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• How to avoid concurrent execution of a time-consuming task without blocking?

  - by Diego V

  I want to efficiently avoid concurrent execution of a time-consuming task in a heavily multi-threaded environment without making threads wait for a lock when another thread is already running the task. Instead, in that scenario, I want them to gracefully fail (i.e. skip its attempt to execute the task) as fast as possible. To illustrate the idea considerer this unsafe (has race condition!) code: private static boolean running = false; public void launchExpensiveTask() { if (running) return; // Do nothing running = true; try { runExpensiveTask(); } finally { running = false; } } I though about using a variation of Double-Checked Locking (consider that running is a primitive 32-bit field, hence atomic, it could work fine even for Java below 5 without the need of volatile). It could look like this: private static boolean running = false; public void launchExpensiveTask() { if (running) return; // Do nothing synchronized (ThisClass.class) { if (running) return; running = true; try { runExpensiveTask(); } finally { running = false; } } } Maybe I should also use a local copy of the field as well (not sure now, please tell me). But then I realized that anyway I will end with an inner synchronization block, that still could hold a thread with the right timing at monitor entrance until the original executor leaves the critical section (I know the odds usually are minimal but in this case we are thinking in several threads competing for this long-running resource). So, could you think in a better approach?

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• is there something equivalent to 'Address of' or offset operator in .net?

  - by Gio

  We have nested stuctures as such, used as an interface for some device drivers. On occasion we have to update individual elements. An 'address of' operator would be helpful, but an 'offset' function or operator is what I'm really looking for, but not sure how to go about it. In other words, how far is structureN.elementX away from the start of the structure in bytes? [StructLayout(LayoutKind.Sequential)] public struct s1 { UInt16 elem1; UInt16 elem2; UInt16 elem3; } [StructLayout(LayoutKind.Sequential)] public struct s2 { UInt16 elem1; UInt16 elem2; UInt16 elem3; } [StructLayout(LayoutKind.Sequential)] public struct driver { public S1 s1; public S2 s2; } For instance we need to send the device driver some data to update driver.s1.elem3, by way of providing an offset address, data block and length. We would update our local copy, then call the device api with the afore mentioned data. Not sure I have to do this with 'unsafe' method calls. Any help?

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• How can a B-tree node be represented?

  - by chronodekar

  We're learning B-trees in class and have been asked to implement them in code. The teacher has left choice of programming language to us and I want to try and do it in C#. My problem is that the following structure is illegal in C#, unsafe struct BtreeNode { int key_num; // The number of keys in a node int[] key; // Array of keys bool leaf; // Is it a leaf node or not? BtreeNode*[] c; // Pointers to next nodes } Specifically, one is not allowed to create a pointer to point to the structure itself. Is there some work-around or alternate approach I could use? I'm fairly certain that there MUST be a way to do this within the managed code, but I can't figure it out. EDIT: Eric's answer pointed me in the right direction. Here's what I ended up using, class BtreeNode { public List<BtreeNode> children; // The child nodes public static int MinDeg; // The Minimum Degree of the tree public bool IsLeaf { get; set; } // Is the current node a leaf or not? public List<int> key; // The list of keys ... }

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• Image resizing efficiency in C# and .NET 3.5

  - by Matthew Nichols

  I have written a web service to resize user uploaded images and all works correctly from a functional point of view, but it causes CPU usage to spike every time it is used. It is running on Windows Server 2008 64 bit. I have tried compiling to 32 and 64 bit and get about the same results. The heart of the service is this function: private Image CreateReducedImage(Image imgOrig, Size NewSize) { var newBM = new Bitmap(NewSize.Width, NewSize.Height); using (var newGrapics = Graphics.FromImage(newBM)) { newGrapics.CompositingQuality = CompositingQuality.HighSpeed; newGrapics.SmoothingMode = SmoothingMode.HighSpeed; newGrapics.InterpolationMode = InterpolationMode.HighQualityBicubic; newGrapics.DrawImage(imgOrig, new Rectangle(0, 0, NewSize.Width, NewSize.Height)); } return newBM; } I put a profiler on the service and it seemed to indicate the vast majority of the time is spent in the GDI+ library itself and there is not much to be gained in my code. Questions: Am I doing something glaringly inefficient in my code here? It seems to conform to the example I have seen. Are there gains to be had in using libraries other than GDI+? The benchmarks I have seen seem to indicate that GDI+ does well compare to other libraries but I didn't find enough of these to be confident. Are there gains to be had by using "unsafe code" blocks? Please let me know if I have not included enough of the code...I am happy to put as much up as requested but don't want to be obnoxious in the post.

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• Pointers to a typed variable in C#: Interfase, Generic, object or Class? (Boxing/Unboxing)

  - by PaulG

  First of all, I apologize if this has been asked a thousand times. I read my C# book, I googled it, but I can't seem to find the answer I am looking for, or I am missing the point big time. I am very confused with the whole boxing/unboxing issue. Say I have fields of different classes, all returning typed variables (e.g. 'double') and I would like to have a variable point to any of these fields. In plain old C I would do something like: double * newVar; newVar = &oldVar; newVar = &anotherVar; ... In C#, it seems I could do an interfase, but would require that all fields be properties and named the same. Breaks apart when one of the properties doesn't have the same name or is not a property. I could also create a generic class returning double, but seems a bit absurd to create a class to represent a 'double', when a 'double' class already exists. If I am not mistaken, it doesn't even need to be generic, could be a simple class returning double. I could create an object and box the typed variable to the newly created object, but then I would have to cast every time I use it. Of course, I always have the unsafe option... but afraid of getting to unknown memory space, divide by zero and bring an end to this world. None of these seem to be the same as the old simple 'double * variable'. Am I missing something here?

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• Is there any good reason for private methods existence in C# (and OOP in general)?

  - by Piotr Lopusiewicz

  I don't mean to troll but I really don't get it. Why would language designers allow private methods instead of some naming convention (see __ in Python) ? I searched for the answer and usual arguments are: a) To make the implementation cleaner/avoid long vertical list of methods in IDE autocompletion b) To announce to the world which methods are public interface and which may change and are just for implementation purpose c) Readability Ok so now, all of those could be achieved by naming all private methods with __ prefix or by "private" keyword which doesn't have any implications other than be information for IDE (don't put those in autocompletion) and other programers (don't use it unless you really must). Hell, one could even require unsafe-like keyword to access private methods to really discourage this. I am asking this because I work with some c# code and I keep changing private methods to public for test purposes as many in-between private methods (like string generators for xml serialization) are very useful for debugging purposes (like writing some part of string to log file etc.). So my question is: Is there anything which is achieved by access restriction but couldn't be achieved by naming conventions without restricting the access ?

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• C# Basic Multi-Threading Question: Call Method on Thread A from Thread B (Thread B started from Thre

  - by Nick

  What is the best way to accomplish this: The main thread (Thread A) creates two other threads (Thread B and Thread C). Threads B and C do heavy disk I/O and eventually need to pass in resources they created to Thread A to then call a method in an external DLL file which requires the thread that created it to be called correctly so only Thread A can call it. The only other time I ever used threads was in a Windows Forms application, and the invoke methods were just what I needed. This program does not use Windows Forms, and as such there are no Control.Invoke methods to use. I have noticed in my testing that if a variable is created in Thread A, I have no trouble accessing and modifying it from Thread B/C which seems very wrong to me. With Winforms, I was sure it threw errors for trying to access things created on other threads. I know it is unsafe to change things from multiple threads, but I really hoped .NET would forbid it altogether to ensure safe coding. Does .NET do this, and I am just missing the boat, or does it only do it with WinForm apps? Since it does seemingly allow this, do I do something like an OS would do, create a flag and monitor it from Thread A to see if it changes. If it does, then call the method. Doesnt the event handler essentially do this, so could an event be used somehow called on the main thread?

