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  • C++ static virtual members?

    - by cvb
    Is it possible in C++ to have a member function that is both static and virtual? Apperantly, there isn't a straight-forward way to do it (static virtual member(); is a complie error), but at least a way to acheive the same effect? I.E: struct Object { struct TypeInformation; static virtual const TypeInformation &GetTypeInformation() const; }; struct SomeObject : public Object { static virtual const TypeInformation &GetTypeInformation() const; }; It makes sence to use GetTypeInformation() both on an instance (object->GetTypeInformation()) and on a class (SomeObject::GetTypeInformation()), which can be useful for comparsions and vital for templates. The only ways I can think of involves writing two functions / a function and a constant, per class, or use macros. Any other solutions?

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  • need a virtual template member workaround

    - by yurib
    Hello, I need to write a program implementing the visitor design pattern. The problem is that the base visitor class is a template class. This means that BaseVisited::accept() takes a template class as a parameter and since it uses 'this' and i need 'this' to point to the correct runtime instance of the object, it also needs to be virtual. I'd like to know if there's any way around this problem. template <typename T> class BaseVisitor { public: BaseVisitor(); T visit(BaseVisited *visited); virtual ~BaseVisitor(); } class BaseVisited { BaseVisited(); template <typename T> virtual void accept(BaseVisitor<T> *visitor) { visitor->visit(this); }; // problem virtual ~BaseVisited(); }

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  • Ubuntu virtual memory caches suck up memory

    - by Tom
    Hey all, I've got an Ubuntu 9.10 64-bit server that seems to use up all available memory. According to my munin graphs, almost all of the memory used up is in the swap cache, cache, and slab cache. (I take this to mean virtual memory caches, am I right in assuming this?) Once memory usage approaches 100%, some (although not all) system services such as SSH become sluggish and unresponsive. After rebooting the system, performance and memory usage become normal for a time. Some interesting tidbits: The system runs Apache 2, MySQL, Munin, and sshd. The memory usage spikes happen at the same time every night (at 10 PM sharp.) There appears to be nothing in the crontab for any of the users, and nothing in /etc/cron.d/* out of the ordinary, let alone something that would occur at 10 PM. My question is, how do I figure out what is causing the memory suckage? I've tried the usual utilities (e.g. ps, top, etc) but I can't seem to find anything unusual. Any ideas? Thanks in advance!

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  • URL Rewriting on GoDaddy Virtual Server

    - by Aristotle
    I migrated a Kohana2 application from a shared-hosting environment over to a virtual dedicated server. After this migration, I can't seem to get my .htaccess file working again. I apologize up front, but over the years I have never experienced so much frustration with anything else as I do with the dreaded .htaccess file. Presently I have my project installed immediately within a directory in my public folder: /var/html/www/info.php (general information about server) /var/html/www/logo.jpg (some flat file) /var/html/www/somesite.com/[kohana site exists here] So my .htaccess file is within that directory, and has the following contents: # Turn on URL rewriting RewriteEngine On # Installation directory RewriteBase /somesite.com/ # Protect application and system files from being viewed # This is only necessary when these files are inside the webserver document root RewriteRule ^(application|modules|system) - [R=404,L] # Allow any files or directories that exist to be displayed directly RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d # Rewrite all other URLs to index.php/URL RewriteRule .* index.php?kohana_uri=$0 [PT,QSA,L] # Alternativly, if the rewrite rule above does not work try this instead: #RewriteRule .* index.php?kohana_uri=$0 [PT,QSA,L] This doesn't work. The initial controller is loaded, since index.php is called up implicitly when nothing else is in the url. But if I try to load up some other non-default controller, the site fails. If I place the index.php back within the url, the call to other controllers works just fine. I'm really at my wits end, and would appreciate some direction here.

