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  • Java loading user-specified classes at runtime

    - by user349043
    I'm working on robot simulation in Java (a Swing application). I have an abstract class "Robot" from which different types of Robots are derived, e.g. public class StupidRobot extends Robot { int m_stupidness; int m_insanityLevel; ... } public class AngryRobot extends Robot { float m_aggression; ... } As you can see, each Robot subclass has a different set of parameters. What I would like to do is control the simulation setup in the initial UI. Choose the number and type of Robots, give it a name, fill in the parameters etc. This is one of those times where being such a dinosaur programmer, and new to Java, I wonder if there is some higher level stuff/thinking that could help me here. So here is what I've got: (1) User Interface Scrolling list of Robot types on the left. "Add " and "<< Remove" buttons in the middle. Default-named scrolling list of Robots on the right. "Set Parameters" button underneath. (So if you wanted an AngryRobot, you'd select AngryRobot on the left list, click "Add" and "AngryRobot1" would show up on the right.) When selecting a Robot on the right, click "Set Parameters..." button which would call yet another model dialog where you'd fill in the parameters. Different dialog called for each Robot type. (2) Data structures an implementation As an end-product I think a HashMap would be most convenient. The keys would be Robot types and the accompanying object would be all of the parameters. The initializer could just retrieve each item one and a time and instantiate. Here's what the data structures would look like: enum ROBOT_TYPE {STUPID, ANGRY, etc} public class RobotInitializer { public ROBOT_TYPE m_type; public string m_name; public int[] m_int_params; public float[] m_float_params; etc. The initializer's constructor would create the appropriate length parameter arrays based on the type: public RobotInitializer(ROBOT_TYPE type, int[] int_array, float[] float_array, etc){ switch (type){ case STUPID: m_int_params = new int[STUPID_INT_PARAM_LENGTH]; System.arraycopy(int_array,0,m_int_params,0,STUPID_INT_PARAM_LENGTH); etc. Once all the RobotInitializers are instantiated, they are added to the HashMap. Iterating through the HashMap, the simulation initializer takes items from the Hashmap and instantiates the appropriate Robots. Is this reasonable? If not, how can it be improved? Thanks

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  • SQL Invalid Object Name 'AddressType'

    - by salvationishere
    I am getting the above error in my VS 2008 C# method when I try to invoke the SQL getColumnNames stored procedure from VS. This SP accepts one input parameter, the table name, and works successfully from SSMS. Currently I am selecting the AdventureWorks AddressType table for it to pull the column names from this table. I can see teh AdventureWorks table available in VS from my Server Explorer / Data Connection. And I see both the AddressType table and getColumnNames SP showing in Server Explorer. But I am still getting this error listed above. Here is the C# code snippet I use to execute this: public static DataTable DisplayTableColumns(string tt) { SqlDataReader dr = null; string TableName = tt; string connString = "Data Source=.;AttachDbFilename=\"C:\Program Files\Microsoft SQL Server\MSSQL10.MSSQLSERVER\MSSQL\DATA\AdventureWorks_Data.mdf\";Initial Catalog=AdventureWorks;Integrated Security=True;Connect Timeout=30;User Instance=False"; string errorMsg; SqlConnection conn2 = new SqlConnection(connString); SqlCommand cmd = conn2.CreateCommand(); try { cmd.CommandText = "dbo.getColumnNames"; cmd.CommandType = CommandType.StoredProcedure; cmd.Connection = conn2; SqlParameter parm = new SqlParameter("@TableName", SqlDbType.VarChar); parm.Value = TableName; parm.Direction = ParameterDirection.Input; cmd.Parameters.Add(parm); conn2.Open(); dr = cmd.ExecuteReader(); } catch (Exception ex) { errorMsg = ex.Message; } And when I examine the errorMsg it says the following: " at System.Data.SqlClient.SqlConnection.OnError(SqlException exception, Boolean breakConnection)\r\n at System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection)\r\n at System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj)\r\n at System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj)\r\n at System.Data.SqlClient.SqlDataReader.ConsumeMetaData()\r\n at System.Data.SqlClient.SqlDataReader.get_MetaData()\r\n at System.Data.SqlClient.SqlCommand.FinishExecuteReader(SqlDataReader ds, RunBehavior runBehavior, String resetOptionsString)\r\n at System.Data.SqlClient.SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, Boolean async)\r\n at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method, DbAsyncResult result)\r\n at System.Data.SqlClient.SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior, RunBehavior runBehavior, Boolean returnStream, String method)\r\n at System.Data.SqlClient.SqlCommand.ExecuteReader(CommandBehavior behavior, String method)\r\n at System.Data.SqlClient.SqlCommand.ExecuteReader()\r\n at ADONET_namespace.ADONET_methods.DisplayTableColumns(String tt) in C:\Documents and Settings\Admin\My Documents\Visual Studio 2008\Projects\AddFileToSQL\AddFileToSQL\ADONET methods.cs:line 35" Where line 35 is dr = cmd.ExecuteReader();

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  • getting Cannot identify image file when trying to create thumbnail in django