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• Squid Proxy: url_regex acl is not working?

  - by bharathi

  I am using squid proxy 3.1 in ubuntu machine. I want to allow only urls matching our pattern through our proxy server. I configured acl like below. Acl for dstdomain is working fine. If i access any url besides .zmedia.com , I got proxy connection refused. But the url_regex is not working. What i am trying here is. Allow only request from ".zmedia.com" domain and the request url should be in "/blog" context. # # Recommended minimum configuration: # acl manager proto cache_object acl localhost src 127.0.0.1/32 ::1 acl to_localhost dst 127.0.0.0/8 ::1 acl urlwhitelist url_regex -i ^http(s)://([a-zA-Z]+).zmedia.com/blog/.*$ acl allowdomain dstdomain .zmedia.com acl Safe_ports port 80 8080 8500 7272 # Example rule allowing access from your local networks. # Adapt to list your (internal) IP networks from where browsing # should be allowed acl SSL_ports port 443 acl Safe_ports port 80 # http acl Safe_ports port 21 # ftp acl Safe_ports port 443 # https acl Safe_ports port 70 # gopher acl Safe_ports port 210 # wais acl Safe_ports port 1025-65535 # unregistered ports acl Safe_ports port 280 # http-mgmt acl Safe_ports port 488 # gss-http acl Safe_ports port 591 # filemaker acl Safe_ports port 777 # multiling http acl SSL_ports port 7272 # multiling http acl CONNECT method CONNECT # # Recommended minimum Access Permission configuration: # # Only allow cachemgr access from localhost http_access allow manager localhost http_access deny manager http_access deny !allowdomain http_access allow urlwhitelist http_access allow CONNECT SSL_ports http_access deny CONNECT !SSL_ports # Deny requests to certain unsafe ports http_access deny !Safe_ports # Deny CONNECT to other than secure SSL ports http_access deny CONNECT !SSL_ports # We strongly recommend the following be uncommented to protect innocent # web applications running on the proxy server who think the only # one who can access services on "localhost" is a local user #http_access deny to_localhost # # INSERT YOUR OWN RULE(S) HERE TO ALLOW ACCESS FROM YOUR CLIENTS # # Example rule allowing access from your local networks. # Adapt localnet in the ACL section to list your (internal) IP networks # from where browsing should be allowed http_access allow localhost # And finally deny all other access to this proxy http_access deny all # Squid normally listens to port 3128 http_port 3128 # We recommend you to use at least the following line. hierarchy_stoplist cgi-bin ? # Uncomment and adjust the following to add a disk cache directory. #cache_dir ufs /var/spool/squid 100 16 256 # Leave coredumps in the first cache dir coredump_dir /var/spool/squid append_domain .zmedia.com # Add any of your own refresh_pattern entries above these. refresh_pattern ^ftp: 1440 20% 10080 refresh_pattern ^gopher: 1440 0% 1440 refresh_pattern -i (/cgi-bin/|\?) 0 0% 0 refresh_pattern . 0 20% 4320 Please correct me , If i did anything wrong?

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• Hibernating and booting into another OS: will my filesystems be corrupted?

  - by Ryan Thompson

  Suppose I have Windows and Linux installed on the same computer. If I hibernate Windows, can I boot into Linux without corrupting the Windows filesystem when I resume Windows? What about the other way around? What if I hibernate one, boot into the other, and mount the hibernated filesystem read/write? Read-only? If this is unsafe, is there any way to detect the hibernated state of the other OS and prevent mounting its filesystem? Basically, how far can I push this before it breaks, and how dangerous is it near the edge? I think I know the answers to some of the above questions, but for other ones, I have no idea, and for obvious reasons I have not tested this on my own computer. If someone has tested these, please enlighten the rest of us. I'm not necessarily looking for a specific answer to every question; I'll accept any response that answers a reasonable portion. EDIT: Let me clarify that when I say "hibernate," I mean the process of writing the contents of RAM to the hard disk and completely powering down the computer. In this state, powering the computer back on brings you through the BIOS and bootloader again, and you could theoretically select another operating system on a multi-boot system. Anyway, on with the original question: RESULTS Ok, after everyone's assurances that this would work, I tested it for myself. I set up Ubuntu to remount all ntfs filesystems and external drives read-only before hibernating. There was no need for a similar Windows setup because Windows does not read Linux filesystems. Then, I tried alternately hibernating one operating system and resuming the other, back and forth a few times. I even tried mounting the Windows filesystem from Ubuntu read-write, and creating a few files. Windows didn't complain when I resumed. So, in conclusion, you can more or less freely hibernate in a dual-boot Windows/Linux scenario. Note that I did not test a dual Linux/Linux co-hibernation situation. If you have two or more Linux installs and you hibernate one of them, you might be able to corrupt the filesystem by mounting it from another.

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• Possible HDD malfunction. Need help in diagnosing

  - by Protheus

  Today when using my PC as I did for almost 4 years I experienced the following: during opening new tab in Opera browser screen froze. Music (AIMP 3) continued to play for about 5 minutes and then stopped too. I tried Ctrl+Alt+Del, but win7 lock screen didn't appear. Caps\Scroll or Num locks didn't switch diodes on keyboard. I rebooted my PC and saw that BIOS suggests me to enter it's settings or load by default. I chose default. It don't see proper boot device (old faitful "insert proper boot" something). After second reboot it said that there is no ExpressGate installed (which i turned off in BIOS years ago). I went into BIOS setting to turn off ExpressGate and see configs: time was not set off, all hard drives present, temp and O.C. settings are nominal (no O.C.) I've inserted my Win7 install disk to try recovery. It did load awfully long (about few minutes) and didn't see current installation. PC was utilized in 24/7 mode for almost all these years. Hardware configuration: ASUS P5Q WS Core 2 Quad Q9300 (2.5GHz no O.C.) MSI geForce GTX 460 4x2 Gb GeIL EVO 2 (AFAIR) Seagate something 750Gb (4 years as system HDD 24/7) WD 1Tb (for random stuff, 5 y.o.) Hitachi 500Gb (for even more random stuff, 6 y.o.) NEC DVDRW (ALL DISKS ARE SATA) Cooler Master Silent Pro 700W Software: Windows 7 AND Kubuntu on the same drive with GRUB loader. Sorry I can't remember HDDs and can't see them right now, but I think their models aren't relevant anyway. My idea is that due to some system error or hard drive glitch i've wrecked my primary HDD's MBR. Nevertheless I don't exclude the possibility of other failure. May it's be that motherboard or it's SATA controller? Doubt it, because all drives are seen in BIOS and I could load from DVD. Maybe GRUB got bugged somehow, although I don't see how it's possible from Windows. But I did install KUbuntu from Windows (i wasn't myself then), maybe GRUB did write itself in some windows partition and got rewriteen in process? Right now I am at work with my flash drive with me and I need some advice how to fix MBR or to hear if it's not MBR. I'm going to buy new HDD (Hitachi 7k2000) because I think that my current HDD is compromised and it's unsafe to use it as system drive, especially 24/7.

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• Where is my app.config for SSIS?