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  • VMWare Fusion: "No Permission to access this virtual machine"

    - by Craig Walker
    I had a VMWare Fusion VM backed up on my home network file server (Ubuntu). I wanted to run it again, so I copied it back to my Macbook. When I tried to launch it in VMWare, I got an error message: No permission to access this virtual machine. Configuration file: /Users/craig/WinXP Clean + Scanner.vmwarevm/WinXP Pro Test.vmx The permissions look fine to me: The bundle directory is 777 The bundle files (including the listed .vmx) are all 666 User is craig (my current user); group is staff. I changed the group to wheel at the suggestion of this page, but that didn't help. Finder shows read & write for craig, staff, and everyone on the bundle directory The bundle dir is also not locked Finder also shows rw and unlocked for the .vmx file The parent directory is also rw & unlocked Disk Utility permissions check doesn't show any problems with any of the associated files It sure looks like I should have wide open access to run this VM; why is Fusion complaining?

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  • Physical-to-virtual for personal use

    - by Journeyman Geek
    One of my current projects involves reducing the number of old computers lying around. So far, the office systems have been downsized from 5 to 2. One system which had no data on it was dumped entirely, while three other identical boxes were consolidated into to one (I swap hard drives as needed and they just work(tm)). I want to make further cuts. The physical systems in question all run windows xp sp3, and were old Pentium 4s with 256 MB of RAM. Currently, I have got a VirtualBox running on another system. My intention is to migrate all services to that. We can assume that disk space and RAM on the host is not an issue. I'd rather not go with a client-server physical-to-virtual (P2V) method like what VirtualBox uses now. I have a few specific concerns as well - specifically whether I'd need to reactivate or sysprep for dissimilar hardware first. An offline tool for imaging (Windows or Linux) would not be an issue since the drives could be mounted onto another system I have anyway or I could use a LiveCD. What would be my options for P2V conversion, and what would I need to keep in mind when doing this?

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  • No LPT port in Windows 7 virtual machines

    - by KeyboardMonkey
    Windows 7 has MS virtual PC integrated, the VM settings don't give a parallel LPT port mapping to the physical machine. Where did it go? Has anyone else noticed this, and found a solution? Update: After much digging, I found the one and only reference to this issue, on the VPC Blog: "Parallel port devices are not supported, as they are relatively rare today." -More details- It's a XP VM I've been using since VPC 2007 days, which did have this functionality. This is to configure barcode printers via the LPT port. Since the (new) MS VM can't map to my physical LPT port, I'm having a hard time configuring printers. My physical ports are enabled in the BIOS. It has worked the past 3 years, before switching to Win 7. Any help is appreciated. This screen shot of the VM settings shows COM ports, but LPT is no more In contrast, here is a screen shot of VPC 2007 (before it got integrated into Win 7). Notice how it has LPT support

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  • Virtual machines with failover setup

    - by kimmmo
    We have three servers and our plan is to run a number of virtual machines on them in such manner, that if one of the nodes blow up, we can either quickly or seamlessly get a spare running on another node. In addition to the normal networking, they're interconnected via dual 10Gbit NIC's, so networked raid/mirroring shouldn't be a problem. The guest VM's are mostly going to be running text mode linux, but of course it wouldn't hurt to be able to spin up a non-mission critical windows guest for running Visual Studio or checking IE compatibility of a web app. We've spent some time trying to get some magical cloud setup running using Stackops and Crowbar but it started to look like they were offering way too much and were too complicated for our needs. The next candidate, I think, is Ubuntu 11.04 server + KVM + Ganeti + Drbd, unless you can come up with a suggestion for a better solution that we have missed. Requirements: Installation should be simple or at least understandable without being in the dev team A browser interface for creating and managing VM's is a nice bonus Single node's hardware failure should cause minimal downtime for VM's that were running on that node Adding more nodes should be possible without shutting down the VM's.

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  • Authenticate domain-user credentials on unjoined virtual machine?

