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• Hash Functions. Commonly used method h(k) = k mod M,, Why we choose value of M to be prime no.

  - by RBA

  Hi, Please share the reason why in Hash Functions, the common method i.e. h(k) = k mod M... Why we choose the value of M to be always prime no. Thanks..

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• Why wont a simple socket to the localhost connect?

  - by Jake M

  I am following a tutorial that teaches me how to use win32 sockets(winsock2). I am attempting to create a simple socket that connects to the "localhost" but my program is failing when I attempt to connect to the local host(at the function connect()). Do I need admin privileges to connect to the localhost? Maybe thats why it fails? Maybe theres a problem with my code? I have tried the ports 8888 & 8000 & they both fail. Also if I change the port to 80 & connect to www.google.com I can connect BUT I get no response back. Is that because I haven't sent a HTTP request or am I meant to get some response back? Here's my code (with the includes removed): // Constants & Globals // typedef unsigned long IPNumber; // IP number typedef for IPv4 const int SOCK_VER = 2; const int SERVER_PORT = 8888; // 8888 SOCKET mSocket = INVALID_SOCKET; SOCKADDR_IN sockAddr = {0}; WSADATA wsaData; HOSTENT* hostent; int _tmain(int argc, _TCHAR* argv[]) { // Initialise winsock version 2.2 if (WSAStartup(MAKEWORD(SOCK_VER,2), &wsaData) != 0) { printf("Failed to initialise winsock\n"); WSACleanup(); system("PAUSE"); return 0; } if (LOBYTE(wsaData.wVersion) != SOCK_VER || HIBYTE(wsaData.wVersion) != 2) { printf("Failed to load the correct winsock version\n"); WSACleanup(); system("PAUSE"); return 0; } // Create socket mSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP); if (mSocket == INVALID_SOCKET) { printf("Failed to create TCP socket\n"); WSACleanup(); system("PAUSE"); return 0; } // Get IP Address of website by the domain name, we do this by contacting(??) the Domain Name Server if ((hostent = gethostbyname("localhost")) == NULL) // "localhost" www.google.com { printf("Failed to resolve website name to an ip address\n"); WSACleanup(); system("PAUSE"); return 0; } sockAddr.sin_port = htons(SERVER_PORT); sockAddr.sin_family = AF_INET; sockAddr.sin_addr.S_un.S_addr = (*reinterpret_cast <IPNumber*> (hostent->h_addr_list[0])); // sockAddr.sin_addr.s_addr=*((unsigned long*)hostent->h_addr); // Can also do this // ERROR OCCURS ON NEXT LINE: Connect to server if (connect(mSocket, (SOCKADDR*)(&sockAddr), sizeof(sockAddr)) != 0) { printf("Failed to connect to server\n"); WSACleanup(); system("PAUSE"); return 0; } printf("Got to here\r\n"); // Display message from server char buffer[1000]; memset(buffer,0,999); int inDataLength=recv(mSocket,buffer,1000,0); printf("Response: %s\r\n", buffer); // Shutdown our socket shutdown(mSocket, SD_SEND); // Close our socket entirely closesocket(mSocket); // Cleanup Winsock WSACleanup(); system("pause"); return 0; }

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• Why does adding a Flex DateChooser component throw an index out of bounds error?

  - by Lo'

  I'm facing an issue with the flex Application I'm currently working on. When I open a pop-up using the 'createPopUp' method, I've got this index out of bounds error message : RangeError: The supplied index is out of bounds. at mx.core::FTETextField/getLineMetrics()[E:\dev\4.y\frameworks\projects\spark\src\mx\core\FTETextField.as:2169] at mx.core::UIFTETextField/get baselinePosition()[E:\dev\4.y\frameworks\projects\spark\src\mx\core\UIFTETextField.as:784] at mx.controls::DateChooser/get baselinePosition()[E:\dev\4.y\frameworks\projects\mx\src\mx\controls\DateChooser.as:994] at spark.components::Group/get baselinePosition()[E:\dev\4.y\frameworks\projects\spark\src\spark\components\Group.as:282] at spark.layouts::ConstraintLayout/parseElementConstraints()[E:\dev\4.y\frameworks\projects\spark\src\spark\layouts\ConstraintLayout.as:1818] at spark.layouts::ConstraintLayout/parseConstraints()[E:\dev\4.y\frameworks\projects\spark\src\spark\layouts\ConstraintLayout.as:1632] at spark.layouts::ConstraintLayout/measure()[E:\dev\4.y\frameworks\projects\spark\src\spark\layouts\ConstraintLayout.as:414] at spark.components.supportClasses::GroupBase/measure()[E:\dev\4.y\frameworks\projects\spark\src\spark\components\supportClasses\GroupBase.as:1148] at mx.core::UIComponent/http://www.adobe.com/2006/flex/mx/internal::measureSizes()[E:\dev\4.y\frameworks\projects\framework\src\mx\core\UIComponent.as:8506] at mx.core::UIComponent/validateSize()[E:\dev\4.y\frameworks\projects\framework\src\mx\core\UIComponent.as:8430] at spark.components::Group/validateSize()[E:\dev\4.y\frameworks\projects\spark\src\spark\components\Group.as:1012] at mx.managers::LayoutManager/validateClient()[E:\dev\4.y\frameworks\projects\framework\src\mx\managers\LayoutManager.as:987] at mx.managers::PopUpManagerImpl/addPopUp()[E:\dev\4.y\frameworks\projects\framework\src\mx\managers\PopUpManagerImpl.as:382] at mx.managers::PopUpManagerImpl/createPopUp()[E:\dev\4.y\frameworks\projects\framework\src\mx\managers\PopUpManagerImpl.as:232] at mx.managers::PopUpManager$/createPopUp()[E:\dev\4.y\frameworks\projects\framework\src\mx\managers\PopUpManager.as:139] at views::AddProjects/loadAddProjectPopUp()[C:\Users\Laura\Web\spidermak\spidermak\src\views\AddProjects.mxml:184] at views::AddProjects/___AddProjects_Button1_click()[C:\Users\Laura\Web\spidermak\spidermak\src\views\AddProjects.mxml:838] It seems that this error is caused by a "dateChooser" component in my popup : <mx:DateChooser id="endDate"/> When I comment this line, the error is no longer thrown and the popup loads correctly. It's really weird because I didn't have this issue until this morning. All I did in the meantime was changing some layout-related stuff, but I don't see what is would have to do with this problem. I don't get it... Does anyone have a clue about how to fix this ? I need my DateChooser ! Thanks ! Laura EDIT - It seems that the problem is not caused by the DateChooser itself, but by the FormItem around it. Here's what my code looks like : <Form width="100%"> [...] <s:HGroup width="100%"> <s:FormItem label="Date de début"> <mx:DateChooser id="startDate" firstDayOfWeek="1"/> </s:FormItem> <s:FormItem label="Date de fin"> <mx:DateChooser id="endDate" firstDayOfWeek="1"/> </s:FormItem> </s:HGroup> </Form> If I remove the two FormItems, it works. Could anyone explain me why? Thanks !

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• Why doesn't my implementation of ElGamal work for long text strings?

  - by angstrom91

  I'm playing with the El Gamal cryptosystem, and my goal is to be able to encipher and decipher long sequences of text. I have come up with a method that works for short sequences, but does not work for long sequences, and I cannot figure out why. El Gamal requires the plaintext to be an integer. I have turned my string into a byte[] using the .getBytes() method for Strings, and then created a BigInteger out of the byte[]. After encryption/decryption, I turn the BigInteger into a byte[] using the .toByteArray() method for BigIntegers, and then create a new String object from the byte[]. This works perfectly when i call ElGamalEncipher with strings up to 129 characters. With 130 or more characters, the output produced from ElGamalDecipher is garbled. Can someone suggest how to solve this issue? Is this an issue with my method of turning the string into a BigInteger? If so, is there a better way to turn my string of text into a BigInteger and back? Below is my encipher/decipher code with a program to demonstrate the problem. import java.math.BigInteger; public class Main { static BigInteger P = new BigInteger("15893293927989454301918026303382412" + "2586402937727056707057089173871237566896685250125642378268385842" + "6917261652781627945428519810052550093673226849059197769795219973" + "9423619267147615314847625134014485225178547696778149706043781174" + "2873134844164791938367765407368476144402513720666965545242487520" + "288928241768306844169"); static BigInteger G = new BigInteger("33234037774370419907086775226926852" + "1714093595439329931523707339920987838600777935381196897157489391" + "8360683761941170467795379762509619438720072694104701372808513985" + "2267495266642743136795903226571831274837537691982486936010899433" + "1742996138863988537349011363534657200181054004755211807985189183" + "22832092343085067869"); static BigInteger R = new BigInteger("72294619754760174015019300613282868" + "7219874058383991405961870844510501809885568825032608592198728334" + "7842806755320938980653857292210955880919036195738252708294945320" + "3969657021169134916999794791553544054426668823852291733234236693" + "4178738081619274342922698767296233937873073756955509269717272907" + "8566607940937442517"); static BigInteger A = new BigInteger("32189274574111378750865973746687106" + "3695160924347574569923113893643975328118502246784387874381928804" + "6865920942258286938666201264395694101012858796521485171319748255" + "4630425677084511454641229993833255506759834486100188932905136959" + "7287419551379203001848457730376230681693887924162381650252270090" + "28296990388507680954"); public static void main(String[] args) { FewChars(); System.out.println(); ManyChars(); } public static void FewChars() { //ElGamalEncipher(String plaintext, BigInteger p, BigInteger g, BigInteger r) BigInteger[] cipherText = ElGamal.ElGamalEncipher("This is a string " + "of 129 characters which works just fine . This is a string " + "of 129 characters which works just fine . This is a s", P, G, R); System.out.println("This is a string of 129 characters which works " + "just fine . This is a string of 129 characters which works " + "just fine . This is a s"); //ElGamalDecipher(BigInteger c, BigInteger d, BigInteger a, BigInteger p) System.out.println("The decrypted text is: " + ElGamal.ElGamalDecipher(cipherText[0], cipherText[1], A, P)); } public static void ManyChars() { //ElGamalEncipher(String plaintext, BigInteger p, BigInteger g, BigInteger r) BigInteger[] cipherText = ElGamal.ElGamalEncipher("This is a string " + "of 130 characters which doesn’t work! This is a string of " + "130 characters which doesn’t work! This is a string of ", P, G, R); System.out.println("This is a string of 130 characters which doesn’t " + "work! This is a string of 130 characters which doesn’t work!" + " This is a string of "); //ElGamalDecipher(BigInteger c, BigInteger d, BigInteger a, BigInteger p) System.out.println("The decrypted text is: " + ElGamal.ElGamalDecipher(cipherText[0], cipherText[1], A, P)); } } import java.math.BigInteger; import java.security.SecureRandom; public class ElGamal { public static BigInteger[] ElGamalEncipher(String plaintext, BigInteger p, BigInteger g, BigInteger r) { // returns a BigInteger[] cipherText // cipherText[0] is c // cipherText[1] is d SecureRandom sr = new SecureRandom(); BigInteger[] cipherText = new BigInteger[2]; BigInteger pText = new BigInteger(plaintext.getBytes()); // 1: select a random integer k such that 1 <= k <= p-2 BigInteger k = new BigInteger(p.bitLength() - 2, sr); // 2: Compute c = g^k(mod p) BigInteger c = g.modPow(k, p); // 3: Compute d= P*r^k = P(g^a)^k(mod p) BigInteger d = pText.multiply(r.modPow(k, p)).mod(p); // C =(c,d) is the ciphertext cipherText[0] = c; cipherText[1] = d; return cipherText; } public static String ElGamalDecipher(BigInteger c, BigInteger d, BigInteger a, BigInteger p) { //returns the plaintext enciphered as (c,d) // 1: use the private key a to compute the least non-negative residue // of an inverse of (c^a)' (mod p) BigInteger z = c.modPow(a, p).modInverse(p); BigInteger P = z.multiply(d).mod(p); byte[] plainTextArray = P.toByteArray(); return new String(plainTextArray); } }