  Sometimes when working with SSIS you need to add or change settings in the .NET application configuration file, which can be a bit confusing when you are building a SSIS package not an application. First of all lets review a couple of examples where you may need to do this. You are using referencing an assembly in a Script Task that uses Enterprise Library (aka EntLib), so you need to add the relevant configuration sections and settings, perhaps for the logging application block. You are using using Enterprise Library in a custom task or component, and again you need to add the relevant configuration sections and settings. You are using a web service with Microsoft Web Services Enhancements (WSE) 3.0 and hosting the proxy in SSIS, in an assembly used by your package, and need to add the configuration sections and settings. You need to change behaviours of the .NET framework which can be influenced by a configuration file, such as the System.Net.Mail default SMTP settings. Perhaps you wish to configure System.Net and the httpWebRequest header for parsing unsafe header (useUnsafeHeaderParsing), which will change the way the HTTP Connection manager behaves. You are consuming a WCF service and wish to specify the endpoint in configuration. There are no doubt plenty more examples but each of these requires us to identify the correct configuration file and and make the relevant changes. There are actually several configuration files, each used by a different execution host depending on how you are working with the SSIS package. The folders we need to look in will actually vary depending on the version of SQL Server as well as the processor architecture, but most are all what we can call the Binn folder. The SQL Server 2005 Binn folder is at C:\Program Files\Microsoft SQL Server\90\DTS\Binn\, compared to C:\Program Files\Microsoft SQL Server\100\DTS\Binn\ for SQL Server 2008. If you are on a 64-bit machine then you will see C:\Program Files (x86)\Microsoft SQL Server\90\DTS\Binn\ for the 32-bit executables and C:\Program Files\Microsoft SQL Server\90\DTS\Binn\ for 64-bit, so be sure to check all relevant locations. Of course SQL Server 2008 may have a C:\Program Files (x86)\Microsoft SQL Server\100\DTS\Binn\ on a 64-bit machine too. To recap, the version of SQL Server determines if you look in the 90 or 100 sub-folder under SQL Server in Program Files (C:\Program Files\Microsoft SQL Server\nn\) . If you are running a 64-bit operating system then you will have two instances program files, C:\Program Files (x86)\ for 32-bit and  C:\Program Files\ for 64-bit. You may wish to check both depending on what you are doing, but this is covered more under each section below. There are a total of five specific configuration files that you may need to change, each one is detailed below: DTExec.exe.config DTExec.exe is the standalone command line tool used for executing SSIS packages, and therefore it is an execution host with an app.config file. e.g. C:\Program Files\Microsoft SQL Server\90\DTS\Binn\DTExec.exe.config The file can be found in both the 32-bit and 64-bit Binn folders. DtsDebugHost.exe.config DtsDebugHost.exe is the execution host used by Business Intelligence Development Studio (BIDS) / Visual Studio when executing a package from the designer in debug mode, which is the default behaviour. e.g. C:\Program Files\Microsoft SQL Server\90\DTS\Binn\DtsDebugHost.exe.config The file can be found in both the 32-bit and 64-bit Binn folders. This may surprise some people as Visual Studio is only 32-bit, but thankfully the debugger supports both. This can be set in the project properties, see the Run64BitRuntime property (true or false) in the Debugging pane of the Project Properties. dtshost.exe.config dtshost.exe is the execution host used by what I think of as the built-in features of SQL Server such as SQL Server Agent e.g. C:\Program Files\Microsoft SQL Server\90\DTS\Binn\dtshost.exe.config This file can be found in both the 32-bit and 64-bit Binn folders devenv.exe.config Something slightly different is devenv.exe which is Visual Studio. This configuration file may also need changing if you need a feature at design-time such as in a Task Editor or Connection Manager editor. Visual Studio 2005 for SQL Server 2005  - C:\Program Files\Microsoft Visual Studio 8\Common7\IDE\devenv.exe.config Visual Studio 2008 for SQL Server 2008  - C:\Program Files\Microsoft Visual Studio 9.0\Common7\IDE\devenv.exe.config Visual Studio is only available for 32-bit so on a 64-bit machine you will have to look in C:\Program Files (x86)\ only. DTExecUI.exe.config The DTExec UI tool can also have a configuration file and these cab be found under the Tools folders for SQL Sever as shown below. C:\Program Files\Microsoft SQL Server\90\Tools\Binn\VSShell\Common7\IDE\DTExecUI.exe C:\Program Files\Microsoft SQL Server\100\Tools\Binn\VSShell\Common7\IDE\DTExecUI.exe A configuration file may not exist, but if you can find the matching executable you know you are in the right place so can go ahead and add a new file yourself. In summary we have covered the assembly configuration files for all of the standard methods of building and running a SSIS package, but obviously if you are working programmatically you will need to make the relevant modifications to your program’s app.config as well.

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• Where is my app.config for SSIS?

  Sometimes when working with SSIS you need to add or change settings in the .NET application configuration file, which can be a bit confusing when you are building a SSIS package not an application. First of all lets review a couple of examples where you may need to do this. You are using referencing an assembly in a Script Task that uses Enterprise Library (aka EntLib), so you need to add the relevant configuration sections and settings, perhaps for the logging application block. You are using using Enterprise Library in a custom task or component, and again you need to add the relevant configuration sections and settings. You are using a web service with Microsoft Web Services Enhancements (WSE) 3.0 and hosting the proxy in SSIS, in an assembly used by your package, and need to add the configuration sections and settings. You need to change behaviours of the .NET framework which can be influenced by a configuration file, such as the System.Net.Mail default SMTP settings. Perhaps you wish to configure System.Net and the httpWebRequest header for parsing unsafe header (useUnsafeHeaderParsing), which will change the way the HTTP Connection manager behaves. You are consuming a WCF service and wish to specify the endpoint in configuration. There are no doubt plenty more examples but each of these requires us to identify the correct configuration file and and make the relevant changes. There are actually several configuration files, each used by a different execution host depending on how you are working with the SSIS package. The folders we need to look in will actually vary depending on the version of SQL Server as well as the processor architecture, but most are all what we can call the Binn folder. The SQL Server 2005 Binn folder is at C:\Program Files\Microsoft SQL Server\90\DTS\Binn\, compared to C:\Program Files\Microsoft SQL Server\100\DTS\Binn\ for SQL Server 2008. If you are on a 64-bit machine then you will see C:\Program Files (x86)\Microsoft SQL Server\90\DTS\Binn\ for the 32-bit executables and C:\Program Files\Microsoft SQL Server\90\DTS\Binn\ for 64-bit, so be sure to check all relevant locations. Of course SQL Server 2008 may have a C:\Program Files (x86)\Microsoft SQL Server\100\DTS\Binn\ on a 64-bit machine too. To recap, the version of SQL Server determines if you look in the 90 or 100 sub-folder under SQL Server in Program Files (C:\Program Files\Microsoft SQL Server\nn\) . If you are running a 64-bit operating system then you will have two instances program files, C:\Program Files (x86)\ for 32-bit and  C:\Program Files\ for 64-bit. You may wish to check both depending on what you are doing, but this is covered more under each section below. There are a total of five specific configuration files that you may need to change, each one is detailed below: DTExec.exe.config DTExec.exe is the standalone command line tool used for executing SSIS packages, and therefore it is an execution host with an app.config file. e.g. C:\Program Files\Microsoft SQL Server\90\DTS\Binn\DTExec.exe.config The file can be found in both the 32-bit and 64-bit Binn folders. DtsDebugHost.exe.config DtsDebugHost.exe is the execution host used by Business Intelligence Development Studio (BIDS) / Visual Studio when executing a package from the designer in debug mode, which is the default behaviour. e.g. C:\Program Files\Microsoft SQL Server\90\DTS\Binn\DtsDebugHost.exe.config The file can be found in both the 32-bit and 64-bit Binn folders. This may surprise some people as Visual Studio is only 32-bit, but thankfully the debugger supports both. This can be set in the project properties, see the Run64BitRuntime property (true or false) in the Debugging pane of the Project Properties. dtshost.exe.config dtshost.exe is the execution host used by what I think of as the built-in features of SQL Server such as SQL Server Agent e.g. C:\Program Files\Microsoft SQL Server\90\DTS\Binn\dtshost.exe.config This file can be found in both the 32-bit and 64-bit Binn folders devenv.exe.config Something slightly different is devenv.exe which is Visual Studio. This configuration file may also need changing if you need a feature at design-time such as in a Task Editor or Connection Manager editor. Visual Studio 2005 for SQL Server 2005  - C:\Program Files\Microsoft Visual Studio 8\Common7\IDE\devenv.exe.config Visual Studio 2008 for SQL Server 2008  - C:\Program Files\Microsoft Visual Studio 9.0\Common7\IDE\devenv.exe.config Visual Studio is only available for 32-bit so on a 64-bit machine you will have to look in C:\Program Files (x86)\ only. DTExecUI.exe.config The DTExec UI tool can also have a configuration file and these cab be found under the Tools folders for SQL Sever as shown below. C:\Program Files\Microsoft SQL Server\90\Tools\Binn\VSShell\Common7\IDE\DTExecUI.exe C:\Program Files\Microsoft SQL Server\100\Tools\Binn\VSShell\Common7\IDE\DTExecUI.exe A configuration file may not exist, but if you can find the matching executable you know you are in the right place so can go ahead and add a new file yourself. In summary we have covered the assembly configuration files for all of the standard methods of building and running a SSIS package, but obviously if you are working programmatically you will need to make the relevant modifications to your program’s app.config as well.

