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• Why is my ipad's wireless so flakey?

  - by Mark

  I'm the proud owner of a new IPad here in the UK. All is good, except for the wifi, which is a bit flakey. It connects fine to my Draytek router which is set for WPA/WPA2 and 56g only, displaying full signal strength. Then, after a few minutes, it goes down to minimum strength... And sometimes it goes back up again. A few times, it seems to loose connection completely, and needs to be turned off and on again. I've looked at the Apple support site, and have tried their recommendations (which are not really very relevant), but still nothing. I've tried setting the router to wpa2 only, and setting long-preamble. Right now, I guess I want to know if it's a hardware problem with my device and should be returned, or if it's a problem with all ipads which will be resolved. Guess I could take it back to the Mac genius bar, but I find those guys so incredibly pretentious and, frankly, rather useless, that i'd rather wait until I've exercised other options!

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• What are the prerequisites for learning embedded systems programming ?

  - by WarDoGG

  I have completed my graduation in Computer engineering. We had some basic electronics courses in Digital signal processing, Information theory etc but my primary field is Programming. However, i was looking to get into Embedded sytems programming with NO knowledge of how it is done. However, i am very keen on going into this field. My questions : what are the languages used to program embedded system programs ? Will i be able to learn without having any basics in electronics ? any other prerequisites that i should know ?

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• Using Unix Process Controll Methods in Ruby

  - by John F. Miller

  Ryan Tomayko touched off quite a fire storm with this post about using Unix process control commands. We should be doing more of this. A lot more of this. I'm talking about fork(2), execve(2), pipe(2), socketpair(2), select(2), kill(2), sigaction(2), and so on and so forth. These are our friends. They want so badly just to help us. I have a bit of code (a delayed_job clone for DataMapper that I think would fit right in with this, but I'm not clear on how to take advantage of the listed commands. Any Ideas on how to improve this code? def start say "*** Starting job worker #{@name}" t = Thread.new do loop do delay = Update.work_off(self) break if $exit sleep delay break if $exit end clear_locks end trap('TERM') { terminate_with t } trap('INT') { terminate_with t } trap('USR1') do say "Wakeup Signal Caught" t.run end end

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• Malloc to a CGPoint Pointer throwing EXC_BAD_ACCESS when accessing

  - by kdbdallas

  I am trying to use a snippet of code from a Apple programming guide, and I am getting a EXC_BAD_ACCESS when trying to pass a pointer to a function, right after doing a malloc. (For Reference: iPhone Application Programming Guide: Event Handling - Listing 3-6) The code in question is really simple: CFMutableDictionaryRef touchBeginPoints; UITouch *touch; .... CGPoint *point = (CGPoint *)CFDictionaryGetValue(touchBeginPoints, touch); if (point == NULL) { point = (CGPoint *)malloc(sizeof(CGPoint)); CFDictionarySetValue(touchBeginPoints, touch, point); } Now when the program goes into the if statement it assigns the 'output' of malloc into the point variable/pointer. Then when it tries to pass point into the CFDictionarySetValue function it crashes the application with: Program received signal: “EXC_BAD_ACCESS”. Someone suggested not doing the malloc and pass the point var/pointer as: &point, however that still gave me a EXC_BAD_ACCESS. What I am (and it looks like Apple) doing wrong??? Thanks in advance.

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• How to associate Wi-Fi beacon info with a virtual "location"?

  - by leander