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• Why are there 3 conflicting OpenCV camera calibration formulas?

  - by John

  I'm having a problem with OpenCV's various parameterization of coordinates used for camera calibration purposes. The problem is that three different sources of information on image distortion formulae apparently give three non-equivalent description of the parameters and equations involved: (1) In their book "Learning OpenCV…" Bradski and Kaehler write regarding lens distortion (page 376): xcorrected = x * ( 1 + k1 * r^2 + k2 * r^4 + k3 * r^6 ) + [ 2 * p1 * x * y + p2 * ( r^2 + 2 * x^2 ) ], ycorrected = y * ( 1 + k1 * r^2 + k2 * r^4 + k3 * r^6 ) + [ p1 * ( r^2 + 2 * y^2 ) + 2 * p2 * x * y ], where r = sqrt( x^2 + y^2 ). Assumably, (x, y) are the coordinates of pixels in the uncorrected captured image corresponding to world-point objects with coordinates (X, Y, Z), camera-frame referenced, for which xcorrected = fx * ( X / Z ) + cx and ycorrected = fy * ( Y / Z ) + cy, where fx, fy, cx, and cy, are the camera's intrinsic parameters. So, having (x, y) from a captured image, we can obtain the desired coordinates ( xcorrected, ycorrected ) to produced an undistorted image of the captured world scene by applying the above first two correction expressions. However... (2) The complication arises as we look at OpenCV 2.0 C Reference entry under the Camera Calibration and 3D Reconstruction section. For ease of comparison we start with all world-point (X, Y, Z) coordinates being expressed with respect to the camera's reference frame, just as in #1. Consequently, the transformation matrix [ R | t ] is of no concern. In the C reference, it is expressed that: x' = X / Z, y' = Y / Z, x'' = x' * ( 1 + k1 * r'^2 + k2 * r'^4 + k3 * r'^6 ) + [ 2 * p1 * x' * y' + p2 * ( r'^2 + 2 * x'^2 ) ], y'' = y' * ( 1 + k1 * r'^2 + k2 * r'^4 + k3 * r'^6 ) + [ p1 * ( r'^2 + 2 * y'^2 ) + 2 * p2 * x' * y' ], where r' = sqrt( x'^2 + y'^2 ), and finally that u = fx * x'' + cx, v = fy * y'' + cy. As one can see these expressions are not equivalent to those presented in #1, with the result that the two sets of corrected coordinates ( xcorrected, ycorrected ) and ( u, v ) are not the same. Why the contradiction? It seems to me the first set makes more sense as I can attach physical meaning to each and every x and y in there, while I find no physical meaning in x' = X / Z and y' = Y / Z when the camera focal length is not exactly 1. Furthermore, one cannot compute x' and y' for we don't know (X, Y, Z). (3) Unfortunately, things get even murkier when we refer to the writings in Intel's Open Source Computer Vision Library Reference Manual's section Lens Distortion (page 6-4), which states in part: "Let ( u, v ) be true pixel image coordinates, that is, coordinates with ideal projection, and ( u ~, v ~ ) be corresponding real observed (distorted) image coordinates. Similarly, ( x, y ) are ideal (distortion-free) and ( x ~, y ~ ) are real (distorted) image physical coordinates. Taking into account two expansion terms gives the following: x ~ = x * ( 1 + k1 * r^2 + k2 * r^4 ) + [ 2 p1 * x * y + p2 * ( r^2 + 2 * x^2 ) ] y ~ = y * ( 1 + k1 * r^2 + k2 * r^4 ] + [ 2 p2 * x * y + p2 * ( r^2 + 2 * y^2 ) ], where r = sqrt( x^2 + y^2 ). ... "Because u ~ = cx + fx * u and v ~ = cy + fy * v , … the resultant system can be rewritten as follows: u ~ = u + ( u – cx ) * [ k1 * r^2 + k2 * r^4 + 2 * p1 * y + p2 * ( r^2 / x + 2 * x ) ] v ~ = v + ( v – cy ) * [ k1 * r^2 + k2 * r^4 + 2 * p2 * x + p1 * ( r^2 / y + 2 * y ) ] The latter relations are used to undistort images from the camera." Well, it would appear that the expressions involving x ~ and y ~ coincided with the two expressions given at the top of this writing involving xcorrected and ycorrected. However, x ~ and y ~ do not refer to corrected coordinates, according to the given description. I don't understand the distinction between the meaning of the coordinates ( x ~, y ~ ) and ( u ~, v ~ ), or for that matter, between the pairs ( x, y ) and ( u, v ). From their descriptions it appears their only distinction is that ( x ~, y ~ ) and ( x, y ) refer to 'physical' coordinates while ( u ~, v ~ ) and ( u, v ) do not. What is this distinction all about? Aren't they all physical coordinates? I'm lost! Thanks for any input!

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• Why does my Ajax function returns my entire code?

  - by JDelage

  I'm playing with sample code from the book "Head first Ajax". Here are the salient pieces of code: Index.php - html piece: <body> <div id="wrapper"> <div id="thumbnailPane"> <img src="images/itemGuitar.jpg" width="301" height="105" alt="guitar" title="itemGuitar" id="itemGuitar" onclick="getDetails(this)"/> <img src="images/itemShades.jpg" alt="sunglasses" width="301" height="88" title="itemShades" id="itemShades" onclick="getDetails(this)" /> <img src="images/itemCowbell.jpg" alt="cowbell" width="301" height="126" title="itemCowbell" id="itemCowbell" onclick="getDetails(this)" /> <img src="images/itemHat.jpg" alt="hat" width="300" height="152" title="itemHat" id="itemHat" onclick="getDetails(this)" /> </div> <div id="detailsPane"> <img src="images/blank-detail.jpg" width="346" height="153" id="itemDetail" /> <div id="description"></div> </div> </div> </body> Index.php - script: function getDetails(img){ var title = img.title; request = createRequest(); if (request == null) { alert("Unable to create request"); return; } var url= "getDetails.php?ImageID=" + escape(title); request.open("GET", url, true); request.onreadystatechange = displayDetails; request.send(null); } function displayDetails() { if (request.readyState == 4) { if (request.status == 200) { detailDiv = document.getElementById("description"); detailDiv.innerHTML = request.responseText; }else{ return; } }else{ return; } request.send(null); } And Index.php: <?php $details = array ( 'itemGuitar' => "<p>Pete Townshend once played this guitar while his own axe was in the shop having bits of drumkit removed from it.</p>", 'itemShades' => "<p>Yoko Ono's sunglasses. While perhaps not valued much by Beatles fans, this pair is rumored to have been licked by John Lennon.</p>", 'itemCowbell' => "<p>Remember the famous \"more cowbell\" skit from Saturday Night Live? Well, this is the actual cowbell.</p>", 'itemHat' => "<p>Michael Jackson's hat, as worn in the \"Billie Jean\" video. Not really rock memorabilia, but it smells better than Slash's tophat.</p>" ); if (isset($_REQUEST['ImageID'])){echo $details[$_REQUEST['ImageID']];} ?> All this code does is that when someone clicks on a thumbnail, a corresponding text description appears on the page. Here is my question. I have tried to bring the getDetails.php code inside Index.php, and modify the getDetails function so that the var url be "Index.php?ImageID="... . When I do that, I get the following problem: the function does not display the snippet of text in the array, as it should. Instead it reproduces the entire code - the webpage, etc - and then at the bottom the expected snippet of text. Why is that?

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• IE / Facebook Issue : Why Facebook Like box not display in Internet Explorer 6 - IE8 ?

