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• Reinterpret a CGImageRef using PyObjC in Python

  - by Michael Rondinelli

  Hi, I'm doing something that's a little complicated to sum up in the title, so please bear with me. I'm writing a Python module that provides an interface to my C++ library, which provides some specialized image manipulation functionality. It would be most convenient to be able to access image buffers as CGImageRefs from Python, so they could be manipulated further using Quartz (using PyObjC, which works well). So I have a C++ function that provides a CGImageRef representation from my own image buffers, like this: CGImageRef CreateCGImageRefForImageBuffer(shared_ptr<ImageBuffer> buffer); I'm using Boost::Python to create my Python bridge. What is the easiest way for me to export this function so that I can use the CGImageRef from Python? Problems: The CGImageRef type can't be exported directly because it is a pointer to an undefined struct. So I could make a wrapper function that wraps it in a PyCObject or something to get it to send the pointer to Python. But then how do I "cast" this object to a CGImageRef from Python? Is there a better way to go about this?

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• Instantiating class with custom allocator in shared memory

  - by recipriversexclusion

  I'm pulling my hair due to the following problem: I am following the example given in boost.interprocess documentation to instantiate a fixed-size ring buffer buffer class that I wrote in shared memory. The skeleton constructor for my class is: template<typename ItemType, class Allocator > SharedMemoryBuffer<ItemType, Allocator>::SharedMemoryBuffer( unsigned long capacity ){ m_capacity = capacity; // Create the buffer nodes. m_start_ptr = this->allocator->allocate(); // allocate first buffer node BufferNode* ptr = m_start_ptr; for( int i = 0 ; i < this->capacity()-1; i++ ) { BufferNode* p = this->allocator->allocate(); // allocate a buffer node } } My first question: Does this sort of allocation guarantee that the buffer nodes are allocated in contiguous memory locations, i.e. when I try to access the n'th node from address m_start_ptr + n*sizeof(BufferNode) in my Read() method would it work? If not, what's a better way to keep the nodes, creating a linked list? My test harness is the following: // Define an STL compatible allocator of ints that allocates from the managed_shared_memory. // This allocator will allow placing containers in the segment typedef allocator<int, managed_shared_memory::segment_manager> ShmemAllocator; //Alias a vector that uses the previous STL-like allocator so that allocates //its values from the segment typedef SharedMemoryBuffer<int, ShmemAllocator> MyBuf; int main(int argc, char *argv[]) { shared_memory_object::remove("MySharedMemory"); //Create a new segment with given name and size managed_shared_memory segment(create_only, "MySharedMemory", 65536); //Initialize shared memory STL-compatible allocator const ShmemAllocator alloc_inst (segment.get_segment_manager()); //Construct a buffer named "MyBuffer" in shared memory with argument alloc_inst MyBuf *pBuf = segment.construct<MyBuf>("MyBuffer")(100, alloc_inst); } This gives me all kinds of compilation errors related to templates for the last statement. What am I doing wrong?

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• A map and set which uses contiguous memory and has a reserve function

  - by edA-qa mort-ora-y

  I use several maps and sets. The lack of contiguous memory, and high number of (de)allocations, is a performance bottleneck. I need a mainly STL-compatbile map and set class which can use a contiguous block of memory for internal objects (or multiple blocks). It also needs to have a reserve function so that I can preallocate for expected sizes. Before I write my own I'd like to check what is available first. Is there something in Boost which does this? Does somebody know of an available implementation elsewhere? Intrusive collection types are not usable here as the same objects need to exist in several collections. As far as I know STL memory pools are per-type, not per instance. These global pools are not efficient with respect to memory locality in mutli-cpu/core processing. Object pools don't work as the types will be shared between instance but their pool should not. In many cases a hash map may be an option in some cases.

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• Parallel version of loop not faster than serial version

  - by Il-Bhima

  I'm writing a program in C++ to perform a simulation of particular system. For each timestep, the biggest part of the execution is taking up by a single loop. Fortunately this is embarassingly parallel, so I decided to use Boost Threads to parallelize it (I'm running on a 2 core machine). I would expect at speedup close to 2 times the serial version, since there is no locking. However I am finding that there is no speedup at all. I implemented the parallel version of the loop as follows: Wake up the two threads (they are blocked on a barrier). Each thread then performs the following: Atomically fetch and increment a global counter. Retrieve the particle with that index. Perform the computation on that particle, storing the result in a separate array Wait on a job finished barrier The main thread waits on the job finished barrier. I used this approach since it should provide good load balancing (since each computation may take differing amounts of time). I am really curious as to what could possibly cause this slowdown. I always read that atomic variables are fast, but now I'm starting to wonder whether they have their performance costs. If anybody has some ideas what to look for or any hints I would really appreciate it. I've been bashing my head on it for a week, and profiling has not revealed much.

