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Search found 1753 results on 71 pages for 'consistent hashing'.

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  • How to Create Own HashMap in Java?

    - by Taranfx
    I know about hashing algorithm and hashCode() to convert "key" into an equivalent integer (using some mathematically random expression) that is then compressed and stored into buckets. But can someone point me to an implementation or at least data structure that should be used as baseline? I haven't found it anywhere on the web.

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  • Saving private data

    - by rajatgoel
    Hi, Can anybody detail some approach on how to save private data in social websites like facebook, etc. They cant save all the updates and friends list in clear text format because of privacy issues. So how do they actually save it? Hashing all the data with user password so that only a valid session view it is one possibility. But I think there are some problem with this approach and there must be some better solution.

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  • How can I hash a string to an int using c++?

    - by zebraman
    I have to write my own hash function. If I wanted to just make the simple hash function that maps each letter in the string to a numerical value (i.e. a=1, b=2, c=3, ...), is there a way I can perform this hash on a string without having to first convert it to a c-string to look at each individual char? Is there a more efficient way of hashing strings?

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  • Webservice for uploading data: security considerations

    - by Philip Daubmeier
    Hi everyone! Im not sure about what authentification method I should use for my webservice. I've searched on SO, and found nothing that helped me. Preliminary Im building an application that uploads data from a local database to a server (running my webservice), where all records are merged and stored in a central database. I am currently binary serializing a DataTable, that holds a small fragment of the local database, where all uninteresting stuff is already filtered out. The byte[] (serialized DataTable), together with the userid and a hash of the users password is then uploaded to the webservice via SOAP. The application together with the webservice already work exactly like intended. The Problem The issue I am thinking about is now: What is if someone just sniffs the network traffic, 'steals' the users id and password hash to send his own SOAP message with modified data that corrupts my database? Options The approaches to solving that problem, I already thought of, are: Using ssl + certificates for establishing the connection: I dont really want to use ssl, I would prefer a simpler solution. After all, every information that is transfered to the webservice can be seen on the website later on. What I want to say is: there is no secret/financial/business-critical information, that has to be hidden. I think ssl would be sort of an overkill for that task. Encrypting the byte[]: I think that would be a performance killer, considering that the goal of the excercise was simply to authenticate the user. Hashing the users password together with the data: I kind of like the idea: Creating a checksum from the data, concatenating that checksum with the password-hash and hashing this whole thing again. That would assure the data was sent from this specific user, and the data wasnt modified. The actual question So, what do you think is the best approach in terms of meeting the following requirements? Rather simple solution (As it doesnt have to be super secure; no secret/business-critical information transfered) Easily implementable retrospectively (Dont want to write it all again :) ) Doesnt impact to much on performance What do you think of my prefered solution, the last one in the list above? Is there any alternative solution I didnt mention, that would fit better? You dont have to answer every question in detail. Just push me in the right direction. I very much appreciate every well-grounded opinion. Thanks in advance!

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  • Are fragments of hashes collision-resistent?

    - by Mark
    Let me see if someone would mind clearing up this elementary point about md5 and hashing. If you only use the first 4 bytes of an md5 hash, would that mean theoretically only 1 in 255^4 chance of collision. iow is that the intention with it (and other hash algorithms) - that you only have to use a small portion of the returned hash (say the hash is of a file of some size).

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  • How to hash a password and store for later verification with another digest

    - by oxygen8
    I am using gsoap's wsseapi plugin and would like to store hashed sha1 passwords rather than plain text. I have spent a rediculous amount of time experimenting with various methods of hashing the plain text password for storage. Can anyone suggest a way to hash a password so it can be later verified against a username token digest sent by the client. I can't seem to get the client password to authenticate against my stored hash

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  • Can I override a query in DJango?

    - by stinkypyper
    I know you can override delete and save methods in DJango models, but can you override a select query somehow to intercept and change a parameter slightly. I have a hashed value I want to check for, and would like to keep the hashing internal to the model.

