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  • 64-bit Archives Needed

    - by user9154181
    A little over a year ago, we received a question from someone who was trying to build software on Solaris. He was getting errors from the ar command when creating an archive. At that time, the ar command on Solaris was a 32-bit command. There was more than 2GB of data, and the ar command was hitting the file size limit for a 32-bit process that doesn't use the largefile APIs. Even in 2011, 2GB is a very large amount of code, so we had not heard this one before. Most of our toolchain was extended to handle 64-bit sized data back in the 1990's, but archives were not changed, presumably because there was no perceived need for it. Since then of course, programs have continued to get larger, and in 2010, the time had finally come to investigate the issue and find a way to provide for larger archives. As part of that process, I had to do a deep dive into the archive format, and also do some Unix archeology. I'm going to record what I learned here, to document what Solaris does, and in the hope that it might help someone else trying to solve the same problem for their platform. Archive Format Details Archives are hardly cutting edge technology. They are still used of course, but their basic form hasn't changed in decades. Other than to fix a bug, which is rare, we don't tend to touch that code much. The archive file format is described in /usr/include/ar.h, and I won't repeat the details here. Instead, here is a rough overview of the archive file format, implemented by System V Release 4 (SVR4) Unix systems such as Solaris: Every archive starts with a "magic number". This is a sequence of 8 characters: "!<arch>\n". The magic number is followed by 1 or more members. A member starts with a fixed header, defined by the ar_hdr structure in/usr/include/ar.h. Immediately following the header comes the data for the member. Members must be padded at the end with newline characters so that they have even length. The requirement to pad members to an even length is a dead giveaway as to the age of the archive format. It tells you that this format dates from the 1970's, and more specifically from the era of 16-bit systems such as the PDP-11 that Unix was originally developed on. A 32-bit system would have required 4 bytes, and 64-bit systems such as we use today would probably have required 8 bytes. 2 byte alignment is a poor choice for ELF object archive members. 32-bit objects require 4 byte alignment, and 64-bit objects require 64-bit alignment. The link-editor uses mmap() to process archives, and if the members have the wrong alignment, we have to slide (copy) them to the correct alignment before we can access the ELF data structures inside. The archive format requires 2 byte padding, but it doesn't prohibit more. The Solaris ar command takes advantage of this, and pads ELF object members to 8 byte boundaries. Anything else is padded to 2 as required by the format. The archive header (ar_hdr) represents all numeric values using an ASCII text representation rather than as binary integers. This means that an archive that contains only text members can be viewed using tools such as cat, more, or a text editor. The original designers of this format clearly thought that archives would be used for many file types, and not just for objects. Things didn't turn out that way of course — nearly all archives contain relocatable objects for a single operating system and machine, and are used primarily as input to the link-editor (ld). Archives can have special members that are created by the ar command rather than being supplied by the user. These special members are all distinguished by having a name that starts with the slash (/) character. This is an unambiguous marker that says that the user could not have supplied it. The reason for this is that regular archive members are given the plain name of the file that was inserted to create them, and any path components are stripped off. Slash is the delimiter character used by Unix to separate path components, and as such cannot occur within a plain file name. The ar command hides the special members from you when you list the contents of an archive, so most users don't know that they exist. There are only two possible special members: A symbol table that maps ELF symbols to the object archive member that provides it, and a string table used to hold member names that exceed 15 characters. The '/' convention for tagging special members provides room for adding more such members should the need arise. As I will discuss below, we took advantage of this fact to add an alternate 64-bit symbol table special member which is used in archives that are larger than 4GB. When an archive contains ELF object members, the ar command builds a special archive member known as the symbol table that maps all ELF symbols in the object to the archive member that provides it. The link-editor uses this symbol table to determine which symbols are provided by the objects in that archive. If an archive has a symbol table, it will always be the first member in the archive, immediately following the magic number. Unlike member headers, symbol tables do use binary integers to represent offsets. These integers are always stored in big-endian format, even on a little endian host such as x86. The archive header (ar_hdr) provides 15 characters for representing the member name. If any member has a name that is longer than this, then the real name is written into a special archive member called the string table, and the member's name field instead contains a slash (/) character followed by a decimal representation of the offset of the real name within the string table. The string table is required to precede all normal archive members, so it will be the second member if the archive contains a symbol table, and the first member otherwise. The archive format is not designed to make finding a given member easy. Such operations move through the archive from front to back examining each member in turn, and run in O(n) time. This would be bad if archives were commonly used in that manner, but in general, they are not. Typically, the ar command is used to build an new archive from scratch, inserting all the objects in one operation, and then the link-editor accesses the members in the archive in constant time by using the offsets provided by the symbol table. Both of these operations are reasonably efficient. However, listing the contents of a large archive with the ar command can be rather slow. Factors That Limit Solaris Archive Size As is often the case, there was more than one limiting factor preventing Solaris archives from growing beyond the 32-bit limits of 2GB (32-bit signed) and 4GB (32-bit unsigned). These limits are listed in the order they are hit as archive size grows, so the earlier ones mask those that follow. The original Solaris archive file format can handle sizes up to 4GB without issue. However, the ar command was delivered as a 32-bit executable that did not use the largefile APIs. As such, the ar command itself could not create a file larger than 2GB. One can solve this by building ar with the largefile APIs which would allow it to reach 4GB, but a simpler and better answer is to deliver a 64-bit ar, which has the ability to scale well past 4GB. Symbol table offsets are stored as 32-bit big-endian binary integers, which limits the maximum archive size to 4GB. To get around this limit requires a different symbol table format, or an extension mechanism to the current one, similar in nature to the way member names longer than 15 characters are handled in member headers. The size field in the archive member header (ar_hdr) is an ASCII string capable of representing a 32-bit unsigned value. This places a 4GB size limit on the size of any individual member in an archive. In considering format extensions to get past these limits, it is important to remember that very few archives will require the ability to scale past 4GB for many years. The old format, while no beauty, continues to be sufficient for its purpose. This argues for a backward compatible fix that