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• Examples of localization in Perl using gettext and Locale::TextDomain, with fallback if Locale::Text

  - by Jakub Narebski

  The "On the state of i18n in Perl" blog post from 26 April 2009 recommends using Locale::TextDomain module from libintl-perl distribution for l10n / i18n in Perl. Besides I have to use gettext anyway, and gettext support in Locale::Messages / Locale::TextDomain is more natural than in gettext emulation in Locale::Maketext. The subsection "15.5.18 Perl" in chapter "15 Other Programming Languages" in GNU gettext manual says: Portability The libintl-perl package is platform independent but is not part of the Perl core. The programmer is responsible for providing a dummy implementation of the required functions if the package is not installed on the target system. However neither of two examples in examples/hello-perl in gettext sources (one using lower level Locale::Messages, one using higher level Locale::TextDomain) includes detecting if the package is installed on the target system, and providing dummy implementation if it is not. What is complicating matter (with respect to detecting if package is installed or not) is the following fragment of Locale::TextDomain manpage: SYNOPSIS use Locale::TextDomain ('my-package', @locale_dirs); use Locale::TextDomain qw (my-package); USAGE It is crucial to remember that you use Locale::TextDomain(3) as specified in the section "SYNOPSIS", that means you have to use it, not require it. The module behaves quite differently compared to other modules. Could you please tell me how one should detect if libintl-perl is present on target system, and how to provide dummy fallthrough implementation if it is not installed? Or give examples of programs / modules which do this?

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• Ellipsize not working for textView inside custom listView

  - by aspartame

  Hi, I have a listView with custom objects defined by the xml-layout below. I want the textView with id "info" to be ellipsized on a single line, and I've tried using the attributes android:singleLine="true" android:ellipsize="end" without success. If I set the layout_width to a fixed width like e.g. android:layout_width="100px" the text is truncated fine. But for portability reasons this is not an acceptable solution. Can you spot the problem? <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="wrap_content" android:paddingBottom="5px" > <TextView android:id="@+id/destination" android:layout_width="fill_parent" android:layout_height="wrap_content" android:textSize="22dp" android:paddingLeft="5px" /> <TextView android:id="@+id/date" android:layout_width="fill_parent" android:layout_height="wrap_content" android:textSize="15dp" android:paddingLeft="5px" /> <TableLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/info_table" android:layout_width="fill_parent" android:layout_height="fill_parent" android:paddingLeft="5px" android:paddingTop="10px" > <TableRow> <TextView android:id="@+id/driver_label" android:gravity="right" android:paddingRight="5px" android:text="@string/driver_label" /> <TextView android:id="@+id/driver" /> </TableRow> <TableRow> <TextView android:id="@+id/passenger_label" android:gravity="right" android:paddingRight="5px" android:text="@string/passenger_label" /> <TextView android:id="@+id/passengers" /> </TableRow> <TableRow> <TextView android:id="@+id/info_label" android:gravity="right" android:paddingRight="5px" android:text="@string/info_label"/> <TextView android:id="@+id/info" android:layout_width="fill_parent" android:singleLine="true" android:ellipsize="end" /> </TableRow> </TableLayout>

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• Hidden features of Perl?

