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• CArray doesn't call copy constructors on memory reallocations, now what?

  - by MMx

  Suppose I have a class that requires copy constructor to be called to make a correct copy of: struct CWeird { CWeird() { number = 47; target = &number; } CWeird(const CWeird &other) : number(other.number), target(&number) { } void output() { printf("%d %d\n", *target, number); } int *target, number; }; Now the trouble is that CArray doesn't call copy constructors on its elements when reallocating memory (only memcpy from the old memory to the new), e.g. this code CArray<CWeird> a; a.SetSize(1); a[0].output(); a.SetSize(2); a[0].output(); results in 47 47 -572662307 47 I don't get this. Why is it that std::vector can copy the same objects properly and CArray can't? What's the lesson here? Should I use only classes that don't require explicit copy constructors? Or is it a bad idea to use CArray for anything serious?

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• Boost shared_ptr use_count function

  - by photo_tom

  My application problem is the following - I have a large structure foo. Because these are large and for memory management reasons, we do not wish to delete them when processing on the data is complete. We are storing them in std::vector<boost::shared_ptr<foo>>. My question is related to knowing when all processing is complete. First decision is that we do not want any of the other application code to mark a complete flag in the structure because there are multiple execution paths in the program and we cannot predict which one is the last. So in our implementation, once processing is complete, we delete all copies of boost::shared_ptr<foo>> except for the one in the vector. This will drop the reference counter in the shared_ptr to 1. Is it practical to use shared_ptr.use_count() to see if it is equal to 1 to know when all other parts of my app are done with the data. One additional reason I'm asking the question is that the boost documentation on the shared pointer shared_ptr recommends not using "use_count" for production code.

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• Finding minimum value in a Map

  - by Sunny

  I have a map and I want to find the minimum value (right hand side) in the map. Right now here is how I did it bool compare(std::pair<std::string ,int> i, pair<std::string, int> j) { return i.second < j.second; } //////////////////////////////////////////////////// std::map<std::string, int> mymap; mymap["key1"] = 50; mymap["key2"] = 20; mymap["key3"] = 100; std::pair<char, int> min = *min_element(mymap.begin(), mymap.end(), compare); std::cout << "min " << min.second<< " " << std::endl; This works fine and I'm able to get the minimum value the problem is when I put this code inside my class it doesn't seem to work int MyClass::getMin(std::map<std::string, int> mymap) { std::pair<std::string, int> min = *min_element(mymap.begin(), mymap.end(), (*this).compare); //error probably due to this return min.second; } bool MyClass::compare( std::pair<std::string, int> i, std::pair<std::string, int> j) { return i.second < j.second; } Also is there a better solution not involving to writing the additional compare function

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• error in a c code while trying to remove whitespace

  - by mekasperasky

  this code is the base of lexer , and it does the basic operation of removing the whitespaces from a source file and rewrites it into another file with each word in separate lines . But i am not able to understand why the file lext.txt not getting updated? #include<stdio.h> /* this is a lexer which recognizes constants , variables ,symbols, identifiers , functions , comments and also header files . It stores the lexemes in 3 different files . One file contains all the headers and the comments . Another file will contain all the variables , another will contain all the symbols. */ int main() { int i; char a,b[20],c; FILE *fp1,*fp2; fp1=fopen("source.txt","r"); //the source file is opened in read only mode which will passed through the lexer fp2=fopen("lext.txt","w"); //now lets remove all the white spaces and store the rest of the words in a file if(fp1==NULL) { perror("failed to open source.txt"); //return EXIT_FAILURE; } i=0; while(!feof(fp1)) { a=fgetc(fp1); if(a!="") { b[i]=a; printf("hello"); } else { b[i]='\0'; fprintf(fp2, "%.20s\n", b); i=0; continue; } i=i+1; /*Switch(a) { case EOF :return eof; case '+':sym=sym+1; case '-':sym=sym+1; case '*':sym=sym+1; case '/':sym=sym+1; case '%':sym=sym+1; case ' */ } return 0; }

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• Refetching a previously visited page