allows newer versions of Solaris to produce archives that are compatible with older versions of the system unless the size of the archive exceeds 4GB. Archive Format Differences Among Unix Variants While considering how to extend Solaris archives to scale to 64-bits, I wanted to know how similar archives from other Unix systems are to those produced by Solaris, and whether they had already solved the 64-bit issue. I've successfully moved archives between different Unix systems before with good luck, so I knew that there was some commonality. If it turned out that there was already a viable defacto standard for 64-bit archives, it would obviously be better to adopt that rather than invent something new. The archive file format is not formally standardized. However, the ar command and archive format were part of the original Unix from Bell Labs. Other systems started with that format, extending it in various often incompatible ways, but usually with the same common shared core. Most of these systems use the same magic number to identify their archives, despite the fact that their archives are not always fully compatible with each other. It is often true that archives can be copied between different Unix variants, and if the member names are short enough, the ar command from one system can often read archives produced on another. In practice, it is rare to find an archive containing anything other than objects for a single operating system and machine type. Such an archive is only of use on the type of system that created it, and is only used on that system. This is probably why cross platform compatibility of archives between Unix variants has never been an issue. Otherwise, the use of the same magic number in archives with incompatible formats would be a problem. I was able to find information for a number of Unix variants, described below. These can be divided roughly into three tribes, SVR4 Unix, BSD Unix, and IBM AIX. Solaris is a SVR4 Unix, and its archives are completely compatible with those from the other members of that group (GNU/Linux, HP-UX, and SGI IRIX). AIX AIX is an exception to rule that Unix archive formats are all based on the original Bell labs Unix format. It appears that AIX supports 2 formats (small and big), both of which differ in fundamental ways from other Unix systems: These formats use a different magic number than the standard one used by Solaris and other Unix variants. They include support for removing archive members from a file without reallocating the file, marking dead areas as unused, and reusing them when new archive items are inserted. They have a special table of contents member (File Member Header) which lets you find out everything that's in the archive without having to actually traverse the entire file. Their symbol table members are quite similar to those from other systems though. Their member headers are doubly linked, containing offsets to both the previous and next members. Of the Unix systems described here, AIX has the only format I saw that will have reasonable insert/delete performance for really large archives. Everyone else has O(n) performance, and are going to be slow to use with large archives. BSD BSD has gone through 4 versions of archive format, which are described in their manpage. They use the same member header as SVR4, but their symbol table format is different, and their scheme for long member names puts the name directly after the member header rather than into a string table. GNU/Linux The GNU toolchain uses the SVR4 format, and is compatible with Solaris. HP-UX HP-UX seems to follow the SVR4 model, and is compatible with Solaris. IRIX IRIX has 32 and 64-bit archives. The 32-bit format is the standard SVR4 format, and is compatible with Solaris. The 64-bit format is the same, except that the symbol table uses 64-bit integers. IRIX assumes that an archive contains objects of a single ELFCLASS/MACHINE, and any archive containing ELFCLASS64 objects receives a 64-bit symbol table. Although they only use it for 64-bit objects, nothing in the archive format limits it to ELFCLASS64. It would be perfectly valid to produce a 64-bit symbol table in an archive containing 32-bit objects, text files, or anything else. Tru64 Unix (Digital/Compaq/HP) Tru64 Unix uses a format much like ours, but their symbol table is a hash table, making specific symbol lookup much faster. The Solaris link-editor uses archives by examining the entire symbol table looking for unsatisfied symbols for the link, and not by looking up individual symbols, so there would be no benefit to Solaris from such a hash table. The Tru64 ld must use a different approach in which the hash table pays off for them. Widening the existing SVR4 archive symbol tables rather than inventing something new is the simplest path forward. There is ample precedent for this approach in the ELF world. When ELF was extended to support 64-bit objects, the approach was largely to take the existing data structures, and define 64-bit versions of them. We called the old set ELF32, and the new set ELF64. My guess is that there was no need to widen the archive format at that time, but had there been, it seems obvious that this is how it would have been done. The Implementation of 64-bit Solaris Archives As mentioned earlier, there was no desire to improve the fundamental nature of archives. They have always had O(n) insert/delete behavior, and for the most part it hasn't mattered. AIX made efforts to improve this, but those efforts did not find widespread adoption. For the purposes of link-editing, which is essentially the only thing that archives are used for, the existing format is adequate, and issues of backward compatibility trump the desire to do something technically better. Widening the existing symbol table format to 64-bits is therefore the obvious way to proceed. For Solaris 11, I implemented that, and I also updated the ar command so that a 64-bit version is run by default. This eliminates the 2 most significant limits to archive size, leaving only the limit on an individual archive member. We only generate a 64-bit symbol table if the archive exceeds 4GB, or when the new -S option to the ar command is used. This maximizes backward compatibility, as an archive produced by Solaris 11 is highly likely to be less than 4GB in size, and will therefore employ the same format understood by older versions of the system. The main reason for the existence of the -S option is to allow us to test the 64-bit format without having to construct huge archives to do so. I don't believe it will find much use outside of that. Other than the new ability to create and use extremely large archives, this change is largely invisible to the end user. When reading an archive, the ar command will transparently accept either form of symbol table. Similarly, the ELF library (libelf) has been updated to understand either format. Users of libelf (such as the link-editor ld) do not need to be modified to use the new format, because these changes are encapsulated behind the existing functions provided by libelf. As mentioned above, this work did not lift the limit on the maximum size of an individual archive member. That limit remains fixed at 4GB for now. This is not because we think objects will never get that large, for the history of computing says otherwise. Rather, this is based on an estimation that single relocatable objects of that size will not appear for a decade or two. A lot can change in that time, and it is better not to overengineer things by writing code that will sit and rot for years without being used. It is not too soon however to have a plan for that eventuality. When the time comes when this limit needs to be lifted, I believe that there is a simple solution that is consistent with the existing format. The archive member header size field is an ASCII string, like the name, and as such, the overflow scheme used for long names can also be used to handle the size. The size string would be placed into the archive string table, and its offset in the string table would then be written into the archive header size field using the same format "/ddd" used for overflowed names.

