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• How to make an mutable C array for this data type?

  - by mystify

  There's this instance variable in my objective-c class: ALuint source; I need to have an mutable array of OpenAL Sources, so in this case probably I need a mutable C-array. But how would I create one? There are many questions regarding that: 1) How to create an mutable C-array? 2) How to add something to that mutable C-array? 3) How to remove something from that mutable C-array? 4) What memory management pitfalls must I be aware of? Must i free() it in my -dealloc method? And yes, I think this is something for the nice community wiki...

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• Performance of Serialized Objects in C++

  - by jm1234567890

  Hi Everyone, I'm wondering if there is a fast way to dump an STL set to disk and then read it back later. The internal structure of a set is a binary tree, so if I serialize it naively, when I read it back the program will have to go though the process of inserting each element again. I think this is slow even if it is read back in correct order, correct me if I am wrong. Is there a way to "dump" the memory containing the set into disk and then read it back later? That is, keep everything in binary format, thus avoiding the re-insertion. Do the boost serialization tools do this? Thanks! EDIT: oh I should probably read, http://www.parashift.com/c++-faq-lite/serialization.html I will read it now... no it doesn't really help

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• converting ip to long string in mysql command !

  - by Mac Taylor

  hey guys I'm trying to use ip2country technique to show my users'flags simple thing to do is to write a sql statement and show users from session table and then query to see if their ip is in what range and show their flags it simple but dengerous becuase when showing 300 users online and fetching from session table and then query once again ip2country table to get the flags there will be surelly memory overusage problem now i wrote a query to make it in one query : SELECT s.session_ip,ipc.* FROM session s left join ip2country ipc ON ipc.ip_lo<=s.session_ip AND ipc.ip_hi>=s.session_ip WHERE s.session_time > '".( time() - 60) )."' now its clear above query is wrong cause ips saved in ip2country table is long string 1000013824 and ips saved in session table are real ip e.g. 193.169.0.0 now i know how to convert from ip to long in php ip2long() but is there any command in mysql to do it with out building another query !?

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• PHP find if file data is an image

  - by Christian Sciberras

  Imagine I have some file data in a variable $data. I need to determine whether it is an image or not. No need for details such as corrupt images etc. Firs thought would be getting the file mime type by looking at the magic number and then see whether "image" is in the mime type. No such luck, even if I have a "file extension to mime type" script, I don't have a reliable way to get mime from magic number. My next option was to have a reasonable list of image file magic numbers and consult them. However, it relatively difficult to find such magic numbers (gif for instance has different magic numbers, some of which could pretty rare - if memory serves me right). A better idea would be some linux program which can do this kind of thing. Any ideas? I'm running RHEL and PHP 5.3. I've got root access - ie able to install stuff if needed. - Chris.

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• Modify input stream data on the fly

  - by Frizi

  I would like to implement a std::stream modifier/parser, that is doing data manipulation on the fly. Is it possible to create it in form of stream manipulator? For example, i want to strip all the line comments (from any // to the end of line) out of the stdin and pass it to stdout. string str; istream strippingCin = cin >> stripcomments; while(strippingCin.good()) { strippingCin >> str; cout << str; } There may be also a large file input instead of cin, so i don't want to load full stream data into memory at once. Is it possible without writing my own stream class? Maybe is there another route i should take instead?

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• Zend_Soap with attachments (server)

  - by Tom

  i'm trying to build a SOAP service with Zend_Soap. Everything is working great but the client needs the ability to send attachments to the service (not base64 encoded strings, as this service will be called multiple times a day with various file sizes so processing all that in memory is not possible. So I'd like to handle a normal SOAP attachment (DIME/MIME) with the SOAP server in Zend Framework however I'm unable to find documentation about it. Can I access it with $_FILES[] or any other way? Is it even possible in Zend_Soap (as there's not that much info available). SOAP is a must - so thanks for the advice but it has to be SOAP, not REST.

