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  • Question about a simple design problem

    - by Uri
    At work I stumbled uppon a method. It made a query, and returned a String based on the result of the query, such as de ID of a customer. If the query didn't return a single customer, it'd return a null. Otherwise, it'd return a String with the ID's of them. It looked like this: String error = getOwners(); if (error != null) { throw new Exception("Can't delete, the flat is owned by: " + error); } ... Ignoring the fact that getCustomers() returns a null when it should instead return an empty String, two things are happening here. It checks if the flat is owned by someone, and then returns them. I think a more readable logic would be to do this: if (isOwned) { throw new Exception("Can't delete, the flat is owned by: " + getOwners()); } ... The problem is that the first way does with one query what I do with two queries to the database. What would be a good solution involving good design and efficiency for this?

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  • Naming a class that processes orders

    - by p.campbell
    I'm in the midst of refactoring a project. I've recently read Clean Code, and want to heed some of the advice within, with particular interest in Single Responsibility Principle (SRP). Currently, there's a class called OrderProcessor in the context of a manufacturing product order system. This class is currently performs the following routine every n minutes: check database for newly submitted + unprocessed orders (via a Data Layer class already, phew!) gather all the details of the orders mark them as in-process iterate through each to: perform some integrity checking call a web service on a 3rd party system to place the order check status return value of the web service for success/fail email somebody if web service returns fail constantly log to a text file on each operation or possible fail point I've started by breaking out this class into new classes like: OrderService - poor name. This is the one that wakes up every n minutes OrderGatherer - calls the DL to get the order from the database OrderIterator (? seems too forced or poorly named) - OrderPlacer - calls web service to place the order EmailSender Logger I'm struggling to find good names for each class, and implementing SRP in a reasonable way. How could this class be separated into new class with discrete responsibilities?

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  • Using 4 monitors with 2 generic video cards... possible?

    - by Ikram
    I'm thinking of setting up 4 monitors in a grid, using two video cards, one card to feed each pair of monitors through the card's two DVI ports. The most important requirement for me is to have the grid of monitors act as one single huge screen. Is this scenario possible by using two generic cards like Radeon 4870s on a Windows 7 computer? (I've heard of Eyefinity, but 4870s don't have it) Another issue is that I only have one PCI-Express slot on my computer's motherboard, therefore I'll need to use one of the lesser PCI cards as the second video card. Will this pose problems?

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  • Slap the App on the VM for every private cloud solution! Really ?

    - by Anand Akela
    One of the key attractions of the general session "Managing Enterprise Private Cloud" at Oracle OpenWorld 2012 was an interactive role play depicting how to address some of the key challenges of planning, deploying and managing an enterprise private cloud. It was a face-off between Don DeVM, IT manager at a fictitious enterprise 'Vulcan' and Ed Muntz, the Enterprise Manager hero .   Don DeVM is really excited about the efficiency and cost savings from virtualization. The success he enjoyed from the infrastructure virtualization made him believe that for all cloud service delivery models ( database, testing or applications as-a-service ), he has a single solution - slap the app on the VM and here you go . However, Ed Muntz believes in delivering cloud services that allows the business units and enterprise users to manage the complete lifecycle of the cloud services they are providing, for example, setting up cloud, provisioning it to users through a self-service portal ,  managing and tuning the performance, monitoring and applying patches for database or applications. Watch the video of the face-off , see how Don and Ed address some of the key challenges of planning, deploying and managing an enterprise private cloud and be the judge ! ?