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  • Resources needed: basics of using make/qmake

    - by Mikey
    I am look for a good book or website that clearly explains the basics of using make, (particularly qmake for Qt development) makefiles, etc. for building C++/Qt executables. I am using open source tools on Ubuntu. Lately have been doing a lot of Qt/C++ development using the CodeLite IDE, which works quite well with Qt, however when I wanted to write my own QObject derivatives with custom signal and slots, I discovered I had to use qmake and I don't know how. (Meanwhile I have been using QtCreator, which handles this, but it not my IDE of choice) I have several books on C++ and Qt but I haven't found that they focus at all on this area. Recommendations please...

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  • Help needed in customizing Ubuntu 13 distribution

    - by Bilal Wajid
    I have been using Ubuntu for over 3 years. I want to custom-build-ubuntu-distribution. I am trying to do the needful using Ubuntu 13.04. I have tried the following:- Remastersys - failed. Relinux - failed. Ubuntu Customization Kit - failed. LiveCDCustomizationFromScratch (help.ubuntu.com) - failed. Kindly guide me how to do this, based on the above failed attempts. I think a manual of how to do it would be very very helpful. Thanks and Best Wishes, B. Wajid

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  • Where can I get a cheap database, no web hosting needed

    - by PhilipK
    I'm building an application which requires a fairly small online MySQL database. I don't need any web hosting. What are some cheap options for an online database? *Edit(a bit more about what I'll be using it for) The database itself is very small it contains market statistics for 5 weeks of time. Once a week the data will be updated, so that it always contains the most recent 5 weeks. Then I will use the data in that to create an XML file which is generated with PHP. The XML file will need to be accessed hundreds-thousands of times per month.*

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  • libgdx rotation (animation, arrays) issues and help needed

