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  • How can I make the storage of C++ lambda objects more efficient?

    - by Peter Ruderman
    I've been thinking about storing C++ lambda's lately. The standard advice you see on the Internet is to store the lambda in a std::function object. However, none of this advice ever considers the storage implications. It occurred to me that there must be some seriously black voodoo going on behind the scenes to make this work. Consider the following class that stores an integer value: class Simple { public: Simple( int value ) { puts( "Constructing simple!" ); this->value = value; } Simple( const Simple& rhs ) { puts( "Copying simple!" ); this->value = rhs.value; } Simple( Simple&& rhs ) { puts( "Moving simple!" ); this->value = rhs.value; } ~Simple() { puts( "Destroying simple!" ); } int Get() const { return this->value; } private: int value; }; Now, consider this simple program: int main() { Simple test( 5 ); std::function<int ()> f = [test] () { return test.Get(); }; printf( "%d\n", f() ); } This is the output I would hope to see from this program: Constructing simple! Copying simple! Moving simple! Destroying simple! 5 Destroying simple! Destroying simple! First, we create the value test. We create a local copy on the stack for the temporary lambda object. We then move the temporary lambda object into memory allocated by std::function. We destroy the temporary lambda. We print our output. We destroy the std::function. And finally, we destroy the test object. Needless to say, this is not what I see. When I compile this on Visual C++ 2010 (release or debug mode), I get this output: Constructing simple! Copying simple! Copying simple! Copying simple! Copying simple! Destroying simple! Destroying simple! Destroying simple! 5 Destroying simple! Destroying simple! Holy crap that's inefficient! Not only did the compiler fail to use my move constructor, but it generated and destroyed two apparently superfluous copies of the lambda during the assignment. So, here finally are the questions: (1) Is all this copying really necessary? (2) Is there some way to coerce the compiler into generating better code? Thanks for reading!

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  • Which is faster in memory, ints or chars? And file-mapping or chunk reading?

    - by Nick
    Okay, so I've written a (rather unoptimized) program before to encode images to JPEGs, however, now I am working with MPEG-2 transport streams and the H.264 encoded video within them. Before I dive into programming all of this, I am curious what the fastest way to deal with the actual file is. Currently I am file-mapping the .mts file into memory to work on it, although I am not sure if it would be faster to (for example) read 100 MB of the file into memory in chunks and deal with it that way. These files require a lot of bit-shifting and such to read flags, so I am wondering that when I reference some of the memory if it is faster to read 4 bytes at once as an integer or 1 byte as a character. I thought I read somewhere that x86 processors are optimized to a 4-byte granularity, but I'm not sure if this is true... Thanks!

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  • Best way to Store Passwords, User information/Profile data and Photo/Video albums for a social websi

    - by Nick
    Need some help figuring out how to best Store Passwords, User information/Profile data and Photo/Video albums for a social website? For photos/videos the actual photo/video + even encrypting the URL with the IDs to the photo/videos so other users cannot figure it out. Creating a site like myspace and designing retirement documents but i am unsure how to specify the security requirements for the database. Two things: 1) Protect from outside users 2) Protect all these from employees being able to access this info For #2, the additional question is: If we encrypt the user info and password so even the system admins cannot get in, how can we retrieve the user data tomorrow if someone flags the user's account as spam and admin needs to check it out or if law enforcement wants info on a user? Thanks.

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  • Why do debug symbols so adversely affect the performance of threaded applications on Linux?

    - by fluffels
    Hi. I'm writing a ray tracer. Recently, I added threading to the program to exploit the additional cores on my i5 Quad Core. In a weird turn of events the debug version of the application is now running slower, but the optimized build is running faster than before I added threading. I'm passing the "-g -pg" flags to gcc for the debug build and the "-O3" flag for the optimized build. Host system: Ubuntu Linux 10.4 AMD64. I know that debug symbols add significant overhead to the program, but the relative performance has always been maintained. I.e. a faster algorithm will always run faster in both debug and optimization builds. Any idea why I'm seeing this behavior?