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  • Storing User-uploaded Images

    - by Nyxynyx
    What is the usual practice for handling user uploaded photos and storing them on the database and server? For a user profile image: After receiving the image file from user, rename file to <image_id>_<username> Move image to /images/userprofile Add img filename to a table users containing their profile details like first_name, last_name, age, gender, birthday For a image for a review done by user: After receiving the image file from user, rename file to <image_id>_<review_id> Move image to /images/reviews Add img filename to a table reviews containing their profile details like review_id, review_content, user_id, score. Question 1: How should I go about storing the image filenames if the user can upload multiple photos for a particular review? Serialize? Question 2: Or have another table review_images with columns review_id, image_id, image_filename just for tracking images? Will doing a JOIN when retriving the image_filename from this table slow down performance noticeably? Question 3: Should all the images be stored in a single folder? Will there be a problem when we have 100K photos in the same folder? Is there a more efficient way to go about doing this?

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  • Staggering java linux process startup to prevent OOM

    - by ctennis
    I am running a number of java processes on a single Linux machine. From a memory and computing standpoint, everything is fine when things are static. However, periodically we use a configuration management package up upgrade the jar or war files, and restart the java process. The problem is, that is restarts them all relatively quickly, and so we get 10 or so java VMs restarting all at the same time (we use daemontools for the service stops/starts), which wreaks havoc on the machine, in terms of OOMs or just really slow. This is because it's spawning the JVM 10x at the same time. Other than trying to stagger the startups, is there a smarter way of handling this? Maybe a sysctl tuning performance parameters, or a JVM parameter?

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  • How to remotely install Linux via SSH?

    - by netvope
    I need to remotely install Ubuntu Server 10.04 (x86) on a server currently running RHEL 3.4 (x86). I'll have to be very careful because no one can press the restart button for me if anything goes wrong. Have you ever remotely installed Linux? Which way would you recommend? Any advice for things to watch out? Update: Thanks for your help. I managed to "change the tires while driving"! The main components of my method are drawn from HOWTO - Install Debian Onto a Remote Linux System, grub legacy: Booting once-only, grub single boot and kernel panic reboot , and Ubuntu Community Documentation: InstallationFromKnoppix Here is the outline of what I did: Run debootstrap on an existing Ubuntu server Transfer the files to the swap partition of the RHEL 3.4 server Boot into tha swap partition (the debootstrap system) Transfer the files to the original root partition Boot into the new Ubuntu system and finish up the installation with tasksel, apt-get, etc I tested the method in a VM and then applied to the server. I was lucky enough that everything went smoothly :)

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  • What is the minimum delay between two consecutive RS232 frames?

    - by Lord Loh.
    I have been working on creating a UART on an FPGA. I can successfully transmit and receive single characters typed on PuTTY. However, when I set my FPGA to constantly write a large sequences of "A", sometimes I end up with a sequences of "@" or some other characters until I reset the FPGA a few times. I believe the UART on the computer looses track of the difference between the start bit and a zero. The delay between the two "A" is ~ 30us (measured with a logic analyzer) and the baud rate is 115200 8N1. Is there a minimum delay that must be maintained between two consecutive RS232 frames?

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  • Possible to draw a select portion of a render target? (in XNA)

    - by TheBroodian
    I'm going to try to do this in reverse fashion and skip straight to the punch line, and then give the back story afterward: Is it possible to, after drawing a scene to a RenderTarget2D, only draw a select portion of the RenderTarget2D, if I don't want the entire thing? I'm using xTile to manage world data in my game (it's a great piece of work, colinvella [xTile's author] has made an amazing product), and for the most part it works great. xTile supports parallax effects in its layers to add some wonderful depth to 2d scenes, which was great, until I implemented a dynamic split-screen system into my game. Wanted to make a co-op game that wouldn't require players to be in close proximity to each other, so I made it so that if the players separate too far apart, the singular full-screen viewport 'snaps-apart', and is replaced by two split-screen viewports, which then smoothly transition to their respective player targets. The effect is pretty smooth aside from the part where the parallax backgrounds become skewed once the viewports split, because xTile's ratio for handling parallax effects is dependent upon viewport size. This is unfortunate, because the effect would otherwise be really snazzy, but the backgrounds become pretty heavily affected when the game goes from single-viewport to multi-viewport. So, Colinvella suggests using rendertargets to record the scene at full viewport size, and then only drawing a portion of it. But as far as I can tell, that isn't even possible? That being said, I've never even used render targets before, so I'm still learning, hence the question here.

