Module: Standard C++ Library Library: Input/output
basic_istringstreambasic_istream
|
allocator_type basic_istringstream() char_type |
int_type off_type pos_type |
rdbuf() str() traits_type |
~basic_istringstream() |
Class that supports reading objects of specializations of class template basic_string from an array in memory
#include <sstream>
namespace std {
template<class charT, class traits = char_traits<charT>,
class Allocator = allocator<charT> >
class basic_istringstream;
}
The class template basic_istringstream reads from an array in memory. It supports reading objects of class basic_string, and uses a basic_stringbuf object to control the associated storage. It inherits from basic_istream, and therefore can use all the formatted and unformatted input functions.
namespace std {
template<class charT, class traits = char_traits<charT>,
class Allocator = allocator<void> >
class basic_istringstream
: public basic_istream<charT, traits>
{
public:
typedef traits traits_type;
typedef charT char_type;
typedef Allocator allocator_type;
typedef typename traits_type::int_type int_type;
typedef typename traits_type::pos_type pos_type;
typedef typename traits_type::off_type off_type;
explicit
basic_istringstream(ios_base::openmode = ios_base::in);
explicit
basic_istringstream(const basic_string<char_type,
traits_type,
allocator_type>&,
ios_base::openmode = ios_base::in);
virtual ~basic_istringstream();
basic_stringbuf<char_type, traits_type, allocator_type> *
rdbuf() const;
basic_string<char_type, traits_type, allocator_type>
str() const;
void
str(const basic_string<char_type, traits_type,
allocator_type>&);
};
}
allocator_type
The type allocator_type is a synonym for the template parameter Allocator.
char_type
The type char_type is a synonym for the template parameter charT.
int_type
The type int_type is a synonym of type traits::in_type.
off_type
The type off_type is a synonym of type traits::off_type.
pos_type
The type pos_type is a synonym of type traits::pos_type.
traits_type
The type traits_type is a synonym for the template parameter traits.
istringstream
The type istringstream is an instantiation of class basic_istringstream on type char:
typedef basic_istringstream<char> istringstream;
wistringstream
The type wistringstream is an instantiation of class basic_istringstream on type wchar_t:
typedef basic_istringstream<wchar_t> wistringstream;
explicit basic_istringstream(ios_base::openmode which = ios_base::in);
Constructs an object of class basic_istringstream, initializing the base class basic_istream with the associated string buffer. The string buffer is initialized by calling the basic_stringbuf constructor:
basic_stringbuf<char_type,traits_type,
allocator_type>(which)
explicit
basic_istringstream(const basic_string<char_type, traits_type,
allocator_type>& str,
ios_base::openmode which = ios_base::in);
Constructs an object of class basic_istringstream, initializing the base class basic_istream with the associated string buffer. The string buffer is initialized by calling the basic_stringbuf constructor:
basic_stringbuf<char_type, traits_type,
allocator_type>(str,which)
virtual ~basic_istringstream();
Destroys an object of class basic_istringstream.
basic_stringbuf<char_type, traits_type, allocator_type>* rdbuf() const;
Returns a pointer to the basic_stringbuf associated with the stream.
basic_string<char_type, traits_type, allocator_type> str() const;
Returns rdbuf()->str().
void
str(const basic_string<char_type, traits_type,
allocator_type>& str);
Calls rdbuf()->str(str).
//
// istringstream.cpp
//
#include <iomanip> // for setw
#include <iostream> // for wcout, dec, endl, hex, oct, wostream
#include <sstream> // for strstream, wistringstream
#include <string> // for wstring
int main ( )
{
try {
// create a read/write stream object
std::wistringstream in (std::ios::in | std::ios::out);
// associate the ostream object's buffer with
// the ifstream object
std::wostream out (in.rdbuf ());
// enable exceptions in both streams
in.exceptions (std::ios::badbit);
out.exceptions (std::ios::failbit | std::ios::badbit);
// write string into out
out << "Il avait l'air heureux." << std::endl;
// seek to the beginning of the stream
in.seekg (0);
wchar_t c;
// output each space-separated word on a separate line
while (in.get (c)) {
if (std::isspace (c, in.getloc ()))
std::wcout << std::endl;
else
std::wcout << c;
}
std::wcout << std::endl;
// clear stream state, failbit | eofbit set by
// last call to get ()
in.clear ();
// move back to the beginning of the stream
in.seekg (0);
wchar_t buf [40];
// guard against buffer overflow
in.width (sizeof buf);
// set right justification
std::wcout << std::right;
// does the same thing as the previous code
// output each word on a separate line
// in a field of width 10
while (in >> buf) {
std::wcout.width (10);
std::wcout << buf << std::endl;
}
std::wcout << std::endl;
// clear flags, last in >> buf set fail bit
// because of a newline at end of string
in.clear ();
// output the base info before each integer
out << std::showbase;
std::wostream::pos_type pos= out.tellp ();
const long l = 10;
// output l in hex with a field with of 10
out << std::hex << std::setw (10) << l << std::endl;
// output l in oct with a field with of 10
out << std::oct << std::setw (10) << l << std::endl;
// output l in dec with a field with of 10
out << std::dec << std::setw (10) << l << std::endl;
// move back to the beginning of the stream
in.seekg (0);
// output the entire stream
std::wcout << in.rdbuf () << std::endl;
// clear the flags
in.clear ();
// seek the input sequence to pos
in.seekg (pos);
in.unsetf (std::ios::basefield);
int a, b, d;
// read the previous outputted integer
in >> a >> b >> d;
// output 3 times 10
std::wcout << a << std::endl << b << std::endl
<< d << std::endl;
}
catch (std::ios::failure &e) {
std::wcerr << e.what () << std::endl;
}
return 0;
}
Program Output:
4848525670694967
0048FE1C
0048FE1C
0xa
012
10
10
10
10
char_traits, ios_base, basic_ios, basic_stringbuf, basic_string, basic_ostringstream, basic_stringstream
ISO/IEC 14882:1998 -- International Standard for Information Systems --Programming Language C++, Section 27.7.2
Copyright (c) 1994-2006 Rogue Wave Software, a Quovadx Division.
Licensed under the Apache License, Version 2.0.
Contact Rogue Wave about documentation or support issues. You can also seek help from other developers through the Apache stdcxx community (see below).