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  • C: Proper syntax for allocating memory using pointers to pointers.

    - by ~kero-05h
    This is my first time posting here, hopefully I will not make a fool of myself. I am trying to use a function to allocate memory to a pointer, copy text to the buffer, and then change a character. I keep getting a segfault and have tried looking up the answer, my syntax is probably wrong, I could use some enlightenment. /* My objective is to pass a buffer to my Copy function, allocate room, and copy text to it. Then I want to modify the text and print it.*/ #include <stdio.h> #include <stdlib.h> #include <string.h> int Copy(char **Buffer, char *Text); int main() { char *Text = malloc(sizeof(char) * 100); char *Buffer; strncpy(Text, "1234567890\n", 100); Copy(&Buffer, Text); } int Copy(char **Buffer, char *Text) { int count; count = strlen(Text)+1; *Buffer = malloc(sizeof(char) * count); strncpy(*Buffer, Text, 5); *Buffer[2] = 'A'; /* This results in a segfault. "*Buffer[1] = 'A';" results in no differece in the output. */ printf("%s\n", *Buffer); }

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  • Raphael.js map default fill colors

    - by RIDER
    I am trying to familiarize myself with raphael.js. I want to create a USA map that already has default colors for each state and those colors stay there. Here is what I came up with. If you look at AK, I'm getting the default color loaded, but if I highlight another state, the default color for AK disappears. I want AK - and other states - to stay the same color. Specifically, I don't know what is clearing out my AK full color. I think part of this statement is clearing out the fill cover when I mouseover a different state: for (var state in aus) { //aus[state].color = Raphael.getColor(); (function (st, state) { st[0].style.cursor = "pointer"; st[0].onmouseover = function () { current && aus[current].animate({fill: "#333", stroke: "#666"}, 500) && (document.getElementById(current).style.display = ""); st.animate({fill: st.color, stroke: "#ccc"}, 500); st.toFront(); R.safari(); document.getElementById(state).style.display = "block"; current = state; }; })(aus[state], state); } Any ideas where I might be going wrong?

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  • Screen capture doesn't work on MFC application in Vista

    - by David Thornley
    We've got some in-house applications built in MFC, with OpenGL drawing routines. They all use the same code to draw on the screen and either print the screen or save it to a JPEG file. Everything's been working fine in Windows XP, and I need to find a way to make them work on Vista. In three of our applications, everything works. In the remaining one, I can get the window border, title bar, menus, and task bar, but the interior never shows up. As I said, these applications use the exact same code to write to the screen and capture the window image, and the only difference I see that looks like it might be relevant is that the problem application uses the MFC multiple document interface, while the ones that work use the single document interface. Either the answer isn't on the net, or I'm worse at Googling than I thought. I asked on the MSDN forums, and the only practical suggestion I got was to use GDI+ rather than GDI, and that did nothing different. I have tried different things with every part of the code that captures and prints or save, given a pointer to the window, so apparently it's a matter of the window itself. I haven't rebuilt the offending application using SDI yet, and I really don't have any other ideas. Has anybody seen anything like this?

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  • Serializing QGraphicsScene contents

    - by Rob
    I am using the Qt QGraphicsScene class, adding pre-defined items such as QGraphicsRectItem, QGraphicsLineItem, etc. and I want to serialize the scene contents to disk. However, the base QGraphicsItem class (that the other items I use derive from) doesn't support serialization so I need to roll my own code. The problem is that all access to these objects is via a base QGraphicsItem pointer, so the serialization code I have is horrible: QGraphicsScene* scene = new QGraphicsScene; scene->addRect(QRectF(0, 0, 100, 100)); scene->addLine(QLineF(0, 0, 100, 100)); ... QList<QGraphicsItem*> list = scene->items(); foreach (QGraphicsItem* item, items) { if (item->type() == QGraphicsRectItem::Type) { QGraphicsRectItem* rect = qgraphicsitem_cast<QGraphicsRectItem*>(item); // Access QGraphicsRectItem members here } else if (item->type() == QGraphicsLineItem::Type) { QGraphicsLineItem* line = qgraphicsitem_cast<QGraphicsLineItem*>(item); // Access QGraphicsLineItem members here } ... } This is not good code IMHO. So, instead I could create an ABC class like this: class Item { public: virtual void serialize(QDataStream& strm, int version) = 0; }; class Rect : public QGraphicsRectItem, public Item { public: void serialize(QDataStream& strm, int version) { // Serialize this object } ... }; I can then add Rect objects using QGraphicsScene::addItem(new Rect(,,,)); But this doesn't really help me as the following will crash: QList<QGraphicsItem*> list = scene->items(); foreach (QGraphicsItem* item, items) { Item* myitem = reinterpret_class<Item*>(item); myitem->serialize(...) // FAIL } Any way I can make this work?

