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  • Decentralized synchronized secure data storage

    - by Alberich
    Introduction Hi, I am going to ask a question which seems utopic for me, but I need to know if there is a way to achieve what I need. And if not, I need to know why not. The idea Suppose I have a database structure, in MySql. I want to create some solution to allow anyone (no matter who, no matter where) to have a synchronized copy (updated clone) of this database (with its content) Well, and it is not going to be just one synchronized copy, it could (and should) be a multiple replication (supposing the basic, this means, for example, ten copies all over the world) And, the most important thing: It must be secure. By secure I mean only real-accepted transactions will be synchronized with all the others (no matter how many) database copies/clones. Note: Since it would be quite difficult to make the synchronization in real-time, I will design everything to make this feature dispensable. So it is not required. My auto-suggestion This is how I am thinking to manage it: Time identifiers and Updates checking: Every action (insert, update, delete...) will be stored as the action instruction itself, associated to the time identifier. [I think better than a DATETIME field, it'll be an INT one, with the number of miliseconds passed from 1st january 2013 on, for example]. So each copy is going to ask to the "neighbour copy" for new actions done since last update, and execute them after checking they are allowed. Problem 1: the "neighbour copy" could be outdated too. Solution 1: do not ask just one neighbour, create a random list with some of the copies/clones and ask them for news (I could avoid the list and ask ALL the clones for updates, but this will be inefficient if clones number ascends too much). Problem 2: Real-time global synchronization is not active. What if... Someone at CLONE_ENTERPRISING inserts a row into TABLE. ... this row goes to every clone ... Someone at CLONE_FIXEMALL deletes this row. ... and at the same time, somewhere in an outdated clone ... Someone at CLONE_DROPOUT edits this row (now inexistent at the other clones) Solution 2: easy stuff, force a GLOBAL synchronization before doing any new "depending-on-third-data action" (edit, for example). This global synch. will be unnecessary when making an INSERT, for instance. Note: Well, someone could have some fun, and make the same insert in two clones... since they're not getting updated in real-time, this row will exist twice. But, it's the same as when we have one single database, in some needed cases we check if there is an existing same-row before doing the final action. Not a problem. Problem 3: It is possible to edit the code and do not filter actions, so someone could spread instructions to delete everything, or just make some trolling activity. This is not a problem, since good clones will always be somewhere. Those who got bad won't interest anymore. I really appreciate if you read. I know this is not the perfect solution, it has possibly hundred of holes, but it is my basic start. I will now appreciate anything you can teach me now. Thanks a lot. PS.: It could be that all this I am trying already exists and has its own name. Sorry for asking then (I'd anyway thank this name, if it exists)

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  • problem downloading movie to iphone for storage and playback

    - by padatronic
    I am basically making a video library where you download videos and I then write them to the applications documents folder. This all works fine and if i stream the video from online it plays fine. Or indeed I can stream it from the resource folder fine. However, after downloading it and saving to the documents folder then attempting to stream I get the error 'movie format not supported' any ideas? thanks very much

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  • Implementing a logging library in .NET with a database as the storage medium

    - by Dave
    I'm just starting to work on a logging library that everyone can use to keep track of any sort of system information while the user is running our application. The simplest example so far is to track Info, Warnings, and Errors. I want all plugins to be able to use this feature, but since each developer might have a different idea of what's important to report, I want to keep this as generic as possible. In the C++ world, I would normally use something like a stl::pair<string,string> to act as a key value pair structure, and have a stl::list of these to act as a "row" in the log. The log cache would then be a list<list<pair<string,string>>> (ugh!). This way, the developers can use a const string key like INFO, WARNING, ERROR to have a consistent naming for a column in the database (for SELECTing specific types of information). I'd like the database to be able to deal with any number of distinct column names. For example, John might have an INFO row with a column called USER, and Bill might have an INFO row with a column called FILENAME. I want the log viewer to be able to display all information, and if one report doesn't have a value for INFO / FILENAME, those fields should just appear blank. So one option is to use List<List<KeyValuePair<String,String>>, and the another is to have the log library consumer somehow "register" its schema, and then have the database do an ALTER TABLE to handle this situation. Yet another idea is to have a table that's just for key value pairs, with a foreign key that maps the key value pairs back to the original log entry. I obviously don't want logging to bog down the system, so I only lock the log cache to make a copy of the data (and remove the already-copied data), then a background thread will dump the information to the database. My specific questions regarding this are: Do you see any performance issues? In other words, have you ever tried something like this and found that certain things just don't work well in practice? Is there a more .NETish way to implement the key value pairs, other than List<List<KeyValuePair<String,String>>>? Even if there is a way to do #2 better, is the ALTER TABLE idea I proposed above a Bad Thing? Would you recommend multiple databases over a single one? I don't yet have an idea of how frequently the log would get written to, but we ideally would like to have lots of low level information. Perhaps there should be a DB with a fixed schema only for the low level stuff, and then another DB that's more flexible for reporting information back to users.

