std::basic_streambuf<CharT,Traits>::sgetn, std::basic_streambuf<CharT,Traits>::xsgetn

 

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std::basic_streambuf

Public member functions basic_streambuf::~basic_streambuf      Locales basic_streambuf::pubimbue basic_streambuf::getloc Positioning basic_streambuf::pubsetbuf basic_streambuf::pubseekoff basic_streambuf::pubseekpos basic_streambuf::pubsync Get area basic_streambuf::in_avail basic_streambuf::snextc basic_streambuf::sbumpc basic_streambuf::sgetc basic_streambuf::sgetn Put area basic_streambuf::sputc basic_streambuf::sputn Putback basic_streambuf::sputbackc basic_streambuf::sungetc

Protected member functions basic_streambuf::basic_streambuf basic_streambuf::operator= (C++11) basic_streambuf::swap (C++11) Locales basic_streambuf::imbue Positioning basic_streambuf::setbuf basic_streambuf::seekoff basic_streambuf::seekpos basic_streambuf::sync Get area basic_streambuf::showmanyc basic_streambuf::underflow basic_streambuf::uflow basic_streambuf::xsgetn basic_streambuf::ebackbasic_streambuf::gptrbasic_streambuf::egptr basic_streambuf::gbump basic_streambuf::setg Put area basic_streambuf::xsputn basic_streambuf::overflow basic_streambuf::pbasebasic_streambuf::pptrbasic_streambuf::epptr basic_streambuf::pbump basic_streambuf::setp Putback basic_streambuf::pbackfail

 

std::streamsize sgetn( char_type* s, std::streamsize count );	(1)
protected: virtual std::streamsize xsgetn( char_type* s, std::streamsize count );	(2)

1) Calls xsgetn(s, count) of the most derived class.

2) Reads count characters from the input sequence and stores them into a character array pointed to by s. The characters are read as if by repeated calls to sbumpc(). That is, if less than count characters are immediately available, the function calls uflow() to provide more until Traits::eof() is returned.

Classes derived from std::basic_streambuf are permitted to provide more efficient implementations of this function.

Parameters

s	-	pointer to the beginning of a char_type array
count	-	maximum number of characters to read.

Return value

The number of characters successfully read. If it is less than count the input sequence has reached the end.

Notes

The rule about "more efficient implementations" permits bulk I/O without intermediate buffering: that's how std::ifstream::read simply passes the pointer to the POSIX read() system call in some implementations of iostreams

See also

sputn

invokes xsputn() (public member function)