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• What makes deployment successful for some users and unsuccessful for others?

  - by Julien

  I am trying to deploy a Visual C++ application (developed with Microsoft Visual Studio 2008) using a Setup and Deployment Project. After installation, users on some target computers get the following error message after launching the application executable: “This application has failed to start because the application configuration is incorrect. Reinstalling the application may fix the problem.” Another user after installation could run the application properly. I cannot find the root cause of this problem, despite spending several hours on the Visual Studio help files and online forums (most postings date back to 2006). Does anyone at Stack Overflow have a suggestion? Thanks in advance. Additional details appear below. The application uses FLTK 1.1.9 for a GUI library, as well as some Boost 1.39 libraries (regex, lexical_cast, date_time, math). I made sure I am trying to deploy the release version (not the debug version) of the application. The Runtime library in the Code Generation settings is Multi-threaded DLL (/MD). The dependency walker of myapp.exe lists the following DLLs: wsock32.dll, comctl32.dll, kernel32.dll, user32.dll, gdi32.dll, shell32.dll, ole32.dll, mvcp90.dll, msvcr90.dll. In the Setup and Deployment Project, I add the following DLLs to the File System on Target Machine: fltkdlld.dll, and a folder named Microsoft.VC90.CRT with msvcm90.dll, msvcp90.dll, mcvcr90.dll and Microsoft.VC90.CRT.manifest. The installation process on the target computers getting the error message requires having the .Net Framework 3.5 installed first. Any suggestion? Thanks in advance!

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• XML parsing by DOM

  - by blackpearl

  NodeList nList2 = doc.getElementsByTagName("dep"); Map<String, List<Map<String, String>>> depMap = new HashMap<String, List<Map<String, String>>>(); for (int temp = 0; temp < nList2.getLength(); temp++) { Element el = (Element)nList2.item(temp); String type=el.getAttribute("type"); Node nNode = nList2.item(temp); if (nNode.getNodeType() == Node.ELEMENT_NODE) { Element eElement = (Element) nNode; List<Map<String,String>> depList = new ArrayList<Map<String,String>>(); String governor = getTagValue("governor", eElement); String dependent = getTagValue("dependent", eElement); Map<String, String> govdepmap = new HashMap<String, String>(); govdepmap.put(governor, dependent); depList.add(govdepmap); List<Map<String,String>> flist = new ArrayList<Map<String,String>>(); flist.add(govdepmap); depMap.put(type, flist); } } I have the following structure in my XML file: going I Now i want to store the "idx" attribute of each "governor" and "dependent" tag. What code should I change or add?

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• What is the nicest way to parse this in C++ ?

  - by ereOn

  Hi, In my program, I have a list of "server address" in the following format: host[:port] The brackets here, indicate that the port is optional. host can be a hostname, an IPv4 or IPv6 address. port, if present can be a numeric port number or a service string (like: "http" or "ssh"). If port is present and host is an IPv6 address, host must be in "bracket-enclosed" notation (Example: [::1]) Here are some valid examples: localhost localhost:11211 127.0.0.1:http [::1]:11211 ::1 [::1] And an invalid example: ::1:80 // Invalid: Is this the IPv6 address ::1:80 and a default port, or the IPv6 address ::1 and the port 80 ? ::1:http // This is not ambigous, but for simplicity sake, let's consider this is forbidden as well. My goal is to separate such entries in two parts (obviously host and port). I don't care if either the host or port are invalid as long as they don't contain a : (290.234.34.34.5 is ok for host, it will be rejected in the next process); I just want to separate the two parts, or if there is no port part, to know it somehow. I tried to do something with std::stringstream but everything I come up to seems hacky and not really elegant. How would you do this in C++ ? I don't mind answers in C but C++ is prefered. Any boost solution is welcome as well. Thank you.

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• Rationale in selecting Hash Key type

  - by Amrish

  Guys, I have a data structure which has 25 distinct keys (integer) and a value. I have a list of these objects (say 50000) and I intend to use a hash table to store/retrieve them. I am planning to take one of these approaches. Create a integer hash from these 25 integer keys and store it on a hash table. (Yeah! I have some means to handle collisions) Make a string concatenation on the individual keys and use it as a hash key for the hash table. For example, if the key values are 1,2,4,6,7 then the hash key would be "12467". Assuming that I have a total of 50000 records each with 25 distinct keys and a value, then will my second approach be a overkill when it comes to the cost of string comparisons it needs to do to retrieve and insert a record? Some more information! Each bucket in the hash table is a balanced binary tree. I am using the boost library's hash_combine method to create the hash from the 25 keys.