    - by bwerks
    Hi all, This question may sound silly, and perhaps a bit insane, but--is there any way to run a process on a machine not joined to a domain using credentials from a user in that domain? In my case, I'm running virtual machines installed with release binaries from our build process, as well as Visual Studio. Visual Studio is there to debug our release binaries, however it's being executed with vm-local user credentials. This means that it can't authenticate to our TFS deployment when executing "tf.exe view" to utilize our Source Server for debugging. Team Explorer manages to authenticate to TFS using a UI prompt, however I suspect that it's because we supply it with the TFS deployment's URI, and it's designed to display a prompt to facilitate workgroup scenarios; i.e. it's not like we're getting it for free. My instincts tell me the only way to authenticate on this vm is to join it or somehow form a one-way trust or something, but is there an easier way? For automation we're going to want to script this eventually, but I'm first surveying the feasibility of the thing.

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  • Missing access log for virtual host on Plesk

    - by Cummander Checkov
    For some reason i don't understand, after creating a new virtual host / domain in Plesk a few months back, i cannot seem to find the access log. I noticed this when running /usr/local/psa/admin/sbin/statistics The host in question is being scanned Main HTML page is 'awstats.<hostname_masked>-http.html'. Create/Update database for config "/opt/psa/etc/awstats/awstats.<hostname_masked>.com-https.conf" by AWStats version 6.95 (build 1.943) From data in log file "-"... Phase 1 : First bypass old records, searching new record... Searching new records from beginning of log file... Jumped lines in file: 0 Parsed lines in file: 0 Found 0 dropped records, Found 0 corrupted records, Found 0 old records, Found 0 new qualified records. So basically no access logs have been parsed/found. I then went on to check if i could find the log myself. I looked in /var/www/vhosts/<hostname_masked>.com/statistics/logs but all i find is error_log Does anybody know what is wrong here and perhaps how i could fix this? Note: in the <hostname_masked>.com/conf/ folder i keep a custom vhost.conf file, which however contains only some rewrite conditions plus a directory statement that contains php_admin_flag and php_admin_value settings. None of them are related to logging though.

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  • backup an existing linux server to a virtualbox virtual machine

    - by user146526
    I have some servers and VPSs to many companies across the world. I want to back them up locally. I have some backup solutions enabled to remote hosts, but I want to have a local backup on a computer at home. What I am thinking is: 1) Create a virtualbox virtual machine, install the same version linux as the server. 2) Use rsync to backup the server to the local virtualbox machine. (something like rsync -av --delete --progress --exclude '/dev/' --exclude '/proc/' root@server_ip:// / ) 3) Repeat the command every few days update files. 4) In case of a hard disk failure, or any other bad event, reverse the rsync command and get the files back and continue my bussiness. I tried it with 2 openvz VPS, the one was a backup of the other. I also tried to transfer normal linux server host to openvz machine and it worked great. That way looks pretty clean and easy to me, this is the kind of solution I am looking for. However I need to be sure that this will work if I am going to do it. The question is, will that work ok ? Does anyone see any problem with that ? Do you have any other suggestions ? Thanks

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  • Dedicated Mouse and Keyboard on Virtual Box VM

    - by Myersguy
    To all super users, Currently I am trying to run virtual box on my second monitor, with a dedicated mouse and keyboard. However, doing so has not proven easy. There has been times where the mouse works, but not the keyboard, vice versa, or nothing works at all. The biggest problem I am running into is this: When enabling the USB mouse and keyboard from the VM, I get an error: 'USB Device is busy with a previous request.' The only thing that is using second mouse and keyboard, however, is Windows. The other error I have received stated that the VM was unable to create a proxy for the device. Additionally, the VM occasionally will disable the secondary keyboard entirely, requiring me to unplug and replug it into my PC to re-enable it again. Keyboard auto-capture is disabled, and while a solution I was reading online stated to turn off mouse integration, that option is grayed out on my machine. Any help would be appreciated. Thanks. /firstquestion.

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  • How to connect 2 virtual hosts running on the same machine?

