec.push_back(new Child()); pointerVec[0]->write(); pointerVec[1]->write(); // Output: // // Parent: 1 // Child: 2, 2 // But I can't do it with value semantics vector<Parent> valueVec; valueVec.push_back(Parent()); valueVec.push_back(Child()); // gets turned into a Parent object :( valueVec[0].write(); valueVec[1].write(); // Output: // // Parent: 1 // Parent: 2 }

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  • Applescript: cleaning a string

    - by Mike
    I have this string that has illegal chars that I want to remove but I don't know what kind of chars may be present. I built a list of chars that I want not to be filtered and I built this script (from another one I found on the web). on clean_string(TheString) --Store the current TIDs. To be polite to other scripts. set previousDelimiter to AppleScript's text item delimiters set potentialName to TheString set legalName to {} set legalCharacters to {"a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v", "w", "x", "y", "z", "A", "B", "C", "D", "E", "F", "G", "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y", "Z", "1", "2", "3", "4", "5", "6", "7", "8", "9", "0", "?", "+", "-", "Ç", "ç", "á", "Á", "é", "É", "í", "Í", "ó", "Ó", "ú", "Ú", "â", "Â", "ã", "Ã", "ñ", "Ñ", "õ", "Õ", "à", "À", "è", "È", "ü", "Ü", "ö", "Ö", "!", "$", "%", "/", "(", ")", "&", "€", "#", "@", "=", "*", "+", "-", ",", ".", "–", "_", " ", ":", ";", ASCII character 10, ASCII character 13} --Whatever you want to eliminate. --Now iterate through the characters checking them. repeat with thisCharacter in the characters of potentialName set thisCharacter to thisCharacter as text if thisCharacter is in legalCharacters then set the end of legalName to thisCharacter log (legalName as string) end if end repeat --Make sure that you set the TIDs before making the --list of characters into a string. set AppleScript's text item delimiters to "" --Check the name's length. if length of legalName is greater than 32 then set legalName to items 1 thru 32 of legalName as text else set legalName to legalName as text end if --Restore the current TIDs. To be polite to other scripts. set AppleScript's text item delimiters to previousDelimiter return legalName end clean_string The problem is that this script is slow as hell and gives me timeout. What I am doing is checking character by character and comparing against the legalCharacters list. If the character is there, it is fine. If not, ignore. Is there a fast way to do that? something like "look at every char of TheString and remove those that are not on legalCharacters" ? thanks for any help.

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  • c permutation of a number

    - by Pkp
    I am writing a program for magic box. As the only way around it is brute force, I wrote a program to compute permutations of a given array using bells algorithm. I wrote in the lines similar to http://programminggeeks.com/c-code-for-permutation/. It does work for array of 3 and 4. It does not work for an arryay of 8 numbers (1,2,3,4,5,6,7,8). I see that the combination 1 2 3 4 5 6 7 8 gets repeated couple of times. Also there are other combinations that gets repeated. I see that certain combinations don't get displayed even. So could someone tell me what is wrong in the program below. Code: include<stdio.h> int len,numperm=1,count=0; display(int a[]){ int i; for(i=0;i<len;i++) printf("%d ",a[i]); printf("\n"); count++; } swap(int *a,int *b){ int temp; temp=*a; *a=*b; *b=temp; } no_of_perm(){ int x; for(x=1;x<=len;x++) numperm=numperm*x; } perm(int a[]){ int x,y; while(count < numperm){ for(x=0;x<len-1;x++){ swap(&a[x],&a[x+1]); display(a); } swap(&a[0],&a[1]); display(a); for(y=len-1;y>0;y--){ swap(&a[y],&a[y-1]); display(a); } swap(&a[len-1],&a[len-2]); display(a); } } main(int argc, char *argv[]){ if(argc<2){ printf("Error\n"); exit(0); } int i,*a=malloc(sizeof(int)*atoi(argv[1])); len=atoi(argv[1]); for(i=0;i<len;i++) a[i]=i+1; no_of_perm(); perm(a); }