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• Calling a method at a specific interval rate in C++

  - by Aetius

  This is really annoying me as I have done it before, about a year ago and I cannot for the life of me remember what library it was. Basically, the problem is that I want to be able to call a method a certain number of times or for a certain period of time at a specified interval. One example would be I would like to call a method "x" starting from now, 10 times, once every 0.5 seconds. Alternatively, call method "x" starting from now, 10 times, until 5 seconds have passed. Now I thought I used a boost library for this functionality but I can't seem to find it now and feeling a bit annoyed. Unfortunately I can't look at the code again as I'm not in possession of it any more. Alternatively, I could have dreamt this all up and it could have been proprietary code. Assuming there is nothing out there that does what I would like, what is currently the best way of producing this behaviour? It would need to be high-resolution, up to a millisecond. It doesn't matter if it blocks the thread that it is executed from or not. Thanks!

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• Loading specific files from arbitrary directories?

  - by Haydn V. Harach

  I want to load foo.txt. foo.txt might exist in the data/bar/ directory, or it might exist in the data/New Folder/ directory. There might be a different foo.txt in both of these directories, in which case I would want to either load one and ignore the other according to some order that I've sorted the directories by (perhaps manually, perhaps by date of creation), or else load them both and combine the results somehow. The latter (combining the results of both/all foo.txt files) is circumstantial and beyond the scope of this question, but something I want to be able to do in the future. I'm using SDL and boost::filesystem. I want to keep my list of dependencies as small as possible, and as cross-platform as possible. I'm guessing that my best bet would be to get a list of every directory (within the data/ folder), sort/filter this list, then when I go to load foo.txt, I search for it in each potential directory? This sounds like it would be very inefficient, if I have dozens of potential directories to search through every time. What's the best way to go about accomplishing this? Bonus: What if I want some of the directories to be archives? ie. considering both data/foo/ and data/bar.zip to both be valid, and pull foobar.txt from either one without caring.

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• Safe way for getting/finding a vertex in a graph with custom properties -> good programming practice

  - by Shadow

  Hi, I am writing a Graph-class using boost-graph-library. I use custom vertex and edge properties and a map to store/find the vertices/edges for a given property. I'm satisfied with how it works, so far. However, I have a small problem, where I'm not sure how to solve it "nicely". The class provides a method Vertex getVertex(Vertexproperties v_prop) and a method bool hasVertex(Vertexproperties v_prop) The question now is, would you judge this as good programming practice in C++? My opinion is, that I have first to check if something is available before I can get it. So, before getting a vertex with a desired property, one has to check if hasVertex() would return true for those properties. However, I would like to make getVertex() a bit more robust. ATM it will segfault when one would directly call getVertex() without prior checking if the graph has a corresponding vertex. A first idea was to return a NULL-pointer or a pointer that points past the last stored vertex. For the latter, I haven't found out how to do this. But even with this "robust" version, one would have to check for correctness after getting a vertex or one would also run into a SegFault when dereferencing that vertex-pointer for example. Therefore I am wondering if it is "ok" to let getVertex() SegFault if one does not check for availability beforehand?

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• script to count the occurence of the particular string in the given time interval