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  • Considering HorizontalAlignment and VerticalAlignment while creating a custom panel

    - by sudarsanyes
    I am trying to create a custom panel in wpf. Here the doubts I have, How do I consider the HorizontalAlignment and VerticalAlignment factors while placing the items within my panel. Should I check for these flags in my ArrangeOverride method ?? Consider that I want to write a WrapPanel clone. If the panel's width is set to "Auto", how do I get the actual width of the panel to arrange my child items. I always get the ActualWidth/ActualHeight as 0. Am I missing something??? Please help.

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  • C Language preprocessing doubt

    - by khanna_param
    Hi, There are different kind of macros in C language, nested macro is one of them. Considering a program with the following macro define HYPE(x,y) (SQUR(x)+SQUR(y)) define SQUR(x) (x*x) using this we can successfully complile to get the result. My question:- As we all know the C preprocessor replaces all the occurrence of the identifiers with the replacement-string. Considering the above example i would like to know how many times the C compiler traverses the program to replace the macro with the replacement values. I assume it cannot be done in one go. Thanks.

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  • How to change code settings in eclipse

    - by Maven
    Sorry if the question title is confusing. Let me explain further. I am building a Java project with Eclipse. In my Java product I have conditionals that determine what code is included in the product and relies on static final constants for dead stripping. class BuildFlags { public static final boolean SOME_FLAG = true; // Need to set this programmatically } class SomeOtherClass { public void someMethod() { if (BuildFlags.SOME_FLAG) { // flag specific code } } } My question is how can I change BuildFlags.SOME_FLAG (above) so that I can run a special build without changing the source? Is there some way I can pass flags to the jvm (from eclipse) which I can then access to set this flag programatically?

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  • RadioGroup onCheckedChanged function won't fire

    - by user1758088
    First time/long time. My app keeps track of restaurant servers' shift sales to help them budget. In the activity that displays past shifts, I've created a RadioGroup under the ListView so the server can choose lunch, dinner, or both. I've implemented RadioGroup.onCheckedChangeListener, but onCheckChanged never gets called. I also tried an anonymous inner class as listener, same result. I tried to copy/modify code from this answer: http://stackoverflow.com/a/9595528 ...but when I added the @Override to the callback function, the Eclipse compiler gave me an error (not warning) that the method must override a superclass, and the quick fix was to remove the override. I'm pretty sure the signatures are correct, as they were made with Eclipse's autocomplete and implement methods facilities. I then followed instructions to move my java compiler from 1.5 to 1.6, and none of the above listed behavior seemed to change. Here's the code I thing is relavent: public class DataActivity extends ListActivity implements OnCheckedChangeListener{ RadioButton rbBoth; RadioButton rbDinnerOnly; RadioButton rbLunchOnly; @Override public void onCreate(Bundle savedInstanceState){ super.onCreate(savedInstanceState); setContentView(R.layout.database); ... final RadioGroup rgGroup = (RadioGroup)findViewById(R.id.DataRadioGroup); rbBoth = (RadioButton)findViewById(R.id.RadioBoth); rbDinnerOnly = (RadioButton)findViewById(R.id.RadioDinnerOnly); rbLunchOnly = (RadioButton)findViewById(R.id.RadioLunchOnly); rgGroup.setOnCheckedChangeListener(this); populateAllShifts(); } ... public void onCheckedChanged(RadioGroup group, int checkedId) { rbLunchOnly.setText("Click!"); Toast.makeText(getApplicationContext(), "Lunch Only", Toast.LENGTH_LONG).show(); if(group.getCheckedRadioButtonId() == R.id.RadioBoth){ populateAllShifts(); return; } if(group.getCheckedRadioButtonId() == R.id.RadioLunchOnly){ populatLunchShifts(); return; } if(group.getCheckedRadioButtonId() == R.id.RadioDinnerOnly){ populateDinnerShifts(); return; } } There is a ListView in this class with a custom adapter, but if my understanding and my XML are correct, the RadioGroup should be outside of the list: <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/llDataLayout" android:weightSum="5" android:layout_width="fill_parent" android:layout_height="fill_parent" android:orientation="vertical"> <ListView android:layout_weight="4" android:layout_width="fill_parent" android:id="@android:id/list" android:layout_height="wrap_content"></ListView> <RadioGroup android:layout_weight="1" android:id="@+id/DataRadioGroup" android:orientation="horizontal" android:layout_height="wrap_content" android:layout_width="fill_parent"> <RadioButton android:text="Lunch and Dinner" android:textSize="10dp" android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/RadioBoth"/> <RadioButton android:text="Dinner Only" android:textSize="10dp" android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/RadioDinnerOnly"/> <RadioButton android:text="Lunch Only" android:textSize="10dp" android:layout_width="wrap_content" android:layout_height="wrap_content" android:id="@+id/RadioLunchOnly"/> </RadioGroup> </LinearLayout> Any ideas out there?