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  • I need a dictionary-like mapping between characters and other kinds of objects. Which class would be

    - by nullPointerException
    This is in Squeak/Pharo. If I want to have a mapping between Character objects like $a and $b to other kinds of objects, and want to look up those other objects based on the Character, what is the best class to use? Dictionary is an obvious choice, but seems wasteful to be hashing character objects which are basically already numbers. I guess what I want is a kind of array where the character value (number) is used as an index/offset, but I am not sure if this is possible with Unicode.

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  • How big in bytes is a DataRow

    - by JeffreyABecker
    I have a one-time process (hashing all our user passwords) written using datasets. The performance needs improvement so we've profiled the application and found that increasing the 'batch size' of the update will improve performance. I also know that if I load the entire data set into memory the application will start hitting swap and slow down. The question is: how big is a System.Data.DataRow derived class? I'd like to calculate a batch size which I know won't force the application into swap.

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  • object reference set in java

    - by landon9720
    I need to create a Set of objects. The concern is I do not want to base the hashing or the equality on the objects' hashCode and equals implementation. Instead, I want the hash code and equality to be based only on each object's reference identity (i.e.: the value of the reference pointer). I'm not sure how to do this in Java. The reasoning behind this is my objects do not reliably implement equals or hashCode, and in this case reference identity is good enough.

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  • is there a way to condense a vector (C++)?

    - by zebraman
    I have a sparsely populated vector that I populated via hashing, so elements are scattered randomly in the vector. Now what I want to do is iterate over every element in that vector. What I had in mind was essentially condensing the vector to fit the number of elements present, removing any empty spaces. Is there a way I can do this?

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  • File extensions and MIME Types in .NET

    - by Marc Climent
    I want to get a MIME Content-Type from a given extension (preferably without accessing the physical file). I have seen some questions about this and the methods described to perform this can be resumed in: Use registry information. Use urlmon.dll's FindMimeFromData. Use IIS information. Roll your own MIME mapping function. Based on this table, for example. I've been using no.1 for some time but I realized that the information provided by the registry is not consistent and depends on the software installed on the machine. Some extensions, like .zip don't use to have a Content-Type specified. Solution no.2 forces me to have the file on disk in order to read the first bytes, which is something slow but may get good results. The third method is based on Directory Services and all that stuff, which is something I don't like much because I have to add COM references and I'm not sure it's consistent between IIS6 and IIS7. Also, I don't know the performance of this method. Finally, I didn't want to use my own table but at the end seems the best option if I want a decent performance and consistency of the results between platforms (even Mono). Do you think there's a better option than using my own table or one of other described methods are better? What's your experience?

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  • Frameworks to manage dates (effective date and expiry dates)

    - by user214626
    Hello, We have an object that can has an effective date and expiry date.(Ex. i want to maintain the price of a commodity for a time period) Business Rules - Effective date is always a valid date (a datestamp) but, expiry date can be null to indicate that the object is active throughout. Also, both effective and expiry date can be set to some valid dates. Are there any frameworks that manage objects such that the objects are consistent,i.e there are no overlaps of the validity periods ? Ex. class XBOX { double price; Date effectiveDate; Date expiryDate; } XBOX x1 = new XBOX(400$, '2007-01-01','2008-12-31' ); XBOX x2 = new XBOX(200$, '2009-01-01',null ); Assume that we get a new rate from '2010-01-01' and a new XBOX object has to be created (to persist). Is there a framework/pattern that can do the following, so that the XBOX is consistent. x2.setExpiryDate('2009-12-31') XBOX x3 = new XBOX(150$, '2010-01-01',null ); Thanks in advance.