  - by pruthvi

  We are trying to write a script "sendemail.sh" to count the number of occurrence of a particular string in a log file "SendEmail.log" within the given interval. We have a log file. In that we are searching for a pattern "ReqInputMsgLog" and need to count the number of times it occurred in the given period for eg: from "2014-08-19 11:30" to "2014-08-19 11:34". And our script look like this: #!/bin/sh enterdate=$1 echo $enterdate enddate=$2 enterdate1=`date +%s -d $enterdate +"%Y-%m-%d %H:%M"` echo $enterdate1 enddate1=`date +%s -d $enddate +"%Y-%m-%d %H:%M"` echo $enddate count=0 cat SendEmail.log | grep "ReqInputMsgLog" | awk -F "[" '{print $3}' | awk -F "," '{print $1}' > /con/scripts_server/file.txt for line in `cat /con/scripts_server/file.txt` do logdate=`echo $line | awk -F : '{print $1":"$2}'` if [[ $logdate < $enddate1 ]]; then count=`expr $count + 1` fi done echo $count But when we are trying to execute the script by the below command its not showing the proper count. ./sendemail.sh "2014-08-19 11:30" "2014-08-19 11:34" Log file is very big one. Small chunk has been posted here. INFO [SIBJMSRAThreadPool : 5] [2014-08-19 11:18:24,471] SendEmail - 8/19/14 11:18 AM,ECCF25B0-0147-4000-E000-1B830A3C05A9,ReqInputMsgLog,SendEmail,<?xml version="1.0" encoding="UTF-8"?> <in:sendEmailRequestMsg xmlns:in="http://EmailMed/EmailMedInterface" xmlns:ns0="wsdl.http://EmailMed/EmailMedInterface" xmlns:ns1="http://EmailMed/EmailMedInterface" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:me="wsdl.http://EmailMed/EmailMedInterface" xsi:type="me:sendEmailRequestMsg"> <in:sendEmail xmlns:xci0="http://EmailMed/EmailMedInterface"> INFO [SIBJMSRAThreadPool : 7] [2014-08-19 11:18:14,235] SendEmail - 8/19/14 11:18 AM,ECCEFDB2-0147-4000-E000-1B830A3C05A9,ReqInputMsgLog,SendEmail,<?xml version="1.0" encoding="UTF-8"?> <in:sendEmailRequestMsg xmlns:in="http://EmailMed/EmailMedInterface" xmlns:ns0="wsdl.http://EmailMed/EmailMedInterface" xmlns:ns1="http://EmailMed/EmailMedInterface" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:me="wsdl.http://EmailMed/EmailMedInterface" xsi:type="me:sendEmailRequestMsg"> <in:sendEmail xmlns:xci0="http://EmailMed/EmailMedInterface"> INFO [SIBJMSRAThreadPool : 7] [2014-08-19 11:18:14,241] SendEmail - xmlText: <?xml version="1.0" encoding="UTF-8"?> after awk command we will get a file "/con/scripts_server/file.txt" which looks similar like below: 2014-08-19 11:28:03 2014-08-19 11:28:06 2014-08-19 11:28:17 2014-08-19 11:28:53 2014-08-19 11:29:02 2014-08-19 11:29:47 2014-08-19 11:29:57 2014-08-19 11:30:07 2014-08-19 11:30:17 2014-08-19 11:30:19 2014-08-19 11:30:19 2014-08-19 11:30:22 2014-08-19 11:30:25 2014-08-19 11:30:25 2014-08-19 11:30:36 2014-08-19 11:30:51 2014-08-19 11:30:56 2014-08-19 11:30:59 2014-08-19 11:30:59 2014-08-19 11:31:08 2014-08-19 11:31:25 2014-08-19 11:32:19 2014-08-19 11:32:22 2014-08-19 11:32:27 2014-08-19 11:32:28 2014-08-19 11:32:41 2014-08-19 11:32:49 2014-08-19 11:32:59 2014-08-19 11:33:27 2014-08-19 11:33:41 2014-08-19 11:34:07 2014-08-19 11:34:14 2014-08-19 11:34:21 2014-08-19 11:34:25 2014-08-19 11:34:38 2014-08-19 11:34:50 2014-08-19 11:34:58

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• nginx rewrite rule to convert URL segments to query string parameters