    - by johnny-b
    well i am a noob at java and libgdx. i got the homing bullet working with the help of someone. now i am smashing my head as to how i can make it rotate so it faces the ball (which is the main character) when it goes around it or when it is coming towards it. the bullet is facing <--- and the code below is what i have done so far. also i used sprites for the bullet and also animation method. Also how do i make it an array/arraylist which is best so i can have multiple bullets at random or placed places. i tried many things nothing workd :( thank you for the help. // below is the bullet or enemy if you want to call it. public class Bullet extends Sprite { public static final float BULLET_HOMING = 6000; public static final float BULLET_SPEED = 300; private Vector2 velocity; private float lifetime; public Bullet(float x, float y) { velocity = new Vector2(0, 0); setPosition(x, y); } public void update(float delta) { float targetX = GameWorld.getBall().getX(); float targetY = GameWorld.getBall().getY(); float dx = targetX - getX(); float dy = targetY - getY(); float distToTarget = (float) Math.sqrt(dx * dx + dy * dy); dx /= distToTarget; dy /= distToTarget; dx *= BULLET_HOMING; dy *= BULLET_HOMING; velocity.x += dx * delta; velocity.y += dy * delta; float vMag = (float) Math.sqrt(velocity.x * velocity.x + velocity.y * velocity.y); velocity.x /= vMag; velocity.y /= vMag; velocity.x *= BULLET_SPEED; velocity.y *= BULLET_SPEED; Vector2 v = velocity.cpy().scl(delta); setPosition(getX() + v.x, getY() + v.y); setOriginCenter(); setRotation(velocity.angle()); lifetime += delta; setRegion(AssetLoader.bulletAnimation.getKeyFrame(lifetime)); } } // this is where i load the images. public class AssetLoader { public static Animation bulletAnimation; public static Sprite bullet1, bullet2; public static void load() { texture = new Texture(Gdx.files.internal("SpriteN1.png")); texture.setFilter(TextureFilter.Nearest, TextureFilter.Nearest); bullet1 = new Sprite(texture, 380, 350, 45, 20); bullet1.flip(false, true); bullet2 = new Sprite(texture, 425, 350, 45, 20); bullet2.flip(false, true); Sprite[] bullets = { bullet1, bullet2 }; bulletAnimation = new Animation(0.06f, aims); bulletAnimation.setPlayMode(Animation.PlayMode.LOOP); } public static void dispose() { // We must dispose of the texture when we are finished. texture.dispose(); } // this is for the rendering of the images etc public class GameRenderer { private Bullet bullet; private Ball ball; public GameRenderer(GameWorld world) { myWorld = world; cam = new OrthographicCamera(); cam.setToOrtho(true, 480, 320); batcher = new SpriteBatch(); // Attach batcher to camera batcher.setProjectionMatrix(cam.combined); shapeRenderer = new ShapeRenderer(); shapeRenderer.setProjectionMatrix(cam.combined); // Call helper methods to initialize instance variables initGameObjects(); initAssets(); } private void initGameObjects() { ball = GameWorld.getBall(); bullet = myWorld.getBullet(); scroller = myWorld.getScroller(); } private void initAssets() { ballAnimation = AssetLoader.ballAnimation; bulletAnimation = AssetLoader.bulletAnimation; } public void render(float runTime) { Gdx.gl.glClearColor(0, 0, 0, 1); Gdx.gl.glClear(GL30.GL_COLOR_BUFFER_BIT); batcher.begin(); // Disable transparency // This is good for performance when drawing images that do not require // transparency. batcher.disableBlending(); // The ball needs transparency, so we enable that again. batcher.enableBlending(); batcher.draw(AssetLoader.ballAnimation.getKeyFrame(runTime), ball.getX(), ball.getY(), ball.getWidth(), ball.getHeight()); batcher.draw(AssetLoader.bulletAnimation.getKeyFrame(runTime), bullet.getX(), bullet.getY()); // End SpriteBatch batcher.end(); } } // this is to load the image etc on the screen i guess public class GameWorld { public static Ball ball; private Bullet bullet; private ScrollHandler scroller; public GameWorld() { ball = new Ball(480, 273, 32, 32); bullet = new Bullet(10, 10); scroller = new ScrollHandler(0); } public void update(float delta) { ball.update(delta); bullet.update(delta); scroller.update(delta); } public static Ball getBall() { return ball; } public ScrollHandler getScroller() { return scroller; } public Bullet getBullet() { return bullet; } } so there is the whole thing. the images are loaded via the AssetLoader then to the GameRenderer and GameWorld via the Bullet class. i am guessing that is how it is. sorry newbie so still learning. thank you in advace for the help or any advice.

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  • C IDE for Mac needed

    - by StasM
    I'm looking for heavy-duty C/C++ IDE for Mac that would satisfy the following criteria: Work with big projects (~5000 files, some of them 100K big) efficiently. Have good navigation both file-based and symbol-based - i.e. "go to file", "go to function" etc. with autocompletion support. Support for "go to declaration/definition" for symbols - functions, structures, etc. Auto-adding new files in folders already in the project. Support for code completion for values, function names, etc. At least rudimentary CPP macro understanding - i.e. #define foo bar then foo() should take me either to #define or to actual bar. I understand full CPP parsing may be hard, but I hope for at least the obvious cases. Support for displaying parameter names/types by function name, preferably - integrated with the previous item, for functions defined in the project. Support for libc would be nice too :) (optional) Cross-project search support (I can manage with grep -r if everything else works) (optional) SVN support, at least to some extent (update, commit, mark updated) Is there such editor around? Free would be nice, but I'm ready to part with some money if it's good enough. I'm using TextMate now but I'm not satisfied with it. Tried Xcode but it seems to not be able to handle a large project - it just crashed...

