C++Talk.NET C++ language newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  c++ stream to memory address          C++Talk.NET Forum Index -> C++ language (comp.lang.c++) View previous topic :: View next topic   Author Message Dan Elliott Guest Posted: Thu Apr 28, 2005 6:53 pm    Post subject: c++ stream to memory address I am working on some tricky code and need some help from the experts. I have several large data structures (uBLAS matrices) that must be written to a pre-allocated (by another program) chunk of static memory. Currently our code emulates this behavior using BOOST::serialize archives. According to the documentation, these archive objects will write to a given ostream. We would like to define an ostream that writes to this address without copying these large data structures to a buffer. I am open to any elegant solution (if one exists), but we are currently attempting to set the memory given to us as the buffer used by an ostream. Again, if there is a better way, we would gladly use it. I am providing the above information to emphasize that we are pretty tied to using c++ streams for our i/o with the static memory. Below is a *simple* example that I cannot get to work. I am using vacpp on AIX. Thank you in advance for any help provided. - dan struct X { short pad; short version; int x; int y; int z; }; int main() { X dummy; dummy.x = 5; dummy.y = 5; dummy.z = 5; short a = 20; cout << "The sizeof dummy is " << sizeof(dummy) << endl; stringbuf *tempBuf = new stringbuf(ios_base::out|ios_base::binary); streambuf *testBuf = tempBuf->pubsetbuf((char*)(&(dummy.version)),sizeof(dummy)-2); cout << "pubsetbuf: " << (void*)testBuf << " vs " << (void*)tempBuf << endl; ostream ofs(tempBuf); cout << "dummy.version addr: " << &(dummy.version) << endl <<"dummy addr: " << &(dummy) << endl << "ofs good?: " << ofs.good() << endl; ofs << a << 21; cout << dummy.version << " " << dummy.x << " " << dummy.y << " " << dummy.z << endl; } Back to top Dan Elliott Guest Posted: Thu Apr 28, 2005 10:07 pm    Post subject: Re: c++ stream to memory address "Dan Elliott" <dan_elliott_at_cox_dot_net (AT) noSpam (DOT) org> wrote Quote: Below is a *simple* example that I cannot get to work. I am using vacpp on AIX. Thank you in advance for any help provided. - dan struct X { short pad; short version; int x; int y; int z; }; int main() { X dummy; dummy.x = 5; dummy.y = 5; dummy.z = 5; short a = 20; cout << "The sizeof dummy is " << sizeof(dummy) << endl; stringbuf *tempBuf = new stringbuf(ios_base::out|ios_base::binary); streambuf *testBuf = tempBuf->pubsetbuf((char*)(&(dummy.version)),sizeof(dummy)-2); cout << "pubsetbuf: " << (void*)testBuf << " vs " << (void*)tempBuf endl; ostream ofs(tempBuf); cout << "dummy.version addr: " << &(dummy.version) << endl <<"dummy addr: " << &(dummy) << endl << "ofs good?: " << ofs.good() << endl; ofs << a << 21; cout << dummy.version << " " << dummy.x << " " << dummy.y << " " dummy.z << endl; } Here is the output from this example program: The sizeof dummy is 16 pubsetbuf: 11001d470 vs 11001d470 dummy.version addr: fffffffffffe662 dummy addr: fffffffffffe660 ofs good?: 1 0 5 5 5 0 5 5 5 What am I doing wrong? Back to top Uenal Mutlu Guest Posted: Thu Apr 28, 2005 10:12 pm    Post subject: Re: c++ stream to memory address "Dan Elliott" wrote Quote: I am working on some tricky code and need some help from the experts. I have several large data structures (uBLAS matrices) that must be written to a pre-allocated (by another program) chunk of static memory. Currently our code emulates this behavior using BOOST::serialize archives. According to the documentation, these archive objects will write to a given ostream. We would like to define an ostream that writes to this address without copying these large data structures to a buffer. I am open to any elegant solution (if one exists), but we are currently attempting to set the memory given to us as the buffer used by an ostream. Again, if there is a better way, we would gladly use it. I am providing the above information to emphasize that we are pretty tied to using c++ streams for our i/o with the static memory. Try this method: // writing to memory using ostrstream: char szBuf[1024] = ""; ostrstream os(szBuf, sizeof(szBuf)); os << "test datan" << "more test datan"; Quote: Below is a *simple* example that I cannot get to work. I am using vacpp on AIX. Thank you in advance for any help provided. - dan struct X { short pad; short version; int x; int y; int z; }; int main() { X dummy; dummy.x = 5; dummy.y = 5; dummy.z = 5; short a = 20; cout << "The sizeof dummy is " << sizeof(dummy) << endl; stringbuf *tempBuf = new stringbuf(ios_base::out|ios_base::binary); streambuf *testBuf = tempBuf->pubsetbuf((char*)(&(dummy.version)),sizeof(dummy)-2); cout << "pubsetbuf: " << (void*)testBuf << " vs " << (void*)tempBuf endl; ostream ofs(tempBuf); cout << "dummy.version addr: " << &(dummy.version) << endl <<"dummy addr: " << &(dummy) << endl << "ofs good?: " << ofs.good() << endl; ofs << a << 21; cout << dummy.version << " " << dummy.x << " " << dummy.y << " " dummy.z << endl; } Back to top Dan Elliott Guest Posted: Mon May 02, 2005 5:36 pm    Post subject: Re: c++ stream to memory address Thank you for the reply. I am under the impression that ostrstream is no longer a part of the standard. If so, it cannot be used on this project. Thank you, dan "Uenal Mutlu" <520001085531-0001 (AT) t-online (DOT) de> wrote Quote: "Dan Elliott" wrote I am working on some tricky code and need some help from the experts. I have several large data structures (uBLAS matrices) that must be written to a pre-allocated (by another program) chunk of static memory. Currently our code emulates this behavior using BOOST::serialize archives. According to the documentation, these archive objects will write to a given ostream. We would like to define an ostream that writes to this address without copying these large data structures to a buffer. I am open to any elegant solution (if one exists), but we are currently attempting to set the memory given to us as the buffer used by an ostream. Again, if there is a better way, we would gladly use it. I am providing the above information to emphasize that we are pretty tied to using c++ streams for our i/o with the static memory. Try this method: // writing to memory using ostrstream: char szBuf[1024] = ""; ostrstream os(szBuf, sizeof(szBuf)); os << "test datan" "more test datan"; Below is a *simple* example that I cannot get to work. I am using vacpp on AIX. Thank you in advance for any help provided. - dan struct X { short pad; short version; int x; int y; int z; }; int main() { X dummy; dummy.x = 5; dummy.y = 5; dummy.z = 5; short a = 20; cout << "The sizeof dummy is " << sizeof(dummy) << endl; stringbuf *tempBuf = new stringbuf(ios_base::out|ios_base::binary); streambuf *testBuf = tempBuf->pubsetbuf((char*)(&(dummy.version)),sizeof(dummy)-2); cout << "pubsetbuf: " << (void*)testBuf << " vs " << (void*)tempBuf endl; ostream ofs(tempBuf); cout << "dummy.version addr: " << &(dummy.version) << endl <<"dummy addr: " << &(dummy) << endl << "ofs good?: " << ofs.good() << endl; ofs << a << 21; cout << dummy.version << " " << dummy.x << " " << dummy.y << " " dummy.z << endl; } Back to top Dan Elliott Guest Posted: Mon May 02, 2005 5:44 pm    Post subject: Re: c++ stream to memory address - another frustrating examp "Dan Elliott" <dan_elliott_at_cox_dot_net (AT) noSpam (DOT) org> wrote *snip* Quote: I am using vacpp on AIX. Here is another example of code that I feel should (but doesn't) use pre-allocated memory as the buffer for an iostream (or ostream) object: char szBuf[1024] = "test datanmore test datan"; stringbuf myStringBuf; myStringBuf.pubsetbuf(szBuf,1024); iostream myIostream(&myStringBuf); myIostream << "hello hinhow are you doingn"; The memory pointed to by szBuf has not been modified by the iostream operation. I am at a loss here! - dan Back to top red floyd Guest Posted: Mon May 02, 2005 10:49 pm    Post subject: Re: c++ stream to memory address Dan Elliott wrote: Quote: Thank you for the reply. I am under the impression that ostrstream is no longer a part of the standard. If so, it cannot be used on this project. Thank you, dan [redacted] True, but std::ostringstream *is* part of the standard. #include <sstream> Back to top Default User Guest Posted: Mon May 02, 2005 11:20 pm    Post subject: Re: c++ stream to memory address red floyd wrote: Quote: Dan Elliott wrote: Thank you for the reply. I am under the impression that ostrstream is no longer a part of the standard. If so, it cannot be used on this project. Thank you, dan [redacted] True, No, not true. The strstream stuff is deprecated. It's still available and probably will be for some time to come. One definitely should try to avoid it in new code, of course. Quote: but std::ostringstream *is* part of the standard. Yes, this would be the better choice. Brian Back to top Dan Elliott Guest Posted: Mon May 09, 2005 12:58 pm    Post subject: Re: c++ stream to memory address "red floyd" <no.spam (AT) here (DOT) dude> wrote Quote: Dan Elliott wrote: I am under the impression that ostrstream is no longer a part of the standard. If so, it cannot be used on this project. Thank you, dan [redacted] True, but std::ostringstream *is* part of the standard. #include Great, but I do not see a constructor that