    - by Mo J. Mughrabi
    Am trying to create a thumbnail in django, am trying to build a custom class specifically to be used for generating thumbnails. As following from StringIO import StringIO from PIL import Image class Thumbnail(object): source = '' size = (50, 50) output = '' def __init__(self): pass @staticmethod def load(src): self = Thumbnail() self.source = src return self def generate(self, size=(50, 50)): if not isinstance(size, tuple): raise Exception('Thumbnail class: The size parameter must be an instance of a tuple.') self.size = size # resize properties box = self.size factor = 1 fit = True image = Image.open(self.source) # Convert to RGB if necessary if image.mode not in ('L', 'RGB'): image = image.convert('RGB') while image.size[0]/factor > 2*box[0] and image.size[1]*2/factor > 2*box[1]: factor *=2 if factor > 1: image.thumbnail((image.size[0]/factor, image.size[1]/factor), Image.NEAREST) #calculate the cropping box and get the cropped part if fit: x1 = y1 = 0 x2, y2 = image.size wRatio = 1.0 * x2/box[0] hRatio = 1.0 * y2/box[1] if hRatio > wRatio: y1 = int(y2/2-box[1]*wRatio/2) y2 = int(y2/2+box[1]*wRatio/2) else: x1 = int(x2/2-box[0]*hRatio/2) x2 = int(x2/2+box[0]*hRatio/2) image = image.crop((x1,y1,x2,y2)) #Resize the image with best quality algorithm ANTI-ALIAS image.thumbnail(box, Image.ANTIALIAS) # save image to memory temp_handle = StringIO() image.save(temp_handle, 'png') temp_handle.seek(0) self.output = temp_handle return self def get_output(self): return self.output.read() the purpose of the class is so i can use it inside different locations to generate thumbnails on the fly. The class works perfectly, I've tested it directly under a view.. I've implemented the thumbnail class inside the save method of the forms to resize the original images on saving. in my design, I have two fields for thumbnails. I was able to generate one thumbnail, if I try to generate two it crashes and I've been stuck for hours not sure whats the problem. Here is my model class Image(models.Model): article = models.ForeignKey(Article) title = models.CharField(max_length=100, null=True, blank=True) src = models.ImageField(upload_to='publication/image/') r128 = models.ImageField(upload_to='publication/image/128/', blank=True, null=True) r200 = models.ImageField(upload_to='publication/image/200/', blank=True, null=True) uploaded_at = models.DateTimeField(auto_now=True) Here is my forms class ImageForm(models.ModelForm): """ """ class Meta: model = Image fields = ('src',) def save(self, commit=True): instance = super(ImageForm, self).save(commit=True) file = Thumbnail.load(instance.src) instance.r128 = SimpleUploadedFile( instance.src.name, file.generate((128, 128)).get_output(), content_type='image/png' ) instance.r200 = SimpleUploadedFile( instance.src.name, file.generate((200, 200)).get_output(), content_type='image/png' ) if commit: instance.save() return instance the strange part is, when i remove the line which contains instance.r200 in the form save. It works fine, and it does the thumbnail and stores it successfully. Once I add the second thumbnail it fails.. Any ideas what am doing wrong here? Thanks Update: I tried earlier doing the following but I still got the same error class ImageForm(models.ModelForm): """ """ class Meta: model = Image fields = ('src',) def save(self, commit=True): instance = super(ImageForm, self).save(commit=True) instance.r128 = SimpleUploadedFile( instance.src.name, Thumbnail.load(instance.src).generate((128, 128)).get_output(), content_type='image/png' ) instance.r200 = SimpleUploadedFile( instance.src.name, Thumbnail.load(instance.src).generate((200, 200)).get_output(), content_type='image/png' ) if commit: instance.save() return instance

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  • How to pass operators as parameters

    - by Rodion Ingles
    I have to load an array of doubles from a file, multiply each element by a value in a table (different values for different elements), do some work on it, invert the multiplication (that is, divide) and then save the data back to file. Currently I implement the multiplication and division process in two separate methods. Now there is some extra work behind the scenes but apart from the specific statements where the multiplication/division occurs, the rest of the code is identical. As you can imagine, with this approach you have to be very careful making any changes. The surrounding code is not trivial, so its either a case of manually editing each method or copying changes from one method to the other and remembering to change the * and / operators. After too many close calls I am fed up of this and would like to make a common function which implements the common logic and two wrapper functions which pass which operator to use as a parameter. My initial approach was to use function pointers: MultiplyData(double data) { TransformData(data, &(operator *)); } DivideData(double data) { TransformData(data, &(operator /)); } TransformData(double data, double (*func)(double op1, double op2)) { /* Do stuff here... */ } However, I can't pass the operators as pointers (is this because it is an operator on a native type?), so I tried to use function objects. Initially I thought that multiplies and divides functors in <functional> would be ideal: MultiplyData(double data) { std::multiplies<double> multFunct; TransformData(data, &multFunct); } DivideData(double data) { std::divides<double> divFunct; TransformData(data, &divFunct); } TransformData(double data, std::binary_function<double, double, double> *funct) { /* Do stuff here... */ } As you can see I was trying to use a base class pointer to pass the functor polymorphically. The problem is that std::binary_function does not declare an operator() member for the child classes to implement. Is there something I am missing, or is the solution to implement my own functor heirarchy (which really seems more trouble than it is worth)?

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  • template pass by const reference

    - by 7vies
    Hi, I've looked over a few similar questions, but I'm still confused. I'm trying to figure out how to explicitly (not by compiler optimization etc) and C++03-compatible avoid copying of an object when passing it to a template function. Here is my test code: #include <iostream> using namespace std; struct C { C() { cout << "C()" << endl; } C(const C&) { cout << "C(C)" << endl; } ~C() { cout << "~C()" << endl; } }; template<class T> void f(T) { cout << "f<T>" << endl; } template<> void f(C c) { cout << "f<C>" << endl; } // (1) template<> void f(const C& c) { cout << "f<C&>" << endl; } // (2) int main() { C c; f(c); return 0; } (1) accepts the object of type C, and makes a copy. Here is the output: C() C(C) f<C> ~C() ~C() So I've tried to specialize with a const C& parameter (2) to avoid this, but this simply doesn't work (apparently the reason is explained in this question). Well, I could "pass by pointer", but that's kind of ugly. So is there some trick that would allow to do that somehow nicely? EDIT: Oh, probably I wasn't clear. I already have a templated function template<class T> void f(T) {...} But now I want to specialize this function to accept a const& to another object: template<> void f(const SpecificObject&) {...} But it only gets called if I define it as template<> void f(SpecificObject) {...}

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  • How to infer the type of a derived class in base class?

    - by enzi
    I want to create a method that allows me to change arbitrary properties of classes that derive from my base class, the result should look like this: SetPropertyValue("size.height", 50); – where size is a property of my derived class and height is a property of size. I'm almost done with my implementation but there's one final obstacle that I want to solve before moving on, to describe this I will first have to explain my implementation a bit: Properties that can be modified are decorated with an attribute There's a method in my base class that searches for all derived classes and their decorated properties For each property I generate a "property modifier", a class that contains 2 delegates: one to set and one to get the value of the property. Property Modifiers are stored in a dictionary, with the name of the property as key In my base class, there is another dictionary that contains all property-modifier-dictionaries, with the Type of the respective class as key. What the SetPropertyValue method does is this: Get the correct property-modifier-dictionary, using the concrete type of the derived class (<- yet to solve) Get the property modifier of the property to change (e.g. of the property size) Use the get or set delegate to modify the property's value Some example code to clarify further: private static Dictionary<RuntimeTypeHandle, object> EditableTypes; //property-modifier-dictionary protected void SetPropertyValue<T>(EditablePropertyMap<T> map, string property, object value) { var property = map[property]; // get the property modifier property.Set((T)this, value); // use the set delegate (encapsulated in a method) } In the above code, T is the Type of the actual (derived) class. I need this type for the get/set delegates. The problem is how to get the EditablePropertyMap<T> when I don't know what T is. My current (ugly) solution is to pass the map in an overriden virtual method in the derived class: public override void SetPropertyValue(string property, object value) { base.SetPropertyValue((EditablePropertyMap<ExampleType>)EditableTypes[typeof(ExampleType)], property, value); } What this does is: get the correct dictionary containing the property modifiers of this class using the class's type, cast it to the appropiate type and pass it to the SetPropertyValue method. I want to get rid of the SetPropertyValue method in my derived class (since there are a lot of derived classes), but don't know yet how to accomplish that. I cannot just make a virtual GetEditablePropertyMap<T> method because I cannot infer a concrete type for T then. I also cannot acces my dictionary directly with a type and retrieve an EditablePropertyMap<T> from it because I cannot cast to it from object in the base class, since again I do not know T. I found some neat tricks to infere types (e.g. by adding a dummy T parameter), but cannot apply them to my specific problem. I'd highly appreciate any suggestions you may have for me.