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  • What's the best way to build software to not require the newest glibc?

    - by ZorbaTHut
    I'm attempting to build a binary package that can be run on multiple Linux distributions. It's currently built on Ubuntu 10.04, but it fails on Ubuntu 8.04 with the following error: ./test: /usr/lib/libstdc++.so.6: version `GLIBCXX_3.4.11' not found (required by ./test) ./test: /usr/lib/libstdc.so.6: version `GLIBC_2.11' not found (required by ./test) What's the preferred way to solve this problem? Is there a way to install an old glibc on a new box and build against it, or do I have to build on an old distribution? And if I build against an old glibc, will it work on a new glibc? Or, alternatively, are there just some handy compiler flags or packages I could install to solve the problem?

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  • What's the best way to build software that doesn't require the newest glibc?

    - by ZorbaTHut
    I'm attempting to build a binary package that can be run on multiple Linux distributions. It's currently built on Ubuntu 10.04, but it fails on Ubuntu 8.04 with the following error: ./test: /usr/lib/libstdc++.so.6: version `GLIBCXX_3.4.11' not found (required by ./test) ./test: /usr/lib/libstdc.so.6: version `GLIBC_2.11' not found (required by ./test) What's the preferred way to solve this problem? Is there a way to install an old glibc on a new box and build against it, or do I have to build on an old distribution? And if I build against an old glibc, will it work on a new glibc? Or, alternatively, are there just some handy compiler flags or packages I could install to solve the problem?

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  • Howto take a glimpse into mscorlib?

    - by panny
    Hi all! I want to read data into RSAParameters structure ( RSAParameters ) and did check twice, that the data is correct. But still, I get an error "invalid data" exception for this: bei System.Security.Cryptography.CryptographicException.ThrowCryptogaphicException(Int32 hr) bei System.Security.Cryptography.Utils._ImportKey(SafeProvHandle hCSP, Int32 keyNumber, CspProviderFlags flags, Object cspObject, SafeKeyHandle& hKey) bei System.Security.Cryptography.RSACryptoServiceProvider.ImportParameters(RSAParameters parameters) How can I take a look into the source code to check why _ImportKeys is throwing an exception? I have no experience with .dll 'decryption'..are there any symbols to reference somewhere for visual studio 8.0? Thank you.

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  • input URL, output contents of "view page source", i.e. after javascript / etc, library or command-li

    - by Ryan Berckmans
    I need a scalable, automated, method of dumping the contents of "view page source" (DOM) to a file. Programs such as wget or curl will non-interactively retrieve a set of URLs, but do not execute javascript or any of that 'fancy stuff'. My ideal solution looks like any of the following (fantasy solutions): cat urls.txt | google-chrome --quiet --no-gui \ --output-sources-directory=~/urls-source (fantasy command line, no idea if flags like these exist) or cat urls.txt | python -c "import some-library; \ ... use some-library to process urls.txt ; output sources to ~/urls-source" As a secondary concern, I also need: dump all included javascript source to file (a la firebug) dump pdf/image of page to file (print to file)

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  • Preventing FIN_WAIT2 when closing socket