  - by Adam Bellaire

  What are some really useful but esoteric language features in Perl that you've actually been able to employ to do useful work? Guidelines: Try to limit answers to the Perl core and not CPAN Please give an example and a short description Hidden Features also found in other languages' Hidden Features: (These are all from Corion's answer) C# Duff's Device Portability and Standardness Quotes for whitespace delimited lists and strings Aliasable namespaces Java Static Initalizers JavaScript Functions are First Class citizens Block scope and closure Calling methods and accessors indirectly through a variable Ruby Defining methods through code PHP Pervasive online documentation Magic methods Symbolic references Python One line value swapping Ability to replace even core functions with your own functionality Other Hidden Features: Operators: The bool quasi-operator The flip-flop operator Also used for list construction The ++ and unary - operators work on strings The repetition operator The spaceship operator The || operator (and // operator) to select from a set of choices The diamond operator Special cases of the m// operator The tilde-tilde "operator" Quoting constructs: The qw operator Letters can be used as quote delimiters in q{}-like constructs Quoting mechanisms Syntax and Names: There can be a space after a sigil You can give subs numeric names with symbolic references Legal trailing commas Grouped Integer Literals hash slices Populating keys of a hash from an array Modules, Pragmas, and command-line options: use strict and use warnings Taint checking Esoteric use of -n and -p CPAN overload::constant IO::Handle module Safe compartments Attributes Variables: Autovivification The $[ variable tie Dynamic Scoping Variable swapping with a single statement Loops and flow control: Magic goto for on a single variable continue clause Desperation mode Regular expressions: The \G anchor (?{}) and '(??{})` in regexes Other features: The debugger Special code blocks such as BEGIN, CHECK, and END The DATA block New Block Operations Source Filters Signal Hooks map (twice) Wrapping built-in functions The eof function The dbmopen function Turning warnings into errors Other tricks, and meta-answers: cat files, decompressing gzips if needed Perl Tips See Also: Hidden features of C Hidden features of C# Hidden features of C++ Hidden features of Java Hidden features of JavaScript Hidden features of Ruby Hidden features of PHP Hidden features of Python

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• ClassCastException When Calling an EJB that Exists on Same Server

  - by aaronvargas

  I have 2 ejbs. Ejb-A that calls Ejb-B. They are not in the same Ear. For portability Ejb-B may or may not exist on the same server. (There is an external property file that has the provider URLs of Ejb-B. I have no control over this.) Example Code: in Ejb-A EjbBDelegate delegateB = EjbBDelegateHelper.getRemoteDelegate(); // lookup from list of URLs from props... BookOfMagic bom = delegateB.getSomethingInteresting(); Use Cases/Outcomes: When Ejb-B DOES NOT EXIST on the same server as Ejb-A, everything works correctly. (it round-robbins through the URLs) When Ejb-B DOES EXIST on the same server, and Ejb-A happens to call Ejb-B on the same server, everything works correctly. When Ejb-B DOES EXIST on the same server, and Ejb-A calls Ejb-B on a different server, I get: javax.ejb.EJBException: nested exception is: java.lang.ClassCastException: $Proxy126 java.lang.ClassCastException: $Proxy126 NOTE (not normal use case but may help): When Ejb-B DOES EXIST on the same server, and this server is NOT listed in the provider URLs for Ejb-B, and Ejb-A calls Ejb-B on a different server, I get the same Exception as above. I'm using Weblogic 10.0, Java 5, EJB3 Basically, if Ejb-B Exists on the server, it must be called ONLY on that server. Which leads me to believe that the class is getting loaded by a local classloader (on deployment?), then when called remotely, a different classloader is loading it. (causing the Exception) But it should work, as it should be Serialized into the destination classloader... What am I doing wrong?? Also, when reproducing this locally, Ejb-A would favor the Ejb-B on the same server, so it was difficult to reproduce. But this wasn't the case on other machines.

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• How bad is code using std::basic_string<t> as a contiguous buffer?

  - by BillyONeal

  I know technically the std::basic_string template is not required to have contiguous memory. However, I'm curious how many implementations exist for modern compilers that actually take advantage of this freedom. For example, if one wants code like the following it seems silly to allocate a vector just to turn around instantly and return it as a string: DWORD valueLength = 0; DWORD type; LONG errorCheck = RegQueryValueExW( hWin32, value.c_str(), NULL, &type, NULL, &valueLength); if (errorCheck != ERROR_SUCCESS) WindowsApiException::Throw(errorCheck); else if (valueLength == 0) return std::wstring(); std::wstring buffer; do { buffer.resize(valueLength/sizeof(wchar_t)); errorCheck = RegQueryValueExW( hWin32, value.c_str(), NULL, &type, &buffer[0], &valueLength); } while (errorCheck == ERROR_MORE_DATA); if (errorCheck != ERROR_SUCCESS) WindowsApiException::Throw(errorCheck); return buffer; I know code like this might slightly reduce portability because it implies that std::wstring is contiguous -- but I'm wondering just how unportable that makes this code. Put another way, how may compilers actually take advantage of the freedom having noncontiguous memory allows? Oh: And of course given what the code's doing this only matters for Windows compilers.