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  • Unable to read data from the transport connection: the connection was closed

    - by webdreamer
    The exception is Remoting Exception - Authentication Failure. The detailed message says "Unable to read data from the transport connection: the connection was closed." I'm having trouble with creating two simple servers that can comunicate as remote objects in C#. ServerInfo is just a class I created that holds the IP and Port and can give back the address. It works fine, as I used it before, and I've debugged it. Also the server is starting just fine, no exception is thrown, and the channel is registered without problems. I'm using Forms to do the interfaces, and call some of the methods on the server, but didn't find any problems in passing the parameters from the FormsApplication to the server when debugging. All seems fine in that chapter. public ChordServerProgram() { RemotingServices.Marshal(this, "PADIBook"); nodeInt = 0; } public void startServer() { try { serverChannel = new TcpChannel(serverInfo.Port); ChannelServices.RegisterChannel(serverChannel, true); } catch (Exception e) { Console.WriteLine(e.ToString()); } } I run two instances of this program. Then startNode is called on one of the instances of the application. The port is fine, the address generated is fine as well. As you can see, I'm using the IP for localhost, since this server is just for testing purposes. public void startNode(String portStr) { IPAddress address = IPAddress.Parse("127.0.0.1"); Int32 port = Int32.Parse(portStr); serverInfo = new ServerInfo(address, port); startServer(); //node = new ChordNode(serverInfo,this); } Then, in the other istance, through the interface again, I call another startNode method, giving it a seed server to get information from. This is where it goes wrong. When it calls the method on the seedServer proxy it just got, a RemotingException is thrown, due to an authentication failure. (The parameter I'll want to get is the node, I'm just using the int to make sure the ChordNode class has nothing to do with this error.) public void startNode(String portStr, String seedStr) { IPAddress address = IPAddress.Parse("127.0.0.1"); Int32 port = Int32.Parse(portStr); serverInfo = new ServerInfo(address, port); IPAddress addressSeed = IPAddress.Parse("127.0.0.1"); Int32 portSeed = Int32.Parse(seedStr); ServerInfo seedInfo = new ServerInfo(addressSeed, portSeed); startServer(); ChordServerProgram seedServer = (ChordServerProgram)Activator.GetObject(typeof(ChordServerProgram), seedInfo.GetFullAddress()); // node = new ChordNode(serverInfo,this); int seedNode = seedServer.nodeInt; // node.chordJoin(seedNode.self); }

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  • Use format strings that contain %1, %2 etc. instead of %d, %s etc. - Linux, C++

    - by rursw1
    Hello, As a follow-up of this question (Message compiler replacement in Linux gcc), I have the following problem: When using MC.exe on Windows for compiling and generating messages, within the C++ code I call FormatMessage, which retrieves the message and uses the va_list *Arguments parameter to send the varied message arguments. For example: messages.mc file: MessageId=1 Severity=Error SymbolicName=MULTIPLE_MESSAGE_OCCURED Language=English message %1 occured %2 times. . C++ code: void GetMsg(unsigned int errCode, wstring& message,unsigned int paramNumber, ...) { HLOCAL msg; DWORD ret; LANGID lang = GetUserDefaultLangID(); try { va_list argList; va_start( argList, paramNumber ); const TCHAR* dll = L"MyDll.dll"; _hModule = GetModuleHandle(dll); ret =::FormatMessage( FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_HMODULE|FORMAT_MESSAGE_IGNORE_INSERTS, _hModule, errCode, lang, (LPTSTR) &msg, 0, &argList ); if ( 0 != ret ) { unsigned int count = 0 ; message = msg; if (paramNumber>0) { wstring::const_iterator iter; for (iter = message.begin();iter!=message.end();iter++) { wchar_t xx = *iter; if (xx ==L'%') count++; } } if ((count == paramNumber) && (count >0)) { ::LocalFree( msg ); ret =::FormatMessage( FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_HMODULE, _hModule, errCode, GetUserDefaultLangID(), (LPTSTR) &msg, 0, &argList ); } else if (count != paramNumber) { wstringstream tmp; wstring messNumber; tmp << (errCode & 0xFFFF); tmp >> messNumber; message = message +L"("+ messNumber + L"). Bad Format String. "; } } ::LocalFree( msg ); } catch (...) { message << L"last error: " << GetLastError(); } va_end( argList ); } Caller code: wstring message; GetMsg(MULTIPLE_MESSAGE_OCCURED, message,2, "Error message", 5); Now, I wrote a simple script to generate a .msg file from the .mc file, and then I use gencat to generate a catalog from it. But is there a way to use the formatted strings as they contain %1, %2, etc. and NOT the general (%d, %s...) format? Please note, that the solution has to be generic enough for each possible message with each posible types\ arguments order... Is it possible at all? Thank you.

