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Boost.Variant: char[], a bool or std::string ?
by Nindi Singh 01 Jul '06

01 Jul '06

... .. but this works fine .. #include<string> #include<boost/variant.hpp> typedef boost::variant<std::string> BoostVariant; int main () { BoostVariant v("A String"); std::string &Sref(boost::get<std::string&>(v)); // NOW this does NOT throw return 0; }

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Boost.Variant: char[], a bool or std::string ?
by Nindi Singh 01 Jul '06

01 Jul '06

If I instantiate a Boost.Variant templated on a bool and a std::string , then I get the following behaviour ... not sure why #include <string> #include <Boost/Variant.hpp> typedef boost::variant< bool,std::string> BoostVariant; int main () { BoostVariant v("A String"); bool &Bref ( boost::get<bool &>(v)) ; // this is ok std::string &Sref ( boost::get<std::string> &(v) ) ; // but this throws return 0; } Is this what is supposed to happen ? Ninds

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[serialization] Error serializing std::wstring to text_oarchive on VC++
by William Kemper 01 Jul '06

01 Jul '06

The fill method on mb_from_wchar calls std::wctomb, which is backed by 'WideCharToMultiByte'. This function uses the codepage defined in the current locale, however, the utf-8 codepage does not function properly on VC++ 7 or 8. Would it be difficult to have the conversion use the code_cvt facet defined for the stream underlying the archive? It also seems that doing so would ensure serialization / deserialization would be more consistent and self-sufficient, since neither process would depend on a (mutable) global locale setting. At any rate, the serialization library works with certain window's codepages, but *not* with the utf-8 codepage (65001). It would be nice to have the library use its own utf8_code_cvt facet to translate wide characters to multibyte. If there is some work around I'm not aware of, I would appreciate any advice. Thanks.

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Compile-time constant CRCs
by Michael Marcin 01 Jul '06

01 Jul '06

I didn't tag this because I'm not sure if it should belong to [preprocessor], [mpl] or [crc]. Given the black-box (macro, function, class, whatever) I'll call ConstCRC32 that is assignable to a unsigned int is there a way to write: unsigned int hash = ConstCRC32( "HELLO" ); and have an optimized build yield the equivalent of: unsigned int hash = 0x58a10fc0; I had a solution (although obviously non-portable) in msvc7.1 but after moving to msvc8 and stepping through the code I noticed that msvc8's "improved" optimizing compiler cannot optimize away the calculation like msvc7.1's could. I also doubt that the code would work if I ever had to port it to another compiler. I tried using simple TMP techniques I've used in the past but couldn't find a way to access the characters of the string. So looking around I came upon boost.crc which is geared towards computing crcs of blocks of data which isn't really what I care about right now. I also found boost.mpl which is very cool but I have a hard time grasping still. The problems seems solvable with mpl if I could transform the data into boost::mpl::list_c<char,'H','E','L','L','O'> but I still coulnd't find a way to access the characters of the string and I think others at my company would rather revert to the old #define CRC( str, crc ) crc unsigned int hash = CRC( "HELLO", 0x58a10fc0 ); than move to that syntax directly. So looking further I found boost.preprocessor which I haven't explored enough to see if there is away to have PP calculate the CRC directly or have it transform the string into the boost::mpl::list_c form. Can anyone offer some advice? Thanks Mike P.S. The old version was actually fairly simple it just used a precomputed static const unsigned int lookup table and did a strlen and a for loop with a lookup into the table for each character (in a __forceinline function that took a const char * const string).

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Replacing C functions with boost::function for callback functions in OpenGL
by Stephen Torri 01 Jul '06

01 Jul '06

I have a main file from my OpenGL program which contains global variables and the functions that are used by OpenGL as callback functions. For example: int a; float b; void display () { .... display code calls ... } int main (int argc, char **argv) { glutDisplayFunc( display ); } Now I thought I would put all the variables and functions into a class and use that in the main. Here is where I am getting stuck on the use of boost::function. I changed the code to look something like the following: class MyMain { int a; float b; void display() { ... display code calls ... } } int main (int argc, char **argv) { MyMain m_ref; boost::function<void()> disp_func = boost::bind ( &MyMain::display, &m_ref ); glutDisplayFunc ( disp_func ); } What I am getting back from the g++ compiler is the following error message: error: cannot convert `boost::function<void ()(), std::allocator<void> >' to `void (*)()' for argument `1' to `void glutDisplayFunc(void (*)())' Any ideas where I am going wrong? Stephen

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[regex] Support for named captures?
by Olenhouse, Jason 30 Jun '06

30 Jun '06

I've read the boost regex docs and I don't see anything about named captures. I see information about captures using the number notation, $1, $2, etc. I'm assuming that the regex lib doesn't support named captures, correct? I looked at the spirit docs and didn't see any mention of it in the regex parser portions. I'm guessing that spirit doesn't support it either, correct? And by not supporting it I mean an out-of-the-box solution with the regex parser. I'm sure something more complicated than I could understand is possible with spirit. I can post to that mailing list if no one here knows. I'm trying to regex syslog messages for specific pieces of data. Depending on what systems send me syslog messages the order of the pieces of data may be different. I'd like a solution where I can ask for the specific piece of data explicitly, instead of having to remember that on system A dataItem1 is $1, but on system B it's $2. I will always have the same fields that I look for and that won't change. I'm trying to not complicate my database schema or the make the client's use any more difficult since they're the ones that write the regex statement. If named captures with the regex lib or with spirit aren't supported, any ideas on how this might be done would be appreciated. I'm stuck on boost 1.32, but have been looking for a good excuse to force our development dept. to a newer release. -Jason