  - by Vaibhav Bhalke

  IE / Facebook Issue : Why Facebook Like box not display in Internet Explorer6 - IE8 ? Facebook like box display throgh my web application on every browser excluding IE-IE8 Now final Application.html file contains are < !DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/DTD/strict.dtd"><BR> < html xmlns="http://www.w3.org/1999/xhtml" xmlns:fb="http://www.facebook.com/2008/fbml"> <BR>< head> < meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7" /> < /head><BR> < body> < script type="text/javascript" language="javascript" src="http://static.ak.connect.facebook.com/js/api_lib/v0.4/FeatureLoader.js.php"> < /script> <BR> < script type="text/javascript"> FB_RequireFeatures(["Connect"], function(){ var x=1; } ); < /script> <BR> < script src="http://static.ak.connect.facebook.com/connect.php/en_US" type="text/javascript"> < /script> < /body> < /html> My Java code for LIke Box is as follows FBPageFanWidget.java class FBPageFanWidget extends Composite { public FBPageFanWidget() { VerticalPanel mainPanel = new VerticalPanel(); mainPanel .getElement() .setInnerHTML( "< script type='text/javascript' src='http://static.ak.connect.facebook.com/js/api_lib/v0.4/FeatureLoader.js.php/en_US'>< /script>< script type='text/javascript'>FB.init('');< /script>< fb:fan profile_id=\"113106068709539\" stream=\"0\" connections=\"10\" logobar=\"0\" width=\"244\" height=\"240\" css='http://127.0.01:8080/webapplicationname/facebook.css?1'>< /fb:fan>"); initWidget(mainPanel); } } We used proper facebook API_KEY & PAGE_ID It's very important for us to Show Facebook like Box in Our web application Because we have more IE users. If we add FBPageFanWidget.java in our web applicaton then Our Home page is not display in IE because we add Facebook LikeBox so we made changes in Our FBPageFanWidget.java class FBPageFanWidget extends Composite { public FBPageFanWidget() { VerticalPanel mainPanel = new VerticalPanel(); if (!isIE()) { mainPanel.getElement() .setInnerHTML("<script type='text/javascript' src='http://static.ak.connect.facebook.com/js/api_lib/v0.4/FeatureLoader.js.php/en_US'></script><script type='text/javascript'>FB.init('');</script><fb:fan profile_id=\"113106068709539\" stream=\"0\" connections=\"10\" logobar=\"0\" width=\"244\" height=\"240\" css='http://127.0.01:8080/webapplicationname/facebook.css?1'></fb:fan>"); } initWidget(mainPanel); } public native String getUserAgent() /*-{ return navigator.userAgent; }-*/; private boolean isIE() { return (getUserAgent().indexOf("MSIE") > -1); } } when we did this changes Then Facebook Like Box display in every browser excluding IE6 - IE8 :( and also display Our Home page in IE8 excludeing Facebook Like Box. It means There is probelm in IE ? or what changes i need to do in my html file or java file to show facebook like Box properly with displaying our home page It's very important for us to Show Facebook like Box in Our web application Because we have more IE users. Please Reply ASAP. Hope-for Best Co-operation from your side !!!!

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• Why so Long time span in creating Session Factory?

  - by vijay.shad

  Hi My project is web application running in the tomcat container. This application is a spring framework based hibernate application. The problem with this is it takes a lot of time when creates session factory. here is the logs 2010-04-15 23:05:28,053 DEBUG [SessionFactoryImpl] Session factory constructed with filter configurations : {} 2010-04-15 23:05:28,053 DEBUG [SessionFactoryImpl] instantiating session factory with properties: {java.vendor=Sun Microsystems Inc., sun.java.launcher=SUN_STANDARD, catalina.base=/usr/local/InstalledPrograms/apache-tomcat-6.0.20, sun.management.compiler=HotSpot Tiered Compilers, catalina.useNaming=true, os.name=Linux, sun.boot.class.path=/usr/java/jdk1.6.0_17/jre/lib/resources.jar:/usr/java/jdk1.6.0_17/jre/lib/rt.jar:/usr/java/jdk1.6.0_17/jre/lib/sunrsasign.jar:/usr/java/jdk1.6.0_17/jre/lib/jsse.jar:/usr/java/jdk1.6.0_17/jre/lib/jce.jar:/usr/java/jdk1.6.0_17/jre/lib/charsets.jar:/usr/java/jdk1.6.0_17/jre/classes, java.util.logging.config.file=/usr/local/InstalledPrograms/apache-tomcat-6.0.20/conf/logging.properties, java.vm.specification.vendor=Sun Microsystems Inc., hibernate.generate_statistics=true, java.runtime.version=1.6.0_17-b04, hibernate.cache.provider_class=org.hibernate.cache.EhCacheProvider, user.name=root, shared.loader=, tomcat.util.buf.StringCache.byte.enabled=true, hibernate.connection.release_mode=auto, user.language=en, java.naming.factory.initial=org.apache.naming.java.javaURLContextFactory, sun.boot.library.path=/usr/java/jdk1.6.0_17/jre/lib/i386, java.version=1.6.0_17, java.util.logging.manager=org.apache.juli.ClassLoaderLogManager, user.timezone=Canada/Pacific, sun.arch.data.model=32, java.endorsed.dirs=/usr/local/InstalledPrograms/apache-tomcat-6.0.20/endorsed, sun.cpu.isalist=, sun.jnu.encoding=UTF-8, file.encoding.pkg=sun.io, package.access=sun.,org.apache.catalina.,org.apache.coyote.,org.apache.tomcat.,org.apache.jasper.,sun.beans., file.separator=/, java.specification.name=Java Platform API Specification, java.class.version=50.0, user.country=US, java.home=/usr/java/jdk1.6.0_17/jre, java.vm.info=mixed mode, os.version=2.6.18-128.el5, path.separator=:, java.vm.version=14.3-b01, hibernate.jdbc.batch_size=25, java.awt.printerjob=sun.print.PSPrinterJob, sun.io.unicode.encoding=UnicodeLittle, package.definition=sun.,java.,org.apache.catalina.,org.apache.coyote.,org.apache.tomcat.,org.apache.jasper., java.naming.factory.url.pkgs=org.apache.naming, sun.rmi.dgc.client.gcInterval=3600000, user.home=/root, java.specification.vendor=Sun Microsystems Inc., java.library.path=/usr/java/jdk1.6.0_17/jre/lib/i386/server:/usr/java/jdk1.6.0_17/jre/lib/i386:/usr/java/jdk1.6.0_17/jre/../lib/i386:/usr/java/packages/lib/i386:/lib:/usr/lib, java.vendor.url=http://java.sun.com/, java.vm.vendor=Sun Microsystems Inc., hibernate.dialect=org.hibernate.dialect.MySQL5InnoDBDialect, sun.rmi.dgc.server.gcInterval=3600000, common.loader=${catalina.home}/lib,${catalina.home}/lib/*.jar, java.runtime.name=Java(TM) SE Runtime Environment, java.class.path=:/usr/local/InstalledPrograms/apache-tomcat-6.0.20/bin/bootstrap.jar, hibernate.bytecode.use_reflection_optimizer=false, java.vm.specification.name=Java Virtual Machine Specification, java.vm.specification.version=1.0, catalina.home=/usr/local/InstalledPrograms/apache-tomcat-6.0.20, sun.cpu.endian=little, sun.os.patch.level=unknown, hibernate.cache.use_query_cache=true, hibernate.connection.provider_class=org.springframework.orm.hibernate3.LocalDataSourceConnectionProvider, java.io.tmpdir=/usr/local/InstalledPrograms/apache-tomcat-6.0.20/temp, java.vendor.url.bug=http://java.sun.com/cgi-bin/bugreport.cgi, server.loader=, os.arch=i386, java.awt.graphicsenv=sun.awt.X11GraphicsEnvironment, java.ext.dirs=/usr/java/jdk1.6.0_17/jre/lib/ext:/usr/java/packages/lib/ext, user.dir=/, line.separator=, java.vm.name=Java HotSpot(TM) Server VM, hibernate.cache.use_second_level_cache=true, file.encoding=UTF-8, java.specification.version=1.6, hibernate.show_sql=true} 2010-04-15 23:08:53,516 DEBUG [AbstractEntityPersister] Static SQL for entity: com.vsd.model.Order There you can see the time delay of more than 3 mins in executing these processes. My database is mysql and database server is running on the local machine only. The container environment is Centos Linux system. I am clueless about why it takes that much of time in executing these process, But when i do the same task from under eclipse it does not take that much of time. Development environment is Windows.

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• Why do some Flask session values disappear from the session after closing the browser window, but then reappear later without me adding them?

  - by Ben

  So my understanding of Flask sessions is that I can use it like a dictionary and add values to a session by doing: session['key name'] = 'some value here' And that works fine. On a route I have the client call using AJAX post, I assign a value to the session. And it works fine. I can click on various pages of my site and the value stays in the session. If I close the browser window however, and then go back to my site, the session value I had in there is gone. So that's weird and you would think the problem is the session isn't permanent. I also implemented Flask-Openid and that uses the session to store information and that does persist if I close the browser window and open it back up again. I also checked the cookie after closing the browser window, but before going back to my site, and the cookie is indeed still there. Another odd piece of behaviour (which may be related) is that some values I have written to the session for testing purposes will go away when I access the AJAX post route and assign the correct value. So that is odd, but what is truly weird is that when I then close the browser window and open it up again, and have thus lost the value I was trying to retain, the ones that I lost previously actually return! They aren't being reassigned because there's no code in my Python files to reassign those values. Here is some outputs to helper make it clearer. They are all outputed from a route for a real page, and not the AJAX post route I mentioned above. This is the output after I have assigned the value I want to store in the session. The value key is 'userid' - all the other values are dummy ones I have added in trying to solve this problem. 'userid': 8 will stay in the session as long as I don't close the browser window. I can access other routes and the value will stay there just like it should. ['session.=', <SecureCookieSession {'userid': 8, 'test_variable_num': 102, 'adding using before request': 'hi', '_permanent': True, 'test_variable_text': 'hi!'}>] If I do close the browser window, and go back into the site, but without redoing the AJAX post request, I get this output: ['session.=', <SecureCookieSession {'adding using before request': 'hi', '_permanent': True, 'yo': 'yo'}>] The 'yo' value was not in the first first output. I don't know where it came from. I searched my code for 'yo' and there is no instances of me assigning that value anywhere. I think I may have added it to the session days ago. So it seems like it is persisting, but being hidden when the other values are written. And this last one is me accessing the AJAX post route again, and then going to the page that prints out the keys using debug. Same output as the first output I pasted above, which you would expect, and the 'yo' value is gone again (but it will come back if I close the browser window) ['session.=', <SecureCookieSession {'userid': 8, 'test_variable_num': 102, 'adding using before request': 'hi', '_permanent': True, 'test_variable_text': 'hi!'}>] I tested this in both Chrome and Firefox. So I find this all weird and I am guessing it stems from a misunderstanding of how sessions work. I think they're dictionaries and I can write dictionary values into them and retrieve them days later as long as I set the session to permanent and the cookie doesn't get deleted. Any ideas why this weird behaviour is happening?