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  • SAX parser does not resolve filename

    - by phantom-99w
    Another day, another strange error with SAX, Java, and friends. I need to iterate over a list of File objects and pass them to a SAX parser. However, the parser fails because of an IOException. However, the various File object methods confirm that the file does indeed exist. The output which I get: 11:53:57.838 [MainThread] DEBUG DefaultReactionFinder - C:\project\trunk\application\config\reactions\TestReactions.xml 11:53:57.841 [MainThread] ERROR DefaultReactionFinder - C:\project\trunk\application\config\reactions\null (The system cannot find the file specified) So the problem is obviously that null in the second line. I've tried nearly all variations of passing the file as a parameter to the parser, including as a String (both from getAbsolutePath() and entered by hand), as a URI and, even more weirdly, as a FileInputStream (for this I get the same error, except that the entire relative path gets reported as null, so C:\project\trunk\null). All that I can think of is that the SAXParserFactory is incorrectly configured. I have no idea what is wrong, though. Here is the code concerned: SAXParserFactory factory = SAXParserFactory.newInstance(); factory.setValidating(true); try { parser = factory.newSAXParser(); } catch (ParserConfigurationException e) { throw new InstantiationException("Error configuring an XML parser. Given error message: \"" + e.getMessage() + "\"."); } catch (SAXException e) { throw new InstantiationException("Error creating a SAX parser. Given error message: \"" + e.getMessage() + "\"."); } ... for (File f : fileLister.getFileList()) { logger.debug(f.getAbsolutePath()); try { parser.parse(f, new ReactionHandler(input)); //FileInputStream fs = new FileInputStream(f); //parser.parse(fs, new ReactionHandler(input)); //fs.close(); } catch (IOException e) { logger.error(e.getMessage()); throw new ReactionNotFoundException("An error occurred processing file \"" + f + "\"."); } ... } I have made no special provisions to provide a custom SAX parser implementation: I use the system default. Any help would be greatly appreciated!

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  • Implementing default constructors

    - by James
    Implement the default constructor, the constructors with one and two int parameters. The one-parameter constructor should initialize the first member of the pair, the second member of the pair is to be 0. Overload binary operator + to add the pairs as follows: (a, b) + (c, d) = (a + c, b + d); Overload the - analogously. Overload the * on pairs ant int as follows: (a, b) * c = (a * c, b * c). Write a program to test all the member functions and overloaded operators in your class definition. You will also need to write accessor (get) functions for each member. The definition of the class Pairs: class Pairs { public: Pairs(); Pairs(int first, int second); Pairs(int first); // other members and friends friend istream& operator>> (istream&, Pair&); friend ostream& operator<< (ostream&, const Pair&); private: int f; int s; }; Self-Test Exercise #17: istream& operator (istream& ins, Pair& second) { char ch; ins ch; // discard init '(' ins second.f; ins ch; // discard comma ',' ins second.s; ins ch; // discard final '(' return ins; } ostream& operator<< (ostream& outs, const Pair& second) { outs << '('; outs << second.f; outs << ", " ;// I followed the Author's suggestion here. outs << second.s; outs << ")"; return outs; }

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  • Best approach for using Scanner Objects in Java?

    - by devjeetroy
    Although I'm more of a C++/ASM guy, I have to work with java as a part of my undergrad course at college. Our teacher taught us input using Scanner(System.in), and told us that if multiple functions are were taking user input, it would be advisable that a single Scanner object is passed around so as to reduce chances of the input stream getting screwed up. Now using this approach has gotten me into a situation where I'm trying to use a Scanner.nextLine(), and this statement does not wait for user input. It just moves on to the following statement. I figured there may be some residual cr/lf or other characters in the Scanner that might not have been retrieved are causing the problem. Here is the code. while(lineScanner.hasNext()) { if(isPlaceHolder(temp = lineScanner.next())) { temp = temp.replace("<",""); temp = temp.replace(">", ""); System.out.print("Enter "+aOrA(temp.charAt(0)) +" " +temp + " : "); temp = consoleInput.nextLine(); } outputFileStream.print(temp + " "); } All of the code is inside a function which receives a Scanner object consoleInput. Ok, so what happens when i run it is that when the program enters the if() the first time, It carries out theSystem.out.print, does not wait for user input, and moves on to the second time that it enters the 'if' block. This time, it takes the input and the rest of the program operates normally. What is even more surprising is that when i check the output file created by the program, it is perfect, just as i want to be. Almost as if the first time input using the scanner is correct. I have solved this problem by creating a new system.in Scanner in the function itself, instead of receiving the Scanner object as a parameter. But I am still very curious to know what the hell is happening and why it couldn't be solved using a simple Scanner.reset(). Would it be better to just simply create a Scanner Object for each function? Thanks, Devjeet PS. Although I know how to take input using fileinputstreams and the like, we are not supposed to use it with the homework.

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  • Jumping into argv?

    - by jth
    Hi, I`am experimenting with shellcode and stumbled upon the nop-slide technique. I wrote a little tool that takes buffer-size as a parameter and constructs a buffer like this: [ NOP | SC | RET ], with NOP taking half of the buffer, followed by the shellcode and the rest filled with the (guessed) return address. Its very similar to the tool aleph1 described in his famous paper. My vulnerable test-app is the same as in his paper: int main(int argc, char **argv) { char little_array[512]; if(argc>1) strcpy(little_array,argv[1]); return 0; } I tested it and well, it works: jth@insecure:~/no_nx_no_aslr$ ./victim $(./exploit 604 0) $ exit But honestly, I have no idea why. Okay, the saved eip was overwritten as intended, but instead of jumping somewhere into the buffer, it jumped into argv, I think. gdb showed up the following addresses before strcpy() was called: (gdb) i f Stack level 0, frame at 0xbffff1f0: eip = 0x80483ed in main (victim.c:7); saved eip 0x154b56 source language c. Arglist at 0xbffff1e8, args: argc=2, argv=0xbffff294 Locals at 0xbffff1e8, Previous frame's sp is 0xbffff1f0 Saved registers: ebp at 0xbffff1e8, eip at 0xbffff1ec Address of little_array: (gdb) print &little_array[0] $1 = 0xbfffefe8 "\020" After strcpy(): (gdb) i f Stack level 0, frame at 0xbffff1f0: eip = 0x804840d in main (victim.c:10); saved eip 0xbffff458 source language c. Arglist at 0xbffff1e8, args: argc=-1073744808, argv=0xbffff458 Locals at 0xbffff1e8, Previous frame's sp is 0xbffff1f0 Saved registers: ebp at 0xbffff1e8, eip at 0xbffff1ec So, what happened here? I used a 604 byte buffer to overflow little_array, so he certainly overwrote saved ebp, saved eip and argc and also argv with the guessed address 0xbffff458. Then, after returning, EIP pointed at 0xbffff458. But little_buffer resides at 0xbfffefe8, that`s a difference of 1136 byte, so he certainly isn't executing little_array. I followed execution with the stepi command and well, at 0xbffff458 and onwards, he executes NOPs and reaches the shellcode. I'am not quite sure why this is happening. First of all, am I correct that he executes my shellcode in argv, not little_array? And where does the loader(?) place argv onto the stack? I thought it follows immediately after argc, but between argc and 0xbffff458, there is a gap of 620 bytes. How is it possible that he successfully "lands" in the NOP-Pad at Address 0xbffff458, which is way above the saved eip at 0xbffff1ec? Can someone clarify this? I have actually no idea why this is working. My test-machine is an Ubuntu 9.10 32-Bit Machine without ASLR. victim has an executable stack, set with execstack -s. Thanks in advance.

