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  • Do null SQLite Data fields take up extra memory?

    - by CSharperWithJava
    I'm using the built in sqlite library on the Android platform. I'm considering adding several general purpose fields that users will be able to use for their own custom applications, but these fields will be blank most of the time. My question is, how much overhead will these blank fields add to my database? Do null fields even take up per record memory in sqlite? If so, how much? I don't quite understand the inner workings of a sqlite database.

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  • How can I get awk input from a file and add my own text to the data?

    - by xs2dhillon
    Assume that I have a text file separated by colons. I understand how to display the entire text file or any specific column using awk. However, what I want to do is to get the awk output and then display it by adding my own text using a shell script? For example, assume that my text file is: England:London:GMT USA:Washington:EST France:Paris:GMT What I want to do is to display this input into the below format: COUNTRY: England CAPITOL: London TIMEZONE: GMT COUNTRY: USA CAPITOL: Washington TIMEZONE: EST COUNTRY: France CAPITOL: Paris TIMEZONE: GMT

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  • Howto display or view encrypted data in encrypted form?

    - by Brian Gianforcaro
    In the Wikipedia Article on Block Cipher Modes they have a neat little diagram of an unencrypted image, the same image encrypted using ECB mode and another version of the same image encrypted using another method. At university I have developed my own implementation of DES (you can find it here) and we must demo our implementation in a presentation. I would like to display a similar example as shown above using our implementation. However most image files have header blocks associated with them, which when encrypting the file with our implementation, also get encrypted. So when you go to open them in an image viewer, they are assumed to be corrupted and can't be viewed. I was wondering if anybody new of a simple header-less image format which we could use to display these? Or if anyone had any idea's as to how the original creator of the images above achieved the above result? Any help would be appreciated, Thanks Note: I realise rolling your own cryptography library is stupid, and DES is considered broken, and ECB mode is very flawed for any useful cryptography, this was purely an academic exercise for school. So please, no lectures, I know the drill.

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  • Can I use part of MD5 hash for data identification?

    - by sharptooth
    I use MD5 hash for identifying files with unknown origin. No attacker here, so I don't care that MD5 has been broken and one can intendedly generate collisions. My problem is I need to provide logging so that different problems are diagnosed easier. If I log every hash as a hex string that's too long, inconvenient and looks ugly, so I'd like to shorten the hash string. Now I know that just taking a small part of a GUID is a very bad idea - GUIDs are designed to be unique, but part of them are not. Is the same true for MD5 - can I take say first 4 bytes of MD5 and assume that I only get collision probability higher due to the reduced number of bytes compared to the original hash?

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  • Rendering field data as a link in Ruby on Rails...

    - by bgadoci
    Ok, I think this is probably an easy question but for the life of my I can't figure it out. I have created a table called ugtags and in that table I have two columns (beyond the basics), 'name' and 'link'. I am trying to allow a user to add a link to a page. Ideally they would enter the link title (name) and the url (link) and in the view it would display the title as a link to the url that was entered in the link column. I there a way to do it by simply affecting the <%= link_to h(ugtag.name) %> code?

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  • click handler after using Ajax

    - by Tom
    I have a site that plays a stream. I perform an AJAX call to the server once a person presses a button. <input type="submit" class="play" data-type="<?php echo $result_cameras[$i]["camera_type"]; ?>" data-hash="<?php echo $result_cameras[$i]["camera_hash"]; ?>" value="<?php echo $result_cameras[$i]["camera_name"]; ?>"> This prints out a bunch of buttons that the user can select. This is processed by the following code: <script> $(document).ready(function(){ $(".play").click(function(){ var camerahash = $(this).data('hash'); var cameratype = $(this).data('type'); function doAjax(){ $.ajax({ url: 'index.php?option=streaming&task=playstream&id_hash=<?php echo $id_hash; ?>&camera_hash='+camerahash+'&format=raw', success: function(data) { if (data == 'Initializing...please wait') { $('#quote p').html(data); setTimeout(doAjax, 2000); } else { if (cameratype == "WEBCAM" && data == 'Stream is ready...') { $('#quote p').html(data); window.location = 'rtsp://<?php echo DEVSTREAMWEB; ?>/<?php echo $session_id;?>/'+camerahash; } else if (cameratype == "AXIS" && data == 'Stream is ready...') { $('#quote p').html(data); window.location = 'rtsp://<?php echo DEVSTREAMIP; ?>/<?php echo $session_id;?>/'+camerahash; } else { $('#quote p').html(data); } } } }); } doAjax(); }); }); </script> The server returns the messages such as Stream is ready.... My problem is that everything is working great except on additional button clicks. Specifically when they get success (video plays) and they exit back out, they don't get any other messages if they click another button. It is as if the click event is not triggered. Do I need to be doing something to the click handler to respond?

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  • Are methods also serialized along with the data members in C#?

    - by Shaza
    Hey all, The title is obvious, I need to know if methods are serialized along with object instances in C#, I know that they don't in Java but I'm a little new to C#. If they don't, do I have to put the original class with the byte stream(serialized object) in one package when sending it to another PC? Can the original class be like a DLL file?

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  • What are all the concurrent things [data structure, algorithm, locking mechanism] missing in .Net 3.

    - by user49767
    First time I am bit disappointed in StackOverflow cause my http://stackoverflow.com/questions/2571727/c-concurrency-vs-java-concurrency-which-is-neatly-designed-which-is-better question was closed. My intension was just trying to gather knowledge from programming guru's who worked in both the programming technologies. Rather closing this question, please help me by discussing what is good, bad, and ugly in multi-threading part in both the platforms. It is also welcome, if someone would like to compare with .Net 4.0 with JDK 6 (or JDK 7)

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  • I just wanted to DES 4096 bytes of data with a 128 bits key...