    - by patrickvacek
    I have a server program that connects to another program via a given socket, and in certain cases I need to close the connection and almost immediately re-open it on the same socket. This by and large works, except that I have to wait exactly one minute for the socket to reset. In the meantime, netstat indicates that the server sees the socket in FIN_WAIT2 and the client sees it as CLOSE_WAIT. I'm already using SO_REUSEADDR, which I thought would prevent the wait, but that isn't doing the trick. Setting SO_LINGER to zero also does not help. What else can I do to resolve this? Here are the relevant code snippets: SetUpSocket() { // Set up the socket and listen for a connection from the exelerate client. // Open a TCP/IP socket. m_baseSock = socket(PF_INET, SOCK_STREAM, IPPROTO_IP); if (m_baseSock < 0) { return XERROR; } // Set the socket options to reuse local addresses. int flag = 1; if (setsockopt(m_baseSock, SOL_SOCKET, SO_REUSEADDR, &flag, sizeof(flag)) == -1) { return XERROR; } // Set the socket options to prevent lingering after closing the socket. //~ linger li = {1,0}; //~ if (setsockopt(m_baseSock, SOL_SOCKET, SO_LINGER, &li, sizeof(li)) == -1) //~ { //~ return XERROR; //~ } // Bind the socket to the address of the current host and our given port. struct sockaddr_in addr; memset(&addr, 0, sizeof(addr)); addr.sin_family = AF_INET; addr.sin_addr.s_addr = INADDR_ANY; addr.sin_port = htons(m_port); if (bind(m_baseSock, (struct sockaddr*)&addr, sizeof(addr)) != 0) { return XERROR; } // Tell the socket to listen for a connection from client. if (listen(m_baseSock, 4) != 0) { return XERROR; } return XSUCCESS; } ConnectSocket() { // Add the socket to a file descriptor set. fd_set readfds; FD_ZERO(&readfds); FD_SET(m_baseSock, &readfds); // Set timeout to ten seconds. Plenty of time. struct timeval timeout; timeout.tv_sec = 10; timeout.tv_usec = 0; // Check to see if the socket is ready for reading. int numReady = select(m_baseSock + 1, &readfds, NULL, NULL, &timeout); if (numReady > 0) { int flags = fcntl(m_baseSock, F_GETFL, 0); fcntl(m_baseSock, flags | O_NONBLOCK, 1); // Wait for a connection attempt from the client. Do not block - we shouldn't // need to since we just selected. m_connectedSock = accept(m_baseSock, NULL, NULL); if (m_connectedSock > 0) { m_failedSend = false; m_logout = false; // Spawn a thread to accept commands from client. CreateThread(&m_controlThread, ControlThread, (void *)&m_connectedSock); return XSUCCESS; } } return XERROR; } ControlThread(void *arg) { // Get the socket from the argument. socket sock = *((socket*)arg); while (true) { // Add the socket to a file descriptor set. fd_set readfds; FD_ZERO(&readfds); FD_SET(sock, &readfds); // Set timeout to ten seconds. Plenty of time. struct timeval timeout; timeout.tv_sec = 10; timeout.tv_usec = 0; // Check if there is any readable data on the socket. int num_ready = select(sock + 1, &readfds, NULL, NULL, &timeout); if (num_ready < 0) { return NULL; } // If there is data, read it. else if (num_ready > 0) { // Check the read buffer. xuint8 buf[128]; ssize_t size_read = recv(sock, buf, sizeof(buf)); if (size_read > 0) { // Get the message out of the buffer. char msg = *buf; if (msg == CONNECTED) { // Do some things... } // If we get the log-out message, log out. else if (msg == LOGOUT) { return NULL; } } } } // while return NULL; } ~Server() { // Close the sockets. if (m_baseSock != SOCKET_ERROR) { close(m_baseSock); m_baseSock = SOCKET_ERROR; } if (m_connectedSock != SOCKET_ERROR) { close(m_connectedSock); m_connectedSock = SOCKET_ERROR; } } SOCKET_ERROR is equal to -1. The server object gets destroyed, at which point the connection should close, and then recreated, at which point the SetUpSocket() and ConnectSocket() routines are called. So why do I have to wait a minute for the socket to clear? Any ideas would be appreaciated.