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  • Submit button not focused even though tabindex is properly set

    - by Nicsoft
    Hello, I have defined tabindex for the input fields in a form. When tabbing through the input fields the submit button is never getting the focus, some other input fields in a different form on the page gets the focus. Those are all having tabindexes higher than 3. How come? <form action="subscription.php" name="subscribe" method="post" onsubmit="return isValidEmailAndEqual()"> <p id="formlabel">E-mail</p> <input type="text" name="email1" tabindex=1> <br/> <p id="formlabel">Repeat e-mail</p> <input type="text" name="email2" tabindex=2> <br/> <input id="inputsubmit" type="submit" value="Subscribe" tabindex=3> </form> .css: input { background-color : #333; border: 1px solid #EEE; color: #EEE; margin-bottom: 6px; margin-top: 4px; padding: 1px; width : 200px; } #inputsubmit { background-color : #d7e6f1; border: 1px solid #EEE; color: #0000ff; margin-bottom: 6px; margin-top: 4px; padding: 1px; width : 200px; } #inputsubmit:hover { cursor: pointer; cursor: hand; background-color : #d7e6f1; border: 1px solid #0000ff; color: #0000ff; margin-bottom: 6px; margin-top: 4px; padding: 1px; width : 200px; } p#formlabel{ width: 100; } Thanks in advance!

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  • Safe to pass objects to C functions when working in JNI Invocation API?

    - by bubbadoughball
    I am coding up something using the JNI Invocation API. A C program starts up a JVM and makes calls into it. The JNIenv pointer is global to the C file. I have numerous C functions which need to perform the same operation on a given class of jobject. So I wrote helper functions which take a jobject and process it, returning the needed data (a C data type...for example, an int status value). Is it safe to write C helper functions and pass jobjects to them as arguments? i.e. (a simple example - designed to illustrate the question): int getStatusValue(jobject jStatus) { return (*jenv)->CallIntMethod(jenv,jStatus,statusMethod); } int function1() { int status; jobject aObj = (*jenv)->NewObject (jenv, aDefinedClass, aDefinedCtor); jobject j = (*jenv)->CallObjectMethod (jenv, aObj, aDefinedObjGetMethod) status = getStatusValue(j); (*jenv)->DeleteLocalRef(jenv,aObj); (*jenv)->DeleteLocalRef(jenv,j); return status; } Thanks.

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  • Closing the gap between 2 inline elements

    - by insanepaul
    I have a simple div element that contains 2 inline tags. I've associated a onmouseout event to the div element. The problem is that the onmouseout event is fired when the user hovers their mouse between the two tags in the div and also after the end of the second tag. What I want to do is allow the user to hover their mouse across the whole of the div tag and only fire the onmouseout event when the mouse pointer is outside the div element (which is what I assumed from what I've done). I increased padding to close the gap between the 2 tags. This works but where they meet in IE7 at least the event is fired!!! I must be doing something wrong can someone please help. <div id="Div1" onmouseover="hideDiv()"> <a id="A1" href="HTMLNew.htm">ARTICLES</a> <a id="A2" href="HTMLNew.htm">COURSES & CASES</a> </div>

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  • Problem adding and removing a jquery tab to the existing tabs dynamically.

    - by kranthi
    hi everyone, I have a href tag, upon clicking it a new jquery tab is added to the existing tabs,using the following js. $(function() { //DECLARE FUNCTION: removetab var removetab = function(tabselector, index) { $(".removetab").click(function(){ $(tabselector).tabs('remove',index); }); }; //create tabs $("#tabs").tabs({ add: function(event, ui) { //select newely opened tab $(this).tabs('select',ui.index); //load function to close tab removetab($(this), ui.index); }, show: function(event, ui) { //load function to close selected tabs removetab($(this), ui.index); } }); //load new tab $(".addtab").click(function(){ var href=$(this).attr("href"); var title=$(this).attr("title"); $("#tabs").tabs( 'add' , href , title+' <span class="removetab ui-icon ui-icon-circle-close" style="float:right; margin: -2px -10px 0px 3px; cursor:pointer;"></span>'); return false; }); }); and <a class="addtab" title="Tab Label" href="HTMLPage.htm">Add Tab</a> If the href attribute for 'a' tag corresponds to a '.htm' page I am able to add & remove the tab successfully.Where as if it corresponds to a '.aspx' page I am able to add a new tab ,but unable to remove the tab upon clicking on the 'close' sign next to the tab title. Please help. Thanks in advance

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  • What's the boost way to create a functor that binds out an argument