  We have a piece of embedded hardware that will sense 802.11 beacons, and we're using this to make a map of currently visible bssid -> signalStrength. Given this map, we would like to make a determination: Is this likely to be a location I have been to before? If so, what is its ID? If not, I should remember this location: generate a new ID. Now what should I store (and how should I store it) to make future determinations easier? This is for an augmented-reality app/game. We will be using it to associate particular characters and events with "locations". The device does not have internet or cellular access, so using a geolocation service is out of consideration for the time being. (We don't really need to know where we are in reality, just be able to determine if we return there.) It isn't crucial that it be extremely accurate, but it would be nice if it was tolerant to signal strength changes or the occasional missing beacon. It should be usable in relatively low numbers of access points (e.g. rural house with one wireless router) or many (wandering around a dense metropolis). In the case of a city, it should change location every few minutes of walking (continuously-overlapping signals make this a bit more tricky in naive code). A reasonable number of false positives (match a location when we aren't actually there) is acceptable. The wrong character/event showing up just adds a bit of variety. False negatives (no location match) are a bit more troublesome: this will tend to add a better-matching new location to the saved locations, masking the old one. While we will have additional logic to ensure locations that the device hasn't seen in a while will "orphan" any associated characters or events (if e.g. you move to a different country), we'd prefer not to mask and eventually orphan locations you do visit regularly. Some technical complications: signalStrength is returned as 1-4; presumably it's related to dB, but we are not sure exactly how; in my experiments it tends to stick to either 1 or 4, but occasionally we see numbers in between. (Tech docs on the hardware are sparse.) The device completes a scan of one-quarter of the channel space every second; so it takes about 4-5 seconds to get a complete picture of what's around. The list isn't always complete. (We are making strides to fix this using some slight sampling period randomization, as recommended by the library docs. We're also investigating ways to increase the number of scans without killing our performance; the hardware/libs are poorly behaved when it comes to saturating the bus.) We have only kilobytes to store our history. We have a "working" impl now, but it is relatively naive, and flaky in the face of real-world Wi-Fi behavior. Rough pseudocode: // recordLocation() -- only store strength 4 locations m_savedLocations[g_nextId++] = filterForStrengthGE( m_currentAPs, 4 ); // determineLocation() bestPoints = -inf; foreach ( oldLoc in m_savedLocations ) { points = 0.0; foreach ( ap in m_currentAPs ) { if ( oldLoc.has( ap ) ) { switch ( ap.signalStrength ) { case 3: points += 1.0; break; case 4: points += 2.0; break; } } } points /= oldLoc.numAPs; if ( points > bestPoints ) { bestLoc = oldLoc; bestPoints = points; } } if ( bestLoc && bestPoints > 1.0 ) { if ( bestPoints >= (2.0 - epsilon) ) { // near-perfect match. // update location with any new high-strength APs that have appeared bestLoc.addAPs( filterForStrengthGE( m_currentAPs, 4 ) ); } return bestLoc; } else { return NO_MATCH; } We record a location currently only when we have NO_MATCH and the app determines it's time for a new event. (The "near-perfect match" code above would appear to make it harder to match in the future... It's mostly to keep new powerful APs from being associated with other locations, but you'd think we'd need something to counter this if e.g. an AP doesn't show up in the next 10 times I match a location.) I have a feeling that we're missing some things from set theory or graph theory that would assist in grouping/classification of this data, and perhaps providing a better "confidence level" on matches, and better robustness against missed beacons, signal strength changes, and the like. Also it would be useful to have a good method for mutating locations over time. Any useful resources out there for this sort of thing? Simple and/or robust approaches we're missing?

