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

Re: [Boost-users] Is there any existing/similar C++ lib for Java FileChannel
by Tan, Tom (Shanghai) 07 Jul '10

07 Jul '10

I did not look too much into details, but it seems to be related to memory-mapped files. Boost.iostream does support memory mapped files: http://www.boost.org/doc/libs/1_43_0/libs/iostreams/doc/classes/mapped_f ile.html >Date: Tue, 6 Jul 2010 07:25:12 +0800 >From: Bo Xie <xiebopublic(a)gmail.com> >To: boost-users(a)lists.boost.org > >Hello, > >Java FileChannel ( >http://java.sun.com/j2se/1.4.2/docs/api/java/nio/channels/FileChannel.h tml) >supports to lock a region of the file [e.g.lock(long position, long size, boolean shared)]. Is there any existing/similar C++ lib for it (so than I need not to reinvent the wheel)? > >Best Regards, >Bo Xie

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Compiler error when using property map get()
by Trevor Harmon 06 Jul '10

06 Jul '10

Hi, The get() function for property maps has me puzzled. Calling it in one context gives a compiler error, while in another context it does not. A trivial example is below. Note that the code in foo() and main() are identical. Any guesses as to why the foo() version gives a compiler error while the main() version does not? FWIW, the error is: subgraph.cpp: In member function ‘virtual void MyGraph::foo()’: subgraph.cpp:15: error: conversion from ‘boost::subgraph_global_property_map<Subgraph*, boost::adj_list_edge_property_map<boost::bidirectional_tag, size_t, size_t&, size_t, boost::property<boost::edge_index_t, size_t, boost::no_property>, boost::edge_index_t>, boost::edge_index_t>’ to non-scalar type ‘boost::adj_list_edge_property_map<boost::bidirectional_tag, size_t, size_t&, size_t, boost::property<boost::edge_index_t, size_t, boost::no_property>, boost::edge_index_t>’ requested Thanks, Trevor #include <boost/graph/adjacency_list.hpp> #include <boost/graph/subgraph.hpp> using namespace boost; typedef subgraph<adjacency_list<vecS, vecS, bidirectionalS, int, property<edge_index_t, std::size_t> > > Subgraph; typedef property_map<Subgraph, edge_index_t>::type EdgeIndexMap; class MyGraph : public Subgraph { virtual void foo(); }; void MyGraph::foo() { Subgraph g; EdgeIndexMap edgeMap = get(edge_index, g); } int main(int, char**) { Subgraph g; EdgeIndexMap edgeMap = get(edge_index, g); return 0; }

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Error in [Range] document
by John Dlugosz 06 Jul '10

06 Jul '10

In <http://www.boost.org/doc/libs/1_43_0/libs/range/doc/html/range/reference/ad…>, the example: std::vector<int> vec; boost::replace_copy_if( rng, std::back_inserter(vec), pred ); should have a with_what argument after pred. To match the following example, it should be called new_value. --John (stupid footer; sorry) TradeStation Group, Inc. is a publicly-traded holding company (NASDAQ GS: TRAD) of three operating subsidiaries, TradeStation Securities, Inc. (Member NYSE, FINRA, SIPC and NFA), TradeStation Technologies, Inc., a trading software and subscription company, and TradeStation Europe Limited, a United Kingdom, FSA-authorized introducing brokerage firm. None of these companies provides trading or investment advice, recommendations or endorsements of any kind. The information transmitted is intended only for the person or entity to which it is addressed and may contain confidential and/or privileged material. Any review, retransmission, dissemination or other use of, or taking of any action in reliance upon, this information by persons or entities other than the intended recipient is prohibited. If you received this in error, please contact the sender and delete the material from any computer.

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[Interprocess] Shared Mutex - Permission Denied
by Matt Cupp 06 Jul '10

06 Jul '10

From: http://groups.google.com/group/boost-list/browse_thread/thread/fc728b9d416c… > Interprocess has this embarrasing permission limitations, but I still > don't know how to fix it. Does the permissions limitation apply to Linux (CentOS) and shared mutexes or segments created by other users or root? I have a mutex in the /dev/shm folder created by another user with these permissions (from ls -l): -rwxr-xr-x 1 webers users 160 Jul 1 15:24 Lookup_Mutex My user account is a member of the users group, but since it defaults to just read only access I can't actually use the mutex as a mutex. Is there any way to get around it? Thanks, Matt

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[Assign] reservation and insert efficiency
by John Dlugosz 06 Jul '10