    - by Mordachai
    I have need for a function pointer that takes two arguments and returns a string. I would like to pass an adapter that wraps a function that takes one argument, and returns the string (i.e. discard one of the arguments). I can trivially build my own adapter, that takes the 2 arguments, calls the wrapped function passing just the one argument through. But I'd much rather have a simple way to create an adapter on the fly, if there is an easy way to do so in C++/boost? Here's some details to make this a bit more concrete: typedef boost::function<CString (int,int)> TooltipTextFn; class MyCtrl { public: MyCtrl(TooltipTextFn callback = boost::bind(&MyCtrl::GetCellText, this, _1, _2)) : m_callback(callback) { } // QUESTION: how to trivially wrapper GetRowText to conform to TooltipTextFn by just discarding _2 ?! void UseRowText() { m_callback = boost::bind(&MyCtrl::GetRowText, this, _1, ??); } private: CString GetCellText(int row, int column); CString GetRowText(int row); TooltipTextFn m_callback; } Obviously, I can supply a member that adapts GetRowText to take two arguments and only passes the first to GetRowText() itself. But is there already a boost binder / adapter that lets me do that?

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  • function pointers callbacks C

    - by robUK
    Hello, I have started to review callbacks. I found this link: http://stackoverflow.com/questions/142789/what-is-a-callback-in-c-and-how-are-they-implemented which has a good example of callback which is very similar to what we use at work. However, I have tried to get it to work, but I have many errors. #include <stdio.h> /* Is the actual function pointer? */ typedef void (*event_cb_t)(const struct event *evt, void *user_data); struct event_cb { event_cb_t cb; void *data; }; int event_cb_register(event_ct_t cb, void *user_data); static void my_event_cb(const struct event *evt, void *data) { /* do some stuff */ } int main(void) { event_cb_register(my_event_cb, &my_custom_data); struct event_cb *callback; callback->cb(event, callback->data); return 0; } I know that callback use function pointers to store an address of a function. But there is a few things that I find I don't understand. That is what is meet by "registering the callback" and "event dispatcher"? Many thanks for any advice,

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  • Drag and Drop in Silverlight with F# and Asynchronous Workflows

    - by knotig
    Hello everyone! I'm trying to implement drag and drop in Silverlight using F# and asynchronous workflows. I'm simply trying to drag around a rectangle on the canvas, using two loops for the the two states (waiting and dragging), an idea I got from Tomas Petricek's book "Real-world Functional Programming", but I ran into a problem: Unlike WPF or WinForms, Silverlight's MouseEventArgs do not carry information about the button state, so I can't return from the drag-loop by checking if the left mouse button is no longer pressed. I only managed to solve this by introducing a mutable flag. Would anyone have a solution for this, that does not involve mutable state? Here's the relevant code part (please excuse the sloppy dragging code, which snaps the rectangle to the mouse pointer): type MainPage() as this = inherit UserControl() do Application.LoadComponent(this, new System.Uri("/SilverlightApplication1;component/Page.xaml", System.UriKind.Relative)) let layoutRoot : Canvas = downcast this.FindName("LayoutRoot") let rectangle1 : Rectangle = downcast this.FindName("Rectangle1") let mutable isDragged = false do rectangle1.MouseLeftButtonUp.Add(fun _ -> isDragged <- false) let rec drag() = async { let! args = layoutRoot.MouseMove |> Async.AwaitEvent if (isDragged) then Canvas.SetLeft(rectangle1, args.GetPosition(layoutRoot).X) Canvas.SetTop(rectangle1, args.GetPosition(layoutRoot).Y) return! drag() else return() } let wait() = async { while true do let! args = Async.AwaitEvent rectangle1.MouseLeftButtonDown isDragged <- true do! drag() } Async.StartImmediate(wait()) () Thank you very much for your time!

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  • C dynamic memory allocation for table of structs

    - by JosiP
    Hi here is my code. I want to dynamincly change no of elemnts in table with structs __state: typedef struct __state{ long int timestamp; int val; int prev_value; }*state_p, state_t; int main(int argc, char **argv){ int zm; int previous_state = 0; int state = 0; int i = 0; int j; state_p st; //here i want to have 20 structs st. st = (state_p) malloc(sizeof(state_t) * 20); while(1){ previous_state = state; scanf("%d", &state); printf("%d, %d\n", state, previous_state); if (previous_state != state){ printf("state changed %d %d\n", previous_state, state); // here i got compile error: main.c: In function ‘main’: main.c:30: error: incompatible type for argument 1 of ‘save_state’ main.c:34: error: invalid type argument of ‘->’ main.c:34: error: invalid type argument of ‘->’ save_state(st[i],previous_state, state); } i++; } return 0; } I suppose i have to change that st[i] to smth like st+ptr ? where pointer is incermeting in each loop iteration ? Or am I wrong ? When i change code: initialization into state_p st[20] and in each loop iteration i put st[i] = (state_p)malloc(sizeof(state_t)) everything works fine, but i want to dynammicly change number of elemets in that table. Thx in advance for any help

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  • Why do compiled Haskell libraries see invalid static FFI storage?