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• Fibre channel long distance woes

  - by Marki

  I need a fresh pair of eyes. We're using a 15km fibre optic line across which fibrechannel and 10GbE is multiplexed (passive optical CWDM). For FC we have long distance lasers suitable up to 40km (Skylane SFCxx0404F0D). The multiplexer is limited by the SFPs which can do max. 4Gb fibrechannel. The FC switch is a Brocade 5000 series. The respective wavelengths are 1550,1570,1590 and 1610nm for FC and 1530nm for 10GbE. The problem is the 4GbFC fabrics are almost never clean. Sometimes they are for a while even with a lot of traffic on them. Then they may suddenly start producing errors (RX CRC, RX encoding, RX disparity, ...) even with only marginal traffic on them. I am attaching some error and traffic graphs. Errors are currently in the order of 50-100 errors per 5 minutes when with 1Gb/s traffic. Optics Here is the power output of one port summarized (collected using sfpshow on different switches) SITE-A units=uW (microwatt) SITE-B ********************************************** FAB1 SW1 TX 1234.3 RX 49.1 SW3 1550nm (ko) RX 95.2 TX 1175.6 FAB2 SW2 TX 1422.0 RX 104.6 SW4 1610nm (ok) RX 54.3 TX 1468.4 What I find curious at this point is the asymmetry in the power levels. While SW2 transmits with 1422uW which SW4 receives with 104uW, SW2 only receives the SW4 signal with similar original power only with 54uW. Vice versa for SW1-3. Anyway the SFPs have RX sensitivity down to -18dBm (ca. 20uW) so in any case it should be fine... But nothing is. Some SFPs have been diagnosed as malfunctioning by the manufacturer (the 1550nm ones shown above with "ko"). The 1610nm ones apparently are ok, they have been tested using a traffic generator. The leased line has also been tested more than once. All is within tolerances. I'm awaiting the replacements but for some reason I don't believe it will make things better as the apparently good ones don't produce ZERO errors either. Earlier there was active equipment involved (some kind of 4GFC retimer) before putting the signal on the line. No idea why. That equipment was eliminated because of the problems so we now only have: the long distance laser in the switch, (new) 10m LC-SC monomode cable to the mux (for each fabric), the leased line, the same thing but reversed on the other side of the link. FC switches Here is a port config from the Brocade portcfgshow (it's like that on both sides, obviously) Area Number: 0 Speed Level: 4G Fill Word(On Active) 0(Idle-Idle) Fill Word(Current) 0(Idle-Idle) AL_PA Offset 13: OFF Trunk Port ON Long Distance LS VC Link Init OFF Desired Distance 32 Km Reserved Buffers 70 Locked L_Port OFF Locked G_Port OFF Disabled E_Port OFF Locked E_Port OFF ISL R_RDY Mode OFF RSCN Suppressed OFF Persistent Disable OFF LOS TOV enable OFF NPIV capability ON QOS E_Port OFF Port Auto Disable: OFF Rate Limit OFF EX Port OFF Mirror Port OFF Credit Recovery ON F_Port Buffers OFF Fault Delay: 0(R_A_TOV) NPIV PP Limit: 126 CSCTL mode: OFF Forcing the links to 2GbFC produces no errors, but we bought 4GbFC and we want 4GbFC. I don't know where to look anymore. Any ideas what to try next or how to proceed? If we can't make 4GbFC work reliably I wonder what the people working with 8 or 16 do... I don't assume that "a few errors here and there" are acceptable. Oh and BTW we are in contact with everyone of the manufacturers (FC switch, MUX, SFPs, ...) Except for the SFPs to be changed (some have been changed before) nobody has a clue. Brocade SAN Health says the fabric is ok. MUX, well, it's passive, it's only a prism, nature at it's best. Any shots in the dark? APPENDIX: Answers to your questions @Chopper3: This is the second generation of Brocades exhibiting the problem. Before we had 5000s, now we have 5100s. In the beginning when we still had the active MUX we rented a longdistance laser once to put it into the switch directly in order to make tests for a day, during that day of course it was clean. But as I said, sometimes it's clean just like that. And sometimes it's not. Alternative switches would mean to rebuild the entire SAN with those only to test. Alternative SFPs, well they're hard to come by just like that. @longneck: The line is rented. It's a dark fibre (9um monomode) so there's noone else on it. Sure there are splices. I can't go and look but I have to trust they have been done correctly. As I said the line has been checked and rechecked (using an optical time-domain reflectometer). Obviously you don't have all this equipment yourself because it's way too expensive. @mdpc: What would be the "wrong" type of cable according to you? Up to the switch everything is monomode, yes. The connectors are the correct ones too. Yeah I know there are the green ones where the fibre is cut off at a certain angle etc. But we have the correct ones for all that I know. Progress Report #1 We have had two fabrics (=2x2 switches) with Brocade 5100s with FabricOS 6.4.1 and two fabrics (another 2x4 switches) on FabricOS 7.0.2. On the longdistance ISLs (one in each fabric) it turned out that with FOS 6.4.1 setting it to long distance issues warnings about the VC Init setting and consequently the fill word. But those are only warnings. FOS 7.0.2 requires you to do modifications to VCI and the fillword for long distance links. Setting FOS 6.4.1 to the LS (long-distance static distance) setting with wrong VCI and fillword setting made the whole fabric inoperational (stuck in an SCN loop, use fabriclog -s to see, you don't see it anywhere else, no port error counters or anything increasing). Currently I'm giving the one fabric with the IMHO more correct settings a beating and it seems to do fine, whereas the other one without much traffic still has errors here and there. In short: We have eliminated the active part of the MUX (the FC retimer). We are putting the long distance SFPs into the end equipment themselves. Just to be sure we bought new monomode cables to connect the end equipment to the remaining passive part of the MUX. We are now trying out several long distance configs. It's almost black magic. Everything that happens is mostly empirical, noone seems to have a clue what are the exact reasons to do something. ("We have tried this, and it didn't work, then we tried that and it worked, so we stuck with that." But noone really seems to know why.) I'll keep you updated. Progress Report #2 We got the new lasers for one of the fabrics on warranty. It's ultra clean even on 4GbFC. They're transmitting with roughly 2mW (3dBm) whereas the others are only at 1.5mW (1.5dBm) although that should really be enough. The other fabric (where the lasers are apparently ok) still produces one or two CRCs infrequently. Using sfpshow the SFP producing the actual RX errors shows Status/Ctrl: 0x82 Alarm flags[0,1] = 0x5, 0x40 Warn Flags[0,1] = 0x5, 0x40 Now I'll have to find out what that means. Not sure if it was there before. Well I'll first clear my head with a week of vacation. 8-)