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  • How to Embed/Link binary data into a C++ DLL

    - by CrimsonX
    So I have a Visual Studio 2008 project which has a large amount of binary data that it is currently referencing. I would like to package the binary data much like you can do with C# by adding it as a "resource" and compiling it as a DLL. Lets say all my data has an extension of ".data" and is currently being read from the visual studio project. Is there a way that you can compile or link the data into the .dll which it is calling? I've looked at some of the google link for this and so far I haven't come up with anything - the only possible solution I've come up with is to use something like ResGen to create a .resources file and then link it using AssemblyLinker with /Embed or /Link flags. I dont think it'd work properly though because I dont have text files to create the .resources files, but rather binary files themselves. Any advice?

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  • Why does Visual Studio's "Unused References..." button not flag System.Xml and System.Xml.Linq?

    - by mcjabberz
    I was trying to finish up a VB.NET class library project when I tried to remove all unused references. I know for a fact that I'm not explicitly using any thing from the System.Xml and System.Xml.Linq assemblies yet the "Unused References..." button never flags them for removal. In fact I even tried "Unused References..." on a blank project and it still never flagged them. The only reason I could think of is that either mscorlib.dll or System.dll is using System.Xml.dll or System.Xml.Linq.dll. Are they safe to remove?

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  • Regex to find a word, then extract a line containing the first occurence of a different word immedia

    - by Hinchy
    World's most convuluted title I know, an example should explain it better. I have a large txt file in the below format, though details and amount of lines will change everytime: Username: john_joe Owner: John Joe Account: CLI: Default: LGICMD: Flags: Primary days: Secondary days: No access restrictions Expiration: Pwdlifetime: Last Login: Maxjobs: Maxacctjobs: Maxdetach: Prclm: Prio: Queprio: CPU: Authorized Privileges: BYPASS Default Privileges: SYSPRV This sequence is repeated a couple of thousand times for different users. I need to find every user (ideally the entire first line of the above) that has SYSPRV under "Default Permissions". I know I could write an application to do this, I was just hoping their might be a nice regex I could use. Cheers

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  • Parse xml file with same tag multiple times iphone sdk

    - by neha
    Hi all, In my application, I have a tag multiple times. I'm using xml parser. I'm taking a corresponding element with similar name as the one in xml file in my class. So in case of: <photo>abc</photo> <photo>def</photo> What I get in photo element of my class is the second element i.e def, as the first one gets overwritten as there's only one photo element in my class. My question is am I wrong in taking similar elements in class as in case of xml? Is there any better method or a better parser? Or I'm on right path and have to do this manually by setting some flags etc? Thanx in advance.

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  • Is there a way to cause a new C++ class instance to fail, if certain conditions in the contructor ar

    - by Jim Fell
    As I understand it, when a new class is instantiated in C++, a pointer to the new class is returned, or NULL, if there is insufficient memory. I am writing a class that initializes a linked list in the constructor. If there is an error while initializing the list, I would like the class instantiator to return NULL. For example: MyClass * pRags = new MyClass; If the linked list in the MyClass constructor fails to initialize properly, I would like pRags to equal NULL. I know that I can use flags and additional checks to do this, but I would like to avoid that, if possible. Does anyone know of a way to do this? Thanks.

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  • Libxml2: undefined reference to xmlTextReaderConstName

    - by Dmitry
    I have installed the latest libxml2-2.8.0, as usual: $ ./configure, $ make, $ make install. The $ xml2-config --cflags --libs gives this output: -I/usr/local/include/libxml2 -L/usr/local/lib -lxml2 -lm But trying to compile any example... $ gcc `xml2-config --cflags --libs` xmltest.c The linker says: /tmp/cc8ezrPl.o: In function `processNode': xmltest.c:(.text+0x19): undefined reference to `xmlTextReaderConstName' xmltest.c:(.text+0x38): undefined reference to `xmlTextReaderConstValue' ...etc. Anything I've googled can be solved by xml2-config --cflags --libs flags, or upgrading to the latest version of libxml2, or something. Unfortunately, neither works for me. What can be the steps to identify the problem? Using Ubuntu 12.04 64-bit.