    - by John Millikin
    I am using GHC 6.12.1, in Ubuntu 10.04 When I try to use the FFI syntax for static storage, only modules running in interpreted mode (ie GHCI) work properly. Compiled modules have invalid pointers, and do not work. I'd like to know whether anybody can reproduce the problem, whether this an error in my code or GHC, and (if the latter) whether it's a known issue. Given the following three modules: -- A.hs {-# LANGUAGE ForeignFunctionInterface #-} module A where import Foreign import Foreign.C foreign import ccall "&sys_siglist" siglist_a :: Ptr CString -- -- B.hs {-# LANGUAGE ForeignFunctionInterface #-} module B where import Foreign import Foreign.C foreign import ccall "&sys_siglist" siglist_b :: Ptr CString -- -- Main.hs {-# LANGUAGE ForeignFunctionInterface #-} module Main where import Foreign import Foreign.C import A import B foreign import ccall "&sys_siglist" siglist_main :: Ptr CString main = do putStrLn $ "siglist_a = " ++ show siglist_a putStrLn $ "siglist_b = " ++ show siglist_b putStrLn $ "siglist_main = " ++ show siglist_main peekSiglist "a " siglist_a peekSiglist "b " siglist_b peekSiglist "main" siglist_main peekSiglist name siglist = do ptr <- peekElemOff siglist 2 str <- maybePeek peekCString ptr putStrLn $ "siglist_" ++ name ++ "[2] = " ++ show str I would expect something like this output, where all pointer values identical and valid: $ runhaskell Main.hs siglist_a = 0x00007f53a948fe00 siglist_b = 0x00007f53a948fe00 siglist_main = 0x00007f53a948fe00 siglist_a [2] = Just "Interrupt" siglist_b [2] = Just "Interrupt" siglist_main[2] = Just "Interrupt" However, if I compile A.hs (with ghc -c A.hs), then the output changes to: $ runhaskell Main.hs siglist_a = 0x0000000040378918 siglist_b = 0x00007fe7c029ce00 siglist_main = 0x00007fe7c029ce00 siglist_a [2] = Nothing siglist_b [2] = Just "Interrupt" siglist_main[2] = Just "Interrupt"

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  • gcc, strict-aliasing, and horror stories

    - by Joseph Quinsey
    In http://stackoverflow.com/questions/2906365/gcc-strict-aliasing-and-casting-through-a-union I asked whether anyone had encountered problems with union punning through pointers. So far, the answer seems to be No. This question is broader: do you have any horror stories about gcc and strict-aliasing? Background: Quoting from AndreyT's answer in http://stackoverflow.com/questions/2771023/c99-strict-aliasing-rules-in-c-gcc/2771041#2771041: "Strict aliasing rules are rooted in parts of the standard that were present in C and C++ since the beginning of [standardized] times. The clause that prohibits accessing object of one type through a lvalue of another type is present in C89/90 (6.3) as well as in C++98 (3.10/15). ... It is just that not all compilers wanted (or dared) to enforce it or rely on it." Well, gcc is now daring to do so, with its -fstrict-aliasing switch. And this has caused some problems. See, for example, the excellent article http://davmac.wordpress.com/2009/10/ about a Mysql bug, and the equally excellent discussion in http://cellperformance.beyond3d.com/articles/2006/06/understanding-strict-aliasing.html. Some other less-relevant links: http://stackoverflow.com/questions/1225741/performance-impact-of-fno-strict-aliasing http://stackoverflow.com/questions/754929/strict-aliasing http://stackoverflow.com/questions/262379/when-is-char-safe-for-strict-pointer-aliasing http://stackoverflow.com/questions/725138/how-to-detect-strict-aliasing-at-compile-time So to repeat, do you have a horror story of your own? Problems not indicated by -Wstrict-aliasing would, of course, be preferred. And other C compilers are also welcome.

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  • Mixing c++ standard strings and windows API

    - by JB
    Many windows APIs take a pointer to a buffer and a size element but the result needs to go into a c++ string. (I'm using windows unicode here so they are wstrings) Here is an example :- #include <iostream> #include <string> #include <vector> #include <windows.h> using namespace std; // This is the method I'm interested in improving ... wstring getComputerName() { vector<wchar_t> buffer; buffer.resize(MAX_COMPUTERNAME_LENGTH+1); DWORD size = MAX_COMPUTERNAME_LENGTH; GetComputerNameW(&buffer[0], &size); return wstring(&buffer[0], size); } int main() { wcout << getComputerName() << "\n"; } My question really is, is this the best way to write the getComputerName function so that it fits into C++ better, or is there a better way? I don't see any way to use a string directly without going via a vector unless I missed something? It works fine, but somehow seems a little ugly. The question isn't about that particular API, it's just a convenient example.