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• what is the mistake in my code

  - by Solitaire

  class myslot { public: Q_OBJECT myslot() { } ~myslot() { } typedef enum Emycars{volvo,benz,tata}cars; public slots: void hellowslot(myslot::cars); }; void myslot::hellowslot(myslot::cars cars1) { } class mysignal { public: Q_OBJECT public: mysignal(myslot *ourslot) { bool val = QObject::connect(this,SIGNAL(hellowsignal(myslot::Emycars)),ourslot,SLOT(hellowslot(myslot::Emycars))); } ~mysignal() { } signals: void hellowsignal(myslot::Emycars); }; int main(int argc, char *argv[]) { QApplication a(argc, argv); myslot slot; mysignal sig(&slot); // DeleteNow w; // w.showMaximized(); return a.exec(); } what is the mistake in mycode, the way which i have written connect for the function which recive enum is right or not? please let me know where i am wrong.

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• iPhone app crashed: Assertion failed function evict_glyph_entry_from_strike, file Fonts/CGFontCache.

  - by Ross

  this happened quite randomly. I didn't delete any tableview cell, the backtrace information: Assertion failed: (d->entry[identifier.glyph] == g), function evict_glyph_entry_from_strike, file Fonts/CGFontCache.c, line 810. Program received signal: “SIGABRT”. (gdb) bt #0 0x97da5972 in __kill () #1 0x97da5964 in kill$UNIX2003 () #2 0x97e38ba5 in raise () #3 0x97e4ec5c in abort () #4 0x97e3b804 in __assert_rtn () #5 0x0037fe0e in evict_glyph_entry_from_cache () #6 0x003226aa in expire_glyphs_nl () #7 0x00322645 in CGFontCacheUnlock () #8 0x00321fef in CGGlyphLockUnlock () #9 0x0240f9b7 in ripc_DrawGlyphs () #10 0x0031b0d4 in draw_glyphs () #11 0x0031a91f in CGContextShowGlyphsWithAdvances () #12 0x35814178 in WebCore::Font::drawGlyphs () #13 0x35813da5 in WebCore::Font::drawGlyphBuffer () #14 0x35813aca in WebCore::Font::drawSimpleText () #15 0x35813760 in drawAtPoint () #16 0x3581307e in -[NSString(WebStringDrawing) _web_drawAtPoint:forWidth:withFont:ellipsis:letterSpacing:includeEmoji:] () #17 0x3090d2e9 in -[NSString(UIStringDrawing) drawAtPoint:forWidth:withFont:lineBreakMode:letterSpacing:includeEmoji:] () #18 0x3090cfe3 in -[NSString(UIStringDrawing) drawAtPoint:forWidth:withFont:lineBreakMode:] () #19 0x3093d853 in -[UINavigationItemView drawText:inRect:] () #20 0x3093a96b in -[UINavigationItemButtonView drawRect:] () #21 0x3091ff61 in -[UIView(CALayerDelegate) drawLayer:inContext:] () #22 0x0060daeb in -[CALayer drawInContext:] () #23 0x0060d8f9 in backing_callback () #24 0x0060d1b4 in CABackingStoreUpdate () #25 0x0060c3cc in -[CALayer _display] () #26 0x0060bf56 in CALayerDisplayIfNeeded () #27 0x0060b3bd in CA::Context::commit_transaction () #28 0x0060b022 in CA::Transaction::commit () #29 0x006132e0 in CA::Transaction::observer_callback () #30 0x30245c32 in __CFRunLoopDoObservers () #31 0x3024503f in CFRunLoopRunSpecific () #32 0x30244628 in CFRunLoopRunInMode () #33 0x32044c31 in GSEventRunModal () #34 0x32044cf6 in GSEventRun () #35 0x309021ee in UIApplicationMain ()

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• Determining the magnitude of a certain frequency on the iPhone

  - by eagle

  I'm wondering what's the easiest/best way to determine the magnitude of a given frequency in a sound. It's my understanding that a FFT function will return the magnitudes of all frequencies in a signal. I'm wondering if there is any shortcut I could use if I'm only concerned about a specific frequency. I'll be using the iPhone mic to record the audio. My guess is that I'll be using the Audio Queue Services for recording since I don't need to record the audio to a file. I'm using SDK 4.0, so I can use any of the functions defined in the Accelerate framework (e.g. FFT functions) if needed. Update: I updated the question to be more clear as per Conrad's suggestion.

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• iPad crashes that aren't happening on iPhone or iPod Touch

  - by alyoshak

  Has anyone had difficulty getting what has otherwise been a solid iPhone app working on the iPad? I was under the impression that iPhone apps would run without problems on the iPad. We are are experiencing crashes (not intermittent - same place, at same time) that we've never gotten on the iPhone or iPod Touch. I have become suspicious that the crashes are memory-management related, but even if so, why only on the iPad? 2010-05-17 10:19:06.474 ASSIST[82:207] *** Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<UISectionRowData 0x6041480> valueForUndefinedKey:]: this class is not key value coding-compliant for the key deliveryDate.' 2010-05-17 10:19:06.481 ASSIST[82:207] Stack: ( 852041337, 861292157, 852040861, 850755255, 850750995, 850758945, 81279, 123007, 126693, 149141, 851599725, 827486573, 827486477, 827486431, 827485745, 827487359, 827454123, 851903137, 851590065, 851588321, 819339483, 819339655, 827151561, 827144691, 9461, 9324 ) terminate called after throwing an instance of 'NSException' Program received signal: “SIGABRT”.

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• C# Is it possible to interrupt a specific thread inside a ThreadPool?

  - by Lirik

  Suppose that I've queued a work item in a ThreadPool, but the work item blocks if there is no data to process (reading from a BlockingQueue). If the queue is empty and there will be no more work going into the queue, then I must call the Thread.Interrupt method if I want to interrupt the blocking task, but how does one do the same thing with a ThreadPool? The code might look like this: void Run() { try { while(true) { blockingQueue.Dequeue(); doSomething(); } } finally { countDownLatch.Signal(); } } I'm aware that the best thing to do in this situation is use a regular Thread, but I'm wondering if there is a ThreadPool equivalent way to interrupt a work item.

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• Graphics glitch when drawing to a Cairo context obtained from a gtk.DrawingArea inside a gtk.Viewport.