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  • two-part dice pool mechanic

    - by bythenumbers
    I'm working on a dice mechanic/resolution system based off of the Ghost/Echo (hereafter shortened to G/E) tabletop RPG. Specifically, since G/E can be a little harsh with dealing out consequences and failure, I was hoping to soften the system and add a little more player control, as well as offer the chance for players to evolve their characters into something unique, right from creation. So, here's the mechanic: Players roll 2d12 against the two statistics for their character (each is a number from 2-11, and may be rolled above or below depending on the nature of the action attempted, rolling your stat exactly always fails). Depending on the success for that roll, they add dice to the pool rolled for a modified G/E style action. The acting player gets two dice anyhow, and I am debating offering a bonus die for each success, or a single bonus die for succeeding on both of the statistic-compared rolls. One the size of the dice pool is set, the entire pool is rolled, and the players are allowed to assign rolled dice to a goal and a danger. Assigned results are judged as follows: 1-4 means the attempted goal fails, or the danger comes true. 5-8 is a partial success at the goal, or partially avoiding the danger. 9-12 means the goal is achieved, or the danger avoided. My concerns are twofold: Firstly, that the two-stage action is too complicated, with two rolls to judge separately before anything can happen. Secondly, that the statistics involved go too far in softening the game. I've run some basic simulations, and the approximate statistics follow: 2 dice (up to) 3 dice (up to) 4 dice failure ~33% ~25% ~20% partial ~33% ~35% ~35% success ~33% ~40% ~45% I'd appreciate any advice that addresses my concerns or offers to refine my simulation (right now the first roll is statistically modeled as sign(1d12-1d12), where 0 is a success).

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  • How can I get nvidia-96 installed?

    - by Bob
    I'm at my wits end here. This is my last effort before I go back to Windows. I need to get nvidia-96 proprietary driver installed. Synaptic won't install it because it says it has dependencies. I installed every single dependency it listed except for "xorg-video-abi-10" which does not show up as an item that can be installed. I have no idea what to do. Using 11.10 with a NVIDIA Geforce 3 GPU. Anyone know how to get this dang driver installed? @fossfreedom: the opensource driver is extremely slow. So slow that the OS is unusable—words appear seconds after I type them—programs take forever to perform actions. Also it is causing my monitor to turn on and off for no reason. @yossile: synaptic shows that I have xserver-xorg-core installed. And xserver-xorg-core-udeb does not show up as something that can be installed. @papseddy: when I try to install the downloaded nvidia driver it says it won't work until I disable Nouveau kernel driver. I have tried everything to get this dang Nouveau kernel driver disabled. Nothing has been successful.

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  • Setting up Raid 1 Array for Home Server

    - by user1048116
    I'm not sure if this is even possible, but it's worth asking on here! Essentially I have a old machine at home (well, not old hardware wise, but I recently built a new gaming rig), which I decided to install a copy of W2008 R2 on and use as a file/backup server and media center'ish machine. As of now, it has a single drive partitioned into C and D, with D being the Data partition. I have happened to find an old 1TB SATA drive lying around at home, and was wondering if it's possible to setup a Raid 1 array in my rig within Windows without needing to lose everything on my first drive (or maybe even just mirror a specific partition, say the Data partition, as this is just what stores my photos etc). Maybe this isn't possible, but you never know :) Regards, T.C

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  • Wordpress 3 mutli site install

    - by mike
    Hello, Trying to figure out if this is possible... My company has a cms product that was written in Java and we decided to use Wordpress to run blogs for our clients. Obviously, Wordpress does not run on tomcat(at least not by default) so we installed Pound(http://www.apsis.ch/pound/) on our server and have setup any Apache and Tomcat on different ports. When "/blog/" is requested, the request is directed to Apache. This works fine but we would like to use Wordpress multi site so that we can manage all the blogs from a single interface. We would also like the url for every site to be "/blog/" example: http://www.site1.com/blog/ http://www.site2.com/blog/ I'm thinking it would have to be done with apache??? Is it even possible? Thanks!