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  • Using Array Controllers to restrict the view in one popup depending on the selection in another. Not

    - by mjohnh
    I am working on an app that is not core data based - the data feed is a series of web services. Two arrays are created from the data feed. The first holds season data, each array object being an NSDictionary. Two of the NSDictionary entries hold the data to be displayed in the popup ('seasonName') and an id ('seasonID') that acts as a pointer (in an external table) by matches defined for that season. The second array is also a collection of NSDictionaries. Two of the entries hold the data to be displayed in the popup ('matchDescription') and the id ('matchSeasonId') that points to the seasonId defined in the NSDictionaries in first array. I have two NSPopUps. I want the first to display the season names and the second to display the matches defined for that season, depending on the selection in the first. I'm new at bindings, so excuse me if I've missed something obvious. I've tried using ArrayControllers as follows: SeasonsArrayController: content bound to appDelegate seasonsPopUpArrayData. seasonsPopup: content bound to SeasonsArrayController.arrangedObjects; content value bound to SeasonsArrayController.arrangedObjects.seasonName I see the season names fine. I can obviously follow a similar route to see the matches, but I then see them all, instead of restricting the list to the matches for the season highlighted. All the tutorials I can find seem to revolve around core data and utilise the relationships defined therein. I don't have that luxury here. Any help very gratefully received.

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  • Java SWT: wrapping syncExec and asyncExec to clean up code

    - by jonescb
    I have a Java Application using SWT as the toolkit, and I'm getting tired of all the ugly boiler plate code it takes to update a GUI element. Just to set a disabled button to be enabled I have to go through something like this: shell.getDisplay().asyncExec(new Runnable() { public void run() { buttonOk.setEnabled(true); } }); I prefer keeping my source code as flat as I possibly can, but I need a whopping 3 indentation levels just to do something simple. Is there some way I can wrap it? I would like a class like: public class UIUpdater { public static void updateUI(Shell shell, *function_ptr*) { shell.getDisplay().asyncExec(new Runnable() { public void run() { //Execute function_ptr } }); } } And can be used like so: UIUpdater.updateUI(shell, buttonOk.setEnabled(true)); Something like this would be great for hiding that horrible mess SWT seems to think is necessary to do anything. As I understand it, Java cannot do functions pointers. But Java 7 will have something called Closures which should be what I want. But in the meantime is there anything at all I can do to pass a function pointer or callback to another function to be executed? As an aside, I'm starting to think it'd be worth the effort to redo this application in Swing, and I don't have to put up with this ugly crap and non-cross-platformyness of SWT.

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  • Sliding doors HTML buttons in Safari Win

    - by RyanP13
    Hi, I have the following HTML for buttons implementing sliding doors technique that look fine in everything but Safari on Windows: <button type="submit"> <span>Button</span> </button> This is the corresponding CSS: button { background:url("../images/sprBgBtn.png") no-repeat right -47px; border:0; cursor:pointer; font-weight:bold; height:27px; line-height:27px; overflow:visible; padding:0 26px 0 0; position:relative; text-align:center; text-transform:uppercase; width:auto; } button::-moz-focus-inner { border: none; /* overrides extra padding in Firefox */ padding:0; } button span { background:url("../images/sprBgBtn.png") no-repeat left top; display:block; height:27px; line-height:27px; padding:0 0 0 26px; position:relative; white-space:nowrap; } If i omit the following code then the same issue will appear in FFOX: button::-moz-focus-inner { border: none; /* overrides extra padding in Firefox */ padding:0; }

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  • Webcam video stream processing.

    - by vikramtheone
    Hi Guys, I'm working with an image processing project, my final goal is to detect features on a real time video and finally track those features. I will be working with an Embedded Processor Platform called Freescale's i.MX515, it is a 32-bit media processor running on Ubuntu 9.04. Right now I'm working on the algorithms to locate the features, so, I'm using still images. When I'm satisfied with the results I will have to start using a video stream and I don't want to make use of a video file as a source stream, because then I will have to worry about video decoders then. Instead I would like to plug in a USB Wecam to the embedded platform (It has USB ports on it), directly take the frames as they are captured and send it to my application. I will take care to buy a webcam which will be supported in Linux (Device driver). But my question is will I be able to capture the incoming video stream from the webcam and send it to my application? Will I be able to configure the webcam and DMA to write the incoming frames in a particular memory location whose pointer I can simply pass to my application? (Confused!!!) I hope I could convey my doubts, can anyone guide me with what steps that I have to take to achieve all of these easily? Do you foresee any impossibility here? Help!!! Regards Vikram