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  • Changing RGB color image to Grayscale image using Objective C

    - by user567167
    I was developing a application that changes color image to gray image. However, some how the picture comes out wrong. I dont know what is wrong with the code. maybe the parameter that i put in is wrong please help. UIImage *c = [UIImage imageNamed:@"downRed.png"]; CGImageRef cRef = CGImageRetain(c.CGImage); NSData* pixelData = (NSData*) CGDataProviderCopyData(CGImageGetDataProvider(cRef)); size_t w = CGImageGetWidth(cRef); size_t h = CGImageGetHeight(cRef); unsigned char* pixelBytes = (unsigned char *)[pixelData bytes]; unsigned char* greyPixelData = (unsigned char*) malloc(w*h); for (int y = 0; y < h; y++) { for(int x = 0; x < w; x++){ int iter = 4*(w*y+x); int red = pixe lBytes[iter]; int green = pixelBytes[iter+1]; int blue = pixelBytes[iter+2]; greyPixelData[w*y+x] = (unsigned char)(red*0.3 + green*0.59+ blue*0.11); int value = greyPixelData[w*y+x]; } } CFDataRef imgData = CFDataCreate(NULL, greyPixelData, w*h); CGDataProviderRef imgDataProvider = CGDataProviderCreateWithCFData(imgData); size_t width = CGImageGetWidth(cRef); size_t height = CGImageGetHeight(cRef); size_t bitsPerComponent = 8; size_t bitsPerPixel = 8; size_t bytesPerRow = CGImageGetWidth(cRef); CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceGray(); CGBitmapInfo info = kCGImageAlphaNone; CGFloat *decode = NULL; BOOL shouldInteroplate = NO; CGColorRenderingIntent intent = kCGRenderingIntentDefault; CGDataProviderRelease(imgDataProvider); CGImageRef throughCGImage = CGImageCreate(width, height, bitsPerComponent, bitsPerPixel, bytesPerRow, colorSpace, info, imgDataProvider, decode, shouldInteroplate, intent); UIImage* newImage = [UIImage imageWithCGImage:throughCGImage]; CGImageRelease(throughCGImage); newImageView.image = newImage;

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  • What web platform is right for me?

    - by egervari
    I've been looking at web frameworks like Rails, Grails, etc. I'm used to doing applications in Spring Framework with Hibernate... and I want something more productive. One of the things I realized is that while some of the things in Grails is sexy, there are some serious problems with it. Grails' controllers: 1) are implemented awfully. They don't seem to be able to extend from super classes at runtime. I tried this to add base actions and helper methods, and this seems to cause grails to blow up. 2) are based on an obsolete request parameters model (rather than form backing objects, which are much nicer). 3) are hard to test. Command objects are treated totally differently... and it's actually MUCH harder to write the test than it is to write the controller code. 4) Command objects operate totally differently. They are pre-validated and bound, which causes a lot of inconsistencies than basic parameter model. 5) Command objects are not reusable, and it's a pain in the rear to reuse most of the stuff from the domain classes, like constraints and fields. This is TRIVIAL to do in basic Spring. Why the hell was it not trivial to do in Grails? 6) The scaffolding that is generated is pure crap. It doesn't generalize inserts and updates... and it actually copy/pastes a pile of code in two views: create.gsp and edit.gsp. The views themselves are gargantuan piles of doggie do-do. This is further compounded by the fact that it uses low-level parameters and not objects. Integration tests are 30x slower than a Spring integration test. It is disgusting. Some mocking tests are so hard to write and aren't guaranteed to work when it's deployed, that I think it discourages fast, tdd test cycles. Most things seem to screw up grails while it's running, like adding a taglib, or anything really. The server restart problem wasn't solved at all. I'm starting to think going with Spring/Hibernate/Java is the only way to go. While there is a pretty big cost at startup, I know it'll eventually smooth out. It sucks I can't use a language like Scala... because idiomatically, it is so incompatible with Hibernate. This app is also not a run-of-the-mill UI over a database. It's got some of that, but it's not going to be a slouch. I am deathly scared of Grails now because of how crap it is in the Controller layer. Suggestions on what I can do?

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  • How can i maintain last cookie value in flex with jsp?

    - by praveen
    Hi All, my login form in flex when I login I have created a cookie in jsp like this name setValueCookie.jsp <%@ page language="java" import="java.util.* , javax.net.*" contentType="text/html; charset=ISO-8859-1" pageEncoding="ISO-8859-1"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <% String username = request.getParameter("value"); System.out.println("Email got in cookieSet = " + username); if(username==null) username=""; Date now = new Date(); String timestamp = now.toString(); Cookie cookie = new Cookie("username",username); cookie.setMaxAge(365 * 24 * 60 * 60); response.addCookie(cookie); %> <head> <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> <title>DashBoard-Cookie</title> </head> <body> </body> </html> now using Http service request parameter i am passing username 'Value' to this jsp. and i am reading cookie value from getValueCookie.jsp like this <% String cookieName = "username"; Cookie cookies [] = request.getCookies (); Cookie myCookie = null; String result; if (cookies != null) { for (int i = 0; i < cookies.length; i++) { if (cookies [i].getName().equals (cookieName)) { myCookie = cookies[i]; break; } } } %> <data> <status><%=myCookie.getValue().toString()%></status> </data> through the httpservice value i am getting but if i open a new window or any new tab cookie value is not getting how can i solve this? Thanks in advance.

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  • Is order of parameters for database Command object really important?