  - by Nick

  I'm setting up an nginx server for the first time, and having some trouble getting the rewrite rules right for nginx. The Apache rules we used were: See if it's a real file or directory, if so, serve it, then send all requests for / to Director.php DirectoryIndex Director.php If the URL has one segment, pass it as rt RewriteRule ^/([a-zA-Z0-9\-\_]+)/$ /Director.php?rt=$1 [L,QSA] If the URL has two segments, pass it as rt and action RewriteRule ^/([a-zA-Z0-9\-\_]+)/([a-zA-Z0-9\-\_]+)/$ /Director.php?rt=$1&action=$2 [L,QSA] My nginx config file looks like: server { ... location / { try_files $uri $uri/ /index.php; } location ~ \.php$ { fastcgi_pass unix:/var/run/php5-fpm.sock; fastcgi_index index.php; fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name; include fastcgi_params; } } How do I get the URL segments into Query String Parameters like in the Apache rules above? UPDATE 1 Trying Pothi's approach: # serve static files directly location ~* ^.+\.(jpg|jpeg|gif|css|png|js|ico|html)$ { access_log off; expires 30d; } location / { try_files $uri $uri/ /Director.php; rewrite "^/([a-zA-Z0-9\-\_]+)/$" "/Director.php?rt=$1" last; rewrite "^/([a-zA-Z0-9\-\_]+)/([a-zA-Z0-9\-\_]+)/$" "/Director.php?rt=$1&action=$2" last; } location ~ \.php$ { fastcgi_pass unix:/var/run/php5-fpm.sock; fastcgi_index index.php; fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name; include fastcgi_params; } This produces the output No input file specified. on every request. I'm not clear on if the .php location gets triggered (and subsequently passed to php) when a rewrite in any block indicates a .php file or not. UPDATE 2 I'm still confused on how to setup these location blocks and pass the parameters. location /([a-zA-Z0-9\-\_]+)/ { fastcgi_pass unix:/var/run/php5-fpm.sock; fastcgi_index index.php; fastcgi_param SCRIPT_FILENAME ${document_root}Director.php?rt=$1{$args}; include fastcgi_params; } UPDATE 3 It looks like the root directive was missing, which caused the No input file specified. message. Now that this is fixed, I get the index file as if the URL were / on every request regardless of the number of URL segments. It appears that my location regular expression is being ignored. My current config is: # This location is ignored: location /([a-zA-Z0-9\-\_]+)/ { fastcgi_pass unix:/var/run/php5-fpm.sock; fastcgi_index Director.php; set $args $query_string&rt=$1; fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name; include fastcgi_params; } location / { try_files $uri $uri/ /Director.php; } location ~ \.php$ { fastcgi_pass unix:/var/run/php5-fpm.sock; fastcgi_index Director.php; fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name; include fastcgi_params; }

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• Token replacement

  - by ClarkeyBoy

  Hey, I currently have a system on my website whereby I can put something like "[cfe]" anywhere in the site and, when the page is rendered, it will replace it with the root to the customer front end (same for "[afe]" and admin front end - so in the admin front end I can put "[cfe]/Default.aspx" to link to the homepage on the customer front end. This is in place as I have a development version of the site, then a test and a live version too. All 3 may have different roots to each section (for example the way the website is set up, the root to the admin front end in test is "/test/Administration/", but in live and development it is just "/Administration/"). Which version it is depends on the URL - all my development sites are in a folder called "development", whereas test is in a folder called "test" and any live urls do not contain either of these. There are also 3 different databases - one for each. All 3, obviously, require a different connection string. I also have a string replacement function in place which can change, for example, "[Product:Cards]" to point to the Cards catalogue page. Problem is that for this I go through all the products and do a replacement on "[Product:" & Product.Name() & "]". However I would like to take this further. I would like to pick up these custom strings when the page is rendered so it picks up "[Product:Cards]" and then goes off to find product "Cards" and replaces the string with a link to the Cards page, rather than looping through all the products and doing a replace just on the off chance that there are any replacements to make. One use for this, which I may start using in the future if I can figure out how to do this, is like on Wikipedia where you put the title of the page you want to point to, then a divider (think its a pipe from memory) then the link text. I would like to apply this to the above situation. This way broken links can also be picked up, and reported to admin (a major advantage as they can then locate them and remove the link or add the product / page that it refers to). I would like to take this to the stage where content of entire pages can be rearranged (kinda like web parts, but not as advanced as that). I mean like so you can put [layout type="3columnImageTopRight" image="imageurl"]Content here[/layout]. This will display, as specified, an image in the top right (with padding at the left and bottom) and 3 columns - maybe with the image spanning one or two columns). The imageurl can be specified as another token: maybe like [Image:imagename.gif] or something. This replaces it with the root to the image folder and then the specified filename. I have not really looked into how I am going to split the content into 3 columns yet, but this would be something to look at for my dissertation and then implement after my project deadline at least. Does anyone have any ideas or pointers which could help me with this? Also if this is not strictly token replacement then please point me to what it is, so I can further develop this. Thanks in advance, Regards, Richard Clarke

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• I don't understand how work call_once