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  • Very weird C file-handling anomaly

    - by KáGé
    Hello, I got a very weird issue that I cant figure out in my school project, which is the simulation of a simple filesystem in a human-readable textfile. Unfortunately I don't yet have enough time to translate the comments in my code or make it less gibberish, so if you are bothered by that, you don't have to help, I understand. See the code HERE. Now in drive.h, at line 574 is this part: i = getline(); #ifdef DEBUG printf("Free space in all found at %d.\n\n", i); if(drive.disk != NULL){ printf("Disk OK\n\n"); } #endif //write in data state = seekline(i); Before this it finds place for the allocation database entry in the ALL sector (see the "image files" in the mounts folder, this issue was tested on mount_30.efs-dbf), then gets the line with i = getline() fine (getline is in lglobal.h, line 39), but after that any file manipulation (in this case seekline's fseek, but if I comment that out, then the first fprintf after that) crashes the program straight away. I think the file gets somehow corrupted (though the Disk OK message appears) but can't figure out how. I've tried putting i = getline(); into comment, but it didn't make any difference. I've also tried asking at local programming forums but they didn't really help either. The last few lines of the output before it crashes: Dir written. (drive.h line 562) Seekline entered: 268 (called at drive.h line 564) Getline entered. (called at drive.h line 574) Line got: 268. Free space in all found at 268. (drive.h line 576) Seekline entered: 268 (called at drive.h line 582, note that this exact call was run successfully less than 20 lines back. This one should set the pointer to the beginning of the line it is currently in) After this it crashes. Does anyone has any idea of what causes this and how could I fix it? Thank you.