    - by nawfal
    I was debugging a database operation code and I found that proper UPDATE was never happening though the code never failed as such. This is the code: condb.Open(); OleDbCommand dbcom = new OleDbCommand("UPDATE Word SET word=?,sentence=?,mp3=? WHERE id=? AND exercise_id=?", condb); dbcom.Parameters.AddWithValue("id", wd.ID); dbcom.Parameters.AddWithValue("exercise_id", wd.ExID); dbcom.Parameters.AddWithValue("word", wd.Name); dbcom.Parameters.AddWithValue("sentence", wd.Sentence); dbcom.Parameters.AddWithValue("mp3", wd.Mp3); But after some tweaking this worked: condb.Open(); OleDbCommand dbcom = new OleDbCommand("UPDATE Word SET word=?,sentence=?,mp3=? WHERE id=? AND exercise_id=?", condb); dbcom.Parameters.AddWithValue("word", wd.Name); dbcom.Parameters.AddWithValue("sentence", wd.Sentence); dbcom.Parameters.AddWithValue("mp3", wd.Mp3); dbcom.Parameters.AddWithValue("id", wd.ID); dbcom.Parameters.AddWithValue("exercise_id", wd.ExID); Why is it so important that the parameters in WHERE clause has to be given the last in case of OleDb connection? Having worked with MySQL previously, I could (and usually do) write parameters of WHERE clause first because that's more logical to me. Is parameter order important when querying database in general? Some performance concern or something? Is there a specific order to be maintained in case of other databases like DB2, Sqlite etc? Update: I got rid of ? and included proper names with and without @. The order is really important. In both cases only when WHERE clause parameters was mentioned last, actual update happened. To make matter worse, in complex queries, its hard to know ourselves which order is Access expecting, and in all situations where order is changed, the query doesnt do its intended duty with no warning/error!!

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  • How does System.TraceListener prepend message with process name?

    - by btlog
    I have been looking at using System.Diagnostics.Trace for doing logging is a very basic app. Generally it does all I need it to do. The downside is that if I call Trace.TraceInformation("Some info"); The output is "SomeApp.Exe Information: 0: Some info". Initally this entertained me but no longer. I would like to just output "Some info" to console. So I thought writing a cusom TraceListener, rather than using the inbuilt ConsoleTraceListener, would solve the problem. I can see a specific format that I want all the text after the second colon. Here is my attempt to see if this would work. class LogTraceListener : TraceListener { public override void Write(string message) { int firstColon = message.IndexOf(":"); int secondColon = message.IndexOf(":", firstColon + 1); Console.Write(message); } public override void WriteLine(string message) { int firstColon = message.IndexOf(":"); int secondColon = message.IndexOf(":", firstColon + 1); Console.WriteLine(message); } } If I output the value of firstColon it is always -1. If I put a break point the message is always just "Some info". Where does all the other information come from? So I had a look at the call stack at the point just before Console.WriteLine was called. The method that called my WriteLine method is: System.dll!System.Diagnostics.TraceListener.TraceEvent(System.Diagnostics.TraceEventCache eventCache, string source, System.Diagnostics.TraceEventType eventType, int id, string message) + 0x33 bytes When I use Reflector to look at this message it all seems pretty straight forward. I can't see any code that changes the value of the string after I have sent it to Console.WriteLine. The only method that could posibly change the underlying string value is a call to UnsafeNativeMethods.EventWriteString which has a parameter that is a pointer to the message. Does anyone understand what is going on here and whether I can change the output to be just my message with out the additional fluff. It seems like evil magic that I can pass a string "Some info" to Console.WriteLine (or any other method for that matter) and the string that output is different.

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  • Java exercise - display table with 2d array

    - by TheHacker66
    I'm struggling to finish a java exercise, it involves using 2d arrays to dinamically create and display a table based on a command line parameter. Example: java table 5 +-+-+-+-+-+ |1|2|3|4|5| +-+-+-+-+-+ |2|3|4|5|1| +-+-+-+-+-+ |3|4|5|1|2| +-+-+-+-+-+ |4|5|1|2|3| +-+-+-+-+-+ |5|1|2|3|4| +-+-+-+-+-+ What i have done so far: public static void main(String[] args) { int num = Integer.parseInt(args[0]); String[][] table = new String[num*2+1][num]; int[] numbers = new int[num]; int temp = 0; for(int i=0; i<numbers.length; i++) numbers[i] = i+1; // wrong for(int i=0; i<table.length; i++){ for(int j=0; j<num;j++){ if(i%2!=0){ temp=numbers[0]; for(int k=1; k<numbers.length; k++){ numbers[k-1]=numbers[k]; } numbers[numbers.length-1]=temp; for(int l=0; l<numbers.length; l++){ table[i][j] = "|"+numbers[l]; } } else table[i][j] = "+-"; } } for(int i=0; i<table.length; i++){ for(int j=0; j<num; j++) System.out.print(table[i][j]); if(i%2==0) System.out.print("+"); else System.out.print("|"); System.out.println();} } This doesn't work, since it prints 1|2|3|4 in every row, which isn't what i need. I found the issue, and it's because the first for loop changes the array order more times than needed and basically it returns as it was at the beginning. I know that probably there's a way to achieve this by writing more code, but i always tend to nest as much as possible to "optimize" the code while i write it, so that's why i tried solving this exercise by using less variables and loops as possible. Thanks in advance for your help!

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  • Where are the function literals c++?

    - by academicRobot
    First of all, maybe literals is not the right term for this concept, but its the closest I could think of (not literals in the sense of functions as first class citizens). The idea is that when you make a conventional function call, it compiles to something like this: callq <immediate address> But if you make a function call using a function pointer, it compiles to something like this: mov <memory location>,%rax callq *%rax Which is all well and good. However, what if I'm writing a template library that requires a callback of some sort with a specified argument list and the user of the library is expected to know what function they want to call at compile time? Then I would like to write my template to accept a function literal as a template parameter. So, similar to template <int int_literal> struct my_template {...};` I'd like to write template <func_literal_t func_literal> struct my_template {...}; and have calls to func_literal within my_template compile to callq <immediate address>. Is there a facility in C++ for this, or a work around to achieve the same effect? If not, why not (e.g. some cataclysmic side effects)? How about C++0x or another language? Solutions that are not portable are fine. Solutions that include the use of member function pointers would be ideal. I'm not particularly interested in being told "You are a <socially unacceptable term for a person of low IQ>, just use function pointers/functors." This is a curiosity based question, and it seems that it might be useful in some (albeit limited) applications. It seems like this should be possible since function names are just placeholders for a (relative) memory address, so why not allow more liberal use (e.g. aliasing) of this placeholder. p.s. I use function pointers and functions objects all the the time and they are great. But this post got me thinking about the don't pay for what you don't use principle in relation to function calls, and it seems like forcing the use of function pointers or similar facility when the function is known at compile time is a violation of this principle, though a small one.

