- Boost-users - lists.boost.org

Re: [Boost-users] Inheritance
by james.jones＠firstinvestors.com 16 Nov '05

16 Nov '05

Hi Azam, Are you sure you want to inherit? Might it make sense to make a Boost graph object a private variable which you construct and then modify in your constructor? - James Jones Administrative Data Mgmt. (v)732-510-1806 375 Raritan Center Pkwy, Suite A (f)732-510-1855 Edison, NJ 08837 Visit us on the web at http://www.firstinvestors.com/ --- Original Message --- Date: Tue, 15 Nov 2005 18:53:15 -0800 From: "azam ." <boost80(a)gmail.com> Subject: [Boost-users] Inheritance To: boost-users(a)lists.boost.org Message-ID: <825e260c0511151853q4b0d599ek5a0d6d3daa28dec3(a)mail.gmail.com> Content-Type: text/plain; charset="iso-8859-1" Hi, I want to use Boost Graph Library via inheritance. Actually I want to define a graph which is an adjacency_list graph and is created in a special way. I thought of making it a derived class of adjacency_list and then define constructors to construct objects of this class. But my problem is how to (for example) set vertex properties in the constructor? Regularly if I want to add properties to vertices on a graph g, I use vertices(g) to get iterator of vertices and then I use this iterator, but what can I do in the constructor? I have no such graph object there and I can't use "this" reference too. Any help would be really appreciated. Thanks Azam

1 0

Collections of shared_ptr<Base> and shared_ptr<Derived>
by Keith Weintraub 16 Nov '05

16 Nov '05

Folks, What is the best way to pass a std::vector<boost::shared_ptr<Derived> > to a function that expects a std::vector<boost::shared_ptr<Base> >? Can I use a cast or should I create a new std::vector<boost::shared_ptr<Base> > by iterating over the std::vector<boost::shared_ptr<Derived> >? Here is some sample code. What f is doing is not important it is just an example: class A { // This class is from a library I have no control over. public: virtual string getName() { return string("A");} }; class B : public A { // I need to create B from A to have extra functionality public: virtual string getName() { return string("B");} virtual string getLongName() { return string("This is B");} }; void f(std::vector<boost::shared_ptr<A> > &v) { // This function is from a library that I have no control over. for(int i = 0; i < v.size(); i++) cout << v[i]->getName(); } int main(char *argv, int arc) { std::vector<boost::shared_ptr<B> > bvec(10); boost::shared_ptr<B> bPtr(new B); bvec[0] = bPtr; f(bvec); // This should not compile. <------------------------- } The last line (with the arrow) won't compile because std::vector<boost::shared_ptr<B> > cannot be converted to std::vector<boost::shared_ptr<A> >.

1 0

Boost.Iostreams - Filtering Stream questions (flushing, interactive input)
by Michael Rickert 16 Nov '05

16 Nov '05

I've been trying to use Boost.Iostreams, with mixed success. I've got a few more stumbling blocks that hopefully I can get some help with :-). First, I have a socket class, which I've used Boost.Iostreams to create a nice interface for. Quick details: class winsock_device { typedef boost::iostreams::bidirectional_device_tag category; //..implementation.. }; class winsock_socket { typedef winsock_device stream_device_type; typedef boost::iostreams::stream_buffer< stream_device_type > stream_buffer_type; typedef std::iostream stream_type; stream_device_type m_stream_device; stream_buffer_type m_stream_buffer; stream_type m_stream; public: winsock_socket( SOCKET raw_socket ) : m_stream_device( raw_socket ) , m_stream_buffer( m_stream_device ) , m_stream( & m_stream_buffer ) {} stream_type & stream() { return m_stream; } //..more implementation.. }; The implementation seems to work, tests show it to be working fine for input and output (with output needing to be flushed). Only problem is that the newlines are mismatched - a simple telnet chat client gets supurflous \r characters using std::getline, so I decided to wrap around the stream using a boost::iostreams::filtering_stream< boost::iostreams::bidirectional >, which is where things fall apart. I took my simple example, and replaced: std::iostream & ios = socket->stream(); with: namespace bios = boost::iostreams; bios::filtering_stream< bios::bidirectional > ios; ios.push( socket->stream() ); both with the same testing code: std::string nickname; ios << "Welcome, user - please enter a nickname:\n" << std::flush; socket->stream().flush(); std::getline( ios , nickname ); ios << "Welcome, " << nickname << "\n"; ios << "*** actual chatting not yet implemented ***\n"; ios << "Disconnecting you now, bye " << nickname << " !!!\n" << std::flush; socket->stream().flush(); This failed to work at all at first, eventually I figured out I needed to flush first the ios stream, and then the underlying socket->stream. This brings me to: question 1: Is there a workaround to allow an ending stream of (std::iostream &) to be flushed automatically by flushing filtering_stream? Even with no filters installed, however, the program freezes (until I shut down the telnet client) when I attempt to read a line from the stream, even after entering multiple newlines - I'm not exactly sure what's happening here. This brings me to: question 2: How can I get the input moving through my stream? Do I need to start a seperate thread to constantly flush() the stream that the main thread is blocked on i/o for? Thanks, -Mike