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• Why does my Opengl es android testbed app not render anything besides a red screen?

  - by nathan

  For some reason my code here (this is the entire thing) doesnt actually render anything besides a red screen.. can anyone tell me why? package com.ntu.way2fungames.earth.testbed; import java.nio.FloatBuffer; import javax.microedition.khronos.egl.EGLConfig; import javax.microedition.khronos.opengles.GL10; import android.app.Activity; import android.content.Context; import android.opengl.GLSurfaceView; import android.opengl.GLSurfaceView.Renderer; import android.os.Bundle; public class projectiles extends Activity { GLSurfaceView lGLView; Renderer lGLRenderer; float projectilesX[]= new float[5001]; float projectilesY[]= new float[5001]; float projectilesXa[]= new float[5001]; float projectilesYa[]= new float[5001]; float projectilesTheta[]= new float[5001]; float projectilesSpeed[]= new float[5001]; private static FloatBuffer drawBuffer; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); SetupProjectiles(); Context mContext = this.getWindow().getContext(); lGLView= new MyView(mContext); lGLRenderer= new MyRenderer(); lGLView.setRenderer(lGLRenderer); setContentView(lGLView); } private void SetupProjectiles() { int i=0; for (i=5000;i>0;i=i-1){ projectilesX[i] = 240; projectilesY[i] = 427; float theta = (float) ((i/5000)*Math.PI*2); projectilesXa[i] = (float) Math.cos(theta); projectilesYa[i] = (float) Math.sin(theta); projectilesTheta[i]= theta; projectilesSpeed[i]= (float) (Math.random()+1); } } public class MyView extends GLSurfaceView{ public MyView(Context context) { super(context); // TODO Auto-generated constructor stub } } public class MyRenderer implements Renderer{ private float[] projectilecords = new float[] { .0f, .5f, 0, -.5f, 0f, 0, .5f, 0f, 0, 0, -5f, 0, }; @Override public void onDrawFrame(GL10 gl) { gl.glClear(GL10.GL_COLOR_BUFFER_BIT); gl.glMatrixMode(GL10.GL_MODELVIEW); //gl.glLoadIdentity(); gl.glEnableClientState(GL10.GL_VERTEX_ARRAY); for (int i=5000;i>4500;i=i-1){ //drawing section gl.glLoadIdentity(); gl.glColor4f(.9f, .9f,.9f,.9f); gl.glTranslatef(projectilesY[i], projectilesX[i],1); gl.glVertexPointer(3, GL10.GL_FLOAT, 0, drawBuffer); gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP, 0, 12); //physics section projectilesX[i]=projectilesX[i]+projectilesXa[i]; projectilesY[i]=projectilesY[i]+projectilesYa[i]; } gl.glDisableClientState(GL10.GL_VERTEX_ARRAY); } @Override public void onSurfaceChanged(GL10 gl, int width, int height) { if (height == 0) height = 1; // draw on the entire screen gl.glViewport(0, 0, width, height); // setup projection matrix gl.glMatrixMode(GL10.GL_PROJECTION); gl.glLoadIdentity(); gl.glOrthof(0,width,height,0, -100, 100); } @Override public void onSurfaceCreated(GL10 gl, EGLConfig arg1) { gl.glShadeModel(GL10.GL_SMOOTH); gl.glClearColor(1f, .01f, .01f, 1f); gl.glClearDepthf(1.0f); gl.glEnable(GL10.GL_DEPTH_TEST); gl.glDepthFunc(GL10.GL_LEQUAL); gl.glHint(GL10.GL_PERSPECTIVE_CORRECTION_HINT, GL10.GL_NICEST); drawBuffer = FloatBuffer.wrap(projectilecords); } } }

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• Why did I get this error : java.lang.Exception: XMLEncoder: discarding statement Vector.add() ?

  - by Frank

  My Java program look like this : public class Biz_Manager { static Contact_Info_Setting Customer_Contact_Info_Panel; static XMLEncoder XML_Encoder; ...... void Get_Customer_Agent_Shipping_Company_And_Shipping_Agent_Net_Worth_Info() { try { XML_Encoder=new XMLEncoder(new BufferedOutputStream(new FileOutputStream(Customer_Contact_Info_Panel.Contact_Info_File_Path))); XML_Encoder.writeObject(Customer_Contact_Info_Panel.Contacts_Vector); } catch (Exception e) { e.printStackTrace(); } finally { if (XML_Encoder!=null) { XML_Encoder.close(); // <== Error here , line : 9459 XML_Encoder=null; } } } } // ======================================================================= public class Contact_Info_Setting extends JPanel implements ActionListener,KeyListener,ItemListener { public static final long serialVersionUID=26362862L; ...... Vector<Contact_Info_Entry> Contacts_Vector=new Vector<Contact_Info_Entry>(); ...... } // ======================================================================= package Utility; import java.io.*; import java.util.*; import javax.jdo.annotations.IdGeneratorStrategy; import javax.jdo.annotations.IdentityType; import javax.jdo.annotations.PersistenceCapable; import javax.jdo.annotations.Persistent; import javax.jdo.annotations.PrimaryKey; @PersistenceCapable(identityType=IdentityType.APPLICATION) public class Contact_Info_Entry implements Serializable { @PrimaryKey @Persistent(valueStrategy=IdGeneratorStrategy.IDENTITY) public Long Id; public static final long serialVersionUID=26362862L; public String Contact_Id="",First_Name="",Last_Name="",Company_Name="",Branch_Name="",Address_1="",Address_2="",City="",State="",Zip="",Country=""; ...... public boolean B_1; public Vector<String> A_Vector=new Vector<String>(); public Contact_Info_Entry() { } public Contact_Info_Entry(String Other_Id) { this.Other_Id=Other_Id; } ...... public void setId(Long value) { Id=value; } public Long getId() { return Id; } public void setContact_Id(String value) { Contact_Id=value; } public String getContact_Id() { return Contact_Id; } public void setFirst_Name(String value) { First_Name=value; } public String getFirst_Name() { return First_Name; } public void setLast_Name(String value) { Last_Name=value; } public String getLast_Name() { return Last_Name; } public void setCompany_Name(String value) { Company_Name=value; } public String getCompany_Name() { return Company_Name; } ...... } I got this error message : java.lang.Exception: XMLEncoder: discarding statement Vector.add(Contact_Info_Entry); Continuing ... java.lang.Exception: XMLEncoder: discarding statement Vector.add(Contact_Info_Entry); Continuing ... java.lang.Exception: XMLEncoder: discarding statement Vector.add(Contact_Info_Entry); Continuing ... java.lang.Exception: XMLEncoder: discarding statement Vector.add(Contact_Info_Entry); Continuing ... Exception in thread "Thread-8" java.lang.NullPointerException at java.beans.XMLEncoder.outputStatement(XMLEncoder.java:611) at java.beans.XMLEncoder.outputValue(XMLEncoder.java:552) at java.beans.XMLEncoder.outputStatement(XMLEncoder.java:682) at java.beans.XMLEncoder.outputStatement(XMLEncoder.java:687) at java.beans.XMLEncoder.outputValue(XMLEncoder.java:552) at java.beans.XMLEncoder.flush(XMLEncoder.java:398) at java.beans.XMLEncoder.close(XMLEncoder.java:429) at Biz_Manager.Get_Customer_Agent_Shipping_Company_And_Shipping_Agent_Net_Worth_Info(Biz_Manager.java:9459) Seems it can't deal with vector, why ? Anything wrong ? How to fix it ? Frank

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• Why does Keychain Services return the wrong keychain content?

  - by Graham Lee

  I've been trying to use persistent keychain references in an iPhone application. I found that if I created two different keychain items, I would get a different persistent reference each time (they look like 'genp.......1', 'genp.......2', …). However, attempts to look up the items by persistent reference always returned the content of the first item. Why should this be? I confirmed that my keychain-saving code was definitely creating new items in each case (rather than updating existing items), and was not getting any errors. And as I say, Keychain Services is giving a different persistent reference for each item. I've managed to solve my immediate problem by searching for keychain items by attribute rather than persistent references, but it would be easier to use persistent references so I'd appreciate solving this problem. Here's my code: - (NSString *)keychainItemWithName: (NSString *)name { NSString *path = [GLApplicationSupportFolder() stringByAppendingPathComponent: name]; NSData *persistentRef = [NSData dataWithContentsOfFile: path]; if (!persistentRef) { NSLog(@"no persistent reference for name: %@", name); return nil; } NSArray *refs = [NSArray arrayWithObject: persistentRef]; //get the data CFMutableDictionaryRef params = CFDictionaryCreateMutable(NULL, 0, &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks); CFDictionaryAddValue(params, kSecMatchItemList, refs); CFDictionaryAddValue(params, kSecClass, kSecClassGenericPassword); CFDictionaryAddValue(params, kSecReturnData, kCFBooleanTrue); CFDataRef item = NULL; OSStatus result = SecItemCopyMatching(params, (CFTypeRef *)&item); CFRelease(params); if (result != errSecSuccess) { NSLog(@"error %d retrieving keychain reference for name: %@", result, name); return nil; } NSString *token = [[NSString alloc] initWithData: (NSData *)item encoding: NSUTF8StringEncoding]; CFRelease(item); return [token autorelease]; } - (void)setKeychainItem: (NSString *)newToken forName: (NSString *)name { NSData *tokenData = [newToken dataUsingEncoding: NSUTF8StringEncoding]; //firstly, find out whether the item already exists NSDictionary *searchAttributes = [NSDictionary dictionaryWithObjectsAndKeys: name, kSecAttrAccount, kCFBooleanTrue, kSecReturnAttributes, nil]; NSDictionary *foundAttrs = nil; OSStatus searchResult = SecItemCopyMatching((CFDictionaryRef)searchAttributes, (CFTypeRef *)&foundAttrs); if (noErr == searchResult) { NSMutableDictionary *toStore = [foundAttrs mutableCopy]; [toStore setObject: tokenData forKey: (id)kSecValueData]; OSStatus result = SecItemUpdate((CFDictionaryRef)foundAttrs, (CFDictionaryRef)toStore); if (result != errSecSuccess) { NSLog(@"error %d updating keychain", result); } [toStore release]; return; } //need to create the item. CFMutableDictionaryRef params = CFDictionaryCreateMutable(NULL, 0, &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks); CFDictionaryAddValue(params, kSecClass, kSecClassGenericPassword); CFDictionaryAddValue(params, kSecAttrAccount, name); CFDictionaryAddValue(params, kSecReturnPersistentRef, kCFBooleanTrue); CFDictionaryAddValue(params, kSecValueData, tokenData); NSData *persistentRef = nil; OSStatus result = SecItemAdd(params, (CFTypeRef *)&persistentRef); CFRelease(params); if (result != errSecSuccess) { NSLog(@"error %d from keychain services", result); return; } NSString *path = [GLApplicationSupportFolder() stringByAppendingPathComponent: name]; [persistentRef writeToFile: path atomically: NO]; [persistentRef release]; }