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  • Error "fixing recursive fault but reboot is needed"

    - by Gordon
    I am trying to install ubuntu for the first time. (long time windows user, first time linux!) Version = 11.04 Hardware = Acer Travelmate 4050 I can boot from USB or CD and it loads fine I have installed and reinstalled several times from both USB and CD and it completes correctly However, when I boot from the HDD I get the above error I don't see any errors like "kernel panic" mentioned elsewhere It happens whether I boot with AC adapter in or out and also with adapter in but battery out Not sure how to get further info to help with diagnosis Suggestions?

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  • Centralized Project Management Brings Needed Cost Controls to Growing Brazilian Firm

    - by Melissa Centurio Lopes
    Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Fast growth and a significant increase in business activities were creating project management challenges for CPqD, a developer of innovative information and communication technologies for large Brazilian organizations. To bring greater efficiency and centralized project management capabilities to its operations, CPqD chose Oracle’s Primavera P6 Enterprise Project Portfolio Management. “Oracle Primavera is an essential tool for our day-to-day business, and I notice the effort Oracle makes to constantly innovate and to add more functionality in an increasingly shorter period of time,” says Márcio Alexandre da Silva, IT department project coordinator, CPqD. He explains that before CPqD implemented the Oracle solution, the company did not have a corporate view of projects. “Our project monitoring was decentralized and restricted to each coordinator,” the project coordinator says. “With the Oracle solution, we achieved actual shared management, more control, and budgets that stay within projections.” Among the benefits that CPqD now enjoys are The ability to more effectively identify how employees are allocated, enabling managers to increase or reduce resources based on project scope, as well as secure the resources required for unexpected projects and demands A 75 percent reduction in the time it takes to collect project data and indicators—automated and centralized collection means project coordinators no longer have to manually compile information that was spread among various systems Read the complete CPqD company snapshot Read more in the October Edition of the quarterly Information InDepth EPPM Newsletter Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}

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  • Email provider - suggestions needed

    - by Christian Fazzini
    We are looking for a good way to have email support. In theory, we need to allow end-users to send emails directly to support and careers. i.e. support@domain_name_here.com and careers@domain_name_here.com. Second, we need to provide emails to our staff. So each staff member has their own email address. i.e. joe@domain_name_here.com, meghan@domain_name_here.com, etc. Google Apps is one that we are considering. However, they are charging $50 per user, per year. Not so bad, considering the quality and the features they offer. However, there are also cheaper alternatives. i.e. my domain registrar offers an email plan for $20 / year / 10 emails. Go Daddy has a number of plans and still a lot more affordable than Google Apps. So far Namecheap and Go Daddy are the only ones I have looked at for email plans. Is it worth signing up with Google Apps? Or are there better alternatives? Your thoughts?

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  • Is a coding standard even needed any more?

    - by SomeKittens
    I know that it's been proven that a coding standard helps enormously. However, there are many different tools and IDEs that will format to whatever standard the programmer prefers. So long as the code's neat/commented (and not a spaghetti mess), I don't see the need for a coding standard. Are there any arguments for the development of a coding standard (we don't have one, but I was looking into creating one)?

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  • Is a coding standard even needed anymore?

    - by SomeKittens
    I know that it's been proven that a coding standard helps enormously. However, there are many different tools and IDEs that will format to whatever standard the programmer prefers. So long as the code's neat/commented (and not a spaghetti mess), I don't see the need for a coding standard. Are there any arguments for the development of a coding standard (we don't have one, but I was looking into creating one)?

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  • Large sparse (stiff) ODE system needed for testing

    - by macydanim
    I hope this is the right place for this question. I have been working on a sparse stiff implicit ODE solver and have finished the code so far. I now tested the solver with the Van der Pol equation, and another stiff problem, which is of dimension 4. But to perform better tests I am searching for a bigger system. I'm thinking of the order N = 100...1000, if possible stiff and sparse. Does anybody have an example I could use? I really don't know where to search.

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  • When is a Use Case layer needed?

    - by Meta-Knight
    In his blog post The Clean Architecture Uncle Bob suggests a 4-layer architecture. I understand the separation between business rules, interfaces and infrastructure, but I wonder if/when it's necessary to have separate layers for domain objects and use cases. What added value will it bring, compared to just having the uses cases as "domain services" in the domain layer? The only useful info I've found on the web about a use case layer is an article by Martin Fowler, who seems to contradict Uncle Bob about its necessity: At some point I may run into the problems, and then I'll make a Use Case Controller - but only then. And even when I do that I rarely consider the Use Case Controllers to occupy a separate layer in the system architecture. Edit: I stumbled upon a video of Uncle Bob's Architecture: The Lost Years keynote, in which he explains this architecture in depth. Very informative.