  - by user410023

  I am trying to redraw the part of the DrawingArea that is visible in the Viewport in the expose-event handler. However, it seems that I am doing something wrong with the coordinates that are passed to the event handler because there is garbage at the edge of the Viewport when scrolling. Can anyone tell what I am doing wrong? Here is a small example: import pygtk pygtk.require("2.0") import gtk from numpy import array from math import pi class Circle(object): def init(self, position = [0., 0.], radius = 0., edge = (0., 0., 0.), fill = None): self.position = position self.radius = radius self.edge = edge self.fill = fill def draw(self, ctx): rect = array(ctx.clip_extents()) rect[2] -= rect[0] rect[3] -= rect[1] center = rect[2:4] / 2 ctx.arc(center[0], center[1], self.radius, 0., 2. * pi) if self.fill != None: ctx.set_source_rgb(*self.fill) ctx.fill_preserve() ctx.set_source_rgb(*self.edge) ctx.stroke() class Scene(object): class Proxy(object): directory = {} def init(self, target, layers = set()): self.target = target self.layers = layers Scene.Proxy.directory[target] = self def __init__(self, viewport): self.objects = {} self.layers = [set()] self.viewport = viewport self.signals = {} def draw(self, ctx): x = self.viewport.get_hadjustment().value y = self.viewport.get_vadjustment().value ctx.set_source_rgb(1., 1., 1.) ctx.paint() ctx.translate(x, y) for obj in self: obj.draw(ctx) def add(self, item, layer = 0): item = Scene.Proxy(item, layers = set((layer,))) assert(hasattr(item.target, "draw")) assert(isinstance(layer, int)) item.layers.add(layer) while not layer < len(self.layers): self.layers.append(set()) self.layers[layer].add(item) if not item in self.objects: self.objects[item] = set() self.objects[item].add(layer) def remove(self, item, layers = None): item = Scene.Proxy.directory[item] if layers == None: layers = self.objects[item] for layer in layers: layer.remove(item) item.layers.remove(layer) if len(item.layers) == 0: self.objects.remove(item) def __iter__(self): for layer in self.layers: for item in layer: yield item.target class App(object): def init(self): signals = { "canvas_exposed": self.update_canvas, "gtk_main_quit": gtk.main_quit } self.builder = gtk.Builder() self.builder.add_from_file("graphics_glitch.glade") self.window = self.builder.get_object("window") self.viewport = self.builder.get_object("viewport") self.canvas = self.builder.get_object("canvas") self.scene = Scene(self.viewport) signals.update(self.scene.signals) self.builder.connect_signals(signals) self.window.show() def update_canvas(self, widget, event): ctx = self.canvas.window.cairo_create() self.scene.draw(ctx) ctx.clip() if name == "main": app = App() scene = app.scene scene.add(Circle((0., 0.), 10.)) gtk.main() And the Glade file "graphics_glitch.glade": <?xml version="1.0"?> <interface> <requires lib="gtk+" version="2.16"/> <!-- interface-naming-policy project-wide --> <object class="GtkWindow" id="window"> <property name="width_request">200</property> <property name="height_request">200</property> <property name="visible">True</property> <signal name="destroy" handler="gtk_main_quit"/> <child> <object class="GtkScrolledWindow" id="scrolledwindow1"> <property name="visible">True</property> <property name="can_focus">True</property> <property name="hadjustment">h_adjust</property> <property name="vadjustment">v_adjust</property> <property name="hscrollbar_policy">automatic</property> <property name="vscrollbar_policy">automatic</property> <child> <object class="GtkViewport" id="viewport"> <property name="visible">True</property> <property name="resize_mode">queue</property> <child> <object class="GtkDrawingArea" id="canvas"> <property name="width_request">640</property> <property name="height_request">480</property> <property name="visible">True</property> <signal name="expose_event" handler="canvas_exposed"/> </object> </child> </object> </child> </object> </child> </object> <object class="GtkAdjustment" id="h_adjust"> <property name="lower">-1000</property> <property name="upper">1000</property> <property name="step_increment">1</property> <property name="page_increment">25</property> <property name="page_size">25</property> </object> <object class="GtkAdjustment" id="v_adjust"> <property name="lower">-1000</property> <property name="upper">1000</property> <property name="step_increment">1</property> <property name="page_increment">25</property> <property name="page_size">25</property> </object> </interface> Thanks! --Dan

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• GCC destructor behaviour

  - by joveha

  I've noticed a difference in behaviour for gcc's destructor when compiled under linux and crosscompiled with mingw. On linux the destructor will not get called unless the program terminates normally by itself (returns from main). I guess that kind of makes sense if you take signal handlers into account. On Win32 however, the destructor is called if the program is terminated by say a CTRL-C, but not when killed from the Task Manager. Why is this? And what would you suggest to make the destructor get called no matter how the process terminates - on Win32 in particular? Example code: #include <stdio.h> int main(int argc, char **argv) { printf("main\n"); while(1) {} return 0; } __attribute__((destructor)) static void mydestructor(void) { printf("destructor\n"); }

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• Is it safe to catch an access violation in this scenario?

  - by Eloff

  I've read a lot, including here on SO that suggests this is a very bad idea in general and that the only thing you can do safely is exit the program. I'm not sure that this is true. This is for a pooling memory allocator that hands off large allocations to malloc. During pool_free() a pointer needs to be checked it it belongs to a pool or was allocated with malloc. By rounding the address down to the nearest 1MB boundary, I get a pointer to the beginning of a block of memory in the pool, or undefined if malloc was used. In the first case I can easily verify that the block of memory belongs to the pool, but, if it does not I will either fail this verification, or I will get an access violation (note that this is a read-only process). Could I not catch this with SEH (Windows) or handle the signal (POSIX) and simply treat it as a failed verification? (i.e. this is only possible if malloc was used, so pass the ptr to free())

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• SMS war continues, ideas welcome

  - by Pavel Radzivilovsky

  I am trying to make U9 telit modem send SMS messages. I think I handle protocol correctly, at least, I manage to send them, but only under these circumstances: the native application was executed beforehand, and killed by task manager (without giving it a chance to initialize things). It looks like the supplied application is good at doing certain initialization/deinitialization which is critical. I also see the difference between the two states in output of AT+CIND command. When I am trying to do things on my own, it returns zeroes (including signal quality), but when I run the same command after killing the native application, the output looks reasonable. I am out nearly of ideas. I have tried many things, including attempts to spy at modem's COM ports (didn't work). Haven't tried setting windows hooks to see what the application is trying to get thru. Perhaps you have encountered a similar situation?