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• HttpWebRequest response produces HTTP 422. Why?

  - by Simon

  Hi there. I'm trying to programmatically send a POST-request to a web-server in order to login an then perform other requests that require a login. This is my code: Encoding.UTF8.GetBytes( String.Format( "login={0}&password={1}&authenticity_token={2}", username, password, token)); //Create HTTP-request for login HttpWebRequest request = (HttpWebRequest)HttpWebRequest.Create("http://www.xxx.xx/xx/xx"); request.Method = "POST"; request.ContentType = "application/x-www-form-urlencoded"; request.ContentLength = data.Length; request.CookieContainer = new CookieContainer(); request.Accept = "application/xml,application/xhtml+xml,text/html; +"q=0.9,text/plain ;q=0.8,image/png,*/*;q=0.5"; request.Referer = "http://www.garzantilinguistica.it/it/session"; request.Headers.Add("Accept-Language", "de-DE"); request.Headers.Add("Origin", "http://www.xxx.xx"); request.UserAgent = "C#"; request.Headers.Add("Accept-Encoding", "gzip, deflate"); After sending the request //Send post request var requestStream = request.GetRequestStream(); requestStream.Write(data, 0, data.Length); requestStream.Flush(); requestStream.Close(); ... I want to get the servers response: //Get Response StreamReader responseStreamReader = new StreamReader( request.GetResponse().GetResponseStream()); //WebException: HTTP 422! string content = responseStreamReader.ReadToEnd(); This piece of code fires the WebException, that tells me the server responded with HTTP 422 (unprocessable entity due to semantic errors) Then I compared (using a TCP/IP sniffers) the requests of my program and the browser (which of course produces a valid POST-request and gets the right response). (1) My program's request: POST /it/session HTTP/1.1 Content-Type: application/x-www-form-urlencoded Accept: application/xml,application/xhtml+xml,text/html;q=0.9,text/plain; q=0.8,image/png,*/*;q=0.5 Referer: http://www.garzantilinguistica.it/it/session Accept-Language: de-DE Origin: http://www.garzantilinguistica.it User-Agent: C# Accept-Encoding: gzip, deflate Host: www.garzantilinguistica.it Content-Length: 111 Expect: 100-continue Connection: Keep-Alive HTTP/1.1 100 Continue [email protected]&password=machivui&authenticity_token=4vLgtwP3nFNg4NeuG4MbUnU7sy4z91Wi8WJXH0POFmg= HTTP/1.1 422 Unprocessable Entity (2) The browser's request: POST /it/session HTTP/1.1 Host: www.garzantilinguistica.it Referer: http://www.garzantilinguistica.it/it/session Accept: application/xml,application/xhtml+xml,text/html;q=0.9, text/plain;q=0.8,image/png,*/*;q=0.5 Accept-Language: de-DE Origin: http://www.garzantilinguistica.it User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; de-DE) AppleWebKit/531.22.7 (KHTML, like Gecko) Version/4.0.5 Safari/531.22.7 Accept-Encoding: gzip, deflate Content-Type: application/x-www-form-urlencoded Cookie: __utma=244184339.652523587.1275208707.1275208707.1275211298.2; __utmb=244184339.20.10.1275211298; __utmc=244184339; __utmz=244184339.1275208707.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none); _garzanti2009_session=BAh7CDoPc2Vzc2lvbl9pZCIlZDg4MWZjNjg2YTRhZWE0NDQ0ZTJmMTU2YWY4ZTQ1NGU6EF9jc3JmX3Rva2VuIjFqRWdLdll3dTYwOTVVTEpNZkt6dG9jUCtaZ0o4V0FnV2V5ZnpuREx6QUlZPSIKZmxhc2hJQzonQWN0aW9uQ29udHJvbGxlcjo6Rmxhc2g6OkZsYXNoSGFzaHsGOgplcnJvciIVbG9naW4gbm9uIHZhbGlkbwY6CkB1c2VkewY7CFQ%3D--4200fa769898dd156faa49e457baf660cf068d08 Content-Length: 144 Connection: keep-alive authenticity_token=jEgKvYwu6095ULJMfKztocP%2BZgJ8WAgWeyfznDLzAIY%3D&login=thespider14%40hotmail.com&password=machivui&remember_me=1&commit=Entra HTTP/1.1 302 Found Can someone help to understand which part of the request I am missing or what the main difference between the browser's and my request is? Why am I getting that 422?

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• Why is this XMLHttpRequest sample from Mozilla is not working in Firefox 3?

  - by j0rd4n

  I'm trying to get the sample code from Mozilla that consumes a REST web service to work under Firefox 3.0.10. The following code does NOT work in Firefox but does in IE 8! Why is this not working? Does IE 8 have support for XMLHttpRequest? Most examples I've seen use the ActiveX allocation. What should I be doing? XMLHttpRequest seems more standardized. Sample: var req = new XMLHttpRequest(); req.open('GET', 'http://localhost/myRESTfulService/resource', false); // throws 'undefined' exception req.send(null); if(req.status == 0) dump(req.responseText); The open statement is throwing an exception with the description 'undefined'. This is strange as I allocate the req object, am running it in Firefox, and checked to make sure it is defined before calling open (which it says it is of type 'object'). I've also tried the asynchronous version of this with no luck. EDIT 2: Below is my most recent code: function createRequestObject() { if( window.XMLHttpRequest ) { return new XMLHttpRequest(); } else if( window.ActiveXObject ) { return new ActiveXObject( "Microsoft.XMLHTTP" ); } return null; } function handleResponse( req ) { document.writeln( "Handling response..." ); // NEVER GETS CALLED if( req.readyState == 0 ) { document.writeln( "UNITIALIZED" ); } else if( req.readyState == 1 ) { document.writeln( "LOADING" ); } else if( req.readyState == 2 ) { document.writeln( "LOADED" ); } else if( req.readyState == 3 ) { document.writeln( "INTERACTIVE" ); } else if( req.readyState == 4 ) { document.writeln( "COMPLETE" ); if( req.status == 200 ) { document.writeln( "SUCCESS" ); } } } document.writeln( "" ); var req = createRequestObject(); try { document.writeln( "Opening service..." ); req.onreadystatechange = function() { handleResponse( req ); }; req.open('POST', 'http://localhost/test/test2.txt', true); // WORKS IN IE8 & NOT FIREFOX document.writeln( "Sending service request..." ); req.send(''); document.writeln( "Done" ); } catch( err ) { document.writeln( "ERROR: " + err.description ); } EDIT 3: Alright, I reworked this in jQuery. jQuery works great in IE but it throws 'Undefined' when running from Firefox. I double checked and 'Enable JavaScript' is turned on in Firefox - seems to work fine in all other web pages. Below is the jQuery code: function handleResponse( resp ) { alert( "Name: " + resp.Name ); alert( "URL: " + resp.URL ); } $(document).ready( function() { $("a").click( function(event) { try { $.get( "http://localhost/services/ezekielservices/configservice/ezekielservices.svc/test", "{}", function(data) { handleResponse( data ); }, "json" ); } catch( err ) { alert("'$.get' threw an exception: " + err.description); } event.preventDefault(); }); } ); // End 'ready' check Summary of Solution: Alright, web lesson 101. My problem was indeed cross-domain. I was viewing my site unpublished (just on the file system) which was hitting a published service. When I published my site under the same domain it worked. Which also brings up an important distinction between IE and Firefox. When IE experiences this scenario, it prompts the user whether or not they accept the cross-domain call. Firefox throws an exception. While I'm fine with an exception, a more descriptive one would have been helpful. Thanks for all those who helped me.

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• Why might a System.String object not cache its hash code?