  - by user613665

  All, I am having a field day with page refetching. Any help or pointer will be greatly appreciated!! The behavior is a bit specific to mobile browser. Problem: I have two pages and created a shortcut link to pg#1 in the home page. Through a form submit button, user is taken from pg#1 to pg#2. All that is working fine. Now once I am on pg#2. I will leave the browser and click the shortcut later. The browser will stay on pg#2 and won't go to pg#1 even though the path in URLS is different between the two views. It is almost like Django decides that since I have already visited view#1, it doesn't need to fetch it again. This problem or behavior doesn't happen if I move the same code that handle the two views and the templates to a bare bone test project. Setup: I am using django-registration, context session. I am not using any HTML caching tag. I already have DEBUG turned on in my settings.py. Are there other ways that I can tell what the server is doing. Thanks in advance. pdxMobile Update: Here is the code snippets. def sendmsg(request): if request.method =='POST': messages.add_message(request, messages.INFO, "Hello world") return redirect ('rcvmsg') return render_to_response('sendMsg.html',RequestContext(request)) def rcvmsg(request): '''view that receives the msg.''' printMsg ='Didnt get a message' if messages: thisMsg = messages.get_messages(request) for rcvMsg in thisMsg: printMsg = rcvMsg return render_to_response('rcvMsg.html',{'print_msg':printMsg},RequestContext(request)) URL: url(r'^rcvMsg/','mydomain.mainApp.views.rcvmsg',name='rcvmsg'), (r'^sendMsg/code','mydomain.mainApp.views.sendmsg'),

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• Why this doesnt't work in C++?

  - by user3377450

  I'm doing something and I have this: //main.cpp file template<typename t1, typename t2> std::ostream& operator<<(std::ostream& os, const std::pair<t1, t2>& pair) { return os << "< " << pair.first << " , " << pair.second << " >"; } int main() { std::map<int, int> map = { { 1, 2 }, { 2, 3 } }; std::cout << *map.begin() << std::endl;//This works std::copy(map.begin(), map.end(), std::ostream_iterator<std::pair<int,int> >(std::cout, " "));//this doesn't work } I guess this is not working because in the std::copy algorithm the operator isn't defined, but what can I do?

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• Deprecated functions not spotted if using "System::Threading::ThreadState" (and others!) C++ VS2005/

  - by Fishboy

  Hi, I'm facing an issue with c++ on vs2005 and also vs2008... here's how you can reproduce the issue.... create a new (c++) project called 'test' (file|new|project) select "Windows Forms Application" and add the 'stdio.h' include and the code fragment below into the test.cpp source file..... -------------------start of snippet-------------------- #include <stdio.h> ... int main(array<System::String ^> ^args) { int i; System::Threading::ThreadState state; char str[20]; sprintf (str, "%s", "test string"); ... -------------------end of snippet-------------------- If you compile the code as above (you'll have to 'buildall' first), you'll get two warnings about 'i' and 'state' being unreferenced (nothing about sprintf being deprecated). If you comment out "System::Threading :Thread state;", you'll get one warning about 'i' being unreferenced and another warning (C4996) for the 'deprecated' sprintf statement.... This issue also occurs for "System::Windows::Forms::MessageBoxIcon", "System::Base64FormattingOptions" (and perhap all 'enum class' types!) Anyone know of the cause and workaround to the issue demonstrated here ( i have other files that demonstate this issue..). (I had started a thread on msdn, but then found this site! see link below) Visual Studio 2005 has stopped warning about deprecated functions

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• Array Assignment

  - by Mahesh

  Let me explain with an example - #include <iostream> void foo( int a[2], int b[2] ) // I understand that, compiler doesn't bother about the // array index and converts them to int *a, int *b { a = b ; // At this point, how ever assignment operation is valid. } int main() { int a[] = { 1,2 }; int b[] = { 3,4 }; foo( a, b ); a = b; // Why is this invalid here. return 0; } Is it because, array decays to a pointer when passed to a function foo(..), assignment operation is possible. And in main, is it because they are of type int[] which invalidates the assignment operation. Doesn't a,b in both the cases mean the same ? Thanks. Edit 1: When I do it in a function foo, it's assigning the b's starting element location to a. So, thinking in terms of it, what made the language developers not do the same in main(). Want to know the reason.

