March 2010 - Boost-users - lists.preview.boost.org

[CRC] Differences in crc_16_type and crc_32_type
by Ryan McConnehey 05 Mar '10

05 Mar '10

Work is wanting to use standard CRC algorithms for both 16 and 32 bit results. This would simplify documentation by not needing to use examples to define the process. The CRC library has predefined four common CRC algorithms. I've included three of the definitions for ease of discussion. Using Wikipedia and the truncated polynomial values, I identified the following algorithms. typedef crc_optimal<16, 0x8005, 0, 0, true, true> crc_16_type; typedef crc_optimal<16, 0x1021, 0xFFFF, 0, false, false> crc_ccitt_type; typedef crc_optimal<32, 0x04C11DB7, 0xFFFFFFFF, 0xFFFFFFFF, true, true> crc_32_type; crc_16_type = crc-16-IBM crc_ccitt_type = crc-16-ccitt crc_32_type = crc-32-ieee 802.3 Now for the questions. How do I know the CRC parameters for each algorithm? For example, if the reflection input for crc_ccitt_type was changed from false to true, is the algorithm result still crc-16-ccitt? Why are the parameters for crc_16_type and crc_32_type different? I expected only the truncated polynomial to change, not the initial remainder and final XOR value. Is it true that crc-32-ieee 802.3 is also called crc-32-ccitt? If that is correct why is the crc_16_type so different? Any clarification to my understanding would be helpful. Ryan

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Boost ASIO issue
by A.Agrawal＠patrick.com.au 05 Mar '10

05 Mar '10

Hello All, Thanks for resolving my ASIO related issues so far, special thanks to Igor R. Now I am having a very strange problem. My program (based on chat server example in ASIO documentation) work fine on a simulator machine and have been tested thoroughly. But when I put it on another machine, it starts giving strange problems some seems to be random but I observed one of them very consistent. std::vector<boost::asio::const_buffer> buffers; buffers.push_back(boost::asio::buffer(_outbound_header)); buffers.push_back(boost::asio::buffer(_outbound_message)); buffers.push_back(boost::asio::buffer(_outbound_data)); boost::asio::async_write(*_socket, buffers, boost::bind(&DJClient::handle_write, this, boost::asio::placeholders::error)); For the above code, handle_write is never called. I can see on the server side that the server has received the request and has also sent the response. But I do not receive the response in the client side. It seems something is going wrong with io_service but don't know what. The same code has worked on a different machine. Any help will be highly appreciated. Regards, Anil Agrawal Patrick Technology & Systems Phone: +61 2 8333-6340

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Boost.Thread and Boost.Function problems?
by anony 05 Mar '10

05 Mar '10

I have this situation: void my_thread(std::string const& a, std::string const& b) { } void spawner() { boost::thread(boost::function<void (std::string const&, std::string const&>(my_thread), "bla", "lala"); } This works, but is it possible that the string temporaries are destroyed before the thread starts running?

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Problem with boost:thread
by Daniel Veneros 04 Mar '10

04 Mar '10

Hey, I'm trying to start a thread from a Class but the only way I did it was using a pointer. The thing is that when I assign the thread to the pointer it wont start unless I use join(). I need it to star right away is created just like when I create a thread (boost::thread myThread(funcName);) I was trying to use thread_group to do this, but create_thread is not working. *Here's an example of what I was doing:* *(Here I used the pointer)* class Thread { public: Thread(){}; virtual ~Thread(){}; virtual void run() = 0; void start(){m_Thread = new boost::thread( &Thread::run, this ); }; //wont start unless I add m_Thread.join(); private: boost::thread* m_Thread; }; *and now... I am trying to use thread_group:* class Thread { public: Thread(){}; virtual ~Thread(){}; virtual void run() = 0; void start(){g_Thread.create_thread(&Thread::run); }; private: boost::thread_group g_Thread; }; *But I receive an error:* /usr/local/include/boost/thread/detail/thread.hpp: In member function 'void boost::detail::thread_data<F>::run() [with F = void (Thread::*)()]': main.cpp:61: instantiated from here /usr/local/include/boost/thread/detail/thread.hpp:56: error: must use '.*' or '->*' to call pointer-to-member function in '((boost::detail::thread_data<void (Thread::*)()>*)this)->boost::detail::thread_data<void (Thread::*)()>::f (...)' make[2]: *** [build/Debug/GNU-MacOSX/main.o] Error 1 Im using netBeans on Mac OS X 10.6.2 Anyone knows how should I create this? or how to use simple boost::thread and launch it without using join()?? Thanks!!! Dann

