return type of boost::iostreams::stream<T>::read()
I apologize, if i have missed something. Reading the documentation about boost::iostreams library I could not find the information which return type the boost::iostreams::stream's class is giving me calling read(). I searched through the headers and every read() found returns std::streamsize, which sounds reasonable to me. I was surprised, that the code below does not compile --------start code ---------- #include <boost/iostreams/stream.hpp> #include <boost/iostreams/device/file.hpp> int main(void){ boost::iostreams::stream<boost::iostreams::file_source> istr(std::string("in.pdf")); char *buffer = new char[10]; std::streamsize i = istr.read(buffer,10); return 0; } -------end code----------- and gives me: test.cpp:7: error: invalid conversion from ‘void*’ to ‘std::streamsize’ Could someone shed a light on me, please? Thanks in advance. kind regards Axel
Struebing, Axel, le-tex [axel.struebing@le-tex.de]:
Reading the documentation about boost::iostreams library I could not find the information which return type the boost::iostreams::stream's class is giving me calling read().
From the documentation, a boost::iostreams::stream derives from an std::basic_[i|o]stream, depending on the model of its underlying Device. In your example, the device is a Source, so I guess that the stream derives from std::basic_istream, whose read(char*, streamsize) method returns a basic_istream, not a streamsize.
The library offers the "streamsize read(stream, char*, streamsize)" function template. Using it in your example yould give something like (not tested): #include <boost/iostreams/stream.hpp> #include <boost/iostreams/device/file.hpp> #include <boost/iostreams/operations.hpp> int main(void){ namespace bio = boost::iostreams; bio::stream<bio::file_source> istr(std::string("in.pdf")); char buffer[10]; std::streamsize i = bio::read(istr,buffer,10); return 0; } HTH, Éric Malenfant --------------------------------------------- Two wrongs don't make a right but three rights make a left.
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Struebing, Axel, le-tex