  - by SABROG

  Please help me understand how work call_once Here is thread-safe code. I don't understand why this need Thread Local Storage and global_epoch variables. Variable _fast_pthread_once_per_thread_epoch can be changed to constant/enum like {FAST_PTHREAD_ONCE_INIT, BEING_INITIALIZED, FINISH_INITIALIZED}. Why needed count calls in global_epoch? I think this code can be rewriting with logc: if flag FINISH_INITIALIZED do nothing, else go to block with mutexes and this all. #ifndef FAST_PTHREAD_ONCE_H #define FAST_PTHREAD_ONCE_H #include #include typedef sig_atomic_t fast_pthread_once_t; #define FAST_PTHREAD_ONCE_INIT SIG_ATOMIC_MAX extern __thread fast_pthread_once_t _fast_pthread_once_per_thread_epoch; #ifdef __cplusplus extern "C" { #endif extern void fast_pthread_once( pthread_once_t *once, void (*func)(void) ); inline static void fast_pthread_once_inline( fast_pthread_once_t *once, void (*func)(void) ) { fast_pthread_once_t x = *once; /* unprotected access */ if ( x _fast_pthread_once_per_thread_epoch ) { fast_pthread_once( once, func ); } } #ifdef __cplusplus } #endif #endif FAST_PTHREAD_ONCE_H Source fast_pthread_once.c The source is written in C. The lines of the primary function are numbered for reference in the subsequent correctness argument. #include "fast_pthread_once.h" #include static pthread_mutex_t mu = PTHREAD_MUTEX_INITIALIZER; /* protects global_epoch and all fast_pthread_once_t writes */ static pthread_cond_t cv = PTHREAD_COND_INITIALIZER; /* signalled whenever a fast_pthread_once_t is finalized */ #define BEING_INITIALIZED (FAST_PTHREAD_ONCE_INIT - 1) static fast_pthread_once_t global_epoch = 0; /* under mu */ __thread fast_pthread_once_t _fast_pthread_once_per_thread_epoch; static void check( int x ) { if ( x == 0 ) abort(); } void fast_pthread_once( fast_pthread_once_t *once, void (*func)(void) ) { /*01*/ fast_pthread_once_t x = *once; /* unprotected access */ /*02*/ if ( x _fast_pthread_once_per_thread_epoch ) { /*03*/ check( pthread_mutex_lock(µ) == 0 ); /*04*/ if ( *once == FAST_PTHREAD_ONCE_INIT ) { /*05*/ *once = BEING_INITIALIZED; /*06*/ check( pthread_mutex_unlock(µ) == 0 ); /*07*/ (*func)(); /*08*/ check( pthread_mutex_lock(µ) == 0 ); /*09*/ global_epoch++; /*10*/ *once = global_epoch; /*11*/ check( pthread_cond_broadcast(&cv;) == 0 ); /*12*/ } else { /*13*/ while ( *once == BEING_INITIALIZED ) { /*14*/ check( pthread_cond_wait(&cv;, µ) == 0 ); /*15*/ } /*16*/ } /*17*/ _fast_pthread_once_per_thread_epoch = global_epoch; /*18*/ check (pthread_mutex_unlock(µ) == 0); } } This code from BOOST: #ifndef BOOST_THREAD_PTHREAD_ONCE_HPP #define BOOST_THREAD_PTHREAD_ONCE_HPP // once.hpp // // (C) Copyright 2007-8 Anthony Williams // // Distributed under the Boost Software License, Version 1.0. (See // accompanying file LICENSE_1_0.txt or copy at // http://www.boost.org/LICENSE_1_0.txt) #include #include #include #include "pthread_mutex_scoped_lock.hpp" #include #include #include namespace boost { struct once_flag { boost::uintmax_t epoch; }; namespace detail { BOOST_THREAD_DECL boost::uintmax_t& get_once_per_thread_epoch(); BOOST_THREAD_DECL extern boost::uintmax_t once_global_epoch; BOOST_THREAD_DECL extern pthread_mutex_t once_epoch_mutex; BOOST_THREAD_DECL extern pthread_cond_t once_epoch_cv; } #define BOOST_ONCE_INITIAL_FLAG_VALUE 0 #define BOOST_ONCE_INIT {BOOST_ONCE_INITIAL_FLAG_VALUE} // Based on Mike Burrows fast_pthread_once algorithm as described in // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2444.html template void call_once(once_flag& flag,Function f) { static boost::uintmax_t const uninitialized_flag=BOOST_ONCE_INITIAL_FLAG_VALUE; static boost::uintmax_t const being_initialized=uninitialized_flag+1; boost::uintmax_t const epoch=flag.epoch; boost::uintmax_t& this_thread_epoch=detail::get_once_per_thread_epoch(); if(epoch #endif I right understand, boost don't use atomic operation, so code from boost not thread-safe?