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  • Defining a select list through controller and view model

    - by Ibrar Hussain
    I have a View Model that looks like this: public class SomeViewModel { public SomeViewModel(IEnumerable<SelectListItem> orderTemplatesListItems) { OrderTemplateListItems = orderTemplatesListItems; } public IEnumerable<SelectListItem> OrderTemplateListItems { get; set; } } I then have an Action in my Controller that does this: public ActionResult Index() { var items = _repository.GetTemplates(); var selectList = items.Select(i => new SelectListItem { Text = i.Name, Value = i.Id.ToString() }).ToList(); var viewModel = new SomeViewModel { OrderTemplateListItems = selectList }; return View(viewModel); } Lastly my view: @Html.DropDownListFor(n => n.OrderTemplateListItems, new SelectList(Model.OrderTemplateListItems, "value", "text"), "Please select an order template") The code works fine and my select list populates wonderfully. Next thing I need to do is set the selected value that will come from a Session["orderTemplateId"] which is set when the user selects a particular option from the list. Now after looking online the fourth parameter should allow me to set a selected value, so if I do this: @Html.DropDownListFor(n => n.OrderTemplateListItems, new SelectList(Model.OrderTemplateListItems, "value", "text", 56), "Please select an order template") 56 is the Id of the item that I want selected, but to no avail. I then thought why not do it in the Controller? As a final attempt I tried building up my select list items in my Controller and then passing the items into the View: public ActionResult Index() { var items = _repository.GetTemplates(); var orderTemplatesList = new List<SelectListItem>(); foreach (var item in items) { if (Session["orderTemplateId"] != null) { if (item.Id.ToString() == Session["orderTemplateId"].ToString()) { orderTemplatesList.Add(new SelectListItem { Text = item.Name, Value = item.Id.ToString(), Selected = true }); } else { orderTemplatesList.Add(new SelectListItem { Text = item.Name, Value = item.Id.ToString() }); } } else { orderTemplatesList.Add(new SelectListItem { Text = item.Name, Value = item.Id.ToString() }); } } var viewModel = new SomeViewModel { OrderTemplateListItems = orderTemplatesList }; return View(viewModel); } Leaving my View like so: @Html.DropDownListFor(n => n.OrderTemplateListItems, new SelectList(Model.OrderTemplateListItems, "value", "text"), "Please select an order template") Nothing! Why isn't this working for me?

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  • JavaScript - Inheritance in Constructors

    - by j0ker
    For a JavaScript project we want to introduce object inheritance to decrease code duplication. However, I cannot quite get it working the way I want and need some help. We use the module pattern. Suppose there is a super element: a.namespace('a.elements.Element'); a.elements.Element = (function() { // public API -- constructor Element = function(properties) { this.id = properties.id; }; // public API -- prototype Element.prototype = { getID: function() { return this.id; } }; return Element; }()); And an element inheriting from this super element: a.namespace('a.elements.SubElement'); a.elements.SubElement = (function() { // public API -- constructor SubElement = function(properties) { // inheritance happens here // ??? this.color = properties.color; this.bogus = this.id + 1; }; // public API -- prototype SubElement.prototype = { getColor: function() { return this.color; } }; return SubElement; }()); You will notice that I'm not quite sure how to implement the inheritance itself. In the constructor I have to be able to pass the parameter to the super object constructor and create a super element that is then used to create the inherited one. I need a (comfortable) possibility to access the properties of the super object within the constructor of the new object. Ideally I could operate on the super object as if it was part of the new object. I also want to be able to create a new SubElement and call getID() on it. What I want to accomplish seems like the traditional class based inheritance. However, I'd like to do it using prototypal inheritance since that's the JavaScript way. Is that even doable? Thanks in advance! EDIT: Fixed usage of private variables as suggested in the comments. EDIT2: Another change of the code: It's important that id is accessible from the constructor of SubElement.

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  • Delphi / MySql : Problems escpaing strings

    - by mawg
    N00b here, having problems escaping strings. I used the QuotedStr() function - shouldn't that be enough. Unfortunately, the string that I am trying to quote is rather messy, but I will post it here in case anyone wants to paste it into WinMerge or KDiff3, etc. I am trying to store an entire Delphi form into the database, rather than into a .DFM file. It has only one field, a TEdit edit box. The debugger shows the form as text as 'object Form1: TScriptForm'#$D#$A' Left = 0'#$D#$A' Top = 0'#$D#$A' Align = alClient'#$D#$A' BorderStyle = bsNone'#$D#$A' ClientHeight = 517'#$D#$A' ClientWidth = 993'#$D#$A' Color = clBtnFace'#$D#$A' Font.Charset = DEFAULT_CHARSET'#$D#$A' Font.Color = clWindowText'#$D#$A' Font.Height = -11'#$D#$A' Font.Name = 'MS Sans Serif''#$D#$A' Font.Style = []'#$D#$A' OldCreateOrder = False'#$D#$A' SaveProps.Strings = ('#$D#$A' 'Visible=False')'#$D#$A' PixelsPerInch = 96'#$D#$A' TextHeight = 13'#$D#$A' object Edit1: TEdit'#$D#$A' Left = 192'#$D#$A' Top = 64'#$D#$A' Width = 121'#$D#$A' Height = 21'#$D#$A' TabOrder = 8'#$D#$A' end'#$D#$A'end'#$D#$A before calling QuotedStr() and ''object Form1: TScriptForm'#$D#$A' Left = 0'#$D#$A' Top = 0'#$D#$A' Align = alClient'#$D#$A' BorderStyle = bsNone'#$D#$A' ClientHeight = 517'#$D#$A' ClientWidth = 993'#$D#$A' Color = clBtnFace'#$D#$A' Font.Charset = DEFAULT_CHARSET'#$D#$A' Font.Color = clWindowText'#$D#$A' Font.Height = -11'#$D#$A' Font.Name = ''MS Sans Serif'''#$D#$A' Font.Style = []'#$D#$A' OldCreateOrder = False'#$D#$A' SaveProps.Strings = ('#$D#$A' ''Visible=False'')'#$D#$A' PixelsPerInch = 96'#$D#$A' TextHeight = 13'#$D#$A' object Edit1: TEdit'#$D#$A' Left = 192'#$D#$A' Top = 64'#$D#$A' Width = 121'#$D#$A' Height = 21'#$D#$A' TabOrder = 8'#$D#$A' end'#$D#$A'end'#$D#$A''' afterwards. The strange thing is that my complete command 'INSERT INTO designerFormDfm(designerFormDfmText) VALUES ("'object Form1: TScriptForm'#$D#$A' Left = 0'#$D#$A' Top = 0'#$D#$A' Align = alClient'#$D#$A' BorderStyle = bsNone'#$D#$A' ClientHeight = 517'#$D#$A' ClientWidth = 993'#$D#$A' Color = clBtnFace'#$D#$A' Font.Charset = DEFAULT_CHARSET'#$D#$A' Font.Color = clWindowText'#$D#$A' Font.Height = -11'#$D#$A' Font.Name = ''MS Sans Serif'''#$D#$A' Font.Style = []'#$D#$A' OldCreateOrder = False'#$D#$A' SaveProps.Strings = ('#$D#$A' ''Visible=False'')'#$D#$A' PixelsPerInch = 96'#$D#$A' TextHeight = 13'#$D#$A' object Edit1: TEdit'#$D#$A' Left = 192'#$D#$A' Top = 64'#$D#$A' Width = 121'#$D#$A' Height = 21'#$D#$A' TabOrder = 8'#$D#$A' end'#$D#$A'end'#$D#$A''");' executes in a MySql console, but not from Delphi, where I pass that command as parameter command to a function which ADOCommand.CommandText := command; ADOCommand.CommandType := cmdText; ADOCommand.Execute(); I can only assume that I am having problems escpaing sequences which contain single quotes (and QuotedStr() doesn't seem to escape backslahes(?!)) What am I doing that is obviously, glaringly wrong?