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• SWIG interface file questions

  - by morpheous

  I am writing a C/C++ extension module for other languages and I am using SWIG to generate the bindings. I have two questions Can I include more than 1 header file in the declaration part of the interface file e.g.: /* Declarations exposed to wrapper: */ > %{ > #define SWIG_FILE_WITH_INIT > #include "a.h" > #include "b.h" > #include "c.h" %} In all of the examples I have seen so far, after the header include declaration (as shown above), the functions declared in the header are then declared again in the interface file. Is this really necessary, as it means there are two copies of the function declarations that need to be maintained. Note: I can appreciate that some functions/methods declaration may need to be 'decorated' with the 'newobject' declaration so these obviously need to be in the interface file, to avoid memory leaks - however, I would have though that it would be sufficient to include the headers and then ONLY the declarations of the functions/methods that need to be declared with 'newobject' - is this recommended way of doing things?

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• C# how to store those information?

  - by 5YrsLaterDBA

  I have a PrivilegeGroup table, a Privileges table and a link table because the PrivilegeGroup table and the Privileges table is a many to many relationship. I am thinking about load all contents of PrivilegeGroup table and Privilege table into memory from database at beginning when application started. I want to save them in a form easily to look up. Usually we will look up the PrivilegeCode via GroupId. Which structure is good for this purpose? array of list? dictionary?

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• how to update off screen pivot item

  - by Yama moto

  I want to have a pivot with many PivotItems. However, doing so will impact memory. So I bind pivot to my ViewModel, which has 3 item, and pivot will generate 3 PivotItems. My ViewModel is of type ObservableCollection and my item does implement INotifyPropertyChanged. This works fine. But when I update my ViewModel, only the current PivotItem, and the right PivotItem is updated. The left PivotItem, which is off screen, is not updated. You can see it when you drag pivot to the left. How to fix this? Or WP7 doesnot update off screen PivotItem ?

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• Operations on 64bit words in 32bit system

  - by Vilo

  I'm new here same as I'm new with assembly. I hope that you can help me to start. I'm using 32bit (i686) Ubuntu to make programs in assembly, using gcc compiler. I know that general-purpose-registers are 32bit (4 bytes) max, but what when I have to operate on 64 bit numbers? Intel's instruction says that higher bits are stored in %edx and lower in %eax Great... So how can I do something with this 2-registers number? I have to convert 64bit dec to bin, then save it to memory and show on the screen. How to make the 64bit quadword at start of the program in .data section?

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• Updating a database periodically with Java

  - by MSR

  I would like to perform updates to a MySQL database using two separate classes (that do different things) -- one doing so every 10 seconds, and the second every minute. I have a few gaps in my Java knowledge and I'm wondering what the best way to achieve it is. Importantly, if connectivity to the database is lost, I need reconnection attempts to occur indefinitely, and I'm guessing the use of Prepared Statements will make queries more efficient. Should the connection to the database be left open all the time or closed between the updates being run? Maybe I also need to think about clearing objects/resources out of memory if the class instances are going to be run indefinitely.

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• Deleting a element from a vector of pointers in C++.

  - by Kranar

  I remember hearing that the following code is not C++ compliant and was hoping someone with much more C++ legalese than me would be able to confirm or deny it. std::vector<int*> intList; intList.push_back(new int(2)); intList.push_back(new int(10)); intList.push_back(new int(17)); for(std::vector<int*>::iterator i = intList.begin(); i != intList.end(); ++i) { delete *i; } intList.clear() The rationale was that it is illegal for a vector to contain pointers to invalid memory. Now obviously my example will compile and it will even work on all compilers I know of, but is it standard compliant C++ or am I supposed to do the following, which I was told is in fact the standard compliant approach: while(!intList.empty()) { int* element = intList.back(); intList.pop_back(); delete element; }

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• GCC compiler -- bug or unspecified behavior?

  - by Jared P

  When I have conflicting definitions of the ivars of a class in objective-c (not redeclaring the class in the same file, but rather naming the same class with diff ivars, no warnings or better yet errors are issued by the compiler. However, both sets of ivars are useable by the appropriate methods in the respective files. For instance Foo.m: @interface foo { int a; } - (int)method; @end @implementation foo - (int)method { return a; } @end Bar.m: @interface foo { float baz; } @end @implementation foo (category) - (float)blah { return baz; } @end compiles without warnings or errors. Is this intentional? Is this an unchecked error? (for the record, a and baz are actually the same memory location.)