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  • Xubuntu 14.04 with Compton, strange screen tearing, only when playing videos though (advice needed)

    - by LinuxDudester
    Hello beloved community, Yet again I am in need of your great expertise. I ran into a very strange issue and just can't wrap my mind around it. I'm running Xubuntu 14.04 exclusively, with Compton installed. The OS runs great and I have absolutely no screen tearing when I move my windows around, scroll in my web browser, work in Gimp or Photoshop (wine) or even when I play very graphic demanding games, like Metro Last Light, Euro Truck Driver 2 and so on. There's not a tiny bit of tearing to see, but as soon as I play videos, in xbmc, vlc or parole media player the tearing begins (strangely enough this does not apply to youtube videos). I followed all available workarounds on askubuntu and the ubuntu forum,like the 50-xserver-command.conf, startx /etc/X11/Xsession /usr/bin/xbmc-standalone -- -bs or libsdl1.2debian fix and many more, but to no avail. I also tried the Open Source Nouveau display drivers as well, but for some odd reason they don't work so great on my system or at least with my graphics card. Even with Compton installed and configured, I have an extreme amount of screen tearing, as soon as I switch to the proprietary Nvidia drives the screen tearing is gone completely, except for the video playback with xbmc, vlc or parole media player. System info for your reference: OS: Xubuntu 14.04 Linux-x86_64 - Processor: Intel Core i7-4770S CPU @ 3.10GHz - Ram: 16 GB - GeForce GT 750M 1024 MB - Nvidia Driver: 331.38 Has anyone experienced such an odd issue or do you have any advice on how I could fix this? I would appreciate any help! Have a nice day!

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  • Advice needed: Software Development [closed]

    - by Hunter McMillen
    I recently graduated from college with a B.S. in Computer Science, and am now currently attending the same college to get an M.S. in Computer Science. I know lots of things about Computer Science and programming but throughout all of my coursework I have never had to develop a single complete application, the projects were always relatively small (~300-500 lines of code). Basically, my overall I am about to have these two degrees and I feel like I don't know anything about software development or design; which doesn't make a whole lot of sense. I am looking for ways to fill in the gaps in my knowledge, I would love people's advice on these questions: 1) How do you design good software? Where do you start? 2) What makes a good software developer? Sorry for the convoluted question, but in my mind it is a convoluted situation. Thanks Edit Thanks everyone for your advice.

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  • Help needed on a UI/Developer Interview

    - by AJ Seth
    I have a phone interview with a major Internet company and it is a mostly front-end developer position. If anyone has experience with UI/developer interviews and can give some advice/questions asked etc. that'll be great. Additionally, what resources can be read and reviewed for the following: Designing for performance, scalability and availability Internet and OS security fundamentals EDIT: Now I am told that the interview I am told will be mostly on coding, Data Structures, design questions etc. Anyone?

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  • Help needed throwing a ball in AS3

    - by Opoe
    I'm working on a flash game, coding on the time line. What I'm trying to accomplish is the following: With the mouse you swing and throw/release a ball which bounces against the walls and eventualy comes to point where it lays still (like a real ball). I allmost had it working, but now the ball sticks to the mouse, in stead of being released, my question to you is: Can you help me make this work and explain to me what I did wrong? You can simply preview my code by making a movieclip named 'circle' on a 550x400 stage. stage.addEventListener(Event.ENTER_FRAME, circle_update); var previousPostionX:Number; var previousPostionY:Number; var throwSpeedX:Number; var throwSpeedY:Number; var isItDown:Boolean; var xSpeed:Number = 0; var ySpeed:Number = 0; var friction:Number = 0.96; var offsetX:Number = 0; var offsetY:Number = 0; var newY:Number = 0; var oldY:Number = 0; var newX:Number = 0; var oldX:Number = 0; var dragging:Boolean; circle.buttonMode = true; circle.addEventListener(MouseEvent.MOUSE_DOWN, mouseDownHandler); circle.addEventListener(Event.ENTER_FRAME, throwcircle); circle.addEventListener(MouseEvent.MOUSE_DOWN, clicked); circle.addEventListener(MouseEvent.MOUSE_UP, released); function mouseDownHandler(e:MouseEvent):void { dragging = true; stage.addEventListener(MouseEvent.MOUSE_UP, mouseUpHandler); offsetX = mouseX - circle.x; offsetY = mouseY - circle.y; } function mouseUpHandler(e:MouseEvent):void { dragging = false; } function throwcircle(e:Event) { circle.x += xSpeed; circle.y += ySpeed; xSpeed *= friction; ySpeed *= friction; } function changeFriction(e:Event):void { friction = e.target.value; trace(e.target.value); } function circle_update(e:Event){ if ( dragging == true ) { circle.x = mouseX - offsetX; circle.y = mouseY - offsetY; } if(circle.x + (circle.width * 0.50) >= 550){ circle.x = 550 - circle.width * 0.50; } if(circle.x - (circle.width * 0.50) <= 0){ circle.x = circle.width * 0.50; } if(circle.y + (circle.width * 0.50) >= 400){ circle.y = 400 - circle.height * 0.50; } if(circle.y - (circle.width * 0.50) <= 0){ circle.y = circle.height * 0.50; } } function clicked(theEvent:Event) { isItDown =true; addEventListener(Event.ENTER_FRAME, updateView); } function released(theEvent:Event) { isItDown =false; } function updateView(theEvent:Event) { if (isItDown==true){ throwSpeedX = mouseX - previousPostionX; throwSpeedY = mouseY - previousPostionY; circle.x = mouseX; circle.y = mouseY; } else{ circle.x += throwSpeedX; circle.y += throwSpeedY; throwSpeedX *=0.9; throwSpeedY *=0.9; } previousPostionX= circle.x; previousPostionY= circle.y; }