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  • Should we use temporary variables for the returned values of functions?

    - by totymedli
    I thought about this: Is there a performance difference in these two practices: Store the return value of a function in a temporary variable than give that variable as a parameter to another function. Put the function into the other function. Specification Assuming all classes and functions are written correctly. Case 1. ClassA a = function1(); ClassB b = function2(a); function3(b); Case 2. function3(function2(function1())); I know there aren't a big difference with only one run, but supposed that we could run this a lot of times in a loop, I created some tests. Test #include <iostream> #include <ctime> #include <math.h> using namespace std; int main() { clock_t start = clock(); clock_t ends = clock(); // Case 1. start = clock(); for (int i=0; i<10000000; i++) { double a = cos(1); double b = pow(a, 2); sqrt(b); } ends = clock(); cout << (double) (ends - start) / CLOCKS_PER_SEC << endl; // Case 2. start = clock(); for (int i=0; i<10000000; i++) sqrt(pow(cos(1),2)); ends = clock(); cout << (double) (ends - start) / CLOCKS_PER_SEC << endl; return 0; } Results Case 1 = 6.375 Case 2 = 0.031 Why is the first one is much slower, and if the second one is faster why dont we always write code that way? Anyway does the second pratice has a name? I also wondered what happens if I create the variables outside the for loop in the first case, but the result was the same. Why?

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  • Binding on a port with netpipes/netcat

    - by mindas
    I am trying to write a simple bash script that is listening on a port and responding with a trivial HTTP response. My specific issue is that I am not sure if the port is available and in case of bind failure I fall back to next port until bind succeeds. So far to me the easiest way to achieve this was something like: for (( i=$PORT_BASE; i < $(($PORT_BASE+$PORT_RANGE)); i++ )) do if [ $DEBUG -eq 1 ] ; then echo trying to bind on $i fi /usr/bin/faucet $i --out --daemon echo test 2>/dev/null if [ $? -eq 0 ] ; then #success? port=$i if [ $DEBUG -eq 1 ] ; then echo "bound on port $port" fi break fi done Here I am using faucet from netpipes Ubuntu package. The problem with this is that if I simply print "test" to the output, curl complains about non-standard HTTP response (error code 18). That's fair enough as I don't print HTTP-compatible response. If I replace echo test with echo -ne "HTTP/1.0 200 OK\r\n\r\ntest", curl still complains: user@server:$ faucet 10020 --out --daemon echo -ne "HTTP/1.0 200 OK\r\n\r\ntest" ... user@client:$ curl ip.of.the.server:10020 curl: (56) Failure when receiving data from the peer I think the problem lies in how faucet is printing the response and handling the connection. For example if I do the server side in netcat, curl works fine: user@server:$ echo -ne "HTTP/1.0 200 OK\r\n\r\ntest\r\n" | nc -l 10020 ... user@client:$ curl ip.of.the.server:10020 test user@client:$ I would be more than happy to replace faucet with netcat in my main script, but the problem is that I want to spawn independent server process to be able to run client from the same base shell. faucet has a very handy --daemon parameter as it forks to background and I can use $? (exit status code) to check if bind succeeded. If I was to use netcat for a similar purpose, I would have to fork it using & and $? would not work. Does anybody know why faucet isn't responding correctly in this particular case and/or can suggest a solution to this problem. I am not married neither to faucet nor netcat but would like the solution to be implemented using bash or it's utilities (as opposed to write something in yet another scripting language, such as Perl or Python).

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  • Derived template override return type of member function C++

    - by Ruud v A
    I am writing matrix classes. Take a look at this definition: template <typename T, unsigned int dimension_x, unsigned int dimension_y> class generic_matrix { ... generic_matrix<T, dimension_x - 1, dimension_y - 1> minor(unsigned int x, unsigned int y) const { ... } ... } template <typename T, unsigned int dimension> class generic_square_matrix : public generic_matrix<T, dimension, dimension> { ... generic_square_matrix(const generic_matrix<T, dimension, dimension>& other) { ... } ... void foo(); } The generic_square_matrix class provides additional functions like matrix multiplication. Doing this is no problem: generic_square_matrix<T, 4> m = generic_matrix<T, 4, 4>(); It is possible to assign any square matrix to M, even though the type is not generic_square_matrix, due to the constructor. This is possible because the data does not change across children, only the supported functions. This is also possible: generic_square_matrix<T, 4> m = generic_square_matrix<T, 5>().minor(1,1); Same conversion applies here. But now comes the problem: generic_square_matrix<T, 4>().minor(1,1).foo(); //problem, foo is not in generic_matrix<T, 3, 3> To solve this I would like generic_square_matrix::minor to return a generic_square_matrix instead of a generic_matrix. The only possible way to do this, I think is to use template specialisation. But since a specialisation is basically treated like a separate class, I have to redefine all functions. I cannot call the function of the non-specialised class as you would do with a derived class, so I have to copy the entire function. This is not a very nice generic-programming solution, and a lot of work. C++ almost has a solution for my problem: a virtual function of a derived class, can return a pointer or reference to a different class than the base class returns, if this class is derived from the class that the base class returns. generic_square_matrix is derived from generic_matrix, but the function does not return a pointer nor reference, so this doesn't apply here. Is there a solution to this problem (possibly involving an entirely other structure; my only requirements are that the dimensions are a template parameter and that square matrices can have additional functionality). Thanks in advance, Ruud

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