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  • Inconsistency in modified/created/accessed time on mac

    - by Seth Johnson
    I'm having trouble using os.utime to correctly set the modification time on the mac (Mac OS X 10.6.2, running Python 2.6.1 from /usr/bin/python). It's not consistent with the touch utility, and it's not consistent with the properties displayed in the Finder's "get info" window. Consider the following command sequence. The 'created' and 'modified' times in the plain text refer to the "get info" window attributes. As a reminder, os.utime takes arguments (filename, (atime, mtime)). >>> import os >>> open('tempfile','w').close() 'created' and 'modified' are both the current time. >>> os.utime('tempfile', (1000000000, 1500000000) ) 'created' is the current time, 'modified' is July 13, 2017. >>> os.utime('tempfile', (1000000000, 1000000000) ) 'created' and 'modified' are both September 8, 2001. >>> os.path.getmtime('tempfile') 1000000000.0 >>> os.path.getctime('tempfile') 1269021939.0 >>> os.path.getatime('tempfile') 1269021951.0 ...but the os.path.get?time and os.stat don't reflect it. >>> os.utime('tempfile', (1500000000, 1000000000) ) 'created' and 'modified' are still both September 8, 2001. >>> os.utime('tempfile', (1500000000, 1500000000) ) 'created' is September 8, 2001, 'modified' is July 13, 2017. I'm not sure if this is a Python problem or a Mac stat problem. When I exit the Python shell and run touch -a -t 200011221234 tempfile neither the modification nor the creation times are changed, as expected. Then I run touch -m -t 200011221234 tempfile and both 'created' and 'modified' times are changed. Does anyone have any idea what's going on? How do I change the modification and creation times consistently on the mac? (Yes, I am aware that on Unixy systems there is no "creation time.")

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  • Python Django Global Variables

    - by Joe J
    Hi all, I'm looking for simple but recommended way in Django to store a variable in memory only. When Apache restarts or the Django development server restarts, the variable is reset back to 0. More specifically, I want to count how many times a particular action takes place on each model instance (database record), but for performance reasons, I don't want to store these counts in the database. I don't care if the counts disappear after a server restart. But as long as the server is up, I want these counts to be consistent between the Django shell and the web interface, and I want to be able to return how many times the action has taken place on each model instance. I don't want the variables to be associated with a user or session because I might want to return these counts without being logged in (and I want the counts to be consistent no matter what user is logged in). Am I describing a global variable? If so, how do I use one in Django? I've noticed the files like the urls.py, settings.py and models.py seems to be parsed only once per server startup (by contrast to the views.py which seems to be parsed eache time a request is made). Does this mean I should declare my variables in one of those files? Or should I store it in a model attribute somehow (as long as it sticks around for as long as the server is running)? This is probably an easy question, but I'm just not sure how it's done in Django. Any comments or advice is much appreciated. Thanks, Joe

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  • C#/Java: Proper Implementation of CompareTo when Equals tests reference identity

    - by Paul A Jungwirth
    I believe this question applies equally well to C# as to Java, because both require that {c,C}ompareTo be consistent with {e,E}quals: Suppose I want my equals() method to be the same as a reference check, i.e.: public bool equals(Object o) { return this == o; } In that case, how do I implement compareTo(Object o) (or its generic equivalent)? Part of it is easy, but I'm not sure about the other part: public int compareTo(Object o) { if (! (o instanceof MyClass)) return false; MyClass other = (MyClass)o; if (this == other) { return 0; } else { int c = foo.CompareTo(other.foo) if (c == 0) { // what here? } else { return c; } } } I can't just blindly return 1 or -1, because the solution should adhere to the normal requirements of compareTo. I can check all the instance fields, but if they are all equal, I'd still like compareTo to return a value other than 0. It should be true that a.compareTo(b) == -(b.compareTo(a)), and the ordering should stay consistent as long as the objects' state doesn't change. I don't care about ordering across invocations of the virtual machine, however. This makes me think that I could use something like memory address, if I could get at it. Then again, maybe that won't work, because the Garbage Collector could decide to move my objects around. hashCode is another idea, but I'd like something that will be always unique, not just mostly unique. Any ideas?