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  • c++ queue template

    - by Dalton Conley
    ALright, pardon my messy code please. Below is my queue class. #include <iostream> using namespace std; #ifndef QUEUE #define QUEUE /*---------------------------------------------------------------------------- Student Class # Methods # Student() // default constructor Student(string, int) // constructor display() // out puts a student # Data Members # Name // string name Id // int id ----------------------------------------------------------------------------*/ class Student { public: Student() { } Student(string iname, int iid) { name = iname; id = iid; } void display(ostream &out) const { out << "Student Name: " << name << "\tStudent Id: " << id << "\tAddress: " << this << endl; } private: string name; int id; }; // define a typedef of a pointer to a student. typedef Student * StudentPointer; template <typename T> class Queue { public: /*------------------------------------------------------------------------ Queue Default Constructor Preconditions: none Postconditions: assigns default values for front and back to 0 description: constructs a default empty Queue. ------------------------------------------------------------------------*/ Queue() : myFront(0), myBack(0) {} /*------------------------------------------------------------------------ Copy Constructor Preconditions: requres a reference to a value for which you are copying Postconditions: assigns a copy to the parent Queue. description: Copys a queue and assigns it to the parent Queue. ------------------------------------------------------------------------*/ Queue(const T & q) { myFront = myBack = 0; if(!q.empty()) { // copy the first node myFront = myBack = new Node(q.front()); NodePointer qPtr = q.myFront->next; while(qPtr != NULL) { myBack->next = new Node(qPtr->data); myBack = myBack->next; qPtr = qPtr->next; } } } /*------------------------------------------------------------------------ Destructor Preconditions: none Postconditions: deallocates the dynamic memory for the Queue description: deletes the memory stored for a Queue. ------------------------------------------------------------------------*/ ~Queue() { NodePointer prev = myFront, ptr; while(prev != NULL) { ptr = prev->next; delete prev; prev = ptr; } } /*------------------------------------------------------------------------ Empty() Preconditions: none Postconditions: returns a boolean value. description: returns true/false based on if the queue is empty or full. ------------------------------------------------------------------------*/ bool empty() const { return (myFront == NULL); } /*------------------------------------------------------------------------ Enqueue Preconditions: requires a constant reference Postconditions: allocates memory and appends a value at the end of a queue description: ------------------------------------------------------------------------*/ void enqueue(const T & value) { NodePointer newNodePtr = new Node(value); if(empty()) { myFront = myBack = newNodePtr; newNodePtr->next = NULL; } else { myBack->next = newNodePtr; myBack = newNodePtr; newNodePtr->next = NULL; } } /*------------------------------------------------------------------------ Display Preconditions: requires a reference of type ostream Postconditions: returns the ostream value (for chaining) description: outputs the contents of a queue. ------------------------------------------------------------------------*/ void display(ostream & out) const { NodePointer ptr; ptr = myFront; while(ptr != NULL) { out << ptr->data << " "; ptr = ptr->next; } out << endl; } /*------------------------------------------------------------------------ Front Preconditions: none Postconditions: returns a value of type T description: returns the first value in the parent Queue. ------------------------------------------------------------------------*/ T front() const { if ( !empty() ) return (myFront->data); else { cerr << "*** Queue is empty -- returning garbage value ***\n"; T * temp = new(T); T garbage = * temp; delete temp; return garbage; } } /*------------------------------------------------------------------------ Dequeue Preconditions: none Postconditions: removes the first value in a queue ------------------------------------------------------------------------*/ void dequeue() { if ( !empty() ) { NodePointer ptr = myFront; myFront = myFront->next; delete ptr; if(myFront == NULL) myBack = NULL; } else { cerr << "*** Queue is empty -- " "can't remove a value ***\n"; exit(1); } } /*------------------------------------------------------------------------ pverloaded = operator Preconditions: requires a constant reference Postconditions: returns a const type T description: this allows assigning of queues to queues ------------------------------------------------------------------------*/ Queue<T> & operator=(const T &q) { // make sure we arent reassigning ourself // e.g. thisQueue = thisQueue. if(this != &q) { this->~Queue(); if(q.empty()) { myFront = myBack = NULL; } else { myFront = myBack = new Node(q.front()); NodePointer qPtr = q.myFront->next; while(qPtr != NULL) { myBack->next = new Node(qPtr->data); myBack = myBack->next; qPtr = qPtr->next; } } } return *this; } private: class Node { public: T data; Node * next; Node(T value, Node * first = 0) : data(value), next(first) {} }; typedef Node * NodePointer; NodePointer myFront, myBack, queueSize; }; /*------------------------------------------------------------------------ join Preconditions: requires 2 queue values Postconditions: appends queue2 to the end of queue1 description: this function joins 2 queues into 1. ------------------------------------------------------------------------*/ template <typename T> Queue<T> join(Queue<T> q1, Queue<T> q2) { Queue<T> q1Copy(q1), q2Copy(q2); Queue<T> jQueue; while(!q1Copy.empty()) { jQueue.enqueue(q1Copy.front()); q1Copy.dequeue(); } while(!q2Copy.empty()) { jQueue.enqueue(q2Copy.front()); q2Copy.dequeue(); } cout << jQueue << endl; return jQueue; } /*---------------------------------------------------------------------------- Overloaded << operator Preconditions: requires a constant reference and a Queue of type T Postconditions: returns the ostream (for chaining) description: this function is overloaded for outputing a queue with << ----------------------------------------------------------------------------*/ template <typename T> ostream & operator<<(ostream &out, Queue<T> &s) { s.display(out); return out; } /*---------------------------------------------------------------------------- Overloaded << operator Preconditions: requires a constant reference and a reference of type Student Postconditions: none description: this function is overloaded for outputing an object of type Student. ----------------------------------------------------------------------------*/ ostream & operator<<(ostream &out, Student &s) { s.display(out); } /*---------------------------------------------------------------------------- Overloaded << operator Preconditions: requires a constant reference and a reference of a pointer to a Student object. Postconditions: none description: this function is overloaded for outputing pointers to Students ----------------------------------------------------------------------------*/ ostream & operator<<(ostream &out, StudentPointer &s) { s->display(out); } #endif Now I'm having some issues with it. For one, when I add 0 to a queue and then I output the queue like so.. Queue<double> qdub; qdub.enqueue(0); cout << qdub << endl; That works, it will output 0. But for example, if I modify that queue in any way.. like.. assign it to a different queue.. Queue<double> qdub1; Queue<double> qdub2; qdub1.enqueue(0; qdub2 = qdub1; cout << qdub2 << endl; It will give me weird values for 0 like.. 7.86914e-316. Help on this would be much appreciated!