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  • Database storage for high sample rate data in web app

    - by Jim
    I've got multiple sensors feeding data to my web app. Each channel is 5 samples per second and the data gets uploaded bundled together in 1 minute json messages (containing 300 samples). The data will be graphed using flot at multiple zoom levels from 1 day to 1 minute. I'm using Amazon SimpleDB and I'm currently storing the data in the 1 minute chunks that I receive it in. This works well for high zoom levels, but for full days there will be simply be too many rows to retrieve. The idea I've currently got is that every hour I can crawl through the data and collect together 300 samples for the last hour and store them in an hour Domain (table if you like). Does this sound like a reasonable solution? How have others implemented the same sort of systems?

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  • Credit Card storage solution

    - by jtnire
    Hi Everyone, I'm developing a solution that is designed to store membership details, as well as credit card details. I'm trying to comply with PCI DSS as much as I can. Here is my design so far: PAN = Primary account number == long number on credit card Server A is a remote server. It stores all membership details (Names, Address etc..) and provides indivudal Key A's for each PAN stored Server B is a local server, and actually holds the encrypted PANs, as well as Key B, and does the decryption. To get a PAN, the client has to authenticate with BOTH servers, ask Server A for the respective Key A, then give Key A to server B, which will return the PAN to the client (provided authentication was sucessful). Server A will only ever encrypt Key A with Server B's public Key, as it will have it beforehand. Server B will probably have to send a salt first though, however I doin't think that has to be encrypted I havn't really thought about any implementation (i.e. coding) specifics yet regarding the above, however the solution is using Java's Cajo framework (wrapper for RMI) so that is how the servers will communicate with each other (Currently, membership details are transfered in this way). The reason why I want Server B to do the decryption, and not the client, is that I am afraid of decryption keys going into the client's RAM, even though it's probably just as bad on the server... Can anyone see anything wrong with the above design? It doesn't matter if the above has to be changed. Thanks jtnire

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  • .Net 4.0 Memory-Mapped Files verses RDMS Storage

    - by Harry
    I'm interested in people's thoughts comparing storing data in a traditional SQL based Database or utilising a Memory-Mapped File such as the one in the new .Net 4.0 runtime. The data in question would be arrays of simple structures. Obvious pros and cons: SQL Database Pros Adhoc query support SQL Management Tools Schema changes (adding more columns and setting default values) Memory-Mapped Pros Lighter overhead? (this is an assumption on my part) Shareable between process threads Any others? Is it worth it for performance gains?

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  • Visual Studio 2010 "Not enough storage is available to process this command"

    - by Daniel Perez
    I'm fighting with VS 2010 and this error that seems to be very common in previous versions, but it looks like not everyone is having it in the latest version. I've got VS 2010 SP1 and I'm getting this error quite often. The problem is that it's not even enough to restart VS in order to make it go away, I usually have to restart my pc, and i'm losing a lot of time doing this (it's quite frequent) I've got Windows 7 32bits (can't upgrade to 64 bits, the company doesn't allow it), and I can't do things like creating another solution (please don't reply this :) ) I've used the command to make devenv.exe LARGEADDRESSAWARE, but the error keeps on happening My virtual memory size is set to automatic, and the weird thing is that VS doesn't even take 2gb of ram, so I don't know if the error is really because it's lacking memory, or if it's some bug in the program any ideas, things to try, something?

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  • Questions about using git as a backend storage system

    - by XO
    New to git here... I want to commit my personal file share to a git repo (text, docs, images etc). As I make modifications to various files over time, telling git about them along the way, how do go about things so I can: Get out of the business of traditional fulls/incrementals. Be able to do a point-in-time file or full clone restore. Basically, I want something granular, such that, if I make an edit to a file 5 times on a particular day. I will have 5 versions of that file that I can refer back to- forever. Or even just derive the a full copy of everything the way it looked on that particular day. I am currently using rsync for remote incremental syncs (no file versioning).