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• Automatically Persisting a Complex Java Object

  - by VeeArr

  For a project I am working on, I need to persist a number of POJOs to a database. The POJOs class definitions are sometimes highly nested, but they should flatten okay, as the nesting is tree-like and contains no cycles (and the base elements are eventually primitives/Strings). It is preferred that the solution used create one table per data type and that the tables will have one field per primitive member in the POJO. Subclassing and similar problems are not issues for this particular project. Does anybody know of any existing solutions that can: Automatically generate a CREATE TABLE definition from the class definition Automatically generate a query to persist an object to the database, given an instance of the object Automatically generate a query to retrieve an object from the database and return it as a POJO, given a key. Solutions that can do this with minimum modifications/annotions to the class files and minimum external configuration are preferred. Example: Java classes //Class to be persisted class TypeA { String guid; long timestamp; TypeB data1; TypeC data2; } class TypeB { int id; int someData; } class TypeC { int id; int otherData; } Could map to CREATE TABLE TypeA ( guid CHAR(255), timestamp BIGINT, data1_id INT, data1_someData INT, data2_id INt, data2_otherData INT ); Or something similar.

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• Using new (this) to reuse constructors

  - by Brandon Bodnar

  This came up recently in a class for which I am a teaching assistant. We were teaching the students how to do copy constructors in c++, and the students who were originally taught java asked if you can call one constructor from another. I know the answer to this is no, as they are using the pedantic flag for their code in class, and the old standards do not have support for this. I found on Stackoverflow and other sites a suggestion to fake this using new (this) such as follows class MyClass { private: int * storedValue; public: MyClass(int initialValue = 0) { storedValue = new int(initialValue); } ~ MyClass() { delete storedValue; } MyClass(const MyClass &b) { new (this) MyClass(*(b.storedValue)); } int value() { return *storedValue; } }; This is really simple code, and obviously does not save any code by reusing the constructor, but it is just for example. My question is if this is even standard compliant, and if there are any edge cases that should be considered that would prevent this from being sound code?

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• Rotating bits of any integer in C

  - by Tim

  Pass a integer 2 to this function and then return a integer which is 4 x = 2; x = rotateInt('L', x, 1); (left shift the bits by 1) Example: 00000010 - rotate left by 1 - 00000100 but if I pass this: x = rotateInt('R', x, 3); it will return 64, 01000000 Here is the code, can someone correct the error... thanks int rotateInt(char direction, unsigned int x, int y) { unsigned int mask = 0; int num = 0, result = 0; int i; for(i = 0; i < y; i++) { if(direction == 'R') { if((x & 1) == 1) x = (x ^ 129); else x = x >> 1; } else if(direction == 'L') { if((x & 128) == 1) x = (x ^ 129); else x = x << 1; } } result = (result ^ x); return result; }

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• How to delete Drawn Line in java?

  - by Jeyjey

  Hello Folks, well this is my code: import javax.swing.; import javax.; import java.awt.; import java.awt.Color; import java.awt.Graphics.; import java.awt.event.*; import javax.swing.UIManager; public class SimpleGUI extends JFrame{ public SimpleGUI(){ this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE) ; } public void go(){ Drawpanel = new Mypanel(); JFrame frame = new JFrame("Chasing Line"); frame.getContentPane().add(BorderLayout.CENTER, Drawpanel); frame.setSize(300,300); frame.setVisible(true); Drawpanel.addMouseMotionListener(new java.awt.event.MouseMotionAdapter() { public void mouseMoved(java.awt.event.MouseEvent evt) { DrawpanelMouseMoved(evt); } }); } public void DrawpanelMouseMoved(java.awt.event.MouseEvent evt) { xpos=evt.getX(); ypos=evt.getY(); System.out.println("Coordinates : X :"+ xpos+"Y: "+ypos); Drawpanel.paintImage(xpos,ypos); } class Mypanel extends JPanel{ public void paintImage(int xpost,int ypost){ Graphics d = getGraphics(); d.setColor(Color.black); d.drawLine(xpost, 0, xpost, this.getHeight()); d.setColor(Color.red); d.drawLine(0, ypost, this.getWidth(),ypost); this.validate(); } } // end the inner class public static void main(String[] args){ try { UIManager.setLookAndFeel("com.sun.java.swing.plaf.windows.WindowsLookAndFeel"); } catch(Exception e) { System.err.println("Look and feel not set"); } SimpleGUI win = new SimpleGUI(); win.go(); } Mypanel Drawpanel; private int xpos=0; private int ypos=0; } // close SimpleGUI class The problem is how can i delete the old lines?, i mea,make only the current x and y lines appear on the screen, make the intersection between both lines "follow" the mouse pointer. thanks for any reply.