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• what is the idea behind scaling an image using lanczos?

  - by banister

  Hi, I'm interested in image scaling algorithms and have implemented the bilinear and bicubic methods. However, I have heard of the lanczos and other more sophisticated methods for even higher quality image scaling and I am very curious how they work. Could someone here explain the basic idea behind scaling an image using lanczos (both upscaling and downscaling) and why it results in higher quality? I do have a background in fourier analysis and have done some signal processing stuff in the past, but not with relation to image processing, so don't be afraid to use terms like "frequency response" and such in your answer :) EDIT: I guess what i really want to know is the concept and theory behind using a convolution filter for interpolation. (Note: i have already read the wikipedia article on lanczos resampling but it didn't have nearly enough detail for me) thanks alot!

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• Unknown error in Producer/Consumer program, believe it to be an infinite loop.

  - by ray2k

  Hello, I am writing a program that is solving the producer/consumer problem, specifically the bounded-buffer version(i believe they mean the same thing). The producer will be generating x number of random numbers, where x is a command line parameter to my program. At the current moment, I believe my program is entering an infinite loop, but I'm not sure why it is occurring. I believe I am executing the semaphores correctly. You compile it like this: gcc -o prodcon prodcon.cpp -lpthread -lrt Then to run, ./prodcon 100(the number of randum nums to produce) This is my code. typedef int buffer_item; #include <stdlib.h> #include <stdio.h> #include <pthread.h> #include <semaphore.h> #include <unistd.h> #define BUFF_SIZE 10 #define RAND_DIVISOR 100000000 #define TRUE 1 //two threads void *Producer(void *param); void *Consumer(void *param); int insert_item(buffer_item item); int remove_item(buffer_item *item); int returnRandom(); //the global semaphores sem_t empty, full, mutex; //the buffer buffer_item buf[BUFF_SIZE]; //buffer counter int counter; //number of random numbers to produce int numRand; int main(int argc, char** argv) { /* thread ids and attributes */ pthread_t pid, cid; pthread_attr_t attr; pthread_attr_init(&attr); pthread_attr_setscope(&attr, PTHREAD_SCOPE_SYSTEM); numRand = atoi(argv[1]); sem_init(&empty,0,BUFF_SIZE); sem_init(&full,0,0); sem_init(&mutex,0,0); printf("main started\n"); pthread_create(&pid, &attr, Producer, NULL); pthread_create(&cid, &attr, Consumer, NULL); printf("main gets here"); pthread_join(pid, NULL); pthread_join(cid, NULL); printf("main done\n"); return 0; } //generates a randum number between 1 and 100 int returnRandom() { int num; srand(time(NULL)); num = rand() % 100 + 1; return num; } //begin producing items void *Producer(void *param) { buffer_item item; int i; for(i = 0; i < numRand; i++) { //sleep for a random period of time int rNum = rand() / RAND_DIVISOR; sleep(rNum); //generate a random number item = returnRandom(); //acquire the empty lock sem_wait(&empty); //acquire the mutex lock sem_wait(&mutex); if(insert_item(item)) { fprintf(stderr, " Producer report error condition\n"); } else { printf("producer produced %d\n", item); } /* release the mutex lock */ sem_post(&mutex); /* signal full */ sem_post(&full); } return NULL; } /* Consumer Thread */ void *Consumer(void *param) { buffer_item item; int i; for(i = 0; i < numRand; i++) { /* sleep for a random period of time */ int rNum = rand() / RAND_DIVISOR; sleep(rNum); /* aquire the full lock */ sem_wait(&full); /* aquire the mutex lock */ sem_wait(&mutex); if(remove_item(&item)) { fprintf(stderr, "Consumer report error condition\n"); } else { printf("consumer consumed %d\n", item); } /* release the mutex lock */ sem_post(&mutex); /* signal empty */ sem_post(&empty); } return NULL; } /* Add an item to the buffer */ int insert_item(buffer_item item) { /* When the buffer is not full add the item and increment the counter*/ if(counter < BUFF_SIZE) { buf[counter] = item; counter++; return 0; } else { /* Error the buffer is full */ return -1; } } /* Remove an item from the buffer */ int remove_item(buffer_item *item) { /* When the buffer is not empty remove the item and decrement the counter */ if(counter > 0) { *item = buf[(counter-1)]; counter--; return 0; } else { /* Error buffer empty */ return -1; } }

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• Can we represent bit fields in JSON/BSON?