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  • Efficient persistent storage for simple id to table of values map for java

    - by wds
    I need to store some data that follows the simple pattern of mapping an "id" to a full table (with multiple rows) of several columns (i.e. some integer values [u, v, w]). The size of one of these tables would be a couple of KB. Basically what I need is to store a persistent cache of some intermediary results. This could quite easily be implemented as simple sql, but there's a couple of problems, namely I need to compress the size of this structure on disk as much as possible. (because of amount of values I'm storing) Also, it's not transactional, I just need to write once and simply read the contents of the entire table, so a relational DB isn't actually a very good fit. I was wondering if anyone had any good suggestions? For some reason I can't seem to come up with something decent atm. Especially something with an API in java would be nice.

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  • how to check if internal storage file has any data

    - by user3720291
    public class Save extends Activity { int levels = 2; int data_block = 1024; //char[] data = new char[] {'0', '0'}; String blankval = "0"; String targetval = "0"; String temp; String tempwrite; String string = "null"; TextView tex1; TextView tex2; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.save); Intent intent = getIntent(); Bundle b = intent.getExtras(); tex1 = (TextView) findViewById(R.id.textView1); tex2 = (TextView) findViewById(R.id.textView2); if(b!=null) { string =(String) b.get("string"); } loadprev(); save(); } public void save() { if (string.equals("Blank")) blankval = "1"; if (string.equals("Target")) targetval = "1"; temp = blankval + targetval; try { FileOutputStream fos = openFileOutput("data.gds", MODE_PRIVATE); fos.write(temp.getBytes()); fos.close(); } catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();} tex1.setText(blankval); tex2.setText(targetval); } public void loadprev() { String final_data = ""; try { FileInputStream fis = openFileInput("data.gds"); InputStreamReader isr = new InputStreamReader(fis); char[] data = new char[data_block]; int size; while((size = isr.read(data))>0) { String read_data = String.copyValueOf(data, 0, size); final_data += read_data; data = new char[data_block]; } } catch (FileNotFoundException e) {e.printStackTrace();} catch (IOException e) {e.printStackTrace();} char[] tempread = final_data.toCharArray();; blankval = "" + tempread[0]; targetval = "" + tempread[1]; } } After much tinkering i have finally managed to get my save/load function to work, but it does have an error, pretty much i got it to work then i did a fresh reintall deleting data.gds, afterwards the save/load function crashes because the data.gds file has no previous values. can i use a if statment to check if data.gds has any values in it, if so how do i do it and if not, then what could i use instead?

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  • Efficient Array Storage for Binary Tree

    - by Sundararajan S
    We have to write the nodes of a binary tree to a file. What is the most space efficient way of writing a binary tree . We can store it in array format with parent in position 'i' and its childs in 2i,2i+1. But this will waste lot of space in case of sparse binary trees.

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  • Interpreter in C++: Function table storage problem

    - by sub
    In my interpreter I have built-in functions available in the language like print exit input, etc. These functions can obviously be accessed from inside the language. The interpreter then looks for the corresponding function with the right name in a vector and calls it via a pointer stored with its name. So I gather all these functions in files like io.cpp, string.cpp, arithmetic.cpp. But I have to add every function to the function list in the interpreter in order for it to be found. So in these function files I have things like: void print( arg ) { cout << arg.ToString; } I'd add this print function to the interpreter function list with: interpreter.AddFunc( "print", print ); But where should I call the interpreter.AddFunc? I can't just put it there below the print function as it has to be in a function according to the C++ syntax. Where and how should all the functions be added to the list?

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  • nHibernate storage of an object with self referencing many children and many parents

    - by AdamC
    I have an object called MyItem that references children in the same item. How do I set up an nhibernate mapping file to store this item. public class MyItem { public virtual string Id {get;set;} public virtual string Name {get;set;} public virtual string Version {get;set;} public virtual IList<MyItem> Children {get;set;} } So roughly the hbm.xml would be: <class name="MyItem" table="tb_myitem"> <id name="Id" column="id" type="String" length="32"> <generator class="uuid.hex" /> </id> <property name="Name" column="name" /> <property name="Version" column="version" /> <bag name="Children" cascade="all-delete-orphan" lazy="false"> <key column="children_id" /> <one-to-many class="MyItem" not-found="ignore"/> </bag> </class> This wouldn't work I don't think. Perhaps I need to create another class, say MyItemChildren and use that as the Children member and then do the mapping in that class? This would mean having two tables. One table holds the MyItem and the other table holds references from my item. NOTE: A child item could have many parents.