06 Jul '10

Does the initialization form I showed earlier, e.g. std::vector<record_type> newvec= list_of().range(RecVec.begin(),db).range(newdata).range(de,RecVec.end()); know to get the total length first, or will it keep re-allocating storage with each underlying insertion? That is, do I get a performance benifit from manually doing: std::vector<record_type> newvec; newvec.reserve (... add up the sizes of my three ranges ...) newvec += range(RecVec.begin(),db).range(newdata).range(de,RecVec.end()); Hmm, I'm sure the last line would be somewhat different. Anyway, do I need to reserve first, or will it be reasonably smart about that? --John (awkward footer alert!) TradeStation Group, Inc. is a publicly-traded holding company (NASDAQ GS: TRAD) of three operating subsidiaries, TradeStation Securities, Inc. (Member NYSE, FINRA, SIPC and NFA), TradeStation Technologies, Inc., a trading software and subscription company, and TradeStation Europe Limited, a United Kingdom, FSA-authorized introducing brokerage firm. None of these companies provides trading or investment advice, recommendations or endorsements of any kind. The information transmitted is intended only for the person or entity to which it is addressed and may contain confidential and/or privileged material. Any review, retransmission, dissemination or other use of, or taking of any action in reliance upon, this information by persons or entities other than the intended recipient is prohibited. If you received this in error, please contact the sender and delete the material from any computer.

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[Assign]
by John Dlugosz 06 Jul '10

06 Jul '10

This is my first time reaching for the Assign library, but I'm insprired by what I've seen discussed here in the list. I'm creating a vector from three ranges. So something like: std::vector<record_type> newvec= list_of().range(a,b).range(c,d).range(e,f); would be right? The tutorial doesn't show anything where the stuff begins with a range, only stuff in the list_of(). But I'm thinking I have to start with list_of, even if it's empty, to kick it off, right? I'm hoping that correctly kicks it off but doesn't add default elements! Next question: the range c,d is going to be a whole vector. That is, the V.begin(), V.end() pair from another object. Can I just name V alone? Would that be done in a range(V) wrapper, or by itself, or some other function name? --John TradeStation Group, Inc. is a publicly-traded holding company (NASDAQ GS: TRAD) of three operating subsidiaries, TradeStation Securities, Inc. (Member NYSE, FINRA, SIPC and NFA), TradeStation Technologies, Inc., a trading software and subscription company, and TradeStation Europe Limited, a United Kingdom, FSA-authorized introducing brokerage firm. None of these companies provides trading or investment advice, recommendations or endorsements of any kind. The information transmitted is intended only for the person or entity to which it is addressed and may contain confidential and/or privileged material. Any review, retransmission, dissemination or other use of, or taking of any action in reliance upon, this information by persons or entities other than the intended recipient is prohibited. If you received this in error, please contact the sender and delete the material from any computer.

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what are movable objects
by Abbhishek Misra 06 Jul '10

06 Jul '10

Hello Boost Users, I'm trying to learn multi threading in C++. http://www.boost.org/doc/libs/1_39_0/doc/html/thread/thread_management.html says "Objects of type boost::thread are movable, however, so they can be stored in move-aware containers, and returned from functions." Please help me understand what are movable objects. reagrds Abhishek

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using system:error_code
by Lloyd 06 Jul '10

06 Jul '10

Hi, How can I interpret and use the error_code in my application? As an example my ASIO async_read "handler function" receives one argument as error, as shown below void MyClass::AsyncReadHandler(const boost::system::error_code& error,std::size_t bytes_transferred) { } How can I inrterpret the "error" in a meaningful way? error.message() returns the meaning of the error and and error.value() returns an integer code associated with the error. So far fine, but how can I use it in a comparison operator in a portable way... if(error.value()==2) //Not readable { } if(error.value()==END_OF_FILE) //More readable { } So how can I get the respective "enum" associated with the error Thanks a lot, Lloyd ______________________________________ Scanned and protected by Email scanner

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[tuple] set_open manipulator
by Hicham Mouline 06 Jul '10

06 Jul '10

Hello I am trying to remove the ( bracket from the output of a tuple. So I've called stream << boost::tuples::set_open( static_cast<char>(0) ) << boost::tuples::set_close( static_cast<char>(0) ) << tuple; however, the brackets are still printed. PS: when I used '' instead of static_cast<char>(0), gcc complained about empty character constant. Rds,

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Is there any asynchronous file read/write Boost lib?
by Bo Xie 06 Jul '10

06 Jul '10

Hello, As I know, Boost.Asio is for asynchronous network socket, not asynchronous file read/write. Is there any asynchronous file read/write Boost (or other cross platform) lib? Best Regards, Bo Xie

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