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• Socket send recv functions

  - by viswanathan

  I have created a socket using the following lines of code. Now i change the value of the socket i get like this m_Socket++; Even now the send recv socket functions succeeds without throwing SOCKET_ERROR. I expect that it must throw error. Am i doing something wrong. struct sockaddr_in ServerSock; // Socket address structure to bind the Port Number to listen to char *localIP ; SOCKET SocServer; //To Set up the sockaddr structure ServerSock.sin_family = AF_INET; ServerSock.sin_addr.s_addr = INADDR_ANY; ServerSock.sin_port = htons(pLantronics->m_wRIPortNo); // To Create a socket for listening on wPortNumber if(( SocServer = socket( AF_INET, SOCK_STREAM, 0 )) == INVALID_SOCKET ) { return FALSE; } //To bind the socket with wPortNumber if(bind(SocServer,(sockaddr*)&ServerSock,sizeof(ServerSock))!=0) { return FALSE; } // To Listen for the connection on wPortNumber if(listen(SocServer,SOMAXCONN)!=0) { return FALSE; } // Structure to get the IP Address of the connecting Entity sockaddr_in insock; int insocklen=sizeof(insock); //To accept the Incoming connection on the wPortNumber pLantronics->m_Socket=accept(SocServer,(struct sockaddr*)&insock,&insocklen); if(pLantronics->m_Socket == INVALID_SOCKET) { shutdown(SocServer, 2 ); closesocket(SocServer ); return FALSE; } // To make socket non-blocking DWORD dwNonBlocking = 1; if(ioctlsocket( pLantronics->m_Socket, FIONBIO, &dwNonBlocking )) { shutdown(pLantronics->m_Socket, 2); closesocket(pLantronics->m_Socket); return FALSE; } pLantronics->m_sModemName = inet_ntoa(insock.sin_addr); Now i do m_Socket++;//change to some other number ideally expecting send recv to fail. Even now the send recv socket functions succeeds without throwing SOCKET_ERROR. I expect that it must throw error. Am i doing something wrong.

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• Need a set based solution to group rows

  - by KM

  I need to group a set of rows based on the Category column, and also limit the combined rows based on the SUM(Number) column to be less than or equal to the @Limit value. For each distinct Category column I need to identify "buckets" that are <=@limit. If the SUM(Number) of all the rows for a Category column are <=@Limit then there will be only 1 bucket for that Category value (like 'CCCC' in the sample data). However if the SUM(Number)@limit, then there will be multiple bucket rows for that Category value (like 'AAAA' in the sample data), and each bucket must be <=@Limit. There can be as many buckets as necessary. Also, look at Category value 'DDDD', its one row is greater than @Limit all by itself, and gets split into two rows in the result set. Given this simplified data: DECLARE @Detail table (DetailID int primary key, Category char(4), Number int) SET NOCOUNT ON INSERT @Detail VALUES ( 1, 'AAAA',100) INSERT @Detail VALUES ( 2, 'AAAA', 50) INSERT @Detail VALUES ( 3, 'AAAA',300) INSERT @Detail VALUES ( 4, 'AAAA',200) INSERT @Detail VALUES ( 5, 'BBBB',500) INSERT @Detail VALUES ( 6, 'CCCC',200) INSERT @Detail VALUES ( 7, 'CCCC',100) INSERT @Detail VALUES ( 8, 'CCCC', 50) INSERT @Detail VALUES ( 9, 'DDDD',800) INSERT @Detail VALUES (10, 'EEEE',100) SET NOCOUNT OFF DECLARE @Limit int SET @Limit=500 I need one of these result set: DetailID Bucket | DetailID Category Bucket -------- ------ | -------- -------- ------ 1 1 | 1 'AAAA' 1 2 1 | 2 'AAAA' 1 3 1 | 3 'AAAA' 1 4 2 | 4 'AAAA' 2 5 3 OR 5 'BBBB' 1 6 4 | 6 'CCCC' 1 7 4 | 7 'CCCC' 1 8 4 | 8 'CCCC' 1 9 5 | 9 'DDDD' 1 9 6 | 9 'DDDD' 2 10 7 | 10 'EEEE' 1

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• POSIX Sockets: How to detect Ctrl-C sent over Telnet?