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• Why Software Sucks...and What You Can Do About It – book review

  - by DigiMortal

      How do our users see the products we are writing for them and how happy they are with our work? Are they able to get their work done without fighting with cool features and crashes or are they just switching off resistance part of their brain to survive our software? Yeah, the overall picture of software usability landscape is not very nice. Okay, it is not even nice. But, fortunately, Why Software Sucks...and What You Can Do About It by David S. Platt explains everything. Why Software Sucks… is book for software users but I consider it as a-must reading also for developers and specially for their managers whose politics often kills all usability topics as soon as they may appear. For managers usability is soft topic that can be manipulated the way it is best in current state of project. Although developers are not UI designers and usability experts they are still very often forced to deal with these topics and this is how usability problems start (of course, also designers are able to produce designs that are stupid and too hard to use for users, but this blog here is about development). I found this book to be very interesting and funny reading. It is not humor book but it explains you all so you remember later very well what you just read. It took me about three evenings to go through this book and I am still enjoying what I found and how author explains our weird young working field to end users. I suggest this book to all developers – while you are demanding your management to hire or outsource usability expert you are at least causing less pain to end users. So, go and buy this book, just like I did. And… they thanks to mr. Platt :) There is one book more I suggest you to read if you are interested in usability - Don't Make Me Think: A Common Sense Approach to Web Usability, 2nd Edition by Steve Krug. Editorial review from Amazon Today’s software sucks. There’s no other good way to say it. It’s unsafe, allowing criminal programs to creep through the Internet wires into our very bedrooms. It’s unreliable, crashing when we need it most, wiping out hours or days of work with no way to get it back. And it’s hard to use, requiring large amounts of head-banging to figure out the simplest operations. It’s no secret that software sucks. You know that from personal experience, whether you use computers for work or personal tasks. In this book, programming insider David Platt explains why that’s the case and, more importantly, why it doesn’t have to be that way. And he explains it in plain, jargon-free English that’s a joy to read, using real-world examples with which you’re already familiar. In the end, he suggests what you, as a typical user, without a technical background, can do about this sad state of our software—how you, as an informed consumer, don’t have to take the abuse that bad software dishes out. As you might expect from the book’s title, Dave’s expose is laced with humor—sometimes outrageous, but always dead on. You’ll laugh out loud as you recall incidents with your own software that made you cry. You’ll slap your thigh with the same hand that so often pounded your computer desk and wished it was a bad programmer’s face. But Dave hasn’t written this book just for laughs. He’s written it to give long-overdue voice to your own discovery—that software does, indeed, suck, but it shouldn’t. Table of contents Acknowledgments xiii Introduction Chapter 1: Who’re You Calling a Dummy? Where We Came From Why It Still Sucks Today Control versus Ease of Use I Don’t Care How Your Program Works A Bad Feature and a Good One Stopping the Proceedings with Idiocy Testing on Live Animals Where We Are and What You Can Do Chapter 2: Tangled in the Web Where We Came From How It Works Why It Still Sucks Today Client-Centered Design versus Server-Centered Design Where’s My Eye Opener? It’s Obvious—Not! Splash, Flash, and Animation Testing on Live Animals What You Can Do about It Chapter 3: Keep Me Safe The Way It Was Why It Sucks Today What Programmers Need to Know, but Don’t A Human Operation Budgeting for Hassles Users Are Lazy Social Engineering Last Word on Security What You Can Do Chapter 4: Who the Heck Are You? Where We Came From Why It Still Sucks Today Incompatible Requirements OK, So Now What? Chapter 5: Who’re You Looking At? Yes, They Know You Why It Sucks More Than Ever Today Users Don’t Know Where the Risks Are What They Know First Milk You with Cookies? Privacy Policy Nonsense Covering Your Tracks The Google Conundrum Solution Chapter 6: Ten Thousand Geeks, Crazed on Jolt Cola See Them in Their Native Habitat All These Geeks Who Speaks, and When, and about What Selling It The Next Generation of Geeks—Passing It On Chapter 7: Who Are These Crazy Bastards Anyway? Homo Logicus Testosterone Poisoning Control and Contentment Making Models Geeks and Jocks Jargon Brains and Constraints Seven Habits of Geeks Chapter 8: Microsoft: Can’t Live With ’Em and Can’t Live Without ’Em They Run the World Me and Them Where We Came From Why It Sucks Today Damned if You Do, Damned if You Don’t We Love to Hate Them Plus ça Change Growing-Up Pains What You Can Do about It The Last Word Chapter 9: Doing Something About It 1. Buy 2. Tell 3. Ridicule 4. Trust 5. Organize Epilogue About the Author