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  • extern and static variable storage ???

    - by Riyaz
    when will memory created for extern and static variable. Is it in stack or heap. Since its life time is till the program end, it cant be in stack it must be in heap. But size of the heap will known only at the run time. So somewhat confusion here ......

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  • Find out how much storage a row is taking up in the database

    - by Vaccano
    Is there a way to find out how much space (on disk) a row in my database takes up? I would love to see it for SQL Server CE, but failing that SQL Server 2008 works (I am storing about the same data in both). The reason I ask is that I have a Image column in my SQL Server CE db (it is a varbinary[max] in the SQL 2008 db) and I need to know now many rows I can store before I max out the memory on my device.

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  • HTML5 Offline Storage on iPad and iPhone BUG

    - by scaraveos
    Hello everyone, I created a manifest file with 1000 items. Safari, Mozilla browsers are saving the files offline successfully and even Android saves the files correctly offline. On iPad and iPhone when I am trying to save more than 300 items in some point the applicationCache returns "error". When I am trying to save less (e.x.: 200) it saves the files correctly and the applicationCache returns "cached". Any ideas? Thank you.

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  • "java.lang.OutOfMemoryError: Java heap space" in image and array storage

    - by totalconscience
    I am currently working on an image processing demonstration in java (Applet). I am running into the problem where my arrays are too large and I am getting the "java.lang.OutOfMemoryError: Java heap space" error. The algorithm I run creates an NxD float array where: N is the number of pixel in the image and D is the coordinates of each pixel plus the colorspace components of each pixel (usually 1 for grayscale or 3 for RGB). For each iteration of the algorithm it creates one of these NxD float arrays and stores it for later use in a vector, so that the user of the applet may look at the individual steps. My client wants the program to be able to load a 500x500 RGB image and run as the upper bound. There are about 12 to 20 iterations per run so that means I need to be able to store a 12x500x500x5 float in some fashion. Is there a way to process all of this data and, if possible, how? Example of the issue: I am loading a 512 by 512 Grayscale image and even before the first iteration completes I run out of heap space. The line it points me to is: Y.add(new float[N][D]) where Y is a Vector and N and D are described as above. This is the second instance of the code using that line.

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  • client-side data storage and retrieval with html and javascript

    - by pedalpete
    I'm building what I am hoping to be a fairly simple, quick and dirty demo app. So far, I've managed to build a bunch of components using only html and javascript. I know that eventually I'll hook-up a db, but at this point I'm just trying to show off some functionality. In the page, a user can select a bunch of other users (like friends). Then they go to a separate html page and there is some sorting info based on the selected users. So my first attempt was to put the selected users object into a cookie, and retrieve the cookie on the second page. Unfortunately, if the user changed their selection, the cookie wasn't getting updated, and my searches on StackOverflow seemed to say that deleting and updating cookies is unreliable. I tried function updateCookie(updatedUserList){ jQuery.cookie('userList',null); jQuery.cookie('userList',updatedUserList); } but though it set the cookie to null, it wouldn't update it on the second value. So I decided to put the selected users object into a form. Unfortunately, it looks like I can't retrieve the contents from the form on the client-side, only on the server-side. Is there another way to do this? I've worked in PHP and Rails, but I'm trying to do this quickly and simply before building it out into something larger and am trying to avoid any server-side processing for now, which I have managed to do up to this point.

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  • Custom session state provider needed for DB storage?

    - by subt13
    I know this question is related to many others, but please bear with me. I am trying an experiment to store all information in database tables instead of the ASP.NET session. In ASP.NET 4 one can create a custom provider for session. So, again should I implement a Custom Session-State Provider or should I just disable session (in Web.config)? Thanks! From the comments my question can be misunderstood. Hopefully this tidbit will help clarify: I don't want to store the session in the database. I want to store information in the database that you would typically store in the session. One reason why: I don't want to carry around a session on every page, especially if that page doesn't care about 90 percent of the information in the session

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  • String Storage and Retrieval in Android

    - by dweebsonduty
    I have a program that has items with 3 attributes. Name(String) : Count(String) : Amount(String) Currently I am writing the database when someone is trying to access a section then reading from the database. The writing is taking too long. So my question is how can I perhaps create a nested array where I can say if name = carrot then print carrot['count'] and carrot['amount']. I am very new to Java so some sample code would be great. Or any other suggestions that you may have as far as tackling this issue.

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