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• Flex 4 vs JavaScript Options (Cappuccino, JQuery, etc.)

  - by user320681

  Rehashing an older post: http://stackoverflow.com/questions/1570070/jquery-vs-flex-choosing-a-platform-for-saas We are preparing to develop an application that is exceptionally dynamic and interactive. It's particularly heavy on the graphics side. We are 85% convinced that Adobe Flash built atop Flex is the right path to take, however Cappuccino is quite nice and seems as though it may be able to nearly fit the bill. The only pause we have right now is portability for the iPhone. With the lack of blessings from Apple we will most certainly have to create a 2nd interface for the iPhone for the site, however... Having two interfaces may not be bad as it will likely have to be custom anyway to take advantage of the differences that it affords. Any further thoughts or reevaluations of points enumerated in the noted article? Further, Flex 4 adds a lot of strength to the position mentioned previously regarding UI development. Fx4 is very nice vs Fx3 and shaves 90% from the development time when coupled with Flash Catalyst, which is not really always fully appropriate, but with some round trip tricks it seems as though it can cut through things rather well... Please do advise and many thanks.

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• What AOP tools exist for doing aspect-oriented programming at the assembly language level against x8

  - by JohnnySoftware

  Looking for a tool I can use to do aspect-oriented programming at the assembly language level. For experimentation purposes, I would like the code weaver to operate native application level executable and dynamic link libraries. I have already done object-oriented AOP. I know assembly language for x86 and so forth. I would like to be able to do logging and other sorts of things using the familiar before/after/around constructs. I would like to be able to specify certain instructions or sequences/patterns of consecutive instructions as what to do a pointcut on since assembly/machine language is not exactly the most semantically rich computer language on the planet. If debugger and linker symbols are available, naturally, I would like to be able to use them to identify subroutines' entry points , branch/call/jump target addresses, symbolic data addresses, etc. I would like the ability to send notifications out to other diagnostic tools. Thus, support for sending data through connection-oriented sockets and datagrams is highly desirable. So is normal logging to files, UI, etc. This can be done using the action part of an aspect to make a function call, but then there are portability issues so the tool needs to support a flexible, well-abstracted logging/notifying mechanism with a clean, simple yet flexible. The goal is rapid-QA. The idea is to be able to share aspect source code braodly within communties as well as publicly. So, there needs to be a declarative security policy file that users can share. This insures that nothing untoward that is hidden directly or indirectly in an aspect source file slips by the execution manager. The policy file format needs to be simple to read, write, modify, understand, type-in, edit, and generate. Sort of like Java .policy files. Think the exact opposite of anything resembling XML Schema files and you get the idea. Is there such a tool in existence already?

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• Cross-platform game development: ease of development vs security

  - by alcuadrado

  Hi, I'm a member and contributor of the Argentum Online (AO) community, the first MMORPG from Argentina, which is Free Software; which, although it's not 3D, it's really addictive and has some dozens of thousands of users. Really unluckily AO was developed in Visual Basic (yes, you can laugh) but the former community, so imagine, the code not only sucks, it has zero portability. I'm planning, with some friends to rewrite the client, and as a GNU/Linux frantic, want to do it cross-platform. Some other people is doing the same with the server in Java. So my biggest problem is that we would like to use a rapid development language (like Java, Ruby or Python) but the client would be pretty insecure. Ruby/Python version would have all it's code available, and the Java one would be easily decompilable (yes, we have some crackers in the community) We have consider the option to implement the security module in C/C++ as a dynamic library, but it can be replaced with a custom one, so it's not really secure. We are also considering the option of doing the core application in C++ and the GUI in Ruby/Python. But haven't analysed all it's implications yet. But we really don't want to code the entire game in C/C++ as it doesn't need that much performance (the game is played at 18fps on average) and we want to develop it as fast as possible. So what would you choose in my case? Thank you!