    - by Gabrielle
    I have 2 virtual hosts running on my Windows XP laptop. One is Ubuntu running inside vmware player. The other is MS virtual PC (so I can test with IE6 ). The Ubuntu virtual host is running my web application with apache. I can point my browser on my laptop at the Ubuntu IP and view my web app. I read this post http://stackoverflow.com/questions/197792/how-to-connect-to-host-machine-from-within-virtual-pc-image and was able to get my Virtual PC to ping my physical machine using the loopback adapter. But I'm stuck on getting my Virtual PC to see my web application running in the Ubuntu vmware player host. I appreciate any suggestions.

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  • Getting Drag and Drop to Work in Virtual PC 2007 on Windows 7.

    - by Kryten
    Hi, I have Virtual PC 2007 installed on my Windows 7 machine. Before anyone asks, I have installed VPC 2007 because my machine does not support the new Virtual PC for Windows 7. Everythings working fine, except for the drag and drop file feature. On my old Windows XP machine the drag and drop feature works fine, but on Windows 7, nothing happens. I just get the "no drop" cursor. I HAVE installed Virtual Machine Additions and have run Virtual PC under XP Compatability, but still nothing. The Virtual Machines I have tried draging and dropping files onto on are: Windows 2000 Windows XP Windows 98 and as I said they all have Virtual Machine Additions on them. Whats going on? How can I get the drag and drop feature working? I did see this question, but it still doesn't answer my question.

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  • C# 4.0 in a Nutshell, Fourth Edition

    - by outcoldman
    Just became a lucky owner of this book C# IN A NUTSHELL 4th edition. This is a fourth edition of this book’s series. I saw previous third edition of this book, we presented it on one of our events at Yaroslavl State University, but that book was a Russian translated version and published in Russia, this is was bad side of that book – all books at Russia printed on really bad paper. I should say that I didn’t read this book by end, but already I was surprised. Why? Why I heard a lot about Richter CLR via C# (English version of 3rd edition of this book I already have, and this book are waiting my attention), and just a few words about C# IN A NUTSHELL, at least in my sphere. I just listen once about this book at one of the podcast of Alt.Net group, and this words was Richter it is really good book, and C# IN A NUTSHELL it is a good handbook. My opinion is - you should read Richter if you want to develop with .NET. But if you want to develop on .NET with C# you should read C# IN A NUTSHELL too. Read more...

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  • How to create a virtual network with Azure Connect