  - by Dan Tao

  A glance at the source code for string.GetHashCode using Reflector reveals the following (for mscorlib.dll version 4.0): public override unsafe int GetHashCode() { fixed (char* str = ((char*) this)) { char* chPtr = str; int num = 0x15051505; int num2 = num; int* numPtr = (int*) chPtr; for (int i = this.Length; i > 0; i -= 4) { num = (((num << 5) + num) + (num >> 0x1b)) ^ numPtr[0]; if (i <= 2) { break; } num2 = (((num2 << 5) + num2) + (num2 >> 0x1b)) ^ numPtr[1]; numPtr += 2; } return (num + (num2 * 0x5d588b65)); } } Now, I realize that the implementation of GetHashCode is not specified and is implementation-dependent, so the question "is GetHashCode implemented in the form of X or Y?" is not really answerable. I'm just curious about a few things: If Reflector has disassembled the DLL correctly and this is the implementation of GetHashCode (in my environment), am I correct in interpreting this code to indicate that a string object, based on this particular implementation, would not cache its hash code? Assuming the answer is yes, why would this be? It seems to me that the memory cost would be minimal (one more 32-bit integer, a drop in the pond compared to the size of the string itself) whereas the savings would be significant, especially in cases where, e.g., strings are used as keys in a hashtable-based collection like a Dictionary<string, [...]>. And since the string class is immutable, it isn't like the value returned by GetHashCode will ever even change. What could I be missing? UPDATE: In response to Andras Zoltan's closing remark: There's also the point made in Tim's answer(+1 there). If he's right, and I think he is, then there's no guarantee that a string is actually immutable after construction, therefore to cache the result would be wrong. Whoa, whoa there! This is an interesting point to make (and yes it's very true), but I really doubt that this was taken into consideration in the implementation of GetHashCode. The statement "therefore to cache the result would be wrong" implies to me that the framework's attitude regarding strings is "Well, they're supposed to be immutable, but really if developers want to get sneaky they're mutable so we'll treat them as such." This is definitely not how the framework views strings. It fully relies on their immutability in so many ways (interning of string literals, assignment of all zero-length strings to string.Empty, etc.) that, basically, if you mutate a string, you're writing code whose behavior is entirely undefined and unpredictable. I guess my point is that for the author(s) of this implementation to worry, "What if this string instance is modified between calls, even though the class as it is publicly exposed is immutable?" would be like for someone planning a casual outdoor BBQ to think to him-/herself, "What if someone brings an atomic bomb to the party?" Look, if someone brings an atom bomb, party's over.

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• Why is the this-pointer needed to access inherited attributes?

  - by Shadow

  Hi, assume the following class is given: class Base{ public: Base() {} Base( const Base& b) : base_attr(b.base_attr) {} void someBaseFunction() { .... } protected: SomeType base_attr; }; When I want a class to inherit from this one and include a new attribute for the derived class, I would write: class Derived: public Base { public: Derived() {} Derived( const Derived& d ) : derived_attr(d.derived_attr) { this->base_attr = d.base_attr; } void SomeDerivedFunction() { .... } private: SomeOtherType derived_attr; }; This works for me (let's ignore eventually missing semicolons or such please). However, when I remove the "this-" in the copy constructor of the derived class, the compiler complains that "'base_attr' was not declared in this scope". I thought that, when inheriting from a class, the protected attributes would then also be accessible directly. I did not know that the "this-" pointer was needed. I am now confused if it is actually correct what I am doing there, especially the copy-constructor of the Derived-class. Because each Derived object is supposed to have a base_attr and a derived_attr and they obviously need to be initialized/set correctly. And because Derived is inheriting from Base, I don't want to explicitly include an attribute named "base_attr" in the Derived-class. IMHO doing so would generally destroy the idea behind inheritance, as everything would have to be defined again. EDIT Thank you all for the quick answers. I completely forgot the fact that the classes actually are templates. Please, see the new examples below, which are actually compiling when including "this-" and are failing when omiting "this-" in the copy-constructor of the Derived-class: Base-class: #include <iostream> template<class T> class Base{ public: Base() : base_attr(0) {} Base( const Base& b) : base_attr(b.base_attr) {} void baseIncrement() { ++base_attr; } void printAttr() { std::cout << "Base Attribute: " << base_attr << std::endl; } protected: T base_attr; }; Derived-class: #include "base.hpp" template< class T > class Derived: public Base<T>{ public: Derived() : derived_attr(1) {} Derived( const Derived& d) : derived_attr(d.derived_attr) { this->base_attr = d.base_attr; } void derivedIncrement() { ++derived_attr; } protected: T derived_attr; }; and for completeness also the main function: #include "derived.hpp" int main() { Derived<int> d; d.printAttr(); d.baseIncrement(); d.printAttr(); Derived<int> d2(d); d2.printAttr(); return 0; }; I am using g++-4.3.4. Although I understood now that it seems to come from the fact that I use template-class definitions, I did not quite understand what is causing the problem when using templates and why it works when not using templates. Could someone please further clarify this?

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• Why don't I just build the whole web app in Javascript and Javascript HTML Templates?

  - by viatropos

  I'm getting to the point on an app where I need to start caching things, and it got me thinking... In some parts of the app, I render table rows (jqGrid, slickgrid, etc.) or fancy div rows (like in the New Twitter) by grabbing pure JSON and running it through something like Mustache, jquery.tmpl, etc. In other parts of the app, I just render the info in pure HTML (server-side HAML templates), and if there's searching/paginating, I just go to a new URL and load a new HTML page. Now the problem is in caching and maintainability. On one hand I'm thinking, if everything was built using Javascript HTML Templates, then my app would serve just an HTML layout/shell, and a bunch of JSON. If you look at the Facebook and Twitter HTML source, that's basically what they're doing (95% json/javascript, 5% html). This would make it so my app only needed to cache JSON (pages, actions, and/or records). Which means you'd hit the cache no matter if you were some remote api developer accessing a JSON api, or the strait web app. That is, I don't need 2 caches, one for the JSON, one for the HTML. That seems like it'd cut my cache store down in half, and streamline things a little bit. On the other hand, I'm thinking, from what I've seen/experienced, generating static HTML server-side, and caching that, seems to be much better performance wise cross-browser; you get the graphics instantly and don't have to wait that split-second for javascript to render it. StackOverflow seems to do everything in plain HTML, and you can tell... everything appears at once. Notice how though on twitter.com, the page is blank for .5-1 seconds, and the page chunks in: the javascript has to render the json. The downside with this is that, for anything dynamic (like endless scrolling, or grids), I'd have to create javascript templates anyway... so now I have server-side HAML templates, client-side javascript templates, and a lot more to cache. My question is, is there any consensus on how to approach this? What are the benefits and drawbacks from your experience of mixing the two versus going 100% with one over the other? Update: Some reasons that factor into why I haven't yet made the decision to go with 100% javascript templating are: Performance. Haven't formally tested, but from what I've seen, raw html renders faster and more fluidly than javascript-generated html cross-browser. Plus, I'm not sure how mobile devices handle dynamic html performance-wise. Testing. I have a lot of integration tests that work well with static HTML, so switching to javascript-only would require 1) more focused pure-javascript testing (jasmine), and 2) integrating javascript into capybara integration tests. This is just a matter of time and work, but it's probably significant. Maintenance. Getting rid of HAML. I love HAML, it's so easy to write, it prints pretty HTML... It makes code clean, it makes maintenance easy. Going with javascript, there's nothing as concise. SEO. I know google handles the ajax /#!/path, but haven't grasped how this will affect other search engines and how older browsers handle it. Seems like it'd require a significant setup.

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• Why is processing a sorted array faster than an unsorted array?

  - by GManNickG

  Here is a piece of code that shows some very peculiar performance. For some strange reason, sorting the data miraculously speeds up the code by almost 6x: #include <algorithm> #include <ctime> #include <iostream> int main() { // generate data const unsigned arraySize = 32768; int data[arraySize]; for (unsigned c = 0; c < arraySize; ++c) data[c] = std::rand() % 256; // !!! with this, the next loop runs faster std::sort(data, data + arraySize); // test clock_t start = clock(); long long sum = 0; for (unsigned i = 0; i < 100000; ++i) { // primary loop for (unsigned c = 0; c < arraySize; ++c) { if (data[c] >= 128) sum += data[c]; } } double elapsedTime = static_cast<double>(clock() - start) / CLOCKS_PER_SEC; std::cout << elapsedTime << std::endl; std::cout << "sum = " << sum << std::endl; } Without std::sort(data, data + arraySize);, the code runs in 11.54 seconds. With the sorted data, the code runs in 1.93 seconds. Initially I thought this might be just a language or compiler anomaly. So I tried it Java... import java.util.Arrays; import java.util.Random; public class Main { public static void main(String[] args) { // generate data int arraySize = 32768; int data[] = new int[arraySize]; Random rnd = new Random(0); for (int c = 0; c < arraySize; ++c) data[c] = rnd.nextInt() % 256; // !!! with this, the next loop runs faster Arrays.sort(data); // test long start = System.nanoTime(); long sum = 0; for (int i = 0; i < 100000; ++i) { // primary loop for (int c = 0; c < arraySize; ++c) { if (data[c] >= 128) sum += data[c]; } } System.out.println((System.nanoTime() - start) / 1000000000.0); System.out.println("sum = " + sum); } } with a similar but less extreme result. My first thought was that sorting brings the data into cache, but my next thought was how silly that is because the array was just generated. What is going on? Why is a sorted array faster than an unsorted array? The code is summing up some independent terms, the order should not matter.

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• Why does my C++ LinkedList method print out the last word more than once?