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• .NET Security Part 2

  - by Simon Cooper

  So, how do you create partial-trust appdomains? Where do you come across them? There are two main situations in which your assembly runs as partially-trusted using the Microsoft .NET stack: Creating a CLR assembly in SQL Server with anything other than the UNSAFE permission set. The permissions available in each permission set are given here. Loading an assembly in ASP.NET in any trust level other than Full. Information on ASP.NET trust levels can be found here. You can configure the specific permissions available to assemblies using ASP.NET policy files. Alternatively, you can create your own partially-trusted appdomain in code and directly control the permissions and the full-trust API available to the assemblies you load into the appdomain. This is the scenario I’ll be concentrating on in this post. Creating a partially-trusted appdomain There is a single overload of AppDomain.CreateDomain that allows you to specify the permissions granted to assemblies in that appdomain – this one. This is the only call that allows you to specify a PermissionSet for the domain. All the other calls simply use the permissions of the calling code. If the permissions are restricted, then the resulting appdomain is referred to as a sandboxed domain. There are three things you need to create a sandboxed domain: The specific permissions granted to all assemblies in the domain. The application base (aka working directory) of the domain. The list of assemblies that have full-trust if they are loaded into the sandboxed domain. The third item is what allows us to have a fully-trusted API that is callable by partially-trusted code. I’ll be looking at the details of this in a later post. Granting permissions to the appdomain Firstly, the permissions granted to the appdomain. This is encapsulated in a PermissionSet object, initialized either with no permissions or full-trust permissions. For sandboxed appdomains, the PermissionSet is initialized with no permissions, then you add permissions you want assemblies loaded into that appdomain to have by default: PermissionSet restrictedPerms = new PermissionSet(PermissionState.None); // all assemblies need Execution permission to run at all restrictedPerms.AddPermission( new SecurityPermission(SecurityPermissionFlag.Execution)); // grant general read access to C:\config.xml restrictedPerms.AddPermission( new FileIOPermission(FileIOPermissionAccess.Read, @"C:\config.xml")); // grant permission to perform DNS lookups restrictedPerms.AddPermission( new DnsPermission(PermissionState.Unrestricted)); It’s important to point out that the permissions granted to an appdomain, and so to all assemblies loaded into that appdomain, are usable without needing to go through any SafeCritical code (see my last post if you’re unsure what SafeCritical code is). That is, partially-trusted code loaded into an appdomain with the above permissions (and so running under the Transparent security level) is able to create and manipulate a FileStream object to read from C:\config.xml directly. It is only for operations requiring permissions that are not granted to the appdomain that partially-trusted code is required to call a SafeCritical method that then asserts the missing permissions and performs the operation safely on behalf of the partially-trusted code. The application base of the domain This is simply set as a property on an AppDomainSetup object, and is used as the default directory assemblies are loaded from: AppDomainSetup appDomainSetup = new AppDomainSetup { ApplicationBase = @"C:\temp\sandbox", }; If you’ve read the documentation around sandboxed appdomains, you’ll notice that it mentions a security hole if this parameter is set correctly. I’ll be looking at this, and other pitfalls, that will break the sandbox when using sandboxed appdomains, in a later post. Full-trust assemblies in the appdomain Finally, we need the strong names of the assemblies that, when loaded into the appdomain, will be run as full-trust, irregardless of the permissions specified on the appdomain. These assemblies will contain methods and classes decorated with SafeCritical and Critical attributes. I’ll be covering the details of creating full-trust APIs for partial-trust appdomains in a later post. This is how you get the strongnames of an assembly to be executed as full-trust in the sandbox: // get the Assembly object for the assembly Assembly assemblyWithApi = ... // get the StrongName from the assembly's collection of evidence StrongName apiStrongName = assemblyWithApi.Evidence.GetHostEvidence<StrongName>(); Creating the sandboxed appdomain So, putting these three together, you create the appdomain like so: AppDomain sandbox = AppDomain.CreateDomain( "Sandbox", null, appDomainSetup, restrictedPerms, apiStrongName); You can then load and execute assemblies in this appdomain like any other. For example, to load an assembly into the appdomain and get an instance of the Sandboxed.Entrypoint class, implementing IEntrypoint, you do this: IEntrypoint o = (IEntrypoint)sandbox.CreateInstanceFromAndUnwrap( "C:\temp\sandbox\SandboxedAssembly.dll", "Sandboxed.Entrypoint"); // call method the Execute method on this object within the sandbox o.Execute(); The second parameter to CreateDomain is for security evidence used in the appdomain. This was a feature of the .NET 2 security model, and has been (mostly) obsoleted in the .NET 4 model. Unless the evidence is needed elsewhere (eg. isolated storage), you can pass in null for this parameter. Conclusion That’s the basics of sandboxed appdomains. The most important object is the PermissionSet that defines the permissions available to assemblies running in the appdomain; it is this object that defines the appdomain as full or partial-trust. The appdomain also needs a default directory used for assembly lookups as the ApplicationBase parameter, and you can specify an optional list of the strongnames of assemblies that will be given full-trust permissions if they are loaded into the sandboxed appdomain. Next time, I’ll be looking closer at full-trust assemblies running in a sandboxed appdomain, and what you need to do to make an API available to partial-trust code.

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• Scripting out Contained Database Users

  - by Argenis

    Today’s blog post comes from a Twitter thread on which @SQLSoldier, @sqlstudent144 and @SQLTaiob were discussing the internals of contained database users. Unless you have been living under a rock, you’ve heard about the concept of contained users within a SQL Server database (hit the link if you have not). In this article I’d like to show you that you can, indeed, script out contained database users and recreate them on another database, as either contained users or as good old fashioned logins/server principals as well. Why would this be useful? Well, because you would not need to know the password for the user in order to recreate it on another instance. I know there is a limited number of scenarios where this would be necessary, but nonetheless I figured I’d throw this blog post to show how it can be done. A more obscure use case: with the password hash (which I’m about to show you how to obtain) you could also crack the password using a utility like hashcat, as highlighted on this SQLServerCentral article. The Investigation SQL Server uses System Base Tables to save the password hashes of logins and contained database users. For logins it uses sys.sysxlgns, whereas for contained database users it leverages sys.sysowners. I’ll show you what I do to figure this stuff out: I create a login/contained user, and then I immediately browse the transaction log with, for example, fn_dblog. It’s pretty obvious that only two base tables touched by the operation are sys.sysxlgns, and also sys.sysprivs – the latter is used to track permissions. If I connect to the DAC on my instance, I can query for the password hash of this login I’ve just created. A few interesting things about this hash. This was taken on my laptop, and I happen to be running SQL Server 2014 RTM CU2, which is the latest public build of SQL Server 2014 as of time of writing. In 2008 R2 and prior versions (back to 2000), the password hashes would start with 0x0100. The reason why this changed is because starting with SQL Server 2012 password hashes are kept using a SHA512 algorithm, as opposed to SHA-1 (used since 2000) or Snefru (used in 6.5 and 7.0). SHA-1 is nowadays deemed unsafe and is very easy to crack. For regular SQL logins, this information is exposed through the sys.sql_logins catalog view, so there is really no need to connect to the DAC to grab an SID/password hash pair. For contained database users, there is (currently) no method of obtaining SID or password hashes without connecting to the DAC. If we create a contained database user, this is what we get from the transaction log: Note that the System Base Table used in this case is sys.sysowners. sys.sysprivs is used as well, and again this is to track permissions. To query sys.sysowners, you would have to connect to the DAC, as I mentioned previously. And this is what you would get: There are other ways to figure out what SQL Server uses under the hood to store contained database user password hashes, like looking at the execution plan for a query to sys.dm_db_uncontained_entities (Thanks, Robert Davis!) SIDs, Logins, Contained Users, and Why You Care…Or Not. One of the reasons behind the existence of Contained Users was the concept of portability of databases: it is really painful to maintain Server Principals (Logins) synced across most shared-nothing SQL Server HA/DR technologies (Mirroring, Availability Groups, and Log Shipping). Often times you would need the Security Identifier (SID) of these logins to match across instances, and that meant that you had to fetch whatever SID was assigned to the login on the principal instance so you could recreate it on a secondary. With contained users you normally wouldn’t care about SIDs, as the users are always available (and synced, as long as synchronization takes place) across instances. Now you might be presented some particular requirement that might specify that SIDs synced between logins on certain instances and contained database users on other databases. How would you go about creating a contained database user with a specific SID? The answer is that you can’t do it directly, but there’s a little trick that would allow you to do it. Create a login with a specified SID and password hash, create a user for that server principal on a partially contained database, then migrate that user to contained using the system stored procedure sp_user_migrate_to_contained, then drop the login. CREATE LOGIN <login_name> WITH PASSWORD = <password_hash> HASHED, SID = <sid> ; GO USE <partially_contained_db>; GO CREATE USER <user_name> FROM LOGIN <login_name>; GO EXEC sp_migrate_user_to_contained @username = <user_name>, @rename = N’keep_name’, @disablelogin = N‘disable_login’; GO DROP LOGIN <login_name>; GO Here’s how this skeleton would look like in action: And now I have a contained user with a specified SID and password hash. In my example above, I renamed the user after migrated it to contained so that it is, hopefully, easier to understand. Enjoy!