    - by Herve Roggero
    If you are trying to establish a virtual network between machines located in disparate networks, you can either use VPN, Virtual Network or Azure Connect. If you want to establish a connection between machines located in Windows Azure, you should consider using the Virtual Network service. If you want to establish a connection between local machines and Virtual Machines in Windows Azure, you may be able to use your existing VPN device (assuming you have one), as long as the device is supported by Microsoft. If the VPN device you are using isn’t supported, or if you are trying to create a virtual network between machines from disparate networks (such as machines located in another cloud provider), you can use Azure Connect. This blog post explains how Azure Connect can help you create virtual networks between multiple servers in the cloud, various servers in different cloud environments, and on-premise. Note: Azure Connect is currently in Technical Preview. About Azure Connect Let’s do a quick review of Azure Connect. This technology implements an IPSec tunnel from machines to to a relay service located in the Microsoft cloud (Azure). So in essence, Azure Connect doesn’t provide a point-to-point connection between machines; the network communication is tunneled through the relay service. The relay service in turn offers a mechanism to enforce basic communication rules that you define through Groups. We will review this later. You could network two or more VMs in the Azure cloud (although you should consider using a Virtual Network if you go this route), or servers in the Azure cloud and other machines in the Amazon cloud for example, or even two or more on-premise servers located in different locations for which a direct network connection is not an option. You can place any number of machines in your topology. Azure Connect gives you great flexibility on how you want to build your virtual network across various environments. So Azure Connect makes sense when you want to: Connect machines located in different cloud providers Connect on-premise machines running in different locations Connect Azure VMs with on-premise (if you do not have a VPN device, or if your device is not supported) Connect Azure Roles (Worker Roles, Web Roles) with on-premise servers or in other cloud providers The diagram below shows you a high level network topology that involves machines in the Windows Azure cloud, other cloud providers and on-premise. You should note that the only required component in this diagram is the Relay itself. The other machines are optional (although your network is useful only if you have two or more machines involved). Relay agents are currently available in three geographic areas: US, Europe and Asia. You can change which region you want to use in the Windows Azure management portal. High Level Network Topology With Azure Connect Azure Connect Agent Azure Connect establishes a virtual network and creates virtual adapters on your machines; these virtual adapters communicate through the Relay using IPSec. This is achieved by installing an agent (the Azure Connect Agent) on all the machines you want in your network topology. However, you do not need to install the agent on Worker Roles and Web Roles; that’s because the agent is already installed for you. Any other machine, including Virtual Machines in Windows Azure, needs the agent installed.  To install the agent, simply go to your Windows Azure portal (http://windows.azure.com) and click on Networks on the bottom left panel. You will see a list of subscriptions under Connect. If you select a subscription, you will be able to click on the Install Local Endpoint icon on top. Clicking on this icon will begin the download and installation process for the agent. Activating Roles for Azure Connect As previously mentioned, you do not need to install the Azure Connect Agent on Worker Roles and Web Roles because it is already loaded. However, you do need to activate them if you want the roles to participate in your network topology. To do this, you will need to click on the Get Activation Token icon. The activation token must then be copied and placed in the configuration file of your roles. For more information on how to perform this step, visit MSDN at http://msdn.microsoft.com/en-us/library/windowsazure/gg432964.aspx. Firewall Rules Note that specific firewall rules must exist to allow the agent to communicate through the Relay. You will need to allow TCP 443 and ICMPv6. For additional information, please visit MSDN at http://msdn.microsoft.com/en-us/library/windowsazure/gg433061.aspx. CA Certificates You can optionally require agents to sign their activation request with the Relay using a trusted certificate issued by a Certificate Authority (CA). Click on Activation Options to learn more. Groups To create your network topology you must first create a group. A group represents a logical container of endpoints (or machines) that can communicate through the Relay. You can create multiple groups allowing you to manage network communication differently. For example you could create a DEVELOPMENT group and a PRODUCTION group. To add an endpoint you must first install an agent that will create a virtual adapter on the machine on which it is installed (as discussed in the previous section). Once you have created a group and installed the agents, the machines will appear in the Windows Azure management portal and you can start assigning machines to groups. The next figure shows you that I created a group called LocalGroup and assigned two machines (both on-premise) to that group. Groups and Computers in Azure Connect As I mentioned previously you can allow these machines to establish a network connection. To do this, you must enable the Interconnected option in the group. The following diagram shows you the definition of the group. In this topology I chose to include local machines only, but I could also add worker roles and web roles in the Azure Roles section (you must first activate your roles, as discussed previously). You could also add other Groups, allowing you to manage inter-group communication. Defining a Group in Azure Connect Testing the Connection Now that my agents have been installed on my two machines, the group defined and the Interconnected option checked, I can test the connection between my machines. The next screenshot shows you that I sent a PING request to DEVLAP02 from DEVDSK02. The PING request was successful. Note however that the time is in the hundreds of milliseconds on average. That is to be expected because the machines are connecting through the Relay located in the cloud. Going through the Relay introduces an extra hop in the communication chain, so if your systems rely on high performance, you may want to conduct some basic performance tests. Sending a PING Request Through The Relay Conclusion As you can see, creating a network topology between machines using the Azure Connect service is simple. It took me less than five minutes to create the above configuration, including the time it took to install the Azure Connect agents on the two machines. The flexibility of Azure Connect allows you to create a virtual network between disparate environments, as long as your operating systems are supported by the agent. For more information on Azure Connect, visit the MSDN website at http://msdn.microsoft.com/en-us/library/windowsazure/gg432997.aspx. About Herve Roggero Herve Roggero, Windows Azure MVP, is the founder of Blue Syntax Consulting, a company specialized in cloud computing products and services. Herve's experience includes software development, architecture, database administration and senior management with both global corporations and startup companies. Herve holds multiple certifications, including an MCDBA, MCSE, MCSD. He also holds a Master's degree in Business Administration from Indiana University. Herve is the co-author of "PRO SQL Azure" from Apress and runs the Azure Florida Association (on LinkedIn: http://www.linkedin.com/groups?gid=4177626). For more information on Blue Syntax Consulting, visit www.bluesyntax.net. Special Thanks I would like thank those that helped me figure out how Azure Connect works: Marcel Meijer - http://blogs.msmvps.com/marcelmeijer/ Michael Wood - Http://www.mvwood.com Glenn Block - http://www.codebetter.com/glennblock Yves Goeleven - http://cloudshaper.wordpress.com/ Sandrino Di Mattia - http://fabriccontroller.net/ Mike Martin - http://techmike2kx.wordpress.com