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  • UISlider won't display

    - by user290295
    I have been having a lot of difficulty adding custom track images to a UISlider. Whenever I do this, whether to a nib created UISlider or a hand programmed UISlider the slider refuses to display. Also, I even commented the track image code out below and the UISlider still refuses to display. There are other nib created sliders in the controlView that display and function fine. if (![self loadView:keyboardControlView intoSuperview:controlView withNib:@"KeyboardControl"]) { NSLog(@"Could not load controlView from nib into synthControlView"); } // nibSlider is an outlet to a UISlider in the above loaded nib file CGRect sliderFrame = nibSlider.frame; float sliderMinimum = nibSlider.minimumValue; float sliderMaximum = nibSlider.maximumValue; float sliderValue = nibSlider.value; // remove from superview, implicitly releasing UISlider [nibSlider removeFromSuperview]; // reuse pointer to allocate new UISlider using rect obtained from nib nibSlider = [[UISlider alloc] initWithFrame:sliderFrame]; nibSlider.backgroundColor = [UIColor clearColor]; nibSlider.minimumValue = sliderMinimum; nibSlider.maximumValue = sliderMaximum; nibSlider.continuous = YES; nibSlider.value = sliderValue; //[nibSlider setMinimumTrackImage:[[UIImage imageNamed:@"violetslider.png"] //stretchableImageWithLeftCapWidth:5.0 topCapHeight:0.0] forState:UIControlStateNormal]; // //[nibSlider setMaximumTrackImage:[[UIImage imageNamed:@"violetslider.png"] // stretchableImageWithLeftCapWidth:5.0 topCapHeight:0.0] forState:UIControlStateNormal]; [nibSlider addTarget:delegate action:@selector(sliderUpdate:) forControlEvents:UIControlEventValueChanged]; [controlView addSubview:nibSlider]; // do not release here as slider will need to remain cached. push onto a release stack. [nibSlider setNeedsDisplay];

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  • Audio output from Silverlight

    - by leecarter
    I'm looking to develop a Silverlight application which will take a stream of data (not an audio stream as such) from a web server. The data stream would then be manipulated to give audio of a certain format (G.711 a-Law for example) which would then be converted into PCM so that additional effects can be applied (such as boosting the volume). I'm OK up to this point. I've got my data, converted the G.711 into PCM but my problem is being able to output this PCM audio to the sound card. I basing a solution on some C# code intended for a .Net application but in Silverlight there is a problem with trying to take a copy of a delegate (function pointer) which will be the topic of a separate question once I've produced a simple code sample. So, the question is... How can I output the PCM audio that I have held in a data structure (currently an array) in my Silverlight to the user? (Please don't say write the byte values to a text box) If it were a MP3 or WMA file I would play it using a MediaElement but I don't want to have to make it into a file as this would put a crimp on applying dynamic effects to the audio. I've seen a few posts from people saying low level audio support is poor/non-existant in Silverlight so I'm open to any suggestions/ideas people may have.

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  • Cant' cast a class with multiple inheritance

    - by Jay S.
    I am trying to refactor some code while leaving existing functionality in tact. I'm having trouble casting a pointer to an object into a base interface and then getting the derived class out later. The program uses a factory object to create instances of these objects in certain cases. Here are some examples of the classes I'm working with. // This is the one I'm working with now that is causing all the trouble. // Some, but not all methods in NewAbstract and OldAbstract overlap, so I // used virtual inheritance. class MyObject : virtual public NewAbstract, virtual public OldAbstract { ... } // This is what it looked like before class MyObject : public OldAbstract { ... } // This is an example of most other classes that use the base interface class NormalObject : public ISerializable // The two abstract classes. They inherit from the same object. class NewAbstract : public ISerializable { ... } class OldAbstract : public ISerializable { ... } // A factory object used to create instances of ISerializable objects. template<class T> class Factory { public: ... virtual ISerializable* createObject() const { return static_cast<ISerializable*>(new T()); // current factory code } ... } This question has good information on what the different types of casting do, but it's not helping me figure out this situation. Using static_cast and regular casting give me error C2594: 'static_cast': ambiguous conversions from 'MyObject *' to 'ISerializable *'. Using dynamic_cast causes createObject() to return NULL. The NormalObject style classes and the old version of MyObject work with the existing static_cast in the factory. Is there a way to make this cast work? It seems like it should be possible.

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  • Updating a local sqlite db that is used for local metadata & caching from an service?

    - by Pharaun
    I've searched through the site and haven't found a question/answer that quite answer my question, the closest one I found was: Syncing objects between two disparate systems best approach. Anyway to begun, because there is no RSS feeds available, I'm screen scrapping a webpage, hence it does a fetch then it goes through the webpage to scrap out all of the information that I'm interested in and dumps that information into a sqlite database so that I can query the information at my leisure without doing repeat fetching from the website. However I'm also storing various metadata on the data itself that is stored in the sqlite db, such as: have I looked at the data, is the data new/old, bookmark to a chunk of data (Think of it as a collection of unrelated data, and the bookmark is just a pointer to where I am in processing/reading of the said data). So right now my current problem is trying to figure out how to update the local sqlite database with new data and/or changed data from the website in a manner that is effective and straightforward. Here's my current idea: Download the page itself Create a temporary table for the parsed data to go into Do a comparison between the official and the temporary table and copy updates and/or new information to the official table This process seems kind of complicated because I would have to figure out how to determine if the data in the temporary table is new, updated, or unchanged. So I am wondering if there isn't a better approach or if anyone has any suggestion on how to architecture/structure such system?

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