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  • Weird seg fault problem

    - by bluedaemon
    Greetings, I'm having a weird seg fault problem. My application dumps a core file at runtime. After digging into it I found it died in this block: #include <lib1/c.h> ... x::c obj; obj.func1(); I defined class c in a library lib1: namespace x { struct c { c(); ~c(); void fun1(); vector<char *> _data; }; } x::c::c() { } x::c::~c() { for ( int i = 0; i < _data.size(); ++i ) delete _data[i]; } I could not figure it out for some time till I ran nm on the lib1.so file: there are more function definitions than I defined: x::c::c() x::c::c() x::c::~c() x::c::~c() x::c::func1() x::c::func2() After searching in code base I found someone else defined a class with same name in same namespace, but in another library lib2 as follows: namespace x { struct c { c(); ~c(); void func2(); vector<string> strs_; }; } x::c::c() { } x::c::~c() { } My application links to lib2, which has dependency on lib1. This interesting behavior brings several questions: Why would it even work? I would expect a "multiple definitions" error while linking against lib2 (which depends upon lib1) but never had such. The application seems to be doing what's defined in func1 except it dumps a core at runtime. After attaching debugger, I found my application calls the ctor of class c in lib2, then calls func1 (defined in lib1). When going out of scope it calls dtor of class c in lib2, where the seg fault occurs. Can anybody teach me how this could even occur? How can I prevent such problems from happening again? Is there any C++ syntax I can use? Forgot to mention I'm using g++ 4.1 on RHEL4, thank you very much!

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  • why my test performance class gives me inconsistent results even after proper warm-up?

    - by colinfang
    i made a class which helps me measure time for any methods in Ticks. Basically, it runs testing method 100x, and force GC, then it records time taken for another 100x method runs. x64 release ctrl+f5 VS2012/VS2010 the results are following: 2,914 2,909 2,913 2,909 2,908 2,907 2,909 2,998 2,976 2,855 2,446 2,415 2,435 2,401 2,402 2,402 2,399 2,401 2,401 2,400 2,399 2,400 2,404 2,402 2,401 2,399 2,400 2,402 2,404 2,403 2,401 2,403 2,401 2,400 2,399 2,414 2,405 2,401 2,407 2,399 2,401 2,402 2,401 2,404 2,401 2,404 2,405 2,368 1,577 1,579 1,626 1,578 1,576 1,578 1,577 1,577 1,576 1,578 1,576 1,578 1,577 1,578 1,576 1,578 1,577 1,579 1,585 1,576 1,579 1,577 1,579 1,578 1,579 1,577 1,578 1,577 1,578 1,576 1,578 1,577 1,578 1,599 1,579 1,578 1,582 1,576 1,578 1,576 1,579 1,577 1,578 1,577 1,591 1,577 1,578 1,578 1,576 1,578 1,576 1,578 As you can see there are 3 phases, first is ~2,900, second is ~2,400, then ~1,550 What might be the reason to cause it? the test performance class code follows: public static void RunTests(Func<long> myTest) { const int numTrials = 100; Stopwatch sw = new Stopwatch(); double[] sample = new double[numTrials]; Console.WriteLine("Checksum is {0:N0}", myTest()); sw.Start(); myTest(); sw.Stop(); Console.WriteLine("Estimated time per test is {0:N0} ticks\n", sw.ElapsedTicks); for (int i = 0; i < numTrials; i++) { myTest(); } GC.Collect(); string testName = myTest.Method.Name; Console.WriteLine("----> Starting benchmark {0}\n", myTest.Method.Name); for (int i = 0; i < numTrials; i++) { sw.Restart(); myTest(); sw.Stop(); sample[i] = sw.ElapsedTicks; } double testResult = DataSetAnalysis.Report(sample); for (int j = 0; j < numTrials; j = j + 5) Console.WriteLine("{0,8:N0} {1,8:N0} {2,8:N0} {3,8:N0} {4,8:N0}", sample[j], sample[j + 1], sample[j + 2], sample[j + 3], sample[j + 4]); Console.WriteLine("\n----> End of benchmark"); }