will allow me to do what my original post was asking for: I want to write to a pre-allocated memory address. I am writing a lot of data to this address, so I do not want to use a stream that will force me to copy to memory controlled (and untouchable by me) by the stream and then copy to the pre-allocated memory. In addition, I have tried directing the stringbuf object belonging to a ostringstream to use the pre-allocated memory with negative results. The code I have posted will show an example of what I have tried. Thanks for your help. I am totally clueless at this point. - dan Back to top Ron Natalie Guest Posted: Mon May 09, 2005 9:15 pm    Post subject: Re: c++ stream to memory address Dan Elliott wrote: Quote: Great, but I do not see a constructor that will allow me to do what my original post was asking for: I want to write to a pre-allocated memory address. Use the deprecated strstream interface. It writes to a managed hunka-char array rather than a string object. Back to top Alf P. Steinbach Guest Posted: Mon May 09, 2005 9:24 pm    Post subject: Re: c++ stream to memory address * Dan Elliott: Quote: I am working on some tricky code and need some help from the experts. I have several large data structures (uBLAS matrices) that must be written to a pre-allocated (by another program) chunk of static memory. Currently our code emulates this behavior using BOOST::serialize archives. According to the documentation, these archive objects will write to a given ostream. We would like to define an ostream that writes to this address without copying these large data structures to a buffer. I am open to any elegant solution (if one exists), but we are currently attempting to set the memory given to us as the buffer used by an ostream. Again, if there is a better way, we would gladly use it. I am providing the above information to emphasize that we are pretty tied to using c++ streams for our i/o with the static memory. Below is a *simple* example that I cannot get to work. I am using vacpp on AIX. Thank you in advance for any help provided. - dan struct X { short pad; short version; int x; int y; int z; }; int main() { X dummy; dummy.x = 5; dummy.y = 5; dummy.z = 5; short a = 20; cout << "The sizeof dummy is " << sizeof(dummy) << endl; stringbuf *tempBuf = new stringbuf(ios_base::out|ios_base::binary); streambuf *testBuf = tempBuf->pubsetbuf((char*)(&(dummy.version)),sizeof(dummy)-2); cout << "pubsetbuf: " << (void*)testBuf << " vs " << (void*)tempBuf endl; ostream ofs(tempBuf); cout << "dummy.version addr: " << &(dummy.version) << endl <<"dummy addr: " << &(dummy) << endl << "ofs good?: " << ofs.good() << endl; ofs << a << 21; Here you're converting the integer value 20 (of 'a') to character codes. Quote: cout << dummy.version << " " << dummy.x << " " << dummy.y << " " dummy.z << endl; } -- A: Because it messes up the order in which people normally read text. Q: Why is it such a bad thing? A: Top-posting. Q: What is the most annoying thing on usenet and in e-mail? Back to top Jeff Flinn Guest Posted: Tue May 10, 2005 12:36 pm    Post subject: Re: c++ stream to memory address "Dan Elliott" <dan_elliott_at_cox_dot_net (AT) noSpam (DOT) org> wrote Quote: I am working on some tricky code and need some help from the experts. I have several large data structures (uBLAS matrices) that must be written to a pre-allocated (by another program) chunk of static memory. Currently our code emulates this behavior using BOOST::serialize archives. According to the documentation, these archive objects will write to a given ostream. We would like to define an ostream that writes to this address without copying these large data structures to a buffer. Have you looked at using boost::iostream library from Jonathan Turkanis? I use it along with boost::serialization to stream data to/from the Windows clipboard allocated memory. IIRC, it will be part of boost 1.33.0. It is also available for use from the files section at www.boost.org. Look for: boost::io::array_sink boost::io::array_source which take (const) char*'s and direct input/output from/to externally allocated memory. You might want to join the boost devel and/or user mailing lists to get more immediate response to these sorts of inquiries. Jeff Flinn Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         C++Talk.NET Forum Index -> C++ language (comp.lang.c++) All times are GMT Page 1 of 1   Jump to: Select a forum C/C++----------------C LanguageC Language (Moderated)C++ Language (Moderated)C++ language (comp.lang.c++)C++ language, library and standards Non-English C/C++ Newsgroups----------------C++ (German)C++ (French)  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.