    - by badp
    ...and what the nice folks at OpenSSL gratiously provide me with is this. :) Now, since you shouldn't be guessing when using cryptography, I come here for confirmation: what is the function call I want to use? What I understood A 128 bits key is 16 byte large, so I'll need double DES (2 × 8 byte). This leaves me with only a few function calls: void DES_ede2_cfb64_encrypt(const unsigned char *in, unsigned char *out, long length, DES_key_schedule *ks1, DES_key_schedule *ks2, DES_cblock *ivec, int *num, int enc); void DES_ede2_cbc_encrypt(const unsigned char *input, unsigned char *output, long length, DES_key_schedule *ks1, DES_key_schedule *ks2, DES_cblock *ivec, int enc); void DES_ede2_cfb64_encrypt(const unsigned char *in, unsigned char *out, long length, DES_key_schedule *ks1, DES_key_schedule *ks2, DES_cblock *ivec, int *num, int enc); void DES_ede2_ofb64_encrypt(const unsigned char *in, unsigned char *out, long length, DES_key_schedule *ks1, DES_key_schedule *ks2, DES_cblock *ivec, int *num); In this case, I guess the function I want to call DES_ede2_cfb64_encrypt, although I'm not so sure -- I definitely don't need padding here and I'd have to care about what ivec and num are, and how I want to generate them... What am I missing?

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  • What are provenly scalable data persistence solutions for consumer profiles?

    - by Hubbard
    Consumer profiles with analytical scores [ConsumerID, 1..n demographical variables, 1...n analytical scores e.g. "likely to churn" "likely to buy an item 100$ in worth" etc.] have to be possible to query fast if they are to be used in customizing web-sites, consumer communications etc. Well. If you have: Large number of consumers Large profiles with a huge set of variables (as profiles describing human behaviour are likely to be..) ...you are in trouble. If you really have a physical relational database to which you target a query and then a physical disk starts to rotate someplace to give you an individual profile or a set of profiles, the profile user (a web site customizing a page, a recommendation engine making a recommendation..) has died of boredom before getting any observable results. There is the possibility of having the profiles in memory, which would of course increase the performance hugely. What are the most proven solutions for a fast-response, scalable consumer profile storage? Is there a shootout of these someplace?

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  • Is fetching data from database a get-method thing?

    - by theva
    I have a small class that I call Viewer. This class is supposed to view the proper layout of each page or something like that... I have a method called getFirstPage, when called the user of this method will get a setting value for which page is currently set as the first page. I have some code here, I think it works but I am not really shure that I have done it the right way: class Viewer { private $db; private $user; private $firstPage; function __construct($db, $user) { $this->db = $db; if(isset($user)) { $this->user = $user; } else { $this->user = 'default'; } } function getFistPage() { $std = $db->prepare("SELECT firstPage FROM settings WHERE user = ':user'"); $std->execute(array(':user' => $user)); $result = $std->fetch(); $this->firstPage = $result['firstPage']; return $this->firstPage; } } My get method is fetching the setting from databse (so far so good?). The problem is that then I have to use this get method to set the private variable firstPage. It seems like I should have a set method to do this, but I cannot really have a set method that just fetch some setting from database, right? Because the user of this object should be able to assume that there already is a setting defined in the object... How should I do that?

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  • Validation errors prevent the property setter being called

    - by HA
    Hi, I am looking for a simple solution to the following problem: I am using a simple TextBox control with the Text property bound to a property in the code behind. Additionally I am using a validation rule to notify the user of malformed input. ... error display style here ... Now after entering valid data into the TextBox the user can hit a button to send the data. When clicking the button the data from the bound property UserName in the code behind is evaluated and sent. The problem is that a user can enter valid data into the TextBox and this will be set in the property UserName. If the user then decides to change the text in the TextBox and the data becomes invalid, the setter of the property UserName is not called after the failed validation. This means that the last valid data remains in the property UserName, while the TextBox display the invalid data with the error indicator. If the user then clicks on the button to send the data, the last valid data will be sent instead of the current TextBox content. I know I could deactivate the button if the data is invalid and in fact I do, but the method is called in the setter of UserName. And if that is not called after a failed validation the button stays enabled. So the question is: How do I enable calling of the property setter after a failed validation?

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  • Is it possible to select data with max value for a column using Criteria in Hibernate?

    - by Palo
    Lets say I have the following mapping: <hibernate-mapping package="mypackage"> <class name="User" table="user"> <id name="id" column="id"> <generator class="native"></generator> </id> <property name="name" /> <property name="age" /> </class> </hibernate-mapping> Is it possible to select the oldest user (that is age is maximal) using Criteria in Hibernate? I can imagine that i could do this with 2 selects. (first select total number of users and then order the entries descending by age and select the first entry). But is it possible with a single select? Thank you Palo

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  • Is base method able to use derived base data members?

    - by iTayb
    Lets assume we have the following code: abstract class Base1 { protected int num; } class Der1:Base1 { protected Color color; protected string name; } class Der2:Base1 { protected DateTime dthen; } and so on. An array of base1 type exists and includes many objects created out of classes that are derived from base1. Is it possible to define the toString() method in the base class only? something like: public override string toString() { if (this is Der1) return "num = " + this.num + "color = " + this.color.toString() + " name = " this.name; if (this is Der2) return "num = " + this.num + "dthen = " + this.dthen.toString(); // and so on ... } Thank you very much :) P.S. This is not an homework question. I've just wondered about.

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