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  • making a queue program

    - by seventhief
    Hi can someone help me making a queue program. i want to set the array[0] to be array[1] just in display but in real i am adding value at array[0]. i got how to run the add function to it. but i can't do the view and delete command that will view from ex. array[0] to array[4], when displayed array[1] to array[5] with the value inserted. #include <stdio.h> #include <stdlib.h> #define p printf #define s scanf int rear = 0; int front = 0; int *q_array = NULL; int size = 0; main() { int num, opt; char cont[] = { 'y' }; clrscr(); p("Queue Program\n\n"); p("Queue size: "); s("%d", &size); p("\n"); if(size > 0) { q_array = malloc(size * sizeof(int)); if(q_array == NULL) { p("ERROR: malloc() failed\n"); exit(2); } } else { p("ERROR: size should be positive integer\n"); exit(1); } while((cont[0] == 'y') || (cont[0] == 'Y')) { clrscr(); p("Queue Program"); p("\n\nQueue size: %d\n\n", size); p("MAIN MENU\n1. Add\n2. Delete\n3. View"); p("\n\nYour choice: "); s("%d", &opt); p("\n"); switch(opt) { case 1: if(rear==size) { p("You can't add more data"); } else { p("Enter data for Queue[%d]: ", rear+1); s("%d", &num); add(num); } break; case 2: delt(); break; case 3: view(); break; } p("\n\nDo you want to continue? (Y\/N)"); s("%s", &cont[0]); } } add(int a) { q_array[rear]=a; rear++; } delt() { if(front==rear) { p("Queue Empty"); } else { p("Queue[%d] = %d removed.", front, q_array[front]); front++; } } view() { int i; for(i=front;i<=rear;i++) p("\nQueue[%d] = %d", i, q_array[i]); }

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  • Type casting int into double C++

    - by user1705380
    I am new to programming and this might be an obvious question, though i cannot for life of me figure out why my program is not returning as a double. I am suppose to write a stocks program that takes in shares of stock, whole dollar portion of price and the fraction portion. And the fraction portion is to be inputted as two int values, and include a function definition with 3 int values.The function returns the price as a double. #include <iostream> using namespace std; int price(int, int, int); int main() { int dollars, numerator, denominator, price1, shares; char ans; do { cout<<"Enter the stock price and the number of shares.\n"; cout<<"Enter the price and integers: Dollars, numerator, denominator\n"; cin>>dollars>>numerator>>denominator; cout<<"Enter the number of shares held\n"; cin>>shares; cout<<shares; price1 = price(dollars,numerator,denominator); cout<<" shares of stock with market price of "; cout<< dollars << " " << numerator<<'/'<<denominator<<endl; cout<<"have a value of " << shares * price1<<endl; cout<<"Enter either Y/y to continue"; cin>>ans; }while (ans == 'Y' || ans == 'y'); system("pause"); return 0; } int price(int dollars, int numerator, int denominator) { return dollars + numerator/static_cast<double>(denominator); }

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  • Securing an ASP.NET MVC 2 Application