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• Need help manipulating WAV (RIFF) Files at a byte level

  - by Eric

  I'm writing an an application in C# that will record audio files (*.wav) and automatically tag and name them. Wave files are RIFF files (like AVI) which can contain meta data chunks in addition to the waveform data chunks. So now I'm trying to figure out how to read and write the RIFF meta data to and from recorded wave files. I'm using NAudio for recording the files, and asked on their forums as well on SO for way to read and write RIFF tags. While I received a number of good answers, none of the solutions allowed for reading and writing RIFF chunks as easily as I would like. But more importantly I have very little experience dealing with files at a byte level, and think this could be a good opportunity to learn. So now I want to try writing my own class(es) that can read in a RIFF file and allow meta data to be read, and written from the file. I've used streams in C#, but always with the entire stream at once. So now I'm little lost that I have to consider a file byte by byte. Specifically how would I go about removing or inserting bytes to and from the middle of a file? I've tried reading a file through a FileStream into a byte array (byte[]) as shown in the code below. System.IO.FileStream waveFileStream = System.IO.File.OpenRead(@"C:\sound.wav"); byte[] waveBytes = new byte[waveFileStream.Length]; waveFileStream.Read(waveBytes, 0, waveBytes.Length); And I could see through the Visual Studio debugger that the first four byte are the RIFF header of the file. But arrays are a pain to deal with when performing actions that change their size like inserting or removing values. So I was thinking I could then to the byte[] into a List like this. List<byte> list = waveBytes.ToList<byte>(); Which would make any manipulation of the file byte by byte a whole lot easier, but I'm worried I might be missing something like a class in the System.IO name-space that would make all this even easier. Am I on the right track, or is there a better way to do this? I should also mention that I'm not hugely concerned with performance, and would prefer not to deal with pointers or unsafe code blocks like this guy. If it helps at all here is a good article on the RIFF/WAV file format.

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• How to call a JavaScript function from one frame to another in Chrome/Webkit with file protocol

  - by bambax

  I have developed an application that has a list of items in one frame; when one clicks on an item it does something in another frame (loads an image). This used to work fine in all browsers, including Chrome 3; now it still works fine in Firefox but in recent versions of Chrome (I believe since 4) it throws this error: Unsafe JavaScript attempt to access frame with URL (...) from frame with URL (...). Domains, protocols and ports must match. This is obviously a security "feature" but is it possible to get around it? Here is a simple test: index.html: <html> <frameset cols="50%,50%"> <frame src="left.html" name="left"/> <frame src="right.html" name="right"/> </frameset> </html> left.html: <html> <body> <a href="javascript:parent.right.test('hello');">click me</a> </body> </html> right.html: <html> <body> <script> function test(msg) { alert(msg); } </script> </body> </html> The above works in Firefox 3.6 and Chrome 3 but in Chrome 5 it throws the above error... Edit: added the @cols attribute to the frameset element in fact it works in Chrome if and only if the pages are served with the http protocol (and from the same domain) but my problem is when pages are local and served from a file:// protocol. Then it works in Firefox (all versions) and Chrome 3 but not Chrome 5 (I don't have Chrome 4 so I'm not shure about that specific version (and don't know if it's even possible to download a specific Chrome version?) -- but for Chrome 5 I'm very sure it doesn't work).

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• Partial overriding in Java (or dynamic overriding while overloading)

  - by Lie Ryan

  If I have a parent-child that defines some method .foo() like this: class Parent { public void foo(Parent arg) { System.out.println("foo in Function"); } } class Child extends Parent { public void foo(Child arg) { System.out.println("foo in ChildFunction"); } } When I called them like this: Child f = new Child(); Parent g = f; f.foo(new Parent()); f.foo(new Child()); g.foo(new Parent()); g.foo(new Child()); the output is: foo in Parent foo in Child foo in Parent foo in Parent But, I want this output: foo in Parent foo in Child foo in Parent foo in Child I have a Child class that extends Parent class. In the Child class, I want to "partially override" the Parent's foo(), that is, if the argument arg's type is Child then Child's foo() is called instead of Parent's foo(). That works Ok when I called f.foo(...) as a Child; but if I refer to it from its Parent alias like in g.foo(...) then the Parent's foo(..) get called irrespective of the type of arg. As I understand it, what I'm expecting doesn't happen because method overloading in Java is early binding (i.e. resolved statically at compile time) while method overriding is late binding (i.e. resolved dynamically at compile time) and since I defined a function with a technically different argument type, I'm technically overloading the Parent's class definition with a distinct definition, not overriding it. But what I want to do is conceptually "partially overriding" when .foo()'s argument is a subclass of the parent's foo()'s argument. I know I can define a bucket override foo(Parent arg) in Child that checks whether arg's actual type is Parent or Child and pass it properly, but if I have twenty Child, that would be lots of duplication of type-unsafe code. In my actual code, Parent is an abstract class named "Function" that simply throws NotImplementedException(). The children includes "Polynomial", "Logarithmic", etc and .foo() includes things like Child.add(Child), Child.intersectionsWith(Child), etc. Not all combination of Child.foo(OtherChild) are solvable and in fact not even all Child.foo(Child) is solvable. So I'm best left with defining everything undefined (i.e. throwing NotImplementedException) then defines only those that can be defined. So the question is: Is there any way to override only part the parent's foo()? Or is there a better way to do what I want to do?

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• How to convert a 32bpp image to an indexed format?

  - by Ed Swangren

  So here are the details (I am using C# BTW): I receive a 32bpp image (JPEG compressed) from a server. At some point, I would like to use the Palette property of a bitmap to color over-saturated pixels (brightness 240) red. To do so, I need to get the image into an indexed format. I have tried converting the image to a GIF, but I get quality loss. I have tried creating a new bitmap in an index format by these methods: // causes a "Parameter not valid" error Bitmap indexed = new Bitmap(orig.Width, orig.Height, PixelFormat.Indexed) // no error, but the resulting image is black due to information loss I assume Bitmap indexed = new Bitmap(orig.Width, orig.Height, PixelFormat.Format8bppIndexed) I am at a loss now. The data in this image is changed constantly by the user, so I don't want to manually set pixels that have a brightness 240 if I can avoid it. If I can set the palette once when the image is created, my work is done. If I am going about this the wrong way to begin with please let me know. EDIT: Thanks guys, here is some more detail on what I am attempting to accomplish. We are scanning a tissue slide at high resolution (pathology application). I write the interface to the actual scanner. We use a line-scan camera. To test the line rate of the camera, the user scans a very small portion and looks at the image. The image is displayed next to a track bar. When the user moves the track bar (adjusting line rate), I change the overall intensity of the image in an attempt to model what it would look like at the new line rate. I do this using an ImageAttributes and ColorMatrix object currently. When the user adjusts the track bar, I adjust the matrix. This does not give me per pixel information, but the performance is very nice. I could use LockBits and some unsafe code here, but I would rather not rewrite it if possible. When the new image is created, I would like for all pixels with a brightness value of 240 to be colored red. I was thinking that defining a palette for the bitmap up front would be a clean way of doing this.

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• MacPorts 1.8.2 fails to build db46 on Mac OS X 1.6.3

  - by themoch

  I'm trying to put a development environment on my Mac, and to do so I need to install several packages which require db46. When running sudo port install db46 I get the following error: ---> Computing dependencies for db46 ---> Fetching db46 ---> Attempting to fetch patch.4.6.21.1 from http://www.oracle.com/technology/products/berkeley-db/db/update/4.6.21/ ---> Attempting to fetch patch.4.6.21.2 from http://www.oracle.com/technology/products/berkeley-db/db/update/4.6.21/ ---> Attempting to fetch patch.4.6.21.3 from http://www.oracle.com/technology/products/berkeley-db/db/update/4.6.21/ ---> Attempting to fetch patch.4.6.21.4 from http://www.oracle.com/technology/products/berkeley-db/db/update/4.6.21/ ---> Attempting to fetch db-4.6.21.tar.gz from http://distfiles.macports.org/db4/4.6.21_6 ---> Verifying checksum(s) for db46 ---> Extracting db46 ---> Applying patches to db46 ---> Configuring db46 ---> Building db46 Error: Target org.macports.build returned: shell command " cd "/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_ports_databases_db46/work/db-4.6.21/build_unix" && /usr/bin/make -j2 all " returned error 2 Command output: ../dist/../libdb_java/db_java_wrap.c:9464: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9487: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jlong' ../dist/../libdb_java/db_java_wrap.c:9509: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9532: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jlong' ../dist/../libdb_java/db_java_wrap.c:9563: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jint' ../dist/../libdb_java/db_java_wrap.c:9588: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jlong' ../dist/../libdb_java/db_java_wrap.c:9613: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jint' ../dist/../libdb_java/db_java_wrap.c:9638: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9666: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jlong' ../dist/../libdb_java/db_java_wrap.c:9691: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jlong' ../dist/../libdb_java/db_java_wrap.c:9716: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9739: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9771: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9796: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9819: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9842: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9867: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jobject' ../dist/../libdb_java/db_java_wrap.c:9899: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9920: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9943: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9966: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jstring' ../dist/../libdb_java/db_java_wrap.c:9991: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jint' ../dist/../libdb_java/db_java_wrap.c:10010: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:10046: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:10071: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' make: *** [db_java_wrap.lo] Error 1 make: *** Waiting for unfinished jobs.... Note: Some input files use unchecked or unsafe operations. Note: Recompile with -Xlint:unchecked for details. cd ./classes && jar cf ../db.jar ./com/sleepycat Error: Status 1 encountered during processing. I have removed my /usr/local folder completely and it does not seem to help.