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• The "first past the post election" query problem

  - by MPelletier

  This problem may seem like school work, but it isn't. At best it is self-imposed school work. I encourage any teachers to take is as an example if they wish. "First past the post" elections are single-round, meaning that whoever gets the most votes win, no second rounds. Suppose a table for an election. CREATE TABLE ElectionResults ( DistrictHnd INTEGER NOT NULL, PartyHnd INTEGER NOT NULL, CandidateName VARCHAR2(100) NOT NULL, TotalVotes INTEGER NOT NULL, PRIMARY KEY DistrictHnd, PartyHnd); The table has two foreign keys: DistrictHnd points to a District table (lists all the different electoral districts) and PartyHnd points to a Party table (lists all the different political parties). I won't bother with other tables here, joining them is trivial. This is just a wee bit of context. The question: What SQL query will return a table listing the DistrictHnd, PartyHnd, CandidateName and TotalVotes of the winners (max votes) in each District? This does not suppose any particular database system. If you wish to stick to a particular implementation of SQL, go the way of SQLite and MySQL. If you can devise a better schema (or an easier one), that is acceptable too. Criteria: simplicity, portability to other databases.

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• Modify Executing Jar file

  - by pinkynobrain

  Hello Stack Overflow friends. I have a simple problem which i fear doesnt have a simple solution and i need advice as to how to proceed. I am developing a java application packaged as and executable JAR but it requires to modify some of its JAR file contents during execution. At this stage i hit a problem because some OS lock the file preventing writes to it. It is essential that the user sees an updated version of the jar file by the time the application exits allthough i can be pretty flexible as to how to achieve this. A clean and efficient solution is obviously prefereable but portability is the only hard requirement. The following are three approaches i can see to solving the problem, feel free to comment on them or suggest others. Tell Java to unlock the JAR file for writing(this doesnt seem possible but it would be the easyest solution) Copy the executable class files to a tempory file on application startup, use a class loader to load these files and unload the ones from the initial JAR file.(Not had much experience with the classloaders but hopefully the JVM would then be smart enough to realize that the original JAR is nolonger in use and so unlock it) Put a Second executable JAR File inside the First, on startup extract the inner jar to e temporaryfile, invoke a new java process and pass it the location of the Outer JAR, first process exits, second process modifys the Outer jar unincumbered.(This will work but im not sure there is a platform independant way of one java app invoking another) I know this is a weird question but any help would be appreciated.

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• setcontext and makecontext to call a generic function pointer

  - by Simone Margaritelli

  In another question i had the problem to port the code unsigned long stack[] = { 1, 23, 33, 43 }; /* save all the registers and the stack pointer */ unsigned long esp; asm __volatile__ ( "pusha" ); asm __volatile__ ( "mov %%esp, %0" :"=m" (esp)); for( i = 0; i < sizeof(stack); i++ ){ unsigned long val = stack[i]; asm __volatile__ ( "push %0" :: "m"(val) ); } unsigned long ret = function_pointer(); /* restore registers and stack pointer */ asm __volatile__ ( "mov %0, %%esp" :: "m" (esp) ); asm __volatile__ ( "popa" ); To a 64bit platform and many guys told me i should use the setcontext and makecontext functions set instead due to the calling conversion differences between 32 and 64 bits and portability issues. Well, i really can't find any useful documentation online, or at least not the kind i need to implement this, so, how can i use those functions to push arguments onto the stack, call a generic function pointer, obtain the return value and then restore the registers?

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• Embedded non-relational (nosql) data store

  - by Igor Brejc

  I'm thinking about using/implementing some kind of an embedded key-value (or document) store for my Windows desktop application. I want to be able to store various types of data (GPS tracks would be one example) and of course be able to query this data. The amount of data would be such that it couldn't all be loaded into memory at the same time. I'm thinking about using sqlite as a storage engine for a key-value store, something like y-serial, but written in .NET. I've also read about FriendFeed's usage of MySQL to store schema-less data, which is a good pointer on how to use RDBMS for non-relational data. sqlite seems to be a good option because of its simplicity, portability and library size. My question is whether there are any other options for an embedded non-relational store? It doesn't need to be distributable and it doesn't have to support transactions, but it does have to be accessible from .NET and it should have a small download size. UPDATE: I've found an article titled SQLite as a Key-Value Database which compares sqlite with Berkeley DB, which is an embedded key-value store library.