    - by rajbk
    This post attempts to look at some of the methods that can be used to secure an ASP.NET MVC 2 Application called Northwind Traders Human Resources.  The sample code for the project is attached at the bottom of this post. We are going to use a slightly modified Northwind database. The screen capture from SQL server management studio shows the change. I added a new column called Salary, inserted some random salaries for the employees and then turned off AllowNulls.   The reporting relationship for Northwind Employees is shown below.   The requirements for our application are as follows: Employees can see their LastName, FirstName, Title, Address and Salary Employees are allowed to edit only their Address information Employees can see the LastName, FirstName, Title, Address and Salary of their immediate reports Employees cannot see records of non immediate reports.  Employees are allowed to edit only the Salary and Title information of their immediate reports. Employees are not allowed to edit the Address of an immediate report Employees should be authenticated into the system. Employees by default get the “Employee” role. If a user has direct reports, they will also get assigned a “Manager” role. We use a very basic empId/pwd scheme of EmployeeID (1-9) and password test$1. You should never do this in an actual application. The application should protect from Cross Site Request Forgery (CSRF). For example, Michael could trick Steven, who is already logged on to the HR website, to load a page which contains a malicious request. where without Steven’s knowledge, a form on the site posts information back to the Northwind HR website using Steven’s credentials. Michael could use this technique to give himself a raise :-) UI Notes The layout of our app looks like so: When Nancy (EmpID 1) signs on, she sees the default page with her details and is allowed to edit her address. If Nancy attempts to view the record of employee Andrew who has an employeeID of 2 (Employees/Edit/2), she will get a “Not Authorized” error page. When Andrew (EmpID 2) signs on, he can edit the address field of his record and change the title and salary of employees that directly report to him. Implementation Notes All controllers inherit from a BaseController. The BaseController currently only has error handling code. When a user signs on, we check to see if they are in a Manager role. We then create a FormsAuthenticationTicket, encrypt it (including the roles that the employee belongs to) and add it to a cookie. private void SetAuthenticationCookie(int employeeID, List<string> roles) { HttpCookiesSection cookieSection = (HttpCookiesSection) ConfigurationManager.GetSection("system.web/httpCookies"); AuthenticationSection authenticationSection = (AuthenticationSection) ConfigurationManager.GetSection("system.web/authentication"); FormsAuthenticationTicket authTicket = new FormsAuthenticationTicket( 1, employeeID.ToString(), DateTime.Now, DateTime.Now.AddMinutes(authenticationSection.Forms.Timeout.TotalMinutes), false, string.Join("|", roles.ToArray())); String encryptedTicket = FormsAuthentication.Encrypt(authTicket); HttpCookie authCookie = new HttpCookie(FormsAuthentication.FormsCookieName, encryptedTicket); if (cookieSection.RequireSSL || authenticationSection.Forms.RequireSSL) { authCookie.Secure = true; } HttpContext.Current.Response.Cookies.Add(authCookie); } We read this cookie back in Global.asax and set the Context.User to be a new GenericPrincipal with the roles we assigned earlier. protected void Application_AuthenticateRequest(Object sender, EventArgs e){ if (Context.User != null) { string cookieName = FormsAuthentication.FormsCookieName; HttpCookie authCookie = Context.Request.Cookies[cookieName]; if (authCookie == null) return; FormsAuthenticationTicket authTicket = FormsAuthentication.Decrypt(authCookie.Value); string[] roles = authTicket.UserData.Split(new char[] { '|' }); FormsIdentity fi = (FormsIdentity)(Context.User.Identity); Context.User = new System.Security.Principal.GenericPrincipal(fi, roles); }} We ensure that a user has permissions to view a record by creating a custom attribute AuthorizeToViewID that inherits from ActionFilterAttribute. public class AuthorizeToViewIDAttribute : ActionFilterAttribute{ IEmployeeRepository employeeRepository = new EmployeeRepository(); public override void OnActionExecuting(ActionExecutingContext filterContext) { if (filterContext.ActionParameters.ContainsKey("id") && filterContext.ActionParameters["id"] != null) { if (employeeRepository.IsAuthorizedToView((int)filterContext.ActionParameters["id"])) { return; } } throw new UnauthorizedAccessException("The record does not exist or you do not have permission to access it"); }} We add the AuthorizeToView attribute to any Action method that requires authorization. [HttpPost][Authorize(Order = 1)]//To prevent CSRF[ValidateAntiForgeryToken(Salt = Globals.EditSalt, Order = 2)]//See AuthorizeToViewIDAttribute class[AuthorizeToViewID(Order = 3)] [ActionName("Edit")]public ActionResult Update(int id){ var employeeToEdit = employeeRepository.GetEmployee(id); if (employeeToEdit != null) { //Employees can edit only their address //A manager can edit the title and salary of their subordinate string[] whiteList = (employeeToEdit.IsSubordinate) ? new string[] { "Title", "Salary" } : new string[] { "Address" }; if (TryUpdateModel(employeeToEdit, whiteList)) { employeeRepository.Save(employeeToEdit); return RedirectToAction("Details", new { id = id }); } else { ModelState.AddModelError("", "Please correct the following errors."); } } return View(employeeToEdit);} The Authorize attribute is added to ensure that only authorized users can execute that Action. We use the TryUpdateModel with a white list to ensure that (a) an employee is able to edit only their Address and (b) that a manager is able to edit only the Title and Salary of a subordinate. This works in conjunction with the AuthorizeToViewIDAttribute. The ValidateAntiForgeryToken attribute is added (with a salt) to avoid CSRF. The Order on the attributes specify the order in which the attributes are executed. The Edit View uses the AntiForgeryToken helper to render the hidden token: ......<% using (Html.BeginForm()) {%><%=Html.AntiForgeryToken(NorthwindHR.Models.Globals.EditSalt)%><%= Html.ValidationSummary(true, "Please correct the errors and try again.") %><div class="editor-label"> <%= Html.LabelFor(model => model.LastName) %></div><div class="editor-field">...... The application uses View specific models for ease of model binding. public class EmployeeViewModel{ public int EmployeeID; [Required] [DisplayName("Last Name")] public string LastName { get; set; } [Required] [DisplayName("First Name")] public string FirstName { get; set; } [Required] [DisplayName("Title")] public string Title { get; set; } [Required] [DisplayName("Address")] public string Address { get; set; } [Required] [DisplayName("Salary")] [Range(500, double.MaxValue)] public decimal Salary { get; set; } public bool IsSubordinate { get; set; }} To help with displaying readonly/editable fields, we use a helper method. //Simple extension method to display a TextboxFor or DisplayFor based on the isEditable variablepublic static MvcHtmlString TextBoxOrLabelFor<TModel, TProperty>(this HtmlHelper<TModel> htmlHelper, Expression<Func<TModel, TProperty>> expression, bool isEditable){ if (isEditable) { return htmlHelper.TextBoxFor(expression); } else { return htmlHelper.DisplayFor(expression); }} The helper method is used in the view like so: <%=Html.TextBoxOrLabelFor(model => model.Title, Model.IsSubordinate)%> As mentioned in this post, there is a much easier way to update properties on an object. Download Demo Project VS 2008, ASP.NET MVC 2 RTM Remember to change the connectionString to point to your Northwind DB NorthwindHR.zip Feedback and bugs are always welcome :-)