  - by Anthony Glyadchenko

  When I call the cmremoveNode method in my LinkedList from outside code, I get an EXC_BAD_ACCESS. FIXED: But now the last word using the following test code gets repeated twice: #include <iostream> #include "LinkedList.h" using namespace std; int main (int argc, char * const argv[]) { ctlinkList linkMe; linkMe.cminsertNode("The"); linkMe.cminsertNode("Cat"); linkMe.cminsertNode("Dog"); linkMe.cminsertNode("Cow"); linkMe.cminsertNode("Ran"); linkMe.cminsertNode("Pig"); linkMe.cminsertNode("Away"); linkMe.cmlistList(); cout << endl; linkMe.cmremoveNode("The"); linkMe.cmremoveNode("Cow"); linkMe.cmremoveNode("Away"); linkMe.cmlistList(); return 0; } LinkedList code: /* * LinkedList.h * Lab 6 * * Created by Anthony Glyadchenko on 3/22/10. * Copyright 2010 __MyCompanyName__. All rights reserved. * */ #include <stdio.h> #include <iostream> #include <fstream> #include <iomanip> using namespace std; class ctNode { friend class ctlinkList ; // friend class allowed to access private data private: string sfileWord ; // used to allocate and store input word int iwordCnt ; // number of word occurrances ctNode* ctpnext ; // point of Type Node, points to next link list element }; class ctlinkList { private: ctNode* ctphead ; // initialized by constructor public: ctlinkList () { ctphead = NULL ; } ctNode* gethead () { return ctphead ; } string cminsertNode (string svalue) { ctNode* ctptmpHead = ctphead ; if ( ctphead == NULL ) { // allocate new and set head ctptmpHead = ctphead = new ctNode ; ctphead -> ctpnext = NULL ; ctphead -> sfileWord = svalue ; } else { //find last ctnode do { if ( ctptmpHead -> ctpnext != NULL ) ctptmpHead = ctptmpHead -> ctpnext ; } while ( ctptmpHead -> ctpnext != NULL ) ; // fall thru found last node ctptmpHead -> ctpnext = new ctNode ; ctptmpHead = ctptmpHead -> ctpnext ; ctptmpHead -> ctpnext = NULL; ctptmpHead -> sfileWord = svalue ; } return ctptmpHead -> sfileWord ; } string cmreturnNode (string svalue) { return NULL; } string cmremoveNode (string svalue) { int counter = 0; ctNode *tmpHead = ctphead; if (ctphead == NULL) return NULL; while (tmpHead->sfileWord != svalue && tmpHead->ctpnext != NULL){ tmpHead = tmpHead->ctpnext; counter++; } do{ tmpHead->sfileWord = tmpHead->ctpnext->sfileWord; tmpHead = tmpHead->ctpnext; } while (tmpHead->ctpnext != NULL); return tmpHead->sfileWord; } string cmlistList () { string tempList; ctNode *tmpHead = ctphead; if (ctphead == NULL){ return NULL; } else{ while (tmpHead != NULL){ cout << tmpHead->sfileWord << " "; tempList += tmpHead->sfileWord; tmpHead = tmpHead -> ctpnext; } } return tempList; } }; Why is this happening?

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• Why does sending post data with WebRequest take so long?

  - by Paramiliar

  I am currently creating a C# application to tie into a php / MySQL online system. The application needs to send post data to scripts and get the response. When I send the following data username=test&password=test I get the following responses... Starting request at 22/04/2010 12:15:42 Finished creating request : took 00:00:00.0570057 Transmitting data at 22/04/2010 12:15:42 Transmitted the data : took 00:00:06.9316931 <<-- Getting the response at 22/04/2010 12:15:49 Getting response 00:00:00.0360036 Finished response 00:00:00.0360036 Entire call took 00:00:07.0247024 As you can see it is taking 6 seconds to actually send the data to the script, I have done further testing bye sending data from telnet and by sending post data from a local file to the url and they dont even take a second so this is not a problem with the hosted script on the site. Why is it taking 6 seconds to transmit the data when it is two simple strings? I use a custom class to send the data class httppostdata { WebRequest request; WebResponse response; public string senddata(string url, string postdata) { var start = DateTime.Now; Console.WriteLine("Starting request at " + start.ToString()); // create the request to the url passed in the paramaters request = (WebRequest)WebRequest.Create(url); // set the method to post request.Method = "POST"; // set the content type and the content length request.ContentType = "application/x-www-form-urlencoded"; request.ContentLength = postdata.Length; // convert the post data into a byte array byte[] byteData = Encoding.UTF8.GetBytes(postdata); var end1 = DateTime.Now; Console.WriteLine("Finished creating request : took " + (end1 - start)); var start2 = DateTime.Now; Console.WriteLine("Transmitting data at " + start2.ToString()); // get the request stream and write the data to it Stream dataStream = request.GetRequestStream(); dataStream.Write(byteData, 0, byteData.Length); dataStream.Close(); var end2 = DateTime.Now; Console.WriteLine("Transmitted the data : took " + (end2 - start2)); // get the response var start3 = DateTime.Now; Console.WriteLine("Getting the response at " + start3.ToString()); response = request.GetResponse(); //Console.WriteLine(((WebResponse)response).StatusDescription); dataStream = response.GetResponseStream(); StreamReader reader = new StreamReader(dataStream); var end3 = DateTime.Now; Console.WriteLine("Getting response " + (end3 - start3)); // read the response string serverresponse = reader.ReadToEnd(); var end3a = DateTime.Now; Console.WriteLine("Finished response " + (end3a - start3)); Console.WriteLine("Entire call took " + (end3a - start)); //Console.WriteLine(serverresponse); reader.Close(); dataStream.Close(); response.Close(); return serverresponse; } } And to call it I use private void btnLogin_Click(object sender, EventArgs e) { // string postdata; if (txtUsername.Text.Length < 3 || txtPassword.Text.Length < 3) { MessageBox.Show("Missing your username or password."); } else { string postdata = "username=" + txtUsername.Text + "&password=" + txtPassword.Text; httppostdata myPost = new httppostdata(); string response = myPost.senddata("http://www.domainname.com/scriptname.php", postdata); MessageBox.Show(response); } }

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• Help to argue why to develop software on a physical computer rather than via a remote desktop

  - by s5804

  Remote desktops are great and many times a blessing and cost effective (instead of leasing expensive cables). I am not arguing against remote desktops, just if one have the alternative to use either remote desktop or physical computer, I would choose the later. Also note that I am not arguing for or against remote work practices. But in my case I am required to be physically present in the office when developing software. Background, I work in a company which main business is not to develop software. Therefore the company IT policies are mainly focused on security and to efficiently deploying/maintaing thousands of computer to users. Further, the typical employee runs typical Office applications, like a word processors. Because safety/stability is such a big priority, every non production system/application, shall be deployed into a physical different network, called the test network. Software development of course also belongs in the test network. To access the test network the company has created a standard policy, which dictates that access to the test network shall go only via a remote desktop client. Practically from ones production computer one would open up a remote desktop client to a virtual computer located in the test network. On the virtual computer's remote desktop one would be able to access/run/install all development tools, like Eclipse IDE. Another solution would be to have a dedicated physical computer, which is physically only connected to the test network. Both solutions are available in the company. I have tested both approaches and found running Eclipse IDE, SQL developer, in the remote desktop client to be sluggish (keyboard strokes are delayed), commands like alt-tab takes me out of the remote client, enjoying... Further, screen resolution and colors are different, just to mention a few. Therefore there is nothing technical wrong with the remote client, just not optimal and frankly de-motivating. Now with the new policies put in place, plans are to remove the physical computers connected to the test network. I am looking for help to argue for why software developers shall have a dedicated physical software development computer, to be productive and cost effective. Remember that we are physically in office. Further one can notice that we are talking about approx. 50 computers out of 2000 employees. Therefore the extra budget is relatively small. This is more about policy than cost. Please note that there are lots of similar setups in other companies that work great due to a perfectly tuned systems. However, in my case it is sluggish and it would cost more money to trouble shoot the performance and fine tune it rather than to have a few physical computers. As a business case we have argued that productivity will go down by 25%, however it's my feeling that the reality is probably closer to 50%. This business case isn't really accepted and I find it very difficult to defend it to managers that has never ever used a rich IDE in their life, never mind developed software. Further the test network and remote client has no guaranteed service level, therefore it is down for a few hours per month with the lowest priority on the fix list. Help is appreciated.

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• Why is my GreaseMonkey function unexpectedly being called multiple times?

  - by Ryan Fisher

  I am missing something, I'm not sure why the function 'addIcon()' is being called multiple times. Given: <div class="ticketpostcontainer">Some text</div> <div class="ticketpostcontainer">Some text</div> <div class="ticketpostcontainer">Some text</div> Using the utility function waitForKeyElements, the result is that each div element receives my "collapse icon" three times: // ==UserScript== // @name Collapse Kayako Response // @grant Sandbox // @namespace http://my.chiromatrixbase.com/fisher.chiromatrix.com/collaps_div.js // @include http://imatrixsupport.com/* // @require http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js // ==/UserScript== /*jslint plusplus: true, undef: true, sloppy: true, vars: true, white: true, indent: 2, maxerr: 30 */ //Enable or disable GreaseMonkey function, GM_log var GM_Debug = 1; if (!GM_Debug) { var GM_log = function () {}; } //If FireBig is active, send GM log events to FB. if (unsafeWindow.console && GM_Debug) { var GM_log = unsafeWindow.console.log; } GM_log("Running collapse kayako response script"); //Don't run on frames or iframes. if (window.top !== window.self) { return; } waitForKeyElements(".ticketpostcontainer", addIcon); function addIcon() { var i, toCollapse = document.getElementsByClassName('ticketpostcontainer'), j = toCollapse.length; GM_log("Number of elements to collapse: " + toCollapse.length); for (i = 0; i < j; i++) { var curElement = toCollapse[i]; var p = document.createElement('p'); var a = document.createElement('a'); var span = document.createElement('span'); styleLink(a); styleParagraph(p); styleSpan(span); p.appendChild(a); p.appendChild(span); a.appendChild(document.createTextNode('-')); span.appendChild(document.createTextNode(' Some text')); a.addEventListener("click", toggle, false); curElement.parentNode.insertBefore(p, curElement); } function toggle(e) { if (this.firstChild.nodeValue === '-') { this.parentNode.nextSibling.style.display = 'none'; this.firstChild.nodeValue = '+'; this.nextSibling.style.display = 'inline'; } else { this.parentNode.nextSibling.style.display = 'block'; this.firstChild.nodeValue = '-'; this.nextSibling.style.display = 'none'; } e.preventDefault(); } function styleLink(a) { a.href = '#'; a.style.fontWeight = 'bold'; a.style.background = '#F6F1E7'; a.style.border = '1px solid #cccccc'; a.style.color = '#B24C58'; a.style.textDecoration = 'none'; a.style.width = '15px'; a.style.height = '15px'; a.style.textAlign = 'center'; a.style.fontSize = '100%'; a.style.margin = '0 5px 5px 8px'; a.style.cssFloat = 'left'; a.style.display = 'block'; a.style.lineHeight = '13px'; } function styleParagraph(p) { p.style.margin = '0 0 0 0'; p.style.lineHeight = '16px'; p.style.clear = 'both'; p.style.height = '15px'; } function styleSpan(span) { span.style.display = 'none'; } }

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• Why is SQLite3 using covering indices instead of the indices I created?