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• ClassCastException When Calling an EJB Remotely that Exists on Same Server

  - by aaronvargas

  I have 2 ejbs. Ejb-A that calls Ejb-B. They are not in the same Ear. For portability Ejb-B may or may not exist on the same server. (There is an external property file that has the provider URLs of Ejb-B. I have no control over this.) Example Code: in Ejb-A EjbBDelegate delegateB = EjbBDelegateHelper.getRemoteDelegate(); // lookup from list of URLs from props... BookOfMagic bom = delegateB.getSomethingInteresting(); Use Cases/Outcomes: When Ejb-B DOES NOT EXIST on the same server as Ejb-A, everything works correctly. (it round-robbins through the URLs) When Ejb-B DOES EXIST on the same server, and Ejb-A happens to call Ejb-B on the same server, everything works correctly. When Ejb-B DOES EXIST on the same server, and Ejb-A calls Ejb-B on a different server, I get: javax.ejb.EJBException: nested exception is: java.lang.ClassCastException: $Proxy126 java.lang.ClassCastException: $Proxy126 I'm using Weblogic 10.0, Java 5, EJB3 Basically, if Ejb-B Exists on the server, it must be called ONLY on that server. Which leads me to believe that the class is getting loaded by a local classloader (on deployment?), then when called remotely, a different classloader is loading it. (causing the Exception) But it should work, as it should be Serialized into the destination classloader... What am I doing wrong?? Also, when reproducing this locally, Ejb-A would favor the Ejb-B on the same server, so it was difficult to reproduce. But this wasn't the case on other machines. NOTE: This all worked correctly for EJB2

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• Compare sign of two doubles

  - by bobobobo

  What's the fastest way to compare sign on a double? I know that a double has a "sign bit" but I'm not sure if the way I'm "looking for it" in its binary rep is a good idea or not. Barring "portability" issues, can someone tell me what's going on with this code in MSVC++? #include <stdio.h> int main() { double z = 5.0 ; __int64 bitSign ; __int64 *ptr ; ptr = (__int64*)&z ; for( __int64 sh = 0 ; sh < 65 ; sh++ ) { bitSign = 1L << sh ; // Weird. it doesn't do 1. printf( "Bit# %d (%llx): %lld\n", sh, bitSign, ( (*ptr) & bitSign) ) ; } } First, why is starting at bit 32, even though I only shifted by one bit? Second, is it ok for me to check the 64th bit of a double to check its sign on MSVC++? Or is there a more preferred way?

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• Is JavaEE really portable?

  - by Bozho

  I'm just implementing a JavaEE assignment I was given on an interview. I have some prior experience with EJB, but nothing related to JMS and MDBs. So here's what I find through the numerous examples: application servers bind their topics and queues to different JNDI names - for example topic/queue, jms the activationConfig property is required on JBoss, while in the Sun tutorial it is not. after starting my application, jboss warns me that my topic isn't bound (it isn't actually - I haven't bound it, but I expect it to be bound automatically - in fact, in an example for JBoss 4.0 automatic binding does seem to happen). A suggested solution is to map it in some jboss files or even use jboss-specific annotations. This might be just JBoss, but since it is certified to implement to spec, it appears the spec doesn't specify these these things. And there all the alleged portability vanishes. So I wonder - how come it is claimed that JavaEE is portable and you can take an ear and deploy it on another application server and it magically runs, if such extremely basic things don't appear to be portable at all. P.S. sorry for the rant, but I'm assume I might be doing/getting something wrong, so state your opinions.

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• Asynchronous event loop design and issues.

  - by Artyom

  Hello, I'm designing event loop for asynchronous socket IO using epoll/devpoll/kqueue/poll/select (including windows-select). I have two options of performing, IO operation: Non-blocking mode, poll on EAGAIN Set socket to non-blocking mode. Read/Write to socket. If operation succeeds, post completion notification to event loop. If I get EAGAIN, add socket to "select list" and poll socket. Polling mode: poll and then execute Add socket to select list and poll it. Wait for notification that it is readable writable read/write Post completion notification to event loop of sucseeds To me it looks like first would require less system calls when using in normal mode, especially for writing to socket (buffers are quite big). Also it looks like that it would be possible to reduce the overhead over number of "select" executions, especially it is nice when you do not have something that scales well as epoll/devpoll/kqueue. Questions: Are there any advantages of the second approach? Are there any portability issues with non-blocking operations on sockets/file descriptors over numerous operating systems: Linux, FreeBSD, Solaris, MacOSX, Windows. Notes: Please do not suggest using existing event-loop/socket-api implementations