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  • Fragmented Log files could be slowing down your database

    - by Fatherjack
    Something that is sometimes forgotten by a lot of DBAs is the fact that database log files get fragmented in the same way that you get fragmentation in a data file. The cause is very different but the effect is the same – too much effort reading and writing data. Data files get fragmented as data is changed through normal system activity, INSERTs, UPDATEs and DELETEs cause fragmentation and most experienced DBAs are monitoring their indexes for fragmentation and dealing with it accordingly. However, you don’t hear about so many working on their log files. How can a log file get fragmented? I’m glad you asked. When you create a database there are at least two files created on the disk storage; an mdf for the data and an ldf for the log file (you can also have ndf files for extra data storage but that’s off topic for now). It is wholly possible to have more than one log file but in most cases there is little point in creating more than one as the log file is written to in a ‘wrap-around’ method (more on that later). When a log file is created at the time that a database is created the file is actually sub divided into a number of virtual log files (VLFs). The number and size of these VLFs depends on the size chosen for the log file. VLFs are also created in the space added to a log file when a log file growth event takes place. Do you have your log files set to auto grow? Then you have potentially been introducing many VLFs into your log file. Let’s get to see how many VLFs we have in a brand new database. USE master GO CREATE DATABASE VLF_Test ON ( NAME = VLF_Test, FILENAME = 'C:\Program Files\Microsoft SQL Server\MSSQL10.ROCK_2008\MSSQL\DATA\VLF_Test.mdf', SIZE = 100, MAXSIZE = 500, FILEGROWTH = 50 ) LOG ON ( NAME = VLF_Test_Log, FILENAME = 'C:\Program Files\Microsoft SQL Server\MSSQL10.ROCK_2008\MSSQL\DATA\VLF_Test_log.ldf', SIZE = 5MB, MAXSIZE = 250MB, FILEGROWTH = 5MB ); go USE VLF_Test go DBCC LOGINFO; The results of this are firstly a new database is created with specified files sizes and the the DBCC LOGINFO results are returned to the script editor. The DBCC LOGINFO results have plenty of interesting information in them but lets first note there are 4 rows of information, this relates to the fact that 4 VLFs have been created in the log file. The values in the FileSize column are the sizes of each VLF in bytes, you will see that the last one to be created is slightly larger than the others. So, a 5MB log file has 4 VLFs of roughly 1.25 MB. Lets alter the CREATE DATABASE script to create a log file that’s a bit bigger and see what happens. Alter the code above so that the log file details are replaced by LOG ON ( NAME = VLF_Test_Log, FILENAME = 'C:\Program Files\Microsoft SQL Server\MSSQL10.ROCK_2008\MSSQL\DATA\VLF_Test_log.ldf', SIZE = 1GB, MAXSIZE = 25GB, FILEGROWTH = 1GB ); With a bigger log file specified we get more VLFs What if we make it bigger again? LOG ON ( NAME = VLF_Test_Log, FILENAME = 'C:\Program Files\Microsoft SQL Server\MSSQL10.ROCK_2008\MSSQL\DATA\VLF_Test_log.ldf', SIZE = 5GB, MAXSIZE = 250GB, FILEGROWTH = 5GB ); This time we see more VLFs are created within our log file. We now have our 5GB log file comprised of 16 files of 320MB each. In fact these sizes fall into all the ranges that control the VLF creation criteria – what a coincidence! The rules that are followed when a log file is created or has it’s size increased are pretty basic. If the file growth is lower than 64MB then 4 VLFs are created If the growth is between 64MB and 1GB then 8 VLFs are created If the growth is greater than 1GB then 16 VLFs are created. Now the potential for chaos comes if the default values and settings for log file growth are used. By default a database log file gets a 1MB log file with unlimited growth in steps of 10%. The database we just created is 6 MB, let’s add some data and see what