  - by zubair

  We have a dozen simulators talking to each other on UDP. The interface definition is managed in a database. The simulators are written using different languages; mostly C++, some in Java and C#. Currently, when systems engineer makes changes in the interface definition database, simulator developers manually update the communication data structures in their code. The data is mostly 2-5 bytes with bit fields for each signal. What I want to do is to generate one file from interface definition database describing byte and bit field definitions and let each developer add it to his simulator code with minimal fuss. I looked at JSON/BSON but couldn't find a way to represent bit fields in it. Thanks Zubair

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• Cannot understand NullPointerException with custom adapter

  - by ganesh

  hi, I am trying to create a list view which as TextView that can display html content , an WebView and other basic TextViews.I tried to extend SimpleAdapter but i struck with the problem ,I will be glad if someone can point out the mistake i am doing. In onCreate method ArrayList mylist= resultfromXmlparser(); adap = new MyAdapter(TourLandingPage.this, mylist, R.layout.row, new String[] {"Name", "desc","Duration","Price","imgurl"}, new int[] {R.id.productname,R.id.des,R.id.duration,R.id.pricefrom,R.id.photo}); setListAdapter(adap); My custom Adapter looks like this private class MyAdapter extends SimpleAdapter { ArrayList<HashMap<String,String>> elements; Context ctx; public MyAdapter(Context context, ArrayList<HashMap<String,String>> mylist,int textViewResourceId,String[] names,int[] resouceid) { super(context, mylist,textViewResourceId, names,resouceid); this.elements=mylist; this.ctx=context; } @Override public int getCount() { return elements.size(); } @Override public Object getItem(int position) { return elements.get(position); } @Override public long getItemId(int position) { return position; } @Override public View getView(int position, View convertView, ViewGroup parent) { RelativeLayout rowLayout; if (convertView == null) { rowLayout = (RelativeLayout) LayoutInflater.from(ctx).inflate(R.layout.rowfor_tourlist, parent, false); } else { rowLayout = (RelativeLayout) convertView; } TextView in = (TextView)rowLayout.findViewById(R.id.introduction); TextView du = (TextView)rowLayout.findViewById(R.id.duration); TextView pf = (TextView)rowLayout.findViewById(R.id.pricefrom); TextView pn = (TextView)rowLayout.findViewById(R.id.productname); WebView wv=(WebView)rowLayout.findViewById(R.id.photo); in.setText(Html.fromHtml(mylist.get(position).get("desc"))); du.setText(mylist.get(position).get("Duration")); pf.setText(mylist.get(position).get("Price")); pn.setText(mylist.get(position).get("Name")); wv.getSettings().setJavaScriptEnabled(true); wv.loadUrl(mylist.get(position).get("imgurl")); return convertView; } }//class and my row.xml file looks like RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" TextView android:id="@+id/productname" ...... LinearLayout android:layout_width="wrap_content" android:layout_height="60dip" android:layout_margin="5dip" android:layout_below="@id/productname" android:orientation="horizontal" android:id="@+id/lay1" WebView android:id="@+id/photo" .... TextView android:id="@+id/introduction" ...... LinearLayout TextView android:id="@+id/duration" .... TextView android:id="@+id/pricefrom" ..... RelativeLayout The error i was getting was 04-28 19:46:17.749: ERROR/AndroidRuntime(976): Uncaught handler: thread main exiting due to uncaught exception 04-28 19:46:17.769: ERROR/AndroidRuntime(976): java.lang.NullPointerException 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at android.widget.ListView.setupChild(ListView.java:1693) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at android.widget.ListView.makeAndAddView(ListView.java:1671) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at android.widget.ListView.fillDown(ListView.java:637) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at android.widget.ListView.fillFromTop(ListView.java:694) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at android.widget.ListView.layoutChildren(ListView.java:1521) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at android.widget.AbsListView.onLayout(AbsListView.java:1113) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at android.view.View.layout(View.java:6831) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1119) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at android.widget.LinearLayout.layoutHorizontal(LinearLayout.java:1108) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at android.widget.LinearLayout.onLayout(LinearLayout.java:920) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at android.view.View.layout(View.java:6831) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1119) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:998) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at android.widget.LinearLayout.onLayout(LinearLayout.java:918) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at android.view.View.layout(View.java:6831) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at android.widget.FrameLayout.onLayout(FrameLayout.java:333) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at android.view.View.layout(View.java:6831) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1119) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at android.widget.LinearLayout.layoutVertical(LinearLayout.java:998) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at android.widget.LinearLayout.onLayout(LinearLayout.java:918) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at android.view.View.layout(View.java:6831) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at android.widget.FrameLayout.onLayout(FrameLayout.java:333) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at android.view.View.layout(View.java:6831) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at android.view.ViewRoot.performTraversals(ViewRoot.java:996) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at android.view.ViewRoot.handleMessage(ViewRoot.java:1633) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at android.os.Handler.dispatchMessage(Handler.java:99) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at android.os.Looper.loop(Looper.java:123) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at android.app.ActivityThread.main(ActivityThread.java:4338) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at java.lang.reflect.Method.invokeNative(Native Method) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at java.lang.reflect.Method.invoke(Method.java:521) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618) 04-28 19:46:17.769: ERROR/AndroidRuntime(976): at dalvik.system.NativeStart.main(Native Method) 04-28 19:46:17.789: INFO/Process(52): Sending signal. PID: 976 SIG: 3 04-28 19:46:17.799: INFO/dalvikvm(976): threadid=7: reacting to signal 3 04-28 19:46:17.829: INFO/dalvikvm(976): Wrote stack trace to '/data/anr/traces.txt'

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• Audio processing in C# or C++

  - by melculetz

  Hi, I would like to create an application that uses AI techniques and allows the user to record a part of a song and then tries to find that song in a database of wav files. I would have liked to use some already existing libraries for the audio processing part. So, could you recommend any libraries in C# which can read a wav file, get input from microphone, have some audio filters (low pass, high pass, FFT etc) and maybe have the ability to plot the audio signal as well. I would prefer to develop in C#, but if there aren't good libraries for audio processing, I guess I could work in C++ as well. As far as I know, Mathlab already has the above mentioned functionalities, but I can't use it in my application.