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  • Oracle Announces New Oracle VM Template for MySQL Enterprise Edition

    - by Zeynep Koch
     Oracle announces new Oracle VM template for MySQL Enterprise Edition enabling more efficient and lower cost deployments of virtualized MySQL environments. Here are some of the details and benefits: The new Oracle VM Template for MySQL helps eliminate manual configuration efforts and risks by providing a pre-installed, pre-configured and certified software stack that includes Oracle VM Server for x86, Oracle Linux with the Unbreakable Enterprise Kernel and MySQL Enterprise Edition. By pre-integrating the world’s most popular open source database with Oracle Linux and Oracle Virtualization technologies, enterprise users and ISVs can quickly and easily deploy and manage a virtualized MySQL database server for Web and cloud-based applications. Backed by Oracle’s world-class support organization and the result of extensive integration and quality assurance testing, the Oracle VM Template for MySQL Enterprise Edition further demonstrates Oracle’s investment in MySQL and allows users to benefit from a single point of contact for 24/7 technical support for all pre-configured components. Read more in this white paper. 

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  • Free E-Book - TortoiseSVN and Subversion Cookbook - Oracle Edition

    - by TATWORTH
    Originally posted on: http://geekswithblogs.net/TATWORTH/archive/2013/06/24/free-e-book---tortoisesvn-and-subversion-cookbook---oracle-edition.aspxAt http://www.red-gate.com/products/oracle-development/education/entrypage/svn-tortoise-oracle-ebook?utm_source=simpletalk&utm_medium=pubemail&utm_ad_content=SVNOraclecookbook-20130624&utm_campaign=sourcecontrolfororacle&utm_term=main, Redgate are offering a free eBook - TortoiseSVN and Subversion Cookbook - Oracle Edition "Download your free copy of TortoiseSVN and Subversion Cookbook - Oracle Edition and use these recipes to work better, faster, and do things you never knew you could do with SVN. If you're new to source control, this book provides a concise guide to getting the most out of Subversion."Those of using Oracle for your back-end database, may be interested in a free trial of Source Control for Oracle.

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  • Redehost Transforms Cloud & Hosting Services with MySQL Enterprise Edition

    - by Mat Keep
    RedeHost are one of Brazil's largest cloud computing and web hosting providers, with more than 60,000 customers and 52,000 web sites running on its infrastructure. As the company grew, Redehost needed to automate operations, such as system monitoring, making the operations team more proactive in solving problems. Redehost also sought to improve server uptime, robustness, and availability, especially during backup windows, when performance would often dip. To address the needs of the business, Redehost migrated from the community edition of MySQL to MySQL Enterprise Edition, which has delivered a host of benefits: - Pro-active database management and monitoring using MySQL Enterprise Monitor, enabling Redehost to fulfil customer SLAs. Using the Query Analyzer, Redehost were able to more rapidly identify slow queries, improving customer support - Quadrupled backup speed with MySQL Enterprise Backup, leading to faster data recovery and improved system availability - Reduced DBA overhead by 50% due to the improved support capabilities offered by MySQL Enterprise Edition. - Enabled infrastructure consolidation, avoiding unnecessary energy costs and premature hardware acquisition You can learn more from the full Redehost Case Study Also, take a look at the recently updated MySQL in the Cloud whitepaper for the latest developments that are making it even simpler and more efficient to develop and deploy new services with MySQL in the cloud