  - by ogott

  Short Question What's the right way to handle a Ctrl-C event sent over Telnet on the server side? Long Question After calling recv() on a socket, I'd like to handle some situations appropriately. One of them is to return a certain error code when Ctrl-C was received. What's the correct way to detect this? The following works, but it just doesn't seem right: size_t recv_count; static char ctrl_c[5] = {0xff, 0xf4, 0xff, 0xfd, 0x06}; recv_count = recv(socket, buffer, buffer_size, 0); if (recv_count == sizeof(ctrl_c) && memcmp(buffer, ctrl_c, sizeof(ctrl_c) == 0) { return CTRL_C_RECEIVED; } I found a comment on Ctrl-C in a side-note in this UNIX Socket FAQ: [...] (by the way, out-of-band is often used for that ctrl-C, too). As I understand, receiving out-of-band data is done using recv() with a certain flag as the last parameter. But when I'm waiting for data using recv() as I do in the code above, I can't read out-of-band data at the same time. Apart from that, I'm getting something using recv() without that oob-flag.

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• Java socket bug on linux (0xFF sent, -3 received)

  - by Marius

  While working on a WebSocket server in Java I came across this strange bug. I've reduced it down to two small java files, one is the server, the other is the client. The client simply sends 0x00, the string Hello and then 0xFF (per the WebSocket specification). On my windows machine, the server prints the following: Listening byte: 0 72 101 108 108 111 recieved: 'Hello' While on my unix box the same code prints the following: Listening byte: 0 72 101 108 108 111 -3 Instead of receiving 0xFF it gets -3, never breaks out of the loop and never prints what it has received. The important part of the code looks like this: byte b = (byte)in.read(); System.out.println("byte: "+b); StringBuilder input = new StringBuilder(); b = (byte)in.read(); while((b & 0xFF) != 0xFF){ input.append((char)b); System.out.print(b+" "); b = (byte)in.read(); } inputLine = input.toString(); System.out.println("recieved: '" + inputLine+"'"); if(inputLine.equals("bye")){ break; } I've also uploaded the two files to my server: Server.java Client.java My Windows machine is running windows 7 and my Linux machine is running Debian

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• Summary statistics in visual basic

  - by ben

  Below I am trying to write a script the goal of which is to calculate some summary statistics for a few different columns of numbers. I have gotten some help on it up to the "Need help below" mark. But beyond that I am flabergasted as to how to calculate the simple stats (sum, mean, standard deviation, coefficient of variation). I know VB has scripts for these stats, which I have included in my code, but I guess I need to do some extra declaring or something. Advice much appreciated. Thanks. Sub TOAinput() Const n As Integer = 648 Dim stratum(n), hybrid(n), acres(n), hhsz(n), offinc(n) Dim s1 As Integer Dim s2 As Integer Dim i As Integer For i = 1 To n stratum(i) = Worksheets("hhid level").Cells(i + 1, 2).Value Next i s1 = 0 s2 = 0 For i = 1 To n If stratum(i) = 1 Then s1 = s1 + 1 Else: s2 = s2 + 1 End If Next i Dim acres1(), hhsz1(), offinc1(), acres2(), hhsz2(), offinc2() ReDim acres1(s1), hhsz1(s1), offinc1(s1), acres2(s2), hhsz2(s2), offinc2(s2) 'data infiles: acres, hh size, off-farm income, For i = 1 To n acres(i) = Worksheets("hhid level").Cells(i + 1, 4).Value hhsz(i) = Worksheets("hhid level").Cells(i + 1, 5).Value offinc(i) = Worksheets("hhid level").Cells(i + 1, 6).Value Next i s1 = 0 s2 = 0 For i = 1 To n If stratum(i) = 1 Then s1 = s1 + 1 acres1(s1) = acres(i) hhsz1(s1) = hhsz(i) offinc1(s1) = offinc(i) Else: s2 = s2 + 1 acres2(s2) = acres(i) hhsz2(s2) = hhsz(i) offinc2(s2) = offinc(i) End If Next i '**************************** 'Need help below '**************************** Dim sumac1, sumac2, mhhsz1, mhhsz2, cvhhsz1, cvhhsz2 sumac1 = Sum(acres1) sumac2 = Sum(acres2) mhhsz1 = Average(hhsz1) mhhsz2 = Average(hhsz2) cvhhsz1 = StDev(hhsz1) / Average(hhsz1) cvhhsz2 = StDev(hhsz2) / Average(hhsz2) End Sub

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• C++: Switch statement within while loop?