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• Ultra-Portable Laptop or Tablet PC for Development and Sketching

  - by Nelson LaQuet

  I am a software developer that primarily writes in PHP, [X]HTML, CSS, Javascript, C# and C++. I use Eclipse for web development, Visual Studio 2008 for C++ and C# work, TortoiseSVN, Subversion server for local repositories, SQL Server Express, Apache and MYSQL. I also use Office 2007 for word processing and spreadsheets and use Vista Ultimate 64 as my primary operating system. The only other things I do on my laptop are watch movies, surf the internet and listen to music. I currently have a Acer Aspire 5100 (1.4 GHz AMD Turion X2, 2 GB of RAM and a 15.4" screen). This thing does not cut it in performance or portability, and in addition, my DVD drive failed. And before anybody posts about vista: I have had XP Professional 32 on it for the last two years, and recently upgraded to Vista 64. It is actually faster (with areo disabled) then XP; so it is not the OS that is causing the laptop to be slow. I usually sketch a lot, for explaining things, developing user interfaces and software architecture. Because of my requirements, I was thinking about a Lenovo X61 Tablet PC. It outperforms my current laptop, is significantly more portable, and... is a tablet. My question is: do any other software developers use this (or other tablets) for programming? Does it help to be able to sketch on the computer itself? And is it capable of being a good development machine? Will it handle the above software listed? If not, what is the best ultra-portable laptop that is good for programming? Or are ultra-portable laptops even good for programming? I could manage with my 15.4" screen, but am spoiled by my two 19" at my home desktop and my job's workstation.

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• Compile time float packing/punning

  - by detly

  I'm writing C for the PIC32MX, compiled with Microchip's PIC32 C compiler (based on GCC 3.4). My problem is this: I have some reprogrammable numeric data that is stored either on EEPROM or in the program flash of the chip. This means that when I want to store a float, I have to do some type punning: typedef union { int intval; float floatval; } IntFloat; unsigned int float_as_int(float fval) { IntFloat intf; intf.floatval = fval; return intf.intval; } // Stores an int of data in whatever storage we're using void StoreInt(unsigned int data, unsigned int address); void StoreFPVal(float data, unsigned int address) { StoreInt(float_as_int(data), address); } I also include default values as an array of compile time constants. For (unsigned) integer values this is trivial, I just use the integer literal. For floats, though, I have to use this Python snippet to convert them to their word representation to include them in the array: import struct hex(struct.unpack("I", struct.pack("f", float_value))[0]) ...and so my array of defaults has these indecipherable values like: const unsigned int DEFAULTS[] = { 0x00000001, // Some default integer value, 1 0x3C83126F, // Some default float value, 0.005 } (These actually take the form of X macro constructs, but that doesn't make a difference here.) Commenting is nice, but is there a better way? It's be great to be able to do something like: const unsigned int DEFAULTS[] = { 0x00000001, // Some default integer value, 1 COMPILE_TIME_CONVERT(0.005), // Some default float value, 0.005 } ...but I'm completely at a loss, and I don't even know if such a thing is possible. Notes Obviously "no, it isn't possible" is an acceptable answer if true. I'm not overly concerned about portability, so implementation defined behaviour is fine, undefined behaviour is not (I have the IDB appendix sitting in front of me). As fas as I'm aware, this needs to be a compile time conversion, since DEFAULTS is in the global scope. Please correct me if I'm wrong about this.

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• Should a new language compiler target the JVM?