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  • Video conference/chat tool that can be embedded in own website needed

    - by Olaf
    We are looking for a means (a tool, a commercial service) to enable a closed user group to start a live video conference in a browser, as part of the company website. Something like Skype, but embedded and available for everybody that has access to the page into which the tool is embedded. Most services require registration and the creation of a chat room on their website, or, as Skype or similar solutions, the installation of an extra software. What we need is a solution with some kind of a "hidden login", performed by the site's client script (which knows who the user is and forwards the credentials to the service). Any suggestion?

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  • Help needed with pyparsing [closed]

    - by Zearin
    Overview So, I’m in the middle of refactoring a project, and I’m separating out a bunch of parsing code. The code I’m concerned with is pyparsing. I have a very poor understanding of pyparsing, even after spending a lot of time reading through the official documentation. I’m having trouble because (1) pyparsing takes a (deliberately) unorthodox approach to parsing, and (2) I’m working on code I didn’t write, with poor comments, and a non-elementary set of existing grammars. (I can’t get in touch with the original author, either.) Failing Test I’m using PyVows to test my code. One of my tests is as follows (I think this is clear even if you’re unfamiliar with PyVows; let me know if it isn’t): def test_multiline_command_ends(self, topic): output = parsed_input('multiline command ends\n\n',topic) expect(output).to_equal( r'''['multiline', 'command ends', '\n', '\n'] - args: command ends - multiline_command: multiline - statement: ['multiline', 'command ends', '\n', '\n'] - args: command ends - multiline_command: multiline - terminator: ['\n', '\n'] - terminator: ['\n', '\n']''') But when I run the test, I get the following in the terminal: Failed Test Results Expected topic("['multiline', 'command ends']\n- args: command ends\n- command: multiline\n- statement: ['multiline', 'command ends']\n - args: command ends\n - command: multiline") to equal "['multiline', 'command ends', '\\n', '\\n']\n- args: command ends\n- multiline_command: multiline\n- statement: ['multiline', 'command ends', '\\n', '\\n']\n - args: command ends\n - multiline_command: multiline\n - terminator: ['\\n', '\\n']\n- terminator: ['\\n', '\\n']" Note: Since the output is to a Terminal, the expected output (the second one) has extra backslashes. This is normal. The test ran without issue before this piece of refactoring began. Expected Behavior The first line of output should match the second, but it doesn’t. Specifically, it’s not including the two newline characters in that first list object. So I’m getting this: "['multiline', 'command ends']\n- args: command ends\n- command: multiline\n- statement: ['multiline', 'command ends']\n - args: command ends\n - command: multiline" When I should be getting this: "['multiline', 'command ends', '\\n', '\\n']\n- args: command ends\n- multiline_command: multiline\n- statement: ['multiline', 'command ends', '\\n', '\\n']\n - args: command ends\n - multiline_command: multiline\n - terminator: ['\\n', '\\n']\n- terminator: ['\\n', '\\n']" Earlier in the code, there is also this statement: pyparsing.ParserElement.setDefaultWhitespaceChars(' \t') …Which I think should prevent exactly this kind of error. But I’m not sure. Even if the problem can’t be identified with certainty, simply narrowing down where the problem is would be a HUGE help. Please let me know how I might take a step or two towards fixing this.

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  • Only 5 days left...your vote is needed!

    - by mvaughan
         By Misha Vaughan, Oracle Applications User Experience It is a bit early for the voting season here in the U.S., but there is a very important (to me) voting window now upon us. Until Aug. 31, the public gets to vote on submissions to South by Southwest (SXSW) Interactive in Austin, Texas, in March 2013. This is a thought-leading software conference discussing the up-and-coming trends in industry. I have attended the interactive and the music portions of SXSW before, but I have never attempted a submission. This is my first year trying.  I am building on the themes from this conversation on simplicity with Jeremy Ashley for Oracle OpenWorld 2012. The SXSW session will be a chance to share best practices for moving designs that focus on simplicity successfully through an organization. Please take a moment and cast your vote.  Help me get Oracle on the roster at SXSW! There are only five days left to vote! My colleague Ultan O’Broin has also submitted, and I encourage you to vote for his sessions as well. 