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  • win xp client, win 7 host, only xp drivers

    - by brett
    I have a win 7 64 bit box which has xp on it in a vmware module and also the win7 version. I can use my old usb wifi card under virtual xp as i have the wifi drivers, but apparently the manufacturing company never made any further drivers, nor did it release the source code. Is it possible to get networking between the client and the host, so that my host can browse etc? I thought the microsoft loopback adapter might be the answer but ever example i can find of it's use describes a setup where the host is connected fine and needs to route data to the client as well.

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  • Is there a possibility to run applets on Android or Blackberry?

    - by Maxood
    This is what the Java site www.java.com says: "KVM, the virtual machine for mobile devices, is the counterpart of JVM (Java virtual machine). It is used to run applets and applications written with Java technology on mobile devices. KVM must be installed by the manufacturer. It is NOT available for download or installation by consumers". Now Android has a customized virtual machine called DVM (Dalvik Virtual Machine). Can we compare it with KVM? Wonder if we can further reprogram DVM to incorporate features of KVM to run applets on Android? Same goes for Blacberry, is there a possibility?

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  • C++ Virtual Constructor, without clone()

    - by Julien L.
    I want to perform "deep copies" of an STL container of pointers to polymorphic classes. I know about the Prototype design pattern, implemented by means of the Virtual Ctor Idiom, as explained in the C++ FAQ Lite, Item 20.8. It is simple and straightforward: struct ABC // Abstract Base Class { virtual ~ABC() {} virtual ABC * clone() = 0; }; struct D1 : public ABC { virtual D1 * clone() { return new D1( *this ); } // Covariant Return Type }; A deep copy is then: for( i = 0; i < oldVector.size(); ++i ) newVector.push_back( oldVector[i]->clone() ); Drawbacks As Andrei Alexandrescu states it: The clone() implementation must follow the same pattern in all derived classes; in spite of its repetitive structure, there is no reasonable way to automate defining the clone() member function (beyond macros, that is). Moreover, clients of ABC can possibly do something bad. (I mean, nothing prevents clients to do something bad, so, it will happen.) Better design? My question is: is there another way to make an abstract base class clonable without requiring derived classes to write clone-related code? (Helper class? Templates?) Following is my context. Hopefully, it will help understanding my question. I am designing a class hierarchy to perform operations on a class Image: struct ImgOp { virtual ~ImgOp() {} bool run( Image & ) = 0; }; Image operations are user-defined: clients of the class hierarchy will implement their own classes derived from ImgOp: struct CheckImageSize : public ImgOp { std::size_t w, h; bool run( Image &i ) { return w==i.width() && h==i.height(); } }; struct CheckImageResolution; struct RotateImage; ... Multiple operations can be performed sequentially on an image: bool do_operations( std::vector< ImgOp* > v, Image &i ) { std::for_each( v.begin(), v.end(), /* bind2nd(mem_fun(&ImgOp::run), i ...) don't remember syntax */ ); } int main( ... ) { std::vector< ImgOp* > v; v.push_back( new CheckImageSize ); v.push_back( new CheckImageResolution ); v.push_back( new RotateImage ); Image i; do_operations( v, i ); } If there are multiple images, the set can be split and shared over several threads. To ensure "thread-safety", each thread must have its own copy of all operation objects contained in v -- v becomes a prototype to be deep copied in each thread.

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