basic_ostream(3C++) - basic_ostream(3C++)
Standard C++ Library Copyright 1998, Rogue Wave Software, Inc.
NAME
basic_ostream, ostream, wostream
- Assists in formatting and writing output to sequences controlled by
a stream buffer.
SYNOPSIS
#include <ostream>
template<class charT, class traits = char_traits<charT> >
class basic_ostream
: virtual public basic_ios<charT, traits>
DESCRIPTION
The class basic_ostream defines member functions that assist in format‐
ting and writing output to sequences controlled by a stream buffer.
Two groups of member functions share common properties: the formatted
output functions (or insertors) and the unformatted output functions.
Both groups of functions insert characters by calling basic_streambuf
member functions. They both begin by constructing an object of class
basic_ostream::sentry and, if this object is in good state after con‐
struction, the function tries to perform the requested output. The sen‐
try object performs exception-safe initialization, such as controlling
the status of the stream or locking it in a multithread environment.
Some formatted output functions generate the requested output by con‐
verting a value from some scalar to text form and inserting the con‐
verted text in the output sequence. The conversion behavior is directly
depend on the locale object being imbued in the stream.
INTERFACE
template<class charT, class traits = char_traits<charT> >
class basic_ostream
:virtual public basic_ios<charT, traits> {
public:
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;
typedef basic_ostream<charT, traits> ostream_type;
typedef basic_ios<charT, traits> ios_type;
explicit basic_ostream(basic_streambuf<charT, traits>
*sb);
virtual ~basic_ostream();
class sentry {
public:
explicit sentry(basic_ostream<charT,traits>&);
~sentry();
operator bool ();
};
ostream_type& operator<<(ostream_type&
(*pf)(ostream_type&));
ostream_type& operator<<(ios_base& (*pf)(ios_base&));
ostream_type& operator<<(ios_type& (*pf)(ios_type&));
ostream_type& operator<<(bool n);
ostream_type& operator<<(short n);
ostream_type& operator<<(unsigned short n);
ostream_type& operator<<(int n);
ostream_type& operator<<(unsigned int n);
ostream_type& operator<<(long n);
ostream_type& operator<<(unsigned long n);
ostream_type& operator<<(float f);
ostream_type& operator<<(double f);
ostream_type& operator<<(long double f);
ostream_type& operator<<(const void *p);
ostream_type&
operator<<(basic_streambuf<char_type,traits> &sb);
ostream_type&
operator<<(basic_streambuf<char_type,traits> *sb);
ostream_type& put(char_type c);
ostream_type& write(const char_type *s, streamsize n);
ostream_type& flush();
pos_type tellp();
ostream_type& seekp(pos_type );
ostream_type& seekp(off_type , ios_base::seekdir );
protected:basic_ostream();
};
//global character inserter functions
template <class charT, class traits>
basic_ostream<charT,traits>&
operator<<(basic_ostream<charT,traits>&, charT);
template <class charT, class traits>
basic_ostream<charT,traits>&
operator<<(basic_ostream<charT,traits>&, char);
template <class traits>
basic_ostream<char,traits>&
operator<<(basic_ostream<char,traits>&, char);
template <class traits>
basic_ostream<char,traits>&
operator<<(basic_ostream<char,traits>&, signed char);
template <class traits>
basic_ostream<char,traits>&
operator<<(basic_ostream<char,traits>&, unsigned char);
template <class charT, class traits>
basic_ostream<charT,traits>&
operator<<(basic_ostream<charT,traits>&, const charT*);
template <class charT, class traits>
basic_ostream<charT,traits>&
operator<<(basic_ostream<charT,traits>&, const char*);
template <class traits>
basic_ostream<char,traits>&
operator<<(basic_ostream<char,traits>&, const char*);
template <class traits>
basic_ostream<char,traits>&
operator<<(basic_ostream<char,traits>&, const signed char*);
template <class traits>
basic_ostream<char,traits>&
operator<<(basic_ostream<char,traits>&,
const unsigned char*);
template<class charT, class traits>
basic_ostream<charT, traits>&
endl(basic_ostream<charT, traits>& os);
template<class charT, class traits>
basic_ostream<charT, traits>&
ends(basic_ostream<charT, traits>& os);
template<class charT, class traits>
basic_ostream<charT, traits>&
flush(basic_ostream<charT, traits>& os);
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 a synonym for basic_ios<charT, traits>.
off_type
The type off_type is a synonym of type traits::off_type.
ostream
The type ostream is an instantiation of class basic_ostream on type char:
typedef basic_ostream<char> ostream;
ostream_type
The type ostream_type is a synonym for basic_ostream<charT, traits>.
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.
wostream
The type wostream is an instantiation of class basic_ostream on type
wchar_t:
typedef basic_ostream<wchar_t> wostream;
CONSTRUCTORS
explicit basic_ostream(basic_streambuf<charT, traits>* sb);
Constructs an object of class basic_ostream, assigning initial values to
the base class by calling basic_ios<charT,traits>::init(sb).
DESTRUCTORS
virtual ~basic_ostream();
Destroys an object of class basic_ostream.