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  • what libraries or platforms should I use to build web apps that provide real-time, asynchronous data

    - by Daniel Sterling
    This is a less a question with a simple, practical answer and more a question to foster discussion on the real-time data exchange topic. I'll begin with an example: Google Wave is, at its core, a real-time asynchronous data synchronization engine. Wave supports (or plans to support) concurrent (real-time) document collaboration, disconnected (offline) document editing, conflict resolution, document history and playback with attribution, and server federation. A core part of Wave is the Operational Transformation engine: http://www.waveprotocol.org/whitepapers/operational-transform The OT engine manages document state. Changes between clients are merged and each client has a sane and consistent view of the document at all times; the final document is eventually consistent between all connected clients. My question is: is this system abstract or general enough to be used as a library or generic framework upon which to build web apps that synchronize real-time, asynchronous state in each client? Is the Wave protocol directly used by any current web applications (besides Google's client)? Would it make sense to directly use it for generic state synchronization in a web app? What other existing libraries or frameworks would you consider using when building such a web app? How much code in such an app might be domain-specific logic vs generic state synchronization logic? Or, put another way, how leaky might the state synchronization abstractions be? Comments and discussion welcomed!

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  • Is it possible to do A/B testing by page rather than by individual?

    - by mojones
    Lets say I have a simple ecommerce site that sells 100 different t-shirt designs. I want to do some a/b testing to optimise my sales. Let's say I want to test two different "buy" buttons. Normally, I would use AB testing to randomly assign each visitor to see button A or button B (and try to ensure that that the user experience is consistent by storing that assignment in session, cookies etc). Would it be possible to take a different approach and instead, randomly assign each of my 100 designs to use button A or B, and measure the conversion rate as (number of sales of design n) / (pageviews of design n) This approach would seem to have some advantages; I would not have to worry about keeping the user experience consistent - a given page (e.g. www.example.com/viewdesign?id=6) would always return the same html. If I were to test different prices, it would be far less distressing to the user to see different prices for different designs than different prices for the same design on different computers. I also wonder whether it might be better for SEO - my suspicion is that Google would "prefer" that it always sees the same html when crawling a page. Obviously this approach would only be suitable for a limited number of sites; I was just wondering if anyone has tried it?

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  • Making text align equally in both IE and Chrome

    - by bobo
    <style type="text/css"> h2{ font-size:13px; line-height:16px; color:#000000; margin:0; padding:6px 22px; font-family: 'Times New Roman'; } div{ border:1px solid black; } </style> <div> <h2> ????????</h2> </div> Pasting the above codes here: http://htmledit.squarefree.com/ You will see that the text stays a little bit higher in the div in IE than in Chrome, I would like to make them consistent. By adding a &nbsp; after the text within the <h2>in IE, the text will automatically move up, which is consistent with Chrome. But I don't quite like this hack, so I would like to know if anybody knows what problem this is and recommends a better way to fix it if possible. Many thanks to you all. Note: this problem does not appear if the text is english only.

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  • Non-english domain naming issues in programming

    - by Svend
    Most programming code, I imagine is written in english. But I'm curious how people handling the issue of naming herein. Alot of programming is done within some bussiness domain, usually with well established terms for certain procedures, items. I'm from Denmark for instance, and something I work alot with has a term called "indblikskode", which sorta translates to "insight code". So, do I use the line "string indblikskode = ..." in the C# code for some webservice related to this? Or do I try to use a translation, such as "insightcode"? The bussiness I'm in isn't even consistent in it's language, for instance using the term "organisatorisk enhed" (organizatorical unit), but just as often using the abbreviation "OU", which is obviously abbreviated from the english. How do other people handle this naming issue, while keeping consistent, and sane (in everything from simple variable names in your code, to database tables, to server names)? Duplicates: Should identifiers and comments be always in English or in the native language of the application and developers? Do you use another language instead of english ?

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