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  • Is LSB's init script function "start_daemon" really used for real daemons or should I stick to start-stop-daemon?

    - by Fred
    In the context of init scripts, according to the LSB specification, "Each conforming init script shall execute the commands in the file /lib/lsb/init-function", which then defines a couple of functions to be used when using daemons. One of those functions is start_daemon, which obviously "runs the specified program as a daemon" while checking if the daemon is already running. I'm in the process of daemonizing a service app of mine, and I'm looking at how other daemons are run to try to "fit in". In the process of looking how it's done elsewhere, I noticed that not a single daemon on my Ubuntu 10.04 machine uses start_daemon. They all call start-stop-daemon directly. Same goes for my Fedora 14 machine. Should I try to play nice and be the first one to use start_daemon, or is there really no point and start-stop-daemon is the way to go since everybody is already using that? Why is there no daemons using LSB's functions?

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  • Adobe Reader - Content Preparation progress

    - by kubal5003
    Hello, I was wondering recently if is it just me or anyone else noticed it: why Adobe Reader after opening every single document displays "Content preparation" window with progress bar and it lasts for ages.. ? On linux pdf readers work hell lot better (faster), on windows other readers also work faster. Some years back in the past Adobe Reader also used to be quick. What has happened? PDF files aren't bigger/more complex compared to 3-4 years ago. Computers are at least dual core and with much more ram and displaying pdf files is getting slower and slower..

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  • Ubuntu 12.04 slow boot on ASUS, attached with dmesg and bootchart

    - by stanleyhunk
    I heard that Ubuntu can boot up around 30sec, but I take more than 60sec every time my Ubuntu boot. I also read some forum said need to post the dmesg and bootchart to identify which process slowing down the booting time, as I'm not expert in Ubuntu and wish to learn more about it, I humbly ask any pro here to teach me how. My laptop specs: Model : ASUS K45VS RAM : 8MB CPU : Intel(R) Core(TM) i7-3630QM CPU @ 2.40GHz x 8 Graphic Card : nVidia GeForce GT 645M HDD : 750GB OS : Single boot Ubuntu 12.04LTS System.uname : Linux 3.8.0-39-generic #58~precise1-Ubuntu SMP Fri May 2 21:33:40 UTC 2014 x86_64 System.release : Ubuntu 12.04.4 LTS System.kernel.options : BOOT_IMAGE=/boot/vmlinuz-3.8.0-39-generic root=UUID=c8a71503-bce8-406c-9a5f-5aa8284f5c7c ro quiet splash My dmesg (which highlighted to the huge time frame gap): [ 30.772656] cgroup: libvirtd (1961) created nested cgroup for controller "memory" which has incomplete hierarchy support. Nested cgroups may change behavior in the future. [ 30.772659] cgroup: "memory" requires setting use_hierarchy to 1 on the root. [ 30.772683] cgroup: libvirtd (1961) created nested cgroup for controller "devices" which has incomplete hierarchy support. Nested cgroups may change behavior in the future. [ 30.772710] cgroup: libvirtd (1961) created nested cgroup for controller "blkio" which has incomplete hierarchy support. Nested cgroups may change behavior in the future. [ 32.140335] nvidia 0000:01:00.0: irq 46 for MSI/MSI-X [ 32.505619] ACPI Error: Field [TMPB] at 1081344 exceeds Buffer [ROM1] size 262144 (bits) (20121018/dsopcode-236) [ 32.505624] ACPI Error: Method parse/execution failed [\_SB_.PCI0.PEG0.PEGP._ROM] (Node ffff880224e91f00), AE_AML_BUFFER_LIMIT (20121018/psparse-537) [ 802.034422] audit_printk_skb: 69 callbacks suppressed [ 802.034428] type=1400 audit(1400914804.392:35): apparmor="DENIED" operation="capable" parent=1 profile="/usr/sbin/cupsd" pid=1683 comm="cupsd" pid=1683 comm="cupsd" capability=36 capname="block_suspend" [ 1581.300901] type=1400 audit(1400915584.816:36): apparmor="DENIED" operation="capable" parent=1 profile="/usr/sbin/cupsd" pid=1683 comm="cupsd" pid=1683 comm="cupsd" capability=36 capname="block_suspend" My Bootchart.png: Looking forward to learn to improve both my booting time and knowledge. Thanks in advance :)