1 0

Inheritance
by azam . 16 Nov '05

16 Nov '05

Hi, I want to use Boost Graph Library via inheritance. Actually I want to define a graph which is an adjacency_list graph and is created in a special way. I thought of making it a derived class of adjacency_list and then define constructors to construct objects of this class. But my problem is how to (for example) set vertex properties in the constructor? Regularly if I want to add properties to vertices on a graph g, I use vertices(g) to get iterator of vertices and then I use this iterator, but what can I do in the constructor? I have no such graph object there and I can't use "this" reference too. Any help would be really appreciated. Thanks Azam

1 0

[IOStreams] Memory leaks when using zlib_compressor
by Christian Henning 16 Nov '05

16 Nov '05

Hi there, I couldn't find anything in the archives for my problem. Purify is showing several memory leaks when I execute the following program: int _tmain(int argc, _TCHAR* argv[]) { // prepare some data to write unsigned int nSize = 1000000; char* pBits = new char[nSize]; ::memset( pBits , 0 , nSize ); for( unsigned int i = 0; i < nSize; i++ ) { pBits[i] = i; } // write to file io::filtering_ostream out; out.push( io::zlib_compressor() ); out.push( io::file_sink( "test.zip", std::ios::binary )); out << nSize; out.write( pBits , nSize ); // clean up delete[] pBits; return 0; } I think the program is right. I'm using Boost 1.33 with VC 7.1. Here is what purify spits out: [I] Summary of all memory leaks... {268108 bytes, 6 blocks} [I] MPK: Potential memory leak of 196608 bytes from 3 blocks allocated in boost::iostreams::detail::zlib_base::do_init(zlib_params::iostreams::boost const&,bool,(*)(void *,UINT,UINT),(*)(void *,void *),void *) [IOStreams.exe] [W] MLK: Memory leak of 71360 bytes from 2 blocks allocated in boost::iostreams::detail::zlib_base::do_init(zlib_params::iostreams::boost const&,bool,(*)(void *,UINT,UINT),(*)(void *,void *),void *) [IOStreams.exe] Is that a know issue? I guess so, but has it been resolved? Thanks, Christian

2 3

Too many library variants
by Merrill Cornish 15 Nov '05

15 Nov '05

When I built Boost 1.33.0 for MinGW, I just specified the toolset. As a result I got 28! variants on the set of Boost libraries. >From the various file names, I can figure out most of the variants: d = debug mt = multi-threaded s = static but there are other variants which aren't as obvious. For example, what's the distinction among boost-<libname>-mgw-1_33.dll boost-<libname>-mgw-1_33.lib boost-<libname>-mgw.lib The two .lib files have the same sizes and timestamps, so they appear to be the same file with and without the Boost version in the name. Is the idea that if you use the library WITHOUT the version number suffix, then you can upgrade to a new version without having to modify your make file? OK, what's the distinction between the .dll and .lib? I understand that they linker needs one set of information about library function names and entry points while the actual function bodies are needed at run time. However, I thought all of that information is in the .dll file. On the other hand, the .dll version is so much bigger than the .lib that there must be more than an entry point table involved. Then there are the libboost-* variations... I understand that in the Unix world, the -L linker option specifies the library directory while the -l<name> option tells the Unix linker to look for the lib<name>.a file. OK, but how does that work with MinGW's ld.exe linker on Windows. Some of the libraries are available only in the static version, but the only static libraries are the libboost-* variants. There is a statement somewhere in the Boost library documention that the selection of libraries should be automatic in Windows because of pragma's in the libraries. However, I haven't been able to find where MinGW supports that pragma. Merrill

4 4

split() differences between 1.32.0 and 1.33.0
by Dave Dribin 15 Nov '05

15 Nov '05

Hello, I recently upgrade from Boost 1.32.0 to 1.33.0, since I just upgraded to Mac OS X 10.4 from 10.3. I noticed a slightly different behavior in boost::algorithm::split between these two versions. If you have a trailing delimiter, like: vector<string> results; ba::split(results, ",foo,", ba::is_any_of(",")); This returns 2 elements in 1.32.0 and 3 elements in 1.33.0. Was this changed intentionally? It does seem to make more sense to return 3 elements, but it currently breaks my program. -Dave

3 3

[Review] Boost.Logging review result
by Hartmut Kaiser 15 Nov '05

15 Nov '05

Hi all, today I got the following message from John Torjo: <quote> Due to the feedback I got, I would like you to declare the library as rejected. In the light of what Gennady and others have said, indeed, another interface would be best suited for the Boost Log library. With what I know now, I would like to redesign the library from ground up, and ask for another review, probably 6 months from now or so. </quote> In the light of this announcement the review of the proposed Boost.Logging library submitted by John is closed. The library is not included into Boost. I very much hope John will find the time and energy to redesign and resubmit the library in the future. Regards Hartmut Review Manager

1 0

[Boost][Serialization] reset_object_address in 1.33.1 beta?
by Topi Mäenpää 15 Nov '05

15 Nov '05

Hi, reset_object_address is no more a member of polymorphic_iarchive in 1.33.1 beta. Why not? -- Topi Mäenpää CTO, Intopii +358 40 774 7749

2 1

Re: [Boost-users] Too many library variants
by Merrill Cornish 15 Nov '05

15 Nov '05

Jeff, Thanks for mentioning that. I am a bit weird in that I *do* RTFM. While the Boost documentation has a very professional look, I have found in a number of different libraries that the information seems disjoint. It is often difficult to figure out how to do any one thing without reading and comparing a bunch of different pages. For example, you build Boost with bjam, but try to find one listing of what the command line arguments are to bjam. Merrill

1 0