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  • Drupal 7 Advice Needed: "Portal" Creation

    - by WernerCD
    Question: What is the best game plan for building what I want. I'm rebuilding the company intranet and am trying to get our "Portals" system re-created in Drupal. I'm trying to learn Panels, because thats what I think would do this, but I just can't seem to get it working. Menu at top, drop down lists for various webpages, tools, internal applications... and Department Portals. When you click on a department portal, you get the same menu at top... and on the main part of the page you have a menu on the left, with content on the right. Menu stays on the left, content loads next to it. Each Portal has its own menu and content (least of which is "Home"). Ultimately, I'd like to be able to say - users with role "Foo" can add/edit/delete Portal Bar. - Each Portal starts with a "Home" - Each Portal has its own Menu tree's. (Picture 2 above has a < ul for video tutorials that would be a second level menu. So more than one deep.) - Content on the right side of the portal should be flexible (Video, PDF via fileviewer, etc) - Portal Bar should have its own Folder to contain it's content. I'm trying to do this in Panels, but I can't seem to put the pieces together in my mind and in practice. I hope I'm making sense, because the dizzying array of stuff is killing me lol.

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  • Is it needed to have your blog title and description in H1 and H2

    - by Saif Bechan
    I have read an article that states that it is not necessary to have your blog title and description on your website at all. Just have the titles of the posts in h1, on the index and the post page. And on the post page have your different sections started with h2. Widget headers start with h3. Title and description are most of the time in the logo image. I have looked at the source of my favorite blog, http://net.tutsplus.com, and I see they do the same. Is this recommended?

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  • Working Abroad Advice Needed

    - by RBA
    Hi, First of all, Happy New Year everybody! I wish you for 2011 all the best! For several years I was thinking about to work abroad, and I want to make this step(to work in a/several foreign countries, for several years). I am a Software Developer with a Bachelor of Engineering in Computer Science, with a +4 years of experience in Delphi(and small working experience in other programming languages). Until now I've applied at aprox. 100 positions over the world, and I've been contacted by 4-5 hiring managers. Our technical discussions went good, but then we reached at working visa 'problem'. I don't have legal/health problems, but I don't poses a working permit in other countries except Romania. I've been reading several forums concerning the working visas (here I take out working visa for US or other 'hard to get visa' countries), and there are several steps which companies must do (so I can take out the bureaucracy problem) to make the papers. Concerning the cost of a visa, this goes up to one medium salary from that country(in most of the cases). I've been working for the last years with different clients, from a wide variety of countries, and I don't believe I will have problems with integration in a foreign country So, the problem is that the market don't need Delphi Developers (there is a small amount of open positions on the recruiting sites), and I should start learning other programming language(all the time is better to know other programming languages - but to master it, requires some time) with a higher market 'rank' (Java/C#/etc), OR the problem is only concerning the working visa, and maybe the reticence of the employer to foreign possible candidates? I'm asking this especially for those users who made this step in their life or they want to make it in the future. Best regards,

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  • Decorator not calling the decorated instance - alternative design needed

    - by Daniel Hilgarth
    Assume I have a simple interface for translating text (sample code in C#): public interface ITranslationService { string GetTranslation(string key, CultureInfo targetLanguage); // some other methods... } A first simple implementation of this interface already exists and simply goes to the database for every method call. Assuming a UI that is being translated at start up this results in one database call per control. To improve this, I want to add the following behavior: As soon as a request for one language comes in, fetch all translations from this language and cache them. All translation requests are served from the cache. I thought about implementing this new behavior as a decorator, because all other methods of that interface implemented by the decorater would simple delegate to the decorated instance. However, the implementation of GetTranslation wouldn't use GetTranslation of the decorated instance at all to get all translations of a certain language. It would fire its own query against the database. This breaks the decorator pattern, because every functionality provided by the decorated instance is simply skipped. This becomes a real problem if there are other decorators involved. My understanding is that a Decorator should be additive. In this case however, the decorator is replacing the behavior of the decorated instance. I can't really think of a nice solution for this - how would you solve it? Everything is allowed, even a complete re-design of ITranslationService itself.

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  • Suggestions needed on an architecture for a multiple clients and customisable web application

    - by ValidfroM
    Our product is a web based course managemant system. We have 10+ clients and in future we may get more clients. (Asp.net,SQL Server) Currently if one of our customers need extra functionality or customised business logic, we will change the db schema and code to meet the needs. (we only have one branch code base and one database schema) To make the change wont affect each others route, we use a client flag, which defined in a web config file, thus those extra fields and biz logic only applied to a particular customer's system. if(ClientId = 'ABC') { //DO ABC Stuff } else { //Normal Route } One of our senior colleagues said, in this way, small company like us can save resources on supporting multiple resources. But what I feel is, this strategy makes our code and database even harder to maintain. Anyone there crossed similar situation? How do you handle that?

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