  - by Pindatjuh

  I'm developing a new language. My initial target was to compile to native x86 for the Windows platform, but now I am in doubt. I've seen some new languages target the JVM (most notable Scala and Clojure). Ofcourse it's not possible to port every language easily to the JVM; to do so, it may lead to small changes to the language and it's design. So that's the reason behind this doubt, and thus this question: Is targetting the JVM a good idea, when creating a compiler for a new language? Or should I stick with x86? I have experience in generating JVM bytecode. Are there any workarounds to JVM's GC? The language has deterministic implicit memory management. How to produce JIT-compatible bytecode, such that it will get the highest speedup? Is it similar to compiling for IA-32, such as the 4-1-1 muops pattern on Pentium? I can imagine some advantages (please correct me if I'm wrong): JVM bytecode is easier than x86. Like x86 communicates with Windows, JVM communicates with the Java Foundation Classes. To provide I/O, Threading, GUI, etc. Implementing "lightweight"-threads.I've seen a very clever implementation of this at http://www.malhar.net/sriram/kilim/. Most advantages of the Java Runtime (portability, etc.) The disadvantages, as I imagined, are: Less freedom? On x86 it'll be more easy to create low-level constructs, while JVM has a higher level (more abstract) processor. Most disadvantages of the Java Runtime (no native dynamic typing, etc.)

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• Segmentation in Linux : Segmentation & Paging are redundant?

  - by claws

  Hello, I'm reading "Understanding Linux Kernel". This is the snippet that explains how Linux uses Segmentation which I didn't understand. Segmentation has been included in 80 x 86 microprocessors to encourage programmers to split their applications into logically related entities, such as subroutines or global and local data areas. However, Linux uses segmentation in a very limited way. In fact, segmentation and paging are somewhat redundant, because both can be used to separate the physical address spaces of processes: segmentation can assign a different linear address space to each process, while paging can map the same linear address space into different physical address spaces. Linux prefers paging to segmentation for the following reasons: Memory management is simpler when all processes use the same segment register values that is, when they share the same set of linear addresses. One of the design objectives of Linux is portability to a wide range of architectures; RISC architectures in particular have limited support for segmentation. All Linux processes running in User Mode use the same pair of segments to address instructions and data. These segments are called user code segment and user data segment , respectively. Similarly, all Linux processes running in Kernel Mode use the same pair of segments to address instructions and data: they are called kernel code segment and kernel data segment , respectively. Table 2-3 shows the values of the Segment Descriptor fields for these four crucial segments. I'm unable to understand 1st and last paragraph.

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• Cross-Platform Camera API

  - by Karim

  Hi, I'm now building a video transforming filter that have to transform video frames in real-time. One of the key requirements of the filter is to have high performance to minimize the number of dropped frames during the transform. Another requirement that is of lower priority but also nice to have is to make it cross-platform (both PC's and Mobile devices). The application is built in C++. Now my question is: is there any API that is more portable and has a similar or better performance characteristics than DirectShow? as DirectShow's portability is only limited to Windows-based devices (PCs and Windows Mobile&CE platforms). Also I've notices that for example using HTC's custom camera API has far better performance than what DirectShow offers. If you want to check this, try to build a filter in DirectShow that will multiply each color by 2 and render that in real-time from camera on the screen. Then do the same with HTC's API. There is almost 4-5x performance boost with vendor's specific API. So it'd be very nice if the library used the device-specific implementation of the driver, as performance is critical when doing this transforms on a mobile device (which is about ~500 MHz).

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• Standard and reliable mouse-reporting with GLUT

  - by Victor

  Hello! I'm trying to use GLUT (freeglut) in my OpenGL application, and I need to register some callbacks for mouse wheel events. I managed to dig out a fairly undocumented function: api documentation But the man page and the API entry for this function both state the same thing: Note: Due to lack of information about the mouse, it is impossible to implement this correctly on X at this time. Use of this function limits the portability of your application. (This feature does work on X, just not reliably.) You are encouraged to use the standard, reliable mouse-button reporting, rather than wheel events. Fair enough, but how do I use this standard, reliable mouse-reporting? And how do I know which is the standard? Do I just use glutMouseFunc() and use button values like 4 and 5 for the scroll up and down values respectively, say if 1, 2 and 3 are the left, middle and right buttons? Is this the reliable method? Bonus question: it seems the `xev' tool is reporting different values for my buttons. My mouse buttons are numbered from 1 to 5 with xev, but glut is reporting buttons from 0 to 4, i.e. an off-by-one. Is this common?

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• Are there any downsides in using C++ for network daemons?