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Re: [Boost-users] Replacing C functions with boost::function for callback functions in OpenGL
by Baranowski, Daniel 30 Jun '06

30 Jun '06

[snip] > Now I thought I would put all the variables and functions into a class > and use that in the main. Here is where I am getting stuck on the use of > boost::function. I changed the code to look something like the > following: > > class MyMain { > int a; > float b; > > void display() > { > ... display code calls ... > } > } > > int main (int argc, char **argv) > { > MyMain m_ref; > boost::function<void()> disp_func = boost::bind ( > &MyMain::display, &m_ref ); > glutDisplayFunc ( disp_func ); > } [snip] Maybe you could leave the display function as it was before, have OpenGL call that function, and then have Display call disp_func(). Something like this (though I haven't actually tried it): typedef boost::function<void()> DisplayFuncType; DisplayFuncType CurrentDisplayObject; class MyMain { int a; float b; void display() { ... display code calls ... } } void display () { if(!CurrentDisplayObject.empty()) CurrentDisplayObject(); } int main (int argc, char **argv) { MyMain m_ref; CurrentDisplayObject = boost::bind ( &MyMain::display, &m_ref ); glutDisplayFunc (display); } Let me know if that works out for you! I'd be interested to know. I think that's a good idea, BTW. Daniel ********************************************************************************************** Disclaimer - This email and any files transmitted with it are proprietary and may contain privileged or copyright information. You must not present this message to another party without gaining permission from the sender. If you are not the intended recipient you must not copy, distribute or use this email or the information contained in it for any purpose other than to notify us. If you have received this message in error, please notify the sender immediately, and delete this email from your system. We do not guarantee that this material is free from viruses or any other defects although due care has been taken to minimize the risk. eSafe scanned this email for viruses, vandals and malicious contentAny views expressed in this message are those of the individual sender, except where the sender specifically states them to be the views of LSI. **********************************************************************************************

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[asio] has anybody enabled SSL in a large project?
by Scott 30 Jun '06

30 Jun '06

We've been using ASIO for a while now in a large project and it's been great. I've recently been tasked to add optional SSL support between our client and server. Since there are some SSL classes in ASIO I started with the ASIO SSL example code and got that working. I then pretty much copied the relevant pieces from the sample code over to our project to see if it would work there. Using the same certificates and key files from the sample code, I added the handshaking and got our client and server to communicate. It all seemed great at first, because it seemed to seemlessly work. But eventually the communications break down. I either get asserts in my code from unexpected data in the stream, or the client hangs waiting for data that never appears or any of several different stream problems. It's rarely the exact same thing. But it eventually always fails. Especially on long sustained transfers. I have no idea what I might be doing wrong. There's really no documentation at all on ASIO and SSL. For all I know, it might be a problem with the SSL implementation in ASIO. Which brings me to my question - has anybody successfully used the SSL classes in ASIO on complex projects? If so, that would point to a problem in my code somewhere. Perhaps I need to do more than just add the initial SSL handshake (aside from using the SSL stream beyond that point)? Thanks, Scott

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Re: [Boost-users] multi_array: creating a view to a single element
by Baranowski, Daniel 30 Jun '06

30 Jun '06

[snip] > [snip] > > Basically, I have a 2 Dimensional array and I > > would like to be able to access the center of that array > > using a variable that maps to some index (for example, > > element[3][3] in a 7x7 array). > [snip] > > Would T & center = element[3][3] be satisfactory? > > I don't think multiarray supports any type of reallocation after > construction, so it should be ok. > > Sohail Thanks Sohail. While you can resize a multi_array, I won't be, so it's not an issue. What you've got is pretty obvious, I guess I was just had gone too far down the "view" path to see the simple answer! Thanks also to Cromwell for chiming in too as that is definitely a good, more generic approach, but probably overkill for my particular instance. But, still good to know! Daniel ********************************************************************************************** Disclaimer - This email and any files transmitted with it are proprietary and may contain privileged or copyright information. You must not present this message to another party without gaining permission from the sender. If you are not the intended recipient you must not copy, distribute or use this email or the information contained in it for any purpose other than to notify us. If you have received this message in error, please notify the sender immediately, and delete this email from your system. We do not guarantee that this material is free from viruses or any other defects although due care has been taken to minimize the risk. eSafe scanned this email for viruses, vandals and malicious contentAny views expressed in this message are those of the individual sender, except where the sender specifically states them to be the views of LSI. **********************************************************************************************

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[serialization] customize xml archive
by Jabe 30 Jun '06

30 Jun '06

hello, i try to create a xml archive that fit our needs. the default xml serializer handles not the format i would like to implement. some differences are: - primitive types (int, float, ...) should be written as xml attributes - array types should not provide any parent xml element, all array elements will be serialized as childs from the element containing the array - tagnames should always contain the classname - parent classes should create a new xml child element - and some more, but so far as an example the default xml code looks like this: <foo class_name="Class1" class_id="1"> <name>example</name> <container class_id="2"> <count>2</count> <item class_id_reference="2"> <a>123</a> </item> <item class_id_reference="3" class_name="Class3"> <b>456</b> </item> </foo> i would like this output: <Class1 role="foo" name="example"> <Class2 role="container" a="123" /> <Class3 role="container" b="456" /> </Class1> is that possible with the current boost::serialization and boost::archive libraries? i tried to derive all baseclasses of xml_oarchive and reimplemented it, without success. maybe a first question: why don't i get a classname for each serialized object in common_oarchive::save_override(const class_name_type & t, int)? sometimes i get a class_id, sometimes a class_reference_id and so on. classnames are offered rarely. regards, jabe

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