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• How to detect that a server had closed the socket / crashed in the client side ?

  - by Spredzy

  Hi all, I am developing a Client/Server application. I would like to know how can I detect that a server had closed the socket or had crashed in the client side (my android App) I am running on one side my android app, that is connected. On the other side I am running netcat (for testing purpose). I Would like to know what signal is sent to my client socket or what happen when I kill netcat. Because now, I immediately get an error message that impose me to "Force Close" my application. How can I handle it properly ? Thank you

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• Initiate a PHP class where class name is a variable

  - by ed209

  I need some help with an error I have not encountered before and can't seem to find anywhere. In a PHP mvc framework (just from a tutorial) I have the following: // Initiate the class $className = 'Controller_' . ucfirst($controller); if (class_exists($className)) { $controller = new $className($this->registry); } $className is showing the correct class name (case is also correct). But when I run it I get this in the apache error log (no php error) [Wed Mar 31 10:34:12 2010] [notice] child pid 987 exit signal Segmentation fault (11) Process id is different on every call. I am running PHP 5.3.0 on os x 10.6. This site seems to work on 5.2.11 on another Mac. Not really sure where to go next to debug it. I guess it could be an apache setting as much as a php bug or a problem with the code... any suggestions on where to look next?

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• Multiple Context menus in PyQt based on mouse location

  - by Nader

  I have a window with multiple tables using QTableWidget (PyQt). I created a popup menu using the right click mouse and it works fine. However, I need to create different popup menu based on which table the mouse is hovering over at the time the right mouse is clicked. How can I get the mouse to tell me which table it is hovering over? or, put in another way, how to implement a method so as to have a specific context menu based on mouse location? I am using Python and PyQt. My popup menu is developed similar to this code (PedroMorgan answer from Qt and context menu): class Foo( QtGui.QWidget ): def __init__(self): QtGui.QWidget.__init__(self, None) # Toolbar toolbar = QtGui.QToolBar() # Actions self.actionAdd = toolbar.addAction("New", self.on_action_add) self.actionEdit = toolbar.addAction("Edit", self.on_action_edit) self.actionDelete = toolbar.addAction("Delete", self.on_action_delete) # Tree self.tree = QtGui.QTreeView() self.tree.setContextMenuPolicy( Qt.CustomContextMenu ) self.connect(self.tree, QtCore.SIGNAL('customContextMenuRequested(const QPoint&)'), self.on_context_menu) # Popup Menu self.popMenu = QtGui.QMenu( self ) self.popMenu.addAction( self.actionEdit ) self.popMenu.addAction( self.actionDelete ) self.popMenu.addSeparator() self.popMenu.addAction( self.actionAdd ) def on_context_menu(self, point): self.popMenu.exec_( self.tree.mapToGlobal(point) )

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• Where should I catch WM_HIBERNATE and WM_CLOSE in Windows Mobile/WinCE?

  - by afriza

  I have read about Windows Mobile's X button's behaviour, WM_HIBERNATE, and WM_CLOSE on Low Memory Situation. MSDN on WM_HIBERNATE: This message is sent to an application when system resources are running low. An application should attempt to release as many resources as possible when sent this message by unloading dialog boxes, destroying windows, or freeing up as much local storage as possible without changing the internal state. MSDN on WM_CLOSE: This message is sent as a signal that a window or an application should terminate. Where should I catch the message? in the main message pump? in every window? or only some windows? If I am using MFC, where should I catch it?

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• Coredump in Multithreading Application in RHEL-5(Help Required)

  - by Chinnu

  I am working on multi-threading application it is dumping frequently.I could not able to analyaze the core.The core is showing like this Core was generated by `thread-process '. Program terminated with signal 6, Aborted. 0 0x00000038f4e30045 in raise () from /lib64/libc.so.6 (gdb) where 0 0x00000038f4e30045 in raise () from /lib64/libc.so.6 1 0x00000038f4e31ae0 in abort () from /lib64/libc.so.6 2 0x00000038f4e681bb in __libc_message () from /lib64/libc.so.6 3 0x00000038f4e72b96 in free () from /lib64/libc.so.6 4 0x000000000046a137 in std::string::substr () 5 0x000000000042c549 in std::operator<< , std::allocator () 6 0x000000000042cc1d in std::operator<< , std::allocator () 7 0x000000000046b069 in std::string::substr () 8 0x000000000046c866 in std::string::substr () 9 0x0000000000431062 in std::operator<< , std::allocator () 10 0x00000038f5a062e7 in start_thread () from /lib64/libpthread.so.0 11 0x00000038f4ece3bd in clone () from /lib64/libc.so.6

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