happens. USE vlf_test go -- we need somewhere to put the data so, a table is in order IF OBJECT_ID('A_Table') IS NOT NULL DROP TABLE A_Table go CREATE TABLE A_Table ( Col_A int IDENTITY, Col_B CHAR(8000) ) GO -- Let's check the state of the log file -- 4 VLFs found EXECUTE ('DBCC LOGINFO'); go -- We can go ahead and insert some data and then check the state of the log file again INSERT A_Table (col_b) SELECT TOP 500 REPLICATE('a',2000) FROM sys.columns AS sc, sys.columns AS sc2 GO -- insert 500 rows and we get 22 VLFs EXECUTE ('DBCC LOGINFO'); go -- Let's insert more rows INSERT A_Table (col_b) SELECT TOP 2000 REPLICATE('a',2000) FROM sys.columns AS sc, sys.columns AS sc2 GO 10 -- insert 2000 rows, in 10 batches and we suddenly have 107 VLFs EXECUTE ('DBCC LOGINFO'); Well, that escalated quickly! Our log file is split, internally, into 107 fragments after a few thousand inserts. The same happens with any logged transactions, I just chose to illustrate this with INSERTs. Having too many VLFs can cause performance degradation at times of database start up, log backup and log restore operations so it’s well worth keeping a check on this property. How do we prevent excessive VLF creation? Creating the database with larger files and also with larger growth steps and actively choosing to grow your databases rather than leaving it to the Auto Grow event can make sure that the growths are made with a size that is optimal. How do we resolve a situation of a database with too many VLFs? This process needs to be done when the database is under little or no stress so that you don’t affect system users. The steps are: BACKUP LOG YourDBName TO YourBackupDestinationOfChoice Shrink the log file to its smallest possible size DBCC SHRINKFILE(FileNameOfTLogHere, TRUNCATEONLY) * Re-size the log file to the size you want it to, taking in to account your expected needs for the coming months or year. ALTER DATABASE YourDBName MODIFY FILE ( NAME = FileNameOfTLogHere, SIZE = TheSizeYouWantItToBeIn_MB) * – If you don’t know the file name of your log file then run sp_helpfile while you are connected to the database that you want to work on and you will get the details you need. The resize step can take quite a while This is already detailed far better than I can explain it by Kimberley Tripp in her blog 8-Steps-to-better-Transaction-Log-throughput.aspx. The result of this will be a log file with a VLF count according to the bullet list above. Knowing when VLFs are being created By complete coincidence while I have been writing this blog (it’s been quite some time from it’s inception to going live) Jonathan Kehayias from SQLSkills.com has written a great article on how to track database file growth using Event Notifications and Service Broker. I strongly recommend taking a look at it as this is going to catch any sneaky auto grows that take place and let you know about them right away. Hassle free monitoring of VLFs If you are lucky or wise enough to be using SQL Monitor or another monitoring tool that let’s you write your own custom metrics then you can keep an eye on this very easily. There is a custom metric for VLFs (written by Stuart Ainsworth) already on the site and there are some others there are very useful so take a moment or two to look around while you are there. Resources MSDN – http://msdn.microsoft.com/en-us/library/ms179355(v=sql.105).aspx Kimberly Tripp from SQLSkills.com – http://www.sqlskills.com/BLOGS/KIMBERLY/post/8-Steps-to-better-Transaction-Log-throughput.aspx Thomas LaRock at Simple-Talk.com – http://www.simple-talk.com/sql/database-administration/monitoring-sql-server-virtual-log-file-fragmentation/ Disclosure I am a Friend of Red Gate. This means that I am more than likely to say good things about Red Gate DBA and Developer tools. No matter how awesome I make them sound, take the time to compare them with other products before you contact the Red Gate sales team to make your order.

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