basic_istringstream(3C++)

Standard C++ Library
Copyright 1998, Rogue Wave Software, Inc.

NAME

basic_istringstream

- Supports reading objects of class basic_string<charT,traits,Allocator> from an array in memory.

SYNOPSIS

#include <sstream>
template<class charT, class traits = char_traits<charT>,

class Allocator = allocator<charT> >

class basic_istringstream
: public basic_istream<charT, traits>

DESCRIPTION

The template class basic_istringstream<charT,traits,Allocator> reads from an array in memory. It supports reading objects of class basic_string<charT,traits,Allocator>. It 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.

INTERFACE

template<class charT, class traits = char_traits<charT>,

class Allocator = allocator<void> >

class basic_istringstream
: public basic_istream<charT, traits> {

public:

typedef basic_stringbuf<charT, traits, Allocator> sb_type;
typedef basic_ios<charT, traits> ios_type;
typedef basic_string<charT, traits, Allocator>

string_type;

typedef traits                           traits_type;
typedef charT                            char_type;
typedef typename traits::int_type        int_type;
typedef typename traits::pos_type        pos_type;
typedef typename traits::off_type        off_type;

explicit basic_istringstream(ios_base::openmode which =

ios_base::in);

explicit basic_istringstream(const string_type& str,

ios_base::openmode which =
ios_base::in);

virtual ~basic_istringstream();
basic_stringbuf<charT,traits,Allocator> ∗rdbuf() const;
string_type str() const;
void str(const string_type& str);

};

TYPES

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.

ios_type

The type ios_type is an instantiation of class basic_ios on type charT.

istringstream

The type istringstream is an instantiation of class basic_istringstream on type char:

typedef basic_istringstream<char> istringstream;

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.

sb_type

The type sb_type is an instantiation of class basic_stringbuf on type charT.

string_type

The type string_type is an instantiation of class basic_string on type charT.

traits_type

The type traits_type is a synonym for the template parameter traits.

wistringstream

The type wistringstream is an instantiation of class basic_istringstream on type wchar_t:

typedef basic_istringstream<wchar_t> wistringstream;

CONSTRUCTORS

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<charT,traits,Allocator>(which).

explicit basic_istringstream(const string_type& str,

ios_base::openmode which =
ios_base::in);

DESTRUCTORS

virtual ~basic_istringstream();

Destroys an object of class basic_istringstream.

MEMBER FUNCTIONS

basic_stringbuf<charT,traits,Allocator>∗
rdbuf() const;

Returns a pointer to the basic_stringbuf associated with the stream.

string_type
str() const;

Returns a string object of type string_type, which contains a copy of the underlying buffer contents.

void
str(const string_type& str);

Clears the string buffer and copies the string object str into it. If the opening mode is in, initializes the input sequence to point to the first character of the buffer. If the opening mode is out, initializes the output sequence to point to the first character of the buffer. If the opening mode is out | app, initializes the output sequence to point to the last character of the buffer.

EXAMPLE

//
// stdlib/examples/manual/istringstream.cpp
//
#include<iostream>
#include<sstream>
#include<string>
#include<iomanip>

void main ( )
{

using namespace std;

long l= 20;
wchar_t ∗ntbs=L"Il avait l’air heureux";
wchar_t c;
wchar_t buf[50];

// create a read/write string-stream object on wide char
// and attach it to an wistringstream object

wistringstream in(ios_base::in | ios_base::out);

// tie the ostream object to the wistringstream object

wostream out(in.rdbuf());

// output ntbs in out

out << ntbs;

// output each word on a separate line

while ( in.get(c) )

{

if ( c == L’ ’ )

wcout << endl;

else

wcout << c;

}

wcout << endl << endl;

// move back the input sequence to the beginning

in.seekg(0);

// clear the state flags

in.clear();

// does the same thing as the previous code
// output each word on a separate line

while ( in >> buf )

wcout << buf << endl;

wcout << endl << endl;

// create a tiny string object

string test_string("Il dormait pour l’eternite");

// create a read/write string-stream object on char
// and attach it to an istringstream object

istringstream in_bis(ios_base:: in | ios_base::out |

ios_base::app );

// create an ostream object

ostream out_bis(in_bis.rdbuf());

// initialize the string buffer with test_string

in_bis.str(test_string);

out_bis << endl;

// output the base info before each integer

out_bis << showbase;

ostream::pos_type pos= out_bis.tellp();

// output l in hex with a field with of 20

out_bis << hex << setw(20) << l << endl;

// output l in oct with a field with of 20

out_bis << oct << setw(20) << l << endl;

// output l in dec with a field with of 20

out_bis << dec << setw(20) << l << endl;

// output the all buffer

cout << in_bis.rdbuf();

// seek the input sequence to pos

in_bis.seekg(pos);

int a,b,d;

// read the previous outputted integer

in_bis >> a >> b >> d;

// output 3 times 20

cout << a << endl << b << endl << d << endl;

}

STANDARDS CONFORMANCE

ANSI X3J16/ISO WG21 Joint C++ Committee

Rogue Wave Software — Last change: 02 Apr 1998

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