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• Get specifc value from JSon string using JSon.Net

  - by dean nolan

  I am trying to get a value from a JSon formatted string. It was to get album info from a website called Freebase. My result is like this: { "a0": { "code": "/api/status/error", "messages": [ { "code": "/api/status/error/mql/result", "info": { "count": 20, "result": [ { "album": [ { "name": "Definitely Maybe", "release_date": "1994-08-30" } ], "artist": "Oasis", "name": "Live Forever", "type": "/music/track" }, { "album": [ { "name": "Most Wanted Rock 1", "release_date": null } ], "artist": "Oasis", "name": "Live Forever", "type": "/music/track" }, { "album": [ { "name": "Alternative 90s", "release_date": null } ], "artist": "Oasis", "name": "Live Forever", "type": "/music/track" }, { "album": [ { "name": "Live Forever: Best of Britpop", "release_date": "2003-03-03" } ], "artist": "Oasis", "name": "Live Forever", "type": "/music/track" }, { "album": [ { "name": "The Best... In the World... Ever! Volume 5", "release_date": "1997-03-31" } ], "artist": "Oasis", "name": "Live Forever", "type": "/music/track" }, { "album": [ { "name": "Live 4 Ever", "release_date": "1998-06-29" } ], "artist": "Oasis", "name": "Live Forever", "type": "/music/track" }, { "album": [ { "name": "De Afrekening, Volume 8", "release_date": "1994" } ], "artist": "Oasis", "name": "Live Forever", "type": "/music/track" }, { "album": [ { "name": "Now That's What I Call Music! 33", "release_date": null } ], "artist": "Oasis", "name": "Live Forever", "type": "/music/track" }, { "album": [ { "name": "Q: Anthems", "release_date": null } ], "artist": "Oasis", "name": "Live Forever", "type": "/music/track" }, { "album": [ { "name": "The Best Anthems... Ever! Volume 2", "release_date": null } ], "artist": "Oasis", "name": "Live Forever", "type": "/music/track" }, { "album": [ { "name": "1995 Mercury Music Prize: Ten Albums of the Year", "release_date": null } ], "artist": "Oasis", "name": "Live Forever", "type": "/music/track" }, { "album": [ { "name": "Now That's What I Call Music! 1994", "release_date": null } ], "artist": "Oasis", "name": "Live Forever", "type": "/music/track" }, { "album": [ { "name": "Indie Top 20, Volume 21", "release_date": "1995" } ], "artist": "Oasis", "name": "Live Forever", "type": "/music/track" }, { "album": [ { "name": "Dad Rocks!", "release_date": "2006-06-05" } ], "artist": "Oasis", "name": "Live Forever", "type": "/music/track" }, { "album": [ { "name": "Untitled", "release_date": null } ], "artist": "Oasis", "name": "Live Forever", "type": "/music/track" }, { "album": [ { "name": "The Greatest Hits of 1994", "release_date": "1994-10" } ], "artist": "Oasis", "name": "Live Forever", "type": "/music/track" }, { "album": [ { "name": "Top of the Pops 2", "release_date": "2000-03-27" } ], "artist": "Oasis", "name": "Live Forever", "type": "/music/track" }, { "album": [ { "name": "Q: Anthems (disc 1)", "release_date": null } ], "artist": "Oasis", "name": "Live Forever", "type": "/music/track" }, { "album": [ { "name": "Jamie Oliver's Cookin'", "release_date": "2001" } ], "artist": "Oasis", "name": "Live Forever", "type": "/music/track" }, { "album": [ { "name": "Killer Buzz", "release_date": "2001" } ], "artist": "Oasis", "name": "Live Forever", "type": "/music/track" } ] }, "message": "Unique query may have at most one result. Got 20", "path": "", "query": { "album": [ { "name": null, "release_date": null, "sort": "release_date" } ], "artist": "Oasis", "error_inside": ".", "name": "Live Forever", "type": "/music/track" } } ] }, "code": "/api/status/ok", "status": "200 OK", "transaction_id": "cache;cache04.p01.sjc1:8101;2010-03-30T18:04:20Z;0035" } I am looking to get the first album title, Definitely Maybe, from this list. I have tried parsing the string like this: JObject o = JObject.Parse(jsonString); string album = (string)o[""]; But no matter what I have tried I don't know what to put in those quotes. How would I get this specific value or be able to search for it? Thanks

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• Count string value?