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• MySQL: Query to obtain recipes using all given ingredients.

  - by John_A

  hi I have the following simplified tables: CREATE TABLE recipe(id int, name varchar(25)); CREATE TABLE ingredient(name varchar(25)); CREATE TABLE uses_ingredient(recipe_id int, name varchar(25)); I want to make a query that returns all id's of recipes that contain both Chicken and Cream. I have tried SELECT recipe_id FROM uses_ingredient INNER JOIN (SELECT * FROM ingredient WHERE name="Chicken" OR name="Cream") USING (name) GROUP BY recipe_id HAVING COUNT(recipe_id) >= (SELECT COUNT(*) FROM theme); which gives me :"ERROR 1248 (42000): Every derived table must have its own alias" and is probably wrong too. Next I tried SELECT recipe_id FROM (SELECT * FROM ingredient WHERE name="Chicken" OR name="Cream") AS t INNER JOIN uses_ingredient USING (name) GROUP BY recipe_id HAVING COUNT(recipe_id)>= (SELECT COUNT(*) FROM t); which gives "ERROR 1146 (42S02): Table 'recipedb.t' doesn't exist" I want to avoid creating temporary tables including using ENGINE=MEMORY.

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• Declaration and initialization of local variables - what is most C++ like?

  - by tuergeist

  Hi, I did not find any suitable questions answered yet, so I'd like to know what is "better" C++ style in the mean of performance and/or memory. Both codes are inside a method. The question is: When to declare long prio? And what are the implications? Code 1 while (!myfile.eof()) { getline(myfile, line); long prio = strtol(line); // prio is declared here // put prio in map... // some other things } Code 2 long prio; // prio is declared here while (!myfile.eof()) { getline(myfile, line); prio = strtol(line); // put prio in map... // some other things }

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• Small questions on data structure

  - by John Graveston

  Hi, I'm trying to search the parent of a node with Kruskal's algorithm. My program works just fine, but I think I have heard of a method to improve the speed of the algorithm by reconstructing the tree while searching for the parent node and connecting it to the parent node. I'm pretty sure that I've heard of this somewhere, maybe in a lecture. Can anyone refresh my memory? And also, given a number of arrays, when searching for the minimum and the maximum value from a certain section of an array, what is the name of the tree that can calculate the minimum/maximum value from the array by making a binary tree that has the minimum/maximum value of each array in O(log N)?

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• Object for storing strings in Python

  - by evg

  class MyWriter: def __init__(self, stdout): self.stdout = stdout self.dumps = [] def write(self, text): self.stdout.write(smart_unicode(text).encode('cp1251')) self.dumps.append(text) def close(self): self.stdout.close() writer = MyWriter(sys.stdout) save = sys.stdout sys.stdout = writer I use self.dumps list to store data obtained from prints. Is there a more convenient object for storing string lines in memory? Ideally I want dump it to one big string. I can get it like this "\n".join(self.dumps) from code above. May be it's better to just concatenate strings - self.dumps += text?

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• Find node level in a tree

  - by Álvaro G. Vicario

  I have a tree (nested categories) stored as follows: CREATE TABLE `category` ( `category_id` int(10) unsigned NOT NULL AUTO_INCREMENT, `category_name` varchar(100) NOT NULL, `parent_id` int(10) unsigned DEFAULT NULL, PRIMARY KEY (`category_id`), UNIQUE KEY `category_name_UNIQUE` (`category_name`,`parent_id`), KEY `fk_category_category1` (`parent_id`,`category_id`), CONSTRAINT `fk_category_category1` FOREIGN KEY (`parent_id`) REFERENCES `category` (`category_id`) ON DELETE SET NULL ON UPDATE CASCADE ) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE=utf8_spanish_ci I need to feed my client-side language (PHP) with node information (child+parent) so it can build the tree in memory. I can tweak my PHP code but I think the operation would be way simpler if I could just retrieve the rows in such an order that all parents come before their children. I could do that if I knew the level for each node: SELECT category_id, category_name, parent_id FROM category ORDER BY level -- No `level` column so far :( Can you think of a way (view, stored routine or whatever...) to calculate the node level? I guess it's okay if it's not real-time and I need to recalculate it on node modification.