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  • LVM mirroring VS RAID1

    - by syrenity
    Hi. Having learned a bit about LVM mirroring, I thought about replacing the current RAID-1 scheme I'm using to gain some flexibility. Problem is that according to what I found on the Internet, LVM is: 1) Slower then RAID-1, at least in reading (as only single volume being used for reading). 2) Non-reliable on power interrupts, and requires disk cache disabling for prevention of data loss. http://www.joshbryan.com/blog/2008/01/02/lvm2-mirrors-vs-md-raid-1/ Also it seems, at least to several setup guides I read (http://www.tcpdump.com/kb/os/linux/lvm-mirroring/intro.html), that one actually requires a 3rd disk for storing the LVM log. This makes the setup completely unusable on 2 disks installations, and lowers the amount of used mirror disks on higher amount of disks. Can anyone comment the above facts, and let me know his experience of using LVM mirroring? Thanks.

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  • sudo: cd: command not found when trying to get to /var/log/apache2

    - by Piers
    I'm running Ubuntu 10.04 and am having issues getting to the log files in /var/log/apache2 I can cd to most other places (I haven't tried every single file, obviously) but when I try to get to the above directory, I get the error message sudo: cd: command not found ... I've just tried something else and I can't cd when used in conjunction with sudo. I can use sudo when doing things like apt-get but it seems I can't change directory when using sudo. I haven't been on this server for a while but I know I used to be able to do this.

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  • Which Linux variant to install on VirtualBox?

    - by Rohit
    Answer to one of my previous post suggested me to use VirtualBox for Sandbox experiments with malware files. I installed VirtualBox and now it demands a bootable CD to install the OS. I want Linux to be installed in it. I guess Debian or Ubuntu are the most popular variant. I want an ISO image that creates a bootable CD or a single DVD with that Linux variant and should include only the basic installation not much features. It should fit in at least 3 or 3.5 GB. Which one is more compatible with VirtualBox?

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  • Concatenate two mp4 videos into one file

    - by Jer
    I recently ripped my DVD collection to play them on my media center PC, and several of them are two-disc movies (i.e. The Lord of the Rings). Since I ripped each DVD individually, that gives me two video files for some movies. I am using Ubuntu Linux - how can I concatenate these two MP4/H.264 videos into a single MP4 video file? Preferably from the command line, and without re-encoding everything during the process (although I can try figuring out a video editor like Pitivi if that's the only solution.)

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  • Free NTFS partition recovery

    - by Andrei Tanasescu
    I have a 1Tb disk which was partitioned into a ~700gb ntfs disk and a 300gb HFS+ (mac os X). I've accidentally allowed mac os x to wipe the hard-disk and create a single HFS+ partition over the hard-drive. I want to recover my NTFS partition. TestDisk fails to find the NTFS partition, but the DiskInternals solution does find my files. Are there any free alternatives to DIskInternals Partition recovery solution? THe tool should simply go block by block and attempt to reconstruct the files.