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[Boost.Multi-index] empty container allocates 1 unused node
by Jakub Jablonski 04 Mar '10

04 Mar '10

Hi, I was trying out some examples of using multi_index_container with custom allocator. I found out that even an empty container, on creation, allocates memory for a single node (but no element is stored inside). In other words, if I store N elements, the container allocates memory for N+1 elements. Is it a fault? If not, what is this memory used for? Is there any way to avoid this allocation? Regards, Jakub

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Compiling Boost 1.42 in OS X
by Andrea Moglia 03 Mar '10

03 Mar '10

Hi, I tried many times to compile Boost 1.42 under OS X. However I always get relase mode. I inserted these commands: ./Bootstrap.sh --prefix=destination path ./bjam install I am looking for a way to compile Boost 1.42 in both debug and release mode. Please, could you tell me how to do that? Thank you. Andrea

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Enumerating paths and euler paths in a graph
by Yaron Kretchmer 03 Mar '10

03 Mar '10

Hi There. I'm a boost newbie, so my apologies if this has been discussed before: I need to 1) Enumerate all paths of a certain length in a given graph. 2) Find all Euler paths in a given eulerian graph. Any idea on how to do that with boost? Thanks Yaron

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boost::input_filter and negative char
by eial＠cs.bgu.ac.il 03 Mar '10

03 Mar '10

hello. I've seem to found a strange behavior within boost::input_filter, I'm writing data to a file using bzip2 compressor, in this issue all goes well, now when I read the data (I post process the data after the de/compression) because some of the chars are negative, then cases where there are two sequential -1 causes the filter to end processing even if the file isn't at eof. what can be done to prevent it? should this even happen? here are the test results: http://www.4shared.com/file/233035989/8bde1629/testresults.html

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[traits/function_types/generic] Can F be called with {a0, ..., aN}?
by Rutger ter Borg 03 Mar '10

03 Mar '10

Hello, I have been trying to achieve assignment to a variant of functions, typedef boost::variant< boost::function< int >, boost::function< int, int > > variant_type; which is nice until you try to assign an ambiguous callable object to it, especially if the callable object has templates or similar. This has lead to my question: is there a way to know (without the "no matching function call" compiler error if {a0,...,aN} in F(a0,a1,...,aN) are permissible arguments to callable object/function F? I thought I had a nice solution by overriding boost::result_of< F(a0,a1..,aN)>::type in such way that it doesn't give compile errors if a type doesn't exist, but mpl::na (in conjunction with a has_result_of<T> meta-function). Then, writing functors like struct some_func { template< typename Sig > struct result { // no type defined here, so result_of<>::type is not defined } template< ... > struct result< enable_if arguments are acceptable > { typedef ... type; } R operator()( ... ) {} }; gives you the ability to answer the question for those particular functors. However, some widely used stuff like boost::bind always has a result_type, so this trick was a dead end. So, in short, does anyone know of a generic trick to know if F can be called with a set parameters {a0,...,aN} (without the compile error)? Thanks, Cheers, Rutger

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[boost-users] [test] Boost.Test Mock
by Andrey Torba 03 Mar '10

03 Mar '10

Hi All, Whare can i find information about Boost.Test Mock? -- Regards, Andrey

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