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• Heap Error in C++

  - by BobAlmond

  Dear all, I'm a beginner programmer in C++. Recently, I'm working on image processing thing using C++. but I have some problem that I want to ask. Suppose I have some code as follow: for (int i=0;i<100000;i++) { int * a = new int[10000]; //do something delete [] a; } When I executed that code, I receive runtime error, Heap Error... Is there anything wrong with that code, I mean, can I allocate memory and release it in the same loop? Thanks in advance...

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• Would vector of vectors be contiguous?

  - by user1150989

  I need to allocate a vector of rows where row contains a vector of rows. I know that a vector would be contiguous. I wanted to know whether a vector of vectors would also be contiguous. Example code is given below vector<long> firstRow; firstRow.push_back(0); firstRow.push_back(1); vector<long> secondRow; secondRow.push_back(0); secondRow.push_back(1); vector< vector < long> > data; data.push_back(firstRow); data.push_back(secondRow); Would the sequence in memory be 0 1 0 1?

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• ordering a collection by an association's property

  - by neiled

  class Person belongs_to :team class Status #has last_updated property class Team has_many :members, :class => "Person" Ok, so I have a Team class which has many People in it and each of those people has a status and each status has a last_updated property. I'm currently rendering a partial with a collection similar to: =render :partial => "user", :collection => current_user.team.members Now how do I go about sorting the collection by the last_updated property of the Status class? Thanks in advance! p.s. I've just written the ruby code from memory, it's just an example, it's not meant to compile but I hope you get the idea!

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• Authenticating model - best practices

  - by zerkms

  I come into ASP.NET from php so the reason why i ask my question is because it's totally different nature of how application works and handles requests. well, i have an exists table with user creditians, such as: id, login, password (sha hashed), email, phone, room i have built custom membership provider so it can handle my own database authentication schema. and now i'm confused, because User.Identity.Name contains only user's login, but not the complete object (i'm using linq2sql to communicate with database and i need in it's User object to work). at php applications i just store user object at some static method at Auth class (or some another), but here at ASP.NET MVC i cannot do this, because static member is shared across all requests and permanent, and not lives within only current request (as it was at php). so my question is: how and where should i retrieve and store linq2sql user object to work with it within current and only current request? (after request processed successfully i expect it will be disposed from memory and on next request will be created again). or i'm following totally wrong way?

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• INSERT INTO ... SELECT ... vs dumping/loading a file in MySQL

  - by Daniel Huckstep

  What are the implications of using a INSERT INTO foo ... SELECT FROM bar JOIN baz ... style insert statement versus using the same SELECT statement to dump (bar, baz) to a file, and then insert into foo by loading the file? In my messing around, I haven't seen a huge difference. I would assume the former would use more memory, but the machine that this runs on has 8GB of RAM, and I never even see it go past half used. Are there any huge (or long term) performance implications that I'm not seeing? Advantages/disadvantages of either?

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• How do you ensure a mimetype in asp.net?

  - by Sem Dendoncker

  Hello, I have the following code to export a zip file: byte[] buffer = FileUtil.FileToByteArray(zipLocation, true); // push the memory data to the client. _ctx.Response.ContentType = "application/zip"; _ctx.Response.AddHeader("content-disposition", String.Format("attachment; filename={0}", String.Format("map{0}.zip", mapId))); _ctx.Response.BinaryWrite(buffer); This code works great. After every export I get a perfectly made zipfile. The problem however is that when I try to import it, the mimetype sometimes is "application/empty". Now I wonder how can I ensure that the mimetype is always added? Cheers, M.

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• Should I put a try-finally block after every Object.Create?

  - by max

  I have a general question about best practice in OO Delphi. Currently, I put try-finally blocks anywhere I create an object to free that object after usage (to avoid memory leaks). E.g.: aObject := TObject.Create; try aOBject.AProcedure(); ... finally aObject.Free; end; instead of: aObject := TObject.Create; aObject.AProcedure(); .. aObject.Free; Do you think it is good practice, or too much overhead? And what about the performance?

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