std::basic_streambuf<CharT,Traits>::sputn, std::basic_streambuf<CharT,Traits>::xsputn

 

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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 sputn( const char_type* s, std::streamsize count );	(1)
protected: virtual std::streamsize xsputn( const char_type* s, std::streamsize count );	(2)

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

2) Writes count characters to the output sequence from the character array whose first element is pointed to by s. The characters are written as if by repeated calls to sputc(). Writing stops when either count characters are written or a call to sputc() would have returned Traits::eof().

If the put area becomes full (pptr() == epptr()), it is unspecified whether overflow() is actually called or its effect is achieved by other means.

Parameters

(none)

Return value

The number of characters successfully written.

Notes

"achieved by other means" permits bulk I/O without intermediate buffering: that is how std::ofstream::write() simply passes the pointer to the suitable system call in some implementations.

Example

Run this code

#include <iostream>
#include <sstream>
 
int main()
{
    std::ostringstream s1;
    std::streamsize sz = s1.rdbuf()->sputn("This is a test", 14);
    s1 << '\n';
    std::cout << "The call to sputn() returned " << sz << '\n'
              << "The output sequence contains " << s1.str();
 
    std::istringstream s2;
    sz = s2.rdbuf()->sputn("This is a test", 14);
    std::cout << "The call to sputn() on an input stream returned " << sz << '\n';
}

Output:

The call to sputn() returned 14
The output sequence contains This is a test
The call to sputn() on an input stream returned 0

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 565	C++98	xsputn() always called overflow() if pptr() == epptr()	it does not actually need to be called

See also

sgetn

invokes xsgetn() (public member function)