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  • What type of pattern would be used in this case

    - by Admiral Kunkka
    I want to know how to tackle this type of scenario. We are building a person's background, from scratch, and I want to know, conceptually, how to proceed with a secure object pattern in both design and execution... I've been reading on Factory patterns, Model-View-Controller types, Dependency injection, Singleton approaches... and I can't seem to grasp or 'fit' these types of designs decisions into what I'm trying to do.. First and foremost, I started with having a big jack-of-all-trades class, then I read some more, and some tips were to make sure your classes only have a single purpose.. which makes sense and I started breaking down certain things into other classes. Okay, cool. Now I'm looking at dependency injection and kind of didn't really know what's going on. Example/insight of what kind of heirarchy I need to accomplish... class Person needs to access and build from a multitude of different classes. class Culture needs to access a sub-class for culture benefits class Social needs to access class Culture, and other sub-classes class Birth needs to access Social, Culture, and other sub-classes class Childhood/Adolescence/Adulthood need to access everything. Also, depending on different rolls, this class heirarchy needs to create multiple people as well, such as Family, and their backgrounds using some, if not all, of these same classes. Think of it as a people generator, all random, with backgrounds and things that happen to them. Ageing, death of loved ones, military careers, e.t.c. Most of the generation is done randomly, making calls to a mt_rand function to pick from most of the selections inside the classes, guaranteeing the data to be absolutely random. I have most of the bulk-data down, and was looking for some insight from fellow programmers, what do you think?

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  • How to dual OS 32-bit/64-bit Windows 7 Ultimate.

    - by Cyril Horad
    I have a problem with regards to my nVidia driver not running on 64-bit. I decided to install both 32-bit and 64-bit on my ASUS K42JC (4GB RAM upgrade) in order to function the nVidia on the 32-bit. My question is, how could I make my laptop run on either 32-bit or 64-bit OS. What options I am suppose to use, a single, double, or triple partition? From an answer: Well. When I installed the nVidia driver from either the ASUS site and the prescribed driver from NVIDA site via System Requirements Lab, both ended up freezing my laptop to the point when the desktop is about the finish booting. I have tried three(3) times reformatting and trying to fix the problem. Yet no use. I filed a ticket to the Asus support but for now no replies yet. But this bothers me, why wouldn't the nVidia run on 64bit yet it runs perfectly on 32bit.

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  • Modular Database Structures

    - by John D
    I have been examining the code base we use in work and I am worried about the size the packages have grown to. The actual code is modular, procedures have been broken down into small functional (and testable) parts. The issue I see is that we have 100 procedures in a single package - almost an entire domain model. I had thought of breaking these packages down - to create sub domains that are centered around the procedure relationships to other objects. Group a bunch of procedures that have 80% of their relationships to three tables etc. The end result would be a lot more packages, but the packages would be smaller and I feel the entire code base would be more readable - when procedures cross between two domain models it is less of a struggle to figure which package it belongs to. The problem I now have is what the actual benefit of all this would really be. I looked at the general advantages of modularity: 1. Re-usability 2. Asynchronous Development 3. Maintainability Yet when I consider our latest development, the procedures within the packages are already reusable. At this advanced stage we rarely require asynchronous development - and when it is required we simply ladder the stories across iterations. So I guess my question is if people know of reasons why you would break down classes rather than just the methods inside of classes? Right now I do believe there is an issue with these mega packages forming but the only benefit I can really pin down to break them down is readability - something that experience gained from working with them would solve.

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  • pfSense - DHCP Relay

    - by Patrick
    I have 3 pfSense boxes acting as routers on a single subnet (172.22.12.0/26). Router A - 172.22.12.1 Router B - 172.22.12.17 Router C - 172.22.12.33 I want Router A to be the only DHCP server. Router C has DHCP relay enabled that points to Router B. Router B then has DHCP relay enabled that points to Router A. Like this: Router C -- Router B -- Router A (DHCP Server) Router B gets an IP from Router A, but Router C does not. Any ideas why this configuration isn't working? Thanks.

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