  - by Jason

  I just started C++ but have some prior knowledge to other languages (vb awhile back unfortunately), but have an odd predicament. I disliked using so many IF statements and wanted to use switch/cases as it seemed cleaner, and I wanted to get in the practice.. But.. Lets say I have the following scenario (theorietical code): while(1) { //Loop can be conditional or 1, I use it alot, for example in my game char something; std::cout << "Enter something\n -->"; std::cin >> something; //Switch to read "something" switch(something) { case 'a': cout << "You entered A, which is correct"; break; case 'b': cout << "..."; break; } } And that's my problem. Lets say I wanted to exit the WHILE loop, It'd require two break statements? This obviously looks wrong: case 'a': cout << "You entered A, which is correct"; break; break; So can I only do an IF statement on the 'a' to use break;? Am I missing something really simple? This would solve a lot of my problems that I have right now.

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• Is this an error in "More Effective C++" in Item28?

  - by particle128

  I encountered a question when I was reading the item28 in More Effective C++ .In this item, the author shows to us that we can use member template in SmartPtr such that the SmartPtr<Cassette> can be converted to SmartPtr<MusicProduct>. The following code is not the same as in the book,but has the same effect. #include <iostream> class Base{}; class Derived:public Base{}; template<typename T> class smart{ public: smart(T* ptr):ptr(ptr){} template<typename U> operator smart<U>() { return smart<U>(ptr); } ~smart(){delete ptr;} private: T* ptr; }; void test(const smart<Base>& ) {} int main() { smart<Derived> sd(new Derived); test(sd); return 0; } It indeed can be compiled without compilation error. But when I ran the executable file, I got a core dump. I think that's because the member function of the conversion operator makes a temporary smart, which has a pointer to the same ptr in sd (its type is smart<Derived>). So the delete directive operates twice. What's more, after calling test, we can never use sd any more, since ptr in sd has already been delete. Now my questions are : Is my thought right? Or my code is not the same as the original code in the book? If my thought is right, is there any method to do this? Thanks very much for your help.

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• Picture.writeToStream() not writing out all bitmaps

  - by quickdraw mcgraw

  I'm using webview.capturePicture() to create a Picture object that contains all the drawing objects for a webpage. I can successfully render this Picture object to a bitmap using the canvas.drawPicture(picture, dst) with no problems. However when I use picture.writeToStream(fos) to serialize the picture object out to file, and then Picture.createFromStream(fis) to read the data back in and create a new picture object, the resultant bitmap when rendered as above is missing any larger images (anything over around 20KB! by observation). This occurs on all the Android OS platforms that I have tested 1.5, 1.6 and 2.1. Looking at the native code for Skia which is the underlying Android graphics library and the output file produced from the picture.writeToStream() I can see how the file format is constructed. I can see that some of the images in this Skia spool file are not being written out (the larger ones), the code that appears to be the problem is in skBitmap.cpp in the method void SkBitmap::flatten(SkFlattenableWriteBuffer& buffer) const; It writes out the bitmap fWidth, fHeight, fRowBytes, FConfig and isOpaque values but then just writes out SERIALIZE_PIXELTYPE_NONE (0). This means that the spool file does not contain any pixel information about the actual image and therefore cannot restore the picture object correctly. Effectively this renders the writeToStream and createFromStream() APIs useless as they do not reliably store and recreate the picture data. Has anybody else seen this behaviour and if so am I using the API incorrectly, can it be worked around, is there an explanation i.e. incomplete API / bug and if so are there any plans for a fix in a future release of Android? Thanks in advance.

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• Dynamic SQL and Funtions

  - by Unlimited071

  Hi all, is there any way of accomplishing something like the following: CREATE FUNCTION GetQtyFromID ( @oricod varchar(15), @ccocod varchar(15), @ocmnum int, @oinnum int, @acmnum int, @acttip char(2), @unisim varchar(15) ) AS BEGIN DECLARE @Result decimal(18,8) DECLARE @SQLString nvarchar(max); DECLARE @ParmDefinition nvarchar(max); --I need to execute a query stored in a cell which returns the calculated qty. --i.e of AcuQry: select @cant = sum(smt) from table where oricod = @oricod and ... SELECT @SQLString = AcuQry FROM OinActUni WHERE (OriCod = @oricod) AND (ActTipCod = @acttip) AND (UniSim = @unisim) AND (AcuEst > 0) SET @ParmDefinition = N' @oricod varchar(15), @ccocod varchar(15), @ocmnum int, @oinnum int, @acmnum int, @cant decimal(18,8) output'; EXECUTE sp_executesql @SQLString, @ParmDefinition, @oricod = @oricod, @ccocod = @ccocod, @ocmnum = @ocmnum, @oinnum = @oinnum, @acmnum = @acmnum, @cant = @result OUTPUT; RETURN @Result END The problem with this approach is that it is prohibited to execute sp_excutesql in a function... What I need is to do something like: select id, getQtyFromID(id) as qty from table The main idea is to execute a query stored in a table cell, this is because the qty of something depends on it's unit. the unit can be days or it can be metric tons, so there is no relation between the units, therefore the need of a specific query for each unit.