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• Macports 1.8.2 fails to build db46 on os x 1.6.3

  - by themoch

  i'm trying to put a dev environment on my mac, and to do so i need to install several packages which require db46 when running sudo port install db46 i get the following error: ---> Computing dependencies for db46 ---> Fetching db46 ---> Attempting to fetch patch.4.6.21.1 from http://www.oracle.com/technology/products/berkeley-db/db/update/4.6.21/ ---> Attempting to fetch patch.4.6.21.2 from http://www.oracle.com/technology/products/berkeley-db/db/update/4.6.21/ ---> Attempting to fetch patch.4.6.21.3 from http://www.oracle.com/technology/products/berkeley-db/db/update/4.6.21/ ---> Attempting to fetch patch.4.6.21.4 from http://www.oracle.com/technology/products/berkeley-db/db/update/4.6.21/ ---> Attempting to fetch db-4.6.21.tar.gz from http://distfiles.macports.org/db4/4.6.21_6 ---> Verifying checksum(s) for db46 ---> Extracting db46 ---> Applying patches to db46 ---> Configuring db46 ---> Building db46 Error: Target org.macports.build returned: shell command " cd "/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_release_ports_databases_db46/work/db-4.6.21/build_unix" && /usr/bin/make -j2 all " returned error 2 Command output: ../dist/../libdb_java/db_java_wrap.c:9464: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9487: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jlong' ../dist/../libdb_java/db_java_wrap.c:9509: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9532: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jlong' ../dist/../libdb_java/db_java_wrap.c:9563: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jint' ../dist/../libdb_java/db_java_wrap.c:9588: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jlong' ../dist/../libdb_java/db_java_wrap.c:9613: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jint' ../dist/../libdb_java/db_java_wrap.c:9638: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9666: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jlong' ../dist/../libdb_java/db_java_wrap.c:9691: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jlong' ../dist/../libdb_java/db_java_wrap.c:9716: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9739: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9771: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9796: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9819: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9842: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9867: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jobject' ../dist/../libdb_java/db_java_wrap.c:9899: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9920: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9943: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:9966: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jstring' ../dist/../libdb_java/db_java_wrap.c:9991: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'jint' ../dist/../libdb_java/db_java_wrap.c:10010: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:10046: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' ../dist/../libdb_java/db_java_wrap.c:10071: error: expected '=', ',', ';', 'asm' or '__attribute__' before 'void' make: *** [db_java_wrap.lo] Error 1 make: *** Waiting for unfinished jobs.... Note: Some input files use unchecked or unsafe operations. Note: Recompile with -Xlint:unchecked for details. cd ./classes && jar cf ../db.jar ./com/sleepycat Error: Status 1 encountered during processing. i have removed my /usr/local folder completely and it does not seem to help

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• How can a C/C++ program put itself into background?

  - by Larry Gritz

  What's the best way for a running C or C++ program that's been launched from the command line to put itself into the background, equivalent to if the user had launched from the unix shell with '&' at the end of the command? (But the user didn't.) It's a GUI app and doesn't need any shell I/O, so there's no reason to tie up the shell after launch. But I want a shell command launch to be auto-backgrounded without the '&' (or on Windows). Ideally, I want a solution that would work on any of Linux, OS X, and Windows. (Or separate solutions that I can select with #ifdef.) It's ok to assume that this should be done right at the beginning of execution, as opposed to somewhere in the middle. One solution is to have the main program be a script that launches the real binary, carefully putting it into the background. But it seems unsatisfying to need these coupled shell/binary pairs. Another solution is to immediately launch another executed version (with 'system' or CreateProcess), with the same command line arguments, but putting the child in the background and then having the parent exit. But this seems clunky compared to the process putting itself into background. Edited after a few answers: Yes, a fork() (or system(), or CreateProcess on Windows) is one way to sort of do this, that I hinted at in my original question. But all of these solutions make a SECOND process that is backgrounded, and then terminate the original process. I was wondering if there was a way to put the EXISTING process into the background. One difference is that if the app was launched from a script that recorded its process id (perhaps for later killing or other purpose), the newly forked or created process will have a different id and so will not be controllable by any launching script, if you see what I'm getting at. Edit #2: fork() isn't a good solution for OS X, where the man page for 'fork' says that it's unsafe if certain frameworks or libraries are being used. I tried it, and my app complains loudly at runtime: "The process has forked and you cannot use this CoreFoundation functionality safely. You MUST exec()." I was intrigued by daemon(), but when I tried it on OS X, it gave the same error message, so I assume that it's just a fancy wrapper for fork() and has the same restrictions. Excuse the OS X centrism, it just happens to be the system in front of me at the moment. But I am indeed looking for a solution to all three platforms.

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• Is it a good or bad practice to call instance methods from a java constructor?

  - by Steve

  There are several different ways I can initialize complex objects (with injected dependencies and required set-up of injected members), are all seem reasonable, but have various advantages and disadvantages. I'll give a concrete example: final class MyClass { private final Dependency dependency; @Inject public MyClass(Dependency dependency) { this.dependency = dependency; dependency.addHandler(new Handler() { @Override void handle(int foo) { MyClass.this.doSomething(foo); } }); doSomething(0); } private void doSomething(int foo) { dependency.doSomethingElse(foo+1); } } As you can see, the constructor does 3 things, including calling an instance method. I've been told that calling instance methods from a constructor is unsafe because it circumvents the compiler's checks for uninitialized members. I.e. I could have called doSomething(0) before setting this.dependency, which would have compiled but not worked. What is the best way to refactor this? Make doSomething static and pass in the dependency explicitly? In my actual case I have three instance methods and three member fields that all depend on one another, so this seems like a lot of extra boilerplate to make all three of these static. Move the addHandler and doSomething into an @Inject public void init() method. While use with Guice will be transparent, it requires any manual construction to be sure to call init() or else the object won't be fully-functional if someone forgets. Also, this exposes more of the API, both of which seem like bad ideas. Wrap a nested class to keep the dependency to make sure it behaves properly without exposing additional API:class DependencyManager { private final Dependency dependency; public DependecyManager(Dependency dependency) { ... } public doSomething(int foo) { ... } } @Inject public MyClass(Dependency dependency) { DependencyManager manager = new DependencyManager(dependency); manager.doSomething(0); } This pulls instance methods out of all constructors, but generates an extra layer of classes, and when I already had inner and anonymous classes (e.g. that handler) it can become confusing - when I tried this I was told to move the DependencyManager to a separate file, which is also distasteful because it's now multiple files to do a single thing. So what is the preferred way to deal with this sort of situation?