  - by Adam

  Hey, Im a newbie in cocoa and I have a string and I am trying to count how long it is. I have been searching through Apples docs but I can't find anything. NSString *word = @"word"; How would I figure out how many characters is in a string? Thanks

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• Validate a string in a table in SQL Server - CLR function or T-SQL

  - by Ashish Gupta

  I need to check If a column value (string) in SQL server table starts with a small letter and can only contain '_', '-', numbers and alphabets. I know I can use a SQL server CLR function for that. However, I am trying to implement that validation using a scalar UDF and could make very little here...I can use 'NOT LIKE', but I am not sure how to make sure I validate the string irrespective of the order of characters or in other words write a pattern in SQL for this. Am I better off using a SQL CLR function? Any help will be appreciated.. Thanks in advance Thank you everyone for their comments. This morning, I chose to go CLR function way. For the purpose of what I was trying to achieve, I created one CLR function which does the validation of an input string and have that called from a SQL UDF and It works well. Just to measure the performance of t-SQL UDF using SQL CLR function vs t- SQL UDF, I created a SQL CLR function which will just check if the input string contains only small letters, it should return true else false and have that called from a UDF (IsLowerCaseCLR). After that I also created a regular t-SQL UDF(IsLowerCaseTSQL) which does the same thing using the 'NOT LIKE'. Then I created a table (Person) with columns Name(varchar) and IsValid(bit) columns and populate that with names to test. Data :- 1000 records with 'Ashish' as value for Name column 1000 records with 'ashish' as value for Name column then I ran the following :- UPDATE Person Set IsValid=1 WHERE dbo.IsLowerCaseTSQL (Name) Above updated 1000 records (with Isvalid=1) and took less than a second. I deleted all the data in the table and repopulated the same with same data. Then updated the same table using Sql CLR UDF (with Isvalid=1) and this took 3 seconds! If update happens for 5000 records, regular UDF takes 0 seconds compared to CLR UDF which takes 16 seconds! I am very less knowledgeable on t-SQL regular expression or I could have tested my actual more complex validation criteria. But I just wanted to know, even I could have written that, would that have been faster than the SQL CLR function considering the example above. Are we using SQL CLR because we can implement we can implement lot richer logic which would have been difficult otherwise If we write in regular SQL. Sorry for this long post. I just want to know from the experts. Please feel free to ask if you could not understand anything here. Thank you again for your time.

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• [PHP]RegEx help with a string

  - by Uffo

  So I have a random of strings and I need to parse them, let's take an example: This string - DeleteMe please and some other text So I want to find DDeleteMe please and some other text and remove it, because all I need is This string Best Regards,

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• C# converting string to hex and XOR on Hex numbers

  - by Scott's Oasys

  Im tring to do an XOR on 2 hex numbers to create a unique hex number ex. 7F4 ^ 65D which would equal 1A9 I understand how the XOR should work but every time I try to convert the string hex number: string hex1 = "7F4"; int hexInt = Convert.ToInt32(hex1, 16); I end up with a number: 2036 How do I keep the integrity of the hex number so I can do an XOR on the 2 hex numbers?

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• Utility method - Pass a File or String?

  - by James P.

  Here's an example of a utility method: public static Long getFileSize(String fileString) { File file = new File(fileString); if (file == null || !file.isFile()) return null; return file.length(); } Is it a good practise to pass a String rather than a File to a method like this? In general what reasoning should be applied when making utility methods of this style?

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• ASP.NET MVC Render View to String

  - by Ben

  I'm currently using NVelocity to render some email templates. I'm curious how I can do this with the standard ASP.NET MVC view engine i.e. render a view as a string. Basically I want to pass get the string result of a model binded view and pass this to iTextSharp to generate a PDF. Thanks. Ben

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• jQuery find file extension (from string)

  - by SoulieBaby

  Hi all, I was wondering if it was possible for jQuery to find a file extension based on a returned string? A filename (string) will be passed to a function (openFile) and I wanted that function to do different things based on what file has been passed through, it could be image files or pdf files. function openFile(file) { //if .jpg/.gif/.png do something //if .zip/.rar do something else //if .pdf do something else }; I've been looking for something that will find the file's extension but I can't seem to find anything.

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• Efficient intersection of two List<String> in Java?

  - by Pentium10

  Question is simple: I have two List List<String> columnsOld = DBUtils.GetColumns(db, TableName); List<String> columnsNew = DBUtils.GetColumns(db, TableName); And I need to get the intersection of these. Is there a quick way to achieve this?

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• How to dump ASP.NET Request headers to string

  - by FreshCode

  I'd like to email myself a quick dump of a GET request's headers for debugging. I used to be able to do this in classic ASP simply with the Request object, but Request.ToString() doesn't work. And the following code returned an empty string: using (StreamReader reader = new StreamReader(Request.InputStream)) { string requestHeaders = reader.ReadToEnd(); // ... // send requestHeaders here }

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