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• JS best practice for member functions

  - by MickMalone1983

  I'm writing a little mobile games library, and I'm not sure the best practice for declaring member functions of instantiated function objects. For instance, I might create a simple object with one property, and a method to print it: function Foo(id){ this.id = id; this.print = function(){ console.log(this.id); }; }; However, a function which does not need access to 'private' members of the function does not need to be declared in the function at all. I could equally have written: function print(){ console.log(this.id); }; function Foo(id){ this.id = id; this.print = print; }; When the function is invoked through an instance of Foo, the instance becomes the context for this, so the output is the same in either case. I'm not entirely sure how memory is allocated with JS, and I can't find anything that I can understand about something this specific, but it seems to me that with the first example all members of Foo, including the print function, are duplicated each time it is instantiated - but with the second, it just gets a pointer to one, pre-declared function, which would save any more memory having to be allocated as more instances of Foo are created. Am I correct, and if I am, is there any memory/performance benefit to doing this?

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• C++ : Declaring the array size with a non-constant variable

  - by Jérôme

  I always thought that when declaring an array in C++, the size has to be a constant integer value. For instance : int MyArray[5]; // correct or const int ARRAY_SIZE = 6; int MyArray[ARRAY_SIZE]; // correct but int ArraySize = 5; int MyArray[ArraySize]; // incorrect Here is also what is explained in The C++ Programming Language, by Bjarne Stroustrup : The number of elements of the array, the array bound, must be a constant expression (§C.5). If you need variable bounds, use a vector(§3.7.1, §16.3). For example: void f(int i) { int v1[i]; // error : array size not a constant expression vector<int> v2[i]; // ok } But to my big surprise, the code above does compile fine on my system ! Here is what I tried to compile : void f(int i) { int v2[i]; } int main() { int i = 3; int v1[i]; f(5); } I got no error ! I'm using GCC v4.4.0. Is there something I'm missing ?

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• C++ - Where to throw exception?

  - by HardCoder1986

  Hello! I have some kind of an ideological question, so: Suppose I have some templated function template <typename Stream> void Foo(Stream& stream, Object& object) { ... } which does something with this object and the stream (for example, serializes that object to the stream or something like that). Let's say I also add some plain wrappers like (and let's say the number of these wrappers equals 2 or 3): void FooToFile(const std::string& filename, Object& object) { std::ifstream stream(filename.c_str()); Foo(stream, object); } So, my question is: Where in this case (ideologically) should I throw the exception if my stream is bad? Should I do this in each wrapper or just move that check to my Foo, so that it's body would look like if (!foo.good()) throw (something); // Perform ordinary actions I understand that this may be not the most important part of coding and these solutions are actually equal, but I just wan't to know "the proper" way to implement this. Thank you.

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• Conceptual data modeling: Is RDF the right tool? Other solutions?

  - by paprika

  I'm planning a system that combines various data sources and lets users do simple queries on these. A part of the system needs to act as an abstraction layer that knows all connected data sources: the user shouldn't [need to] know about the underlying data "providers". A data provider could be anything: a relational DBMS, a bug tracking system, ..., a weather station. They are hooked up to the query system through a common API that defines how to "offer" data. The type of queries a certain data provider understands is given by its "offer" (e.g. I know these entities, I can give you aggregates of type X for relationship Y, ...). My concern right now is the unification of the data: the various data providers need to agree on a common vocabulary (e.g. the name of the entity "customer" could vary across different systems). Thus, defining a high level representation of the entities and their relationships is required. So far I have the following requirements: I need to be able to define objects and their properties/attributes. Further, arbitrary relations between these objects need to be represented: a verb that defines the nature of the relation (e.g. "knows"), the multiplicity (e.g. 1:n) and the direction/navigability of the relation. It occurs to me that RDF is a viable option, but is it "the right tool" for this job? What other solutions/frameworks do exist for semantic data modeling that have a machine readable representation and why are they better suited for this task? I'm grateful for every opinion and pointer to helpful resources.

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