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• Calling managed code from unmanaged win32 assembly dll - crash

  - by JustGreg

  I'm developing a serial port dll in win32 assembly (MASM32). It has its own thread checking multiple events and at a specified buffer treshold it'd notify the managed main application by calling a callback function. It just a call with no arguments/return value. At startup the main application stores the callback function's address by calling a function in the dll: pCallBackFunction dd 0 SetCallBackPointer proc pcb:DWORD mov eax, pcb mov pCallBackFunction, eax call DWORD ptr pCallBackFunction ; verify it immediately ret SetCallBackPointer endp The upper function immediately calls back the managed application callback routine for verification purposes. It is working fine. However, when I place the call instruction to other functions in the dll it crashes the application. It doesn't matter if the call is in a simple function or in the threadproc of the dll. For example: OpenPort proc pn:byte,br:dword, inputbuffersize: dword, outputbuffersize:dword, tresholdsize: dword LOCAL dcb: DCB LOCAL SerialTimeOuts: COMMTIMEOUTS call DWORD ptr pCallBackFunction xor eax, eax mov al, pn mov [com_port+3],al etc. etc. will crash at call DWORD ptr pCallBackFunction always. Since I call SetCallBackPointer first to store a valid address in pCallBackFunction, it should have a valid address. My managed app is written in C# and the relevant part is: public partial class Form1 : Form { public delegate void CallBackDelegate(); public static CallBackDelegate mydelegate; [DllImport("serialport.dll")] private static extern void SetCallBackPointer(CallBackDelegate Delegate); [DllImport("serialport.dll")] public static extern int OpenPort(byte com, uint br, uint inbufsize, uint outbufsize, uint treshsize); public Form1() { InitializeComponent(); mydelegate =new CallBackDelegate(CallbackFunction); SetCallBackPointer(mydelegate); unsafe { int sysstat; int hResult; hResult = OpenPort(Convert.ToByte('5'), 9600, 306, 4, 4); } } public static void CallbackFunction() { MessageBox.Show( "CallBack Function Called by Windows DLL"); } The VS debugger reported that the dll had tried to read/write from/to a protected memory address. But when calling SetCallBackPointer there is no such problem. What am I doing wrong here? Any tips would be great!

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• Can't launch glassfish on ec2 - can't open port

  - by orange80

  I'm trying to start glassfish on an EBS-based AMI of Ubuntu 10.04 64-bit. I have used glassfish on non-ec2 servers with no problems, but on ec2 I get this message: $ sudo -u glassfish bin/asadmin start-domain domain1 There is a process already using the admin port 4848 -- it probably is another instance of a GlassFish server. Command start-domain failed. I know that ec2 has requires that firewall rules be modified using ec2-authorize to let outside traffic thru the firewall, as I had to do to make ssh work. This still doesn't explain the port error when all I'm trying to do is start glassfish so I can try $ wget localhost:8080and make sure it's working. This is very frustrating and I'd really appreciate any help. Thanks. FINAL UPDATE: Sorry if you came here looking for answers. I never figured out what was causing the problem. I created another fresh instance, installed the same stuff, and Glassfish worked perfectly. Something obviously got boned during installation, but I have no idea what. I guess it will remain a mystery. UPDATE: Here's what I get from netstat: # netstat -nuptl Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN 462/sshd tcp6 0 0 :::22 :::* LISTEN 462/sshd udp 0 0 0.0.0.0:5353 0.0.0.0:* 483/avahi-daemon: r udp 0 0 0.0.0.0:1194 0.0.0.0:* 589/openvpn udp 0 0 0.0.0.0:37940 0.0.0.0:* 483/avahi-daemon: r udp 0 0 0.0.0.0:68 0.0.0.0:* 377/dhclient3 UPDATE: One more thing... I know that the "net.ipv6.bindv6only" kernel option can cause problems with java networking, so I did set this: # sysctl -w net.ipv6.bindv6only=0 UPDATE: I also verified that it has nothing at all to do with the port number (4848). As you can see here, when I changed the admin-listener port in domain.xml to 4949, I get a similar message: # sudo -u glassfish bin/asadmin start-domain domain1 There is a process already using the admin port 4949 -- it probably is another instance of a GlassFish server. Command start-domain failed. UPDATE: Here are the contents of /etc/hosts: 127.0.0.1 localhost # The following lines are desirable for IPv6 capable hosts ::1 ip6-localhost ip6-loopback fe00::0 ip6-localnet ff00::0 ip6-mcastprefix ff02::1 ip6-allnodes ff02::2 ip6-allrouters ff02::3 ip6-allhosts I should mention that I have another Ubuntu Lucid 10.04 64-bit slice that is NOT hosted on ec2, and set it up the exact same way with no problems whatsoever. Also server.log doesn't offer much insight either: # cat ./server.log Nov 20, 2010 8:46:49 AM com.sun.enterprise.admin.launcher.GFLauncherLogger info INFO: JVM invocation command line: /usr/lib/jvm/java-6-sun-1.6.0.22/bin/java -cp /opt/glassfishv3/glassfish/modules/glassfish.jar -XX:+UnlockDiagnosticVMOptions -XX:MaxPermSize=192m -XX:NewRatio=2 -XX:+LogVMOutput -XX:LogFile=/opt/glassfishv3/glassfish/domains/domain1/logs/jvm.log -Xmx512m -client -javaagent:/opt/glassfishv3/glassfish/lib/monitor/btrace-agent.jar=unsafe=true,noServer=true -Dosgi.shell.telnet.maxconn=1 -Djdbc.drivers=org.apache.derby.jdbc.ClientDriver -Dfelix.fileinstall.dir=/opt/glassfishv3/glassfish/modules/autostart/ -Djavax.net.ssl.keyStore=/opt/glassfishv3/glassfish/domains/domain1/config/keystore.jks -Dosgi.shell.telnet.port=6666 -Djava.security.policy=/opt/glassfishv3/glassfish/domains/domain1/config/server.policy -Dfelix.fileinstall.poll=5000 -Dcom.sun.aas.instanceRoot=/opt/glassfishv3/glassfish/domains/domain1 -Dcom.sun.enterprise.config.config_environment_factory_class=com.sun.enterprise.config.serverbeans.AppserverConfigEnvironmentFactory -Dosgi.shell.telnet.ip=127.0.0.1 -Djava.endorsed.dirs=/opt/glassfishv3/glassfish/modules/endorsed:/opt/glassfishv3/glassfish/lib/endorsed -Dcom.sun.aas.installRoot=/opt/glassfishv3/glassfish -Djava.ext.dirs=/usr/lib/jvm/java-6-sun-1.6.0.22/lib/ext:/usr/lib/jvm/java-6-sun-1.6.0.22/jre/lib/ext:/opt/glassfishv3/glassfish/domains/domain1/lib/ext -Dfelix.fileinstall.bundles.new.start=true -Djavax.net.ssl.trustStore=/opt/glassfishv3/glassfish/domains/domain1/config/cacerts.jks -Dcom.sun.enterprise.security.httpsOutboundKeyAlias=s1as -Djava.security.auth.login.config=/opt/glassfishv3/glassfish/domains/domain1/config/login.conf -DANTLR_USE_DIRECT_CLASS_LOADING=true -Dfelix.fileinstall.debug=1 -Dorg.glassfish.web.rfc2109_cookie_names_enforced=false -Djava.library.path=/opt/glassfishv3/glassfish/lib:/usr/lib/jvm/java-6-sun-1.6.0.22/jre/lib/amd64/server:/usr/lib/jvm/java-6-sun-1.6.0.22/jre/lib/amd64:/usr/lib/jvm/java-6-sun-1.6.0.22/lib/amd64:/usr/java/packages/lib/amd64:/usr/lib64:/lib64:/lib:/usr/lib com.sun.enterprise.glassfish.bootstrap.ASMain -domainname domain1 -asadmin-args start-domain,,,domain1 -instancename server -verbose false -debug false -asadmin-classpath /opt/glassfishv3/glassfish/modules/admin-cli.jar -asadmin-classname com.sun.enterprise.admin.cli.AsadminMain -upgrade false -domaindir /opt/glassfishv3/glassfish/domains/domain1 -read-stdin true

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