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  • SHFileOperation FO_MOVE deletes a file if the destination drive is full

    - by Shailesh Kumar
    I had a piece of code which uses windows SHFileOperation function with FO_MOVE operation. Additional flags specified were FOF_NOCONFIRMATION | FOF_NOERRORUI | FOF_SILENT. A particular weird behavior was observed when the destination drive was full. In this case, MOVE could not place the file in destination folder but the source file was also lost. This was highly unexpected and this caused a loss of data. Is this the standard behavior of SHFileOperation? Can we have something like MOVE if the destination drive has space otherwise leave the file at the original place?

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  • Modify bash variables with sed

    - by Alexander Cska
    I am trying to modify a number of environmental variables containing predefined compiler flags. To do so, I tried using a bash loop that goes over all environmental variables listed with "env". for i in $(env | grep ipo | awk 'BEGIN {FS="="} ; { print $1 } ' ) do echo $(sed -e "s/-ipo/ / ; s/-axAVX/ /" <<< $i) done This is not working since the loop variable $i contains just the name of the environmental variable stored as a character string. I tried searching a method to convert a string into a variable but things started becoming unnecessary complicated. The basic problem is how to properly supply the environmental variable itself to sed. Any ideas how to properly modify my script are welcome. Thanks, Alex

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  • Does writing program using global variables is safer?

    - by ZoZo123
    I was reading about buffer, stack and heap overflows. I read this post as well. my question is like that: if I use only global variables in my code, can I say it prevents all the exploits of overflow? let's say I have this buffers in code declared in the global scope: char buf1[10]; char buf2[100]; If I send buf1 as the buffer to recv(int s, char *buf, int len,int flags); I will overwrite the data segment and may ruin the buf2 content, right? Would I be able to run a code from it because as I know it is not a code segment and data segment is not executable. Can we conclude that using Globals is the safest way?

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  • Android service puts multiple instances of an activity in the history

    - by HenryAdamsJr
    I'm making a music player. When you press play, it loads a notification into the OnGoing section. When you go anywhere else in the system, I want the music to keep playing. All of this is fine. The problem is that when I relaunch my activity from the Notification, it adds a task to the history stack each time, so if I hit back, I have to see the instance of Activity B from where I pressed play, and from every time I clicked on the notification to go back to Activity B. I want the instance of Activity B that I launch from the notification (via the service) to be the only copy of that Activity in the history. I've been playing around with various Intent flags and Activity attributes in the manifest, but I haven't found the proper combination.

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  • Protocol/Packet Design Questions

    - by cam
    I'm looking to a design a protocol for a client-server application and need some links to some resources that may help me. The big part is I'm trying to create my own "packet" format so I can minimize the amount of information being sent. I'm looking for some resources to dissect their protocol, but it seems some completely lack packet design, such as SMTP (which just sends strings terminated by CLRF). What are the advantages/disadvantages of using a system like SMTP over a system that uses a custom made packet? Couldn't SMTP use only a couple bytes to cover all commands through bit flags and save bandwidth/space? Just trying to get my head around all this.

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  • execute external command / application from java

    - by IttayD
    I'm looking for a package to support reliably executing external processes from Java. My criteria: Abstract over OS. So if I want to run 'foo', it will look for 'foo.bat', 'foo.exe' under windows and 'foo' under other OSs (or, have a way of passing a map of os-command) Being able to execute Java classes by simply giving the class name and arguments (so the package locates the java command, copies jvm flags and then executes) Process stdout and stderr properly Watchdog / Monitoring capabilities I've looked at commons-exec but it looks like it answers only 3 & 4. Ant has support for execution but looks like an overkill to use it for this purpose only.

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