  - by Geoff

  I have an extremely large database (contacts has ~3 billion entries, people has ~280 million entries, and the other tables have a negligible number of entries). Most other queries I've run are really fast. However, I've encountered a more complicated query that's really slow. I'm wondering if there's any way to speed this up. First of all, here is my schema: CREATE TABLE activities (id INTEGER PRIMARY KEY, name TEXT NOT NULL); CREATE TABLE contacts ( id INTEGER PRIMARY KEY, person1_id INTEGER NOT NULL, person2_id INTEGER NOT NULL, duration REAL NOT NULL, -- hours activity_id INTEGER NOT NULL -- FOREIGN_KEY(person1_id) REFERENCES people(id), -- FOREIGN_KEY(person2_id) REFERENCES people(id) ); CREATE TABLE people ( id INTEGER PRIMARY KEY, state_id INTEGER NOT NULL, county_id INTEGER NOT NULL, age INTEGER NOT NULL, gender TEXT NOT NULL, -- M or F income INTEGER NOT NULL -- FOREIGN_KEY(state_id) REFERENCES states(id) ); CREATE TABLE states ( id INTEGER PRIMARY KEY, name TEXT NOT NULL, abbreviation TEXT NOT NULL ); CREATE INDEX activities_name_index on activities(name); CREATE INDEX contacts_activity_id_index on contacts(activity_id); CREATE INDEX contacts_duration_index on contacts(duration); CREATE INDEX contacts_person1_id_index on contacts(person1_id); CREATE INDEX contacts_person2_id_index on contacts(person2_id); CREATE INDEX people_age_index on people(age); CREATE INDEX people_county_id_index on people(county_id); CREATE INDEX people_gender_index on people(gender); CREATE INDEX people_income_index on people(income); CREATE INDEX people_state_id_index on people(state_id); CREATE INDEX states_abbreviation_index on states(abbreviation); CREATE INDEX states_name_index on states(name); Note that I've created an index on every column in the database. I don't care about the size of the database; speed is all I care about. Here's an example of a query that, as expected, runs almost instantly: SELECT count(*) FROM people, states WHERE people.state_id=states.id and states.abbreviation='IA'; Here's the troublesome query: SELECT * FROM contacts WHERE rowid IN (SELECT contacts.rowid FROM contacts, people, states WHERE contacts.person1_id=people.id AND people.state_id=states.id AND states.name='Kansas' INTERSECT SELECT contacts.rowid FROM contacts, people, states WHERE contacts.person2_id=people.id AND people.state_id=states.id AND states.name='Missouri'); Now, what I think would happen is that each subquery would use each relevant index I've created to speed this up. However, when I show the query plan, I see this: sqlite> EXPLAIN QUERY PLAN SELECT * FROM contacts WHERE rowid IN (SELECT contacts.rowid FROM contacts, people, states WHERE contacts.person1_id=people.id AND people.state_id=states.id AND states.name='Kansas' INTERSECT SELECT contacts.rowid FROM contacts, people, states WHERE contacts.person2_id=people.id AND people.state_id=states.id AND states.name='Missouri'); 0|0|0|SEARCH TABLE contacts USING INTEGER PRIMARY KEY (rowid=?) (~25 rows) 0|0|0|EXECUTE LIST SUBQUERY 1 2|0|2|SEARCH TABLE states USING COVERING INDEX states_name_index (name=?) (~1 rows) 2|1|1|SEARCH TABLE people USING COVERING INDEX people_state_id_index (state_id=?) (~5569556 rows) 2|2|0|SEARCH TABLE contacts USING COVERING INDEX contacts_person1_id_index (person1_id=?) (~12 rows) 3|0|2|SEARCH TABLE states USING COVERING INDEX states_name_index (name=?) (~1 rows) 3|1|1|SEARCH TABLE people USING COVERING INDEX people_state_id_index (state_id=?) (~5569556 rows) 3|2|0|SEARCH TABLE contacts USING COVERING INDEX contacts_person2_id_index (person2_id=?) (~12 rows) 1|0|0|COMPOUND SUBQUERIES 2 AND 3 USING TEMP B-TREE (INTERSECT) In fact, if I show the query plan for the first query I posted, I get this: sqlite> EXPLAIN QUERY PLAN SELECT count(*) FROM people, states WHERE people.state_id=states.id and states.abbreviation='IA'; 0|0|1|SEARCH TABLE states USING COVERING INDEX states_abbreviation_index (abbreviation=?) (~1 rows) 0|1|0|SEARCH TABLE people USING COVERING INDEX people_state_id_index (state_id=?) (~5569556 rows) Why is SQLite using covering indices instead of the indices I created? Shouldn't the search in the people table be able to happen in log(n) time given state_id which in turn is found in log(n) time?

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• Why do I get an extra newline in the middle of a UTF-8 character with XML::Parser?

  - by René Nyffenegger

  I encountered a problem dealing with UTF-8, XML and Perl. The following is the smallest piece of code and data in order to reproduce the problem. Here's an XML file that needs to be parsed: <?xml version="1.0" encoding="utf-8"?> <test> <words>???????????? ??????? ????????? ???? ???????????? ??????</words> <words>???????????? ??????? ????????? ???? ???????????? ??????</words> <words>???????????? ??????? ????????? ???? ???????????? ??????</words> [<words> .... </words> 148 times repeated] <words>???????????? ??????? ????????? ???? ???????????? ??????</words> <words>???????????? ??????? ????????? ???? ???????????? ??????</words> </test> The parsing is done with this perl script: use warnings; use strict; use XML::Parser; use Data::Dump; my $in_words = 0; my $xml_parser=new XML::Parser(Style=>'Stream'); $xml_parser->setHandlers ( Start => \&start_element, End => \&end_element, Char => \&character_data, Default => \&default); open OUT, '>out.txt'; binmode (OUT, ":utf8"); open XML, 'xml_test.xml' or die; $xml_parser->parse(*XML); close XML; close OUT; sub start_element { my($parseinst, $element, %attributes) = @_; if ($element eq 'words') { $in_words = 1; } else { $in_words = 0; } } sub end_element { my($parseinst, $element, %attributes) = @_; if ($element eq 'words') { $in_words = 0; } } sub default { # nothing to see here; } sub character_data { my($parseinst, $data) = @_; if ($in_words) { if ($in_words) { print OUT "$data\n"; } } } When the script is run, it produces the out.txt file. The problem is in this file on line 147. The 22th character (which in utf-8 consists of \xd6 \xb8) is split between the d6 and b8 with a new line. This should not happen. Now, I am interested if someone else has this problem or can reproduce it. And why I am getting this problem. I am running this script on Windows: C:\temp>perl -v This is perl, v5.10.0 built for MSWin32-x86-multi-thread (with 5 registered patches, see perl -V for more detail) Copyright 1987-2007, Larry Wall Binary build 1003 [285500] provided by ActiveState http://www.ActiveState.com Built May 13 2008 16:52:49

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• Why some pictures are are crooked aftes using my function?

  - by Miko Kronn

  struct BitmapDataAccessor { private readonly byte[] data; private readonly int[] rowStarts; public readonly int Height; public readonly int Width; public BitmapDataAccessor(byte[] data, int width, int height) { this.data = data; this.Height = height; this.Width = width; rowStarts = new int[height]; for (int y = 0; y < Height; y++) rowStarts[y] = y * width; } public byte this[int x, int y, int color] // Maybe use an enum with Red = 0, Green = 1, and Blue = 2 members? { get { return data[(rowStarts[y] + x) * 3 + color]; } set { data[(rowStarts[y] + x) * 3 + color] = value; } } public byte[] Data { get { return data; } } } public static byte[, ,] Bitmap2Byte(Bitmap obraz) { int h = obraz.Height; int w = obraz.Width; byte[, ,] wynik = new byte[w, h, 3]; BitmapData bd = obraz.LockBits(new Rectangle(0, 0, w, h), ImageLockMode.ReadOnly, PixelFormat.Format24bppRgb); int bytes = Math.Abs(bd.Stride) * h; byte[] rgbValues = new byte[bytes]; IntPtr ptr = bd.Scan0; System.Runtime.InteropServices.Marshal.Copy(ptr, rgbValues, 0, bytes); BitmapDataAccessor bda = new BitmapDataAccessor(rgbValues, w, h); for (int i = 0; i < h; i++) { for (int j = 0; j < w; j++) { wynik[j, i, 0] = bda[j, i, 2]; wynik[j, i, 1] = bda[j, i, 1]; wynik[j, i, 2] = bda[j, i, 0]; } } obraz.UnlockBits(bd); return wynik; } public static Bitmap Byte2Bitmap(byte[, ,] tablica) { if (tablica.GetLength(2) != 3) { throw new NieprawidlowyWymiarTablicyException(); } int w = tablica.GetLength(0); int h = tablica.GetLength(1); Bitmap obraz = new Bitmap(w, h, PixelFormat.Format24bppRgb); for (int i = 0; i < w; i++) { for (int j = 0; j < h; j++) { Color kol = Color.FromArgb(tablica[i, j, 0], tablica[i, j, 1], tablica[i, j, 2]); obraz.SetPixel(i, j, kol); } } return obraz; } Now, if I do: private void btnLoad_Click(object sender, EventArgs e) { if (dgOpenFile.ShowDialog() == DialogResult.OK) { try { Bitmap img = new Bitmap(dgOpenFile.FileName); byte[, ,] tab = Grafika.Bitmap2Byte(img); picture.Image = Grafika.Byte2Bitmap(tab); picture.Size = img.Size; } catch (Exception ex) { MessageBox.Show(ex.Message); } } } Most of pictures are handled correctly butsome not. Example of picture that doesn't work: It produce following result (this is only fragment of picture) : Why is that?

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