  - by badcat

  Hey guys! I've been writing a number of network daemons in different languages over the past years, and now I'm about to start a new project which requires a new custom implementation of a properitary network protocol. The said protocol is pretty simple - some basic JSON formatted messages which are transmitted in some basic frame wrapping to have clients know that a message arrived completely and is ready to be parsed. The daemon will need to handle a number of connections (about 200 at the same time) and do some management of them and pass messages along, like in a chat room. In the past I've been using mostly C++ to write my daemons. Often with the Qt4 framework (the network parts, not the GUI parts!), because that's what I also used for the rest of the projects and it was simple to do and very portable. This usually worked just fine, and I didn't have much trouble. Being a Linux administrator for a good while now, I noticed that most of the network daemons in the wild are written in plain C (of course some are written in other languages, too, but I get the feeling that 80% of the daemons are written in plain C). Now I wonder why that is. Is this due to a pure historic UNIX background (like KISS) or for plain portability or reduction of bloat? What are the reasons to not use C++ or any "higher level" languages for things like daemons? Thanks in advance! Update 1: For me using C++ usually is more convenient because of the fact that I have objects which have getter and setter methods and such. Plain C's "context" objects can be a real pain at some point - especially when you are used to object oriented programming. Yes, I'm aware that C++ is a superset of C, and that C code is basically C++. But that's not the point. ;)

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• How to get a unique WindowRef in a dockable Qt application on Mac

  - by Robin

  How do I get a unique WindowRef from a Qt application that includes docked windows on the Mac? My code boils down to: int main(int argc, char* argv[]) { QApplication* qtApp = new QApplication(argc, argv); MyQMainWindow mainwin; mainwin.show(); } class MyQMainWindow : public QMainWindow { //... QDockWidget* mDock; MyQWidget* mDrawArea; QStackedWidget* mCentralStack; }; MyQMainWindow::MyQMainWindow() { mDock = new QDockWidget(tr("Docked Widget"), this); mDock->setMaximumWidth(180); //... addDockWidget(Qt::RightDockWidgetArea, mDock); mDrawArea = new MyQWidget(this); mCentralStack = new QStackedWidget(); mCentralStack->addWidget(mDrawArea); // Other widgets added to stack in production code. setCentralWidget(mCentralStack); //... } (Apologies if the above isn't syntactically correct, it's just easier to illustrate than to describe.) I added the following temporary code at the end of the above constructor: HIViewRef view1 = (HIViewRef) mDrawArea->winId(); HIViewRef view2 = (HIViewRef) mDock->winId(); WindowRef win1 = HIViewGetWindow(view1); WindowRef win2 = HIViewGetWindow(view2); My problem is that view1 and view2 are different, but win1 and win2 are the same! I tried the following equivalent on Windows: HWND win1 = (HWND)(mCentralDrawArea->winId()); HWND win2 = (HWND)(mDock1->winId()); This time win1 and win2 are different. I need the window handle to pass on to a 3rd party SDK so that it can draw into the central area only. BTW, I appreciate that the winId() method comes with lots of portability warnings, but a substantial refactor is out of the question for me. The same goes for using Carbon instead of Cocoa. Thanks.

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• What runs faster? Wordpress or Drupal 6.x?

  - by electblake

  So... I run a pretty large Wordpress blog. Currently it gets around 20k+ pageviews a day, and its always a struggle to keep the bad boy running quickly - I currently run a vps.net with CentOS 5.3 I am also Drupal developer by trade so I love the CMS Framework for its versatility and the portability (I can take work from one site and implement on another with great ease) MY QUESTION IS: What is faster then? Wordpress 3.x & Drupal 6.x I'd love to migrate my site to Drupal to be able to roll out new features etc (which I find awkward to do in Wordpress) but I am scared that Drupal may not be able to handle the traffic. Any opinions? I know that some major players use Drupal - as Dries documents well on his blog but I'm not under any illusions that Drupal can be a real hog. Thanks for any/all help! Please try to avoid server optimization talk unless it pertains to Wordpress or Drupal 6.x specifically, I love to learn more about optimizations but I do want to sort out which platform is quicker :) p.s - I realize the fastest option is to use a lower-level framework (with less overhead) like CakePHP etc but assume that isn't an option ;)

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