SENTRY CLASSES
explicit sentry(basic_ostream<charT,traits>&);
Prepares for formatted or unformatted output. If the basic_ios member func‐
tion tie() is not a null pointer, the function synchronizes the output
sequence with any associated stream. If after any preparation is completed,
the basic_ios member function good() is true, the sentry conversion func‐
tion operator bool() returns true. Otherwise it returns false. In a multi‐
thread environment the sentry object constructor is responsible for locking
the stream and the stream buffer associated with the stream.
~sentry();
Destroys an object of class sentry. If the ios_base member function flags()
& unitbuf == true, then flushes the buffer. In a multithread environment
the sentry object destructor is responsible for unlocking the stream and
the stream buffer associated with the stream.
operator bool();
If after any preparation is completed, the ios_base member function good()
is true, the sentry conversion function operator bool() returns true, else
it returns false.
INSERTORS
ostream_type&
operator<<(ostream_type& (*pf) (ostream_type&));
Calls pf(*this), then returns *this. See, for example, the function signa‐
ture endl(basic_ostream&).
ostream_type&operator<<(ios_type& (*pf) (ios_type&));
Calls pf(*this), then returns *this.
ostream_type&operator<<(ios_base& (*pf) (ios_base&));
Calls pf(*this), then returns *this. See, for example, the function signa‐
ture dec(ios_base&).
ostream_type&operator<<(bool n);
Converts the boolean value n and outputs it into the basic_ostream object's
buffer. If the ios_base member function flag() & ios_base::boolalpha is
false it tries to write an integer value, which must be 0 or 1. If the
boolalpha flag is true, it writes characters according to the locale func‐
tion numpunct<>::truename() or numpunct<>::falsename().
ostream_type&operator<<(short n);
Converts the signed short integer n, and outputs it into the stream buffer,
then returns *this.
ostream_type&operator<<(unsigned short n);
Converts the unsigned short integer n, and outputs it into the stream buf‐
fer, then returns *this.
ostream_type&operator<<(int n);
Converts the signed integer n, and outputs it into the stream buffer, then
returns *this.
ostream_type&operator<<(unsigned int n);
Converts the unsigned integer n, and outputs it into the stream buffer,
then returns *this.
ostream_type&operator<<(long n);
Converts the signed long integer n, and outputs it into the stream buffer,
then returns *this.
ostream_type&operator<<(unsigned long n);
Converts the unsigned long integer n, and outputs it into the stream buf‐
fer, then returns *this.
ostream_type&operator<<(float f);
Converts the float f and outputs it into the stream buffer, then returns
*this.
ostream_type&operator<<(double f);
Converts the double f and outputs it into the stream buffer, then returns
*this.
ostream_type&operator<<(long double f);
Converts the long double f and outputs it into the stream buffer, then
returns *this.
ostream_type&operator<<(void *p);
Converts the pointer p, and outputs it into the stream buffer, then returns
*this.
ostream_type&operator<<(basic_streambuf<charT,traits> *sb);
If sb is null calls the basic_ios member function setstate(badbit). Other‐
wise gets characters from sb and inserts them into the stream buffer until
any of the following occurs:
- An end-of-file on the input sequence.
- A failure when inserting in the output sequence
- An exception while getting a character from sb
If the function inserts no characters or if it stopped because an exception
was thrown while extracting a character, it calls the basic_ios member
function setstate(failbit). If an exception was thrown while extracting a
character, it is rethrown.
ostream_type&operator<<(basic_streambuf<charT,traits>& sb);
Gets characters from sb and inserts them into the stream buffer until any
of the following occurs:
- An end-of-file on the input sequence.
- A failure when inserting in the output sequence
- An exception while getting a character from sb
If the function inserts no characters or if it stopped because an exception
was thrown while extracting a character, it calls the basic_ios member
function setstate(failbit). If an exception was thrown while extracting a
character it is rethrown.
UNFORMATTED FUNCTIONS
ostream_type&
flush();
If rdbuf() is not a null pointer, calls rdbuf()->pubsync() and returns
*this. If that function returns -1, calls setstate(badbit).
ostream_type&put(char_type c);
Inserts the character c. If the operation fails, calls the basic_ios member
function setstate(badbit).
ostream_type&seekp(pos_type pos);
If the basic_ios member function fail() returns false, executes
rdbuf()->pubseekpos(pos), which positions the current pointer of the output
sequence at the position designated by pos.
ostream_type&seekp(off_type off, ios_base::seekdir dir);
If the basic_ios member function fail() returns false, executes
rdbuf()->pubseekpos(off,dir), which positions the current pointer of the
output sequence at the position designated by off and dir.
pos_typetellp();
If the basic_ios member function fail() returns true, tellp() returns
pos_type(off_type(-1)) to indicate failure. Otherwise it returns the cur‐
rent position of the output sequence by calling rdbuf()-> pubseekoff(0,cur,
out).
ostream_type&write(const char_type* s, streamsize n);
Obtains characters to insert from successive locations of an array whose
first element is designated by s. Characters are inserted until either of
the following occurs:
- n characters are inserted
- Inserting in the output sequence fails
In the second case the function calls the basic_ios member function set‐
state(badbit). The function returns *this.
NON-MEMBER FUNCTIONS
template<class charT, class traits>
basic_ostream<charT, traits>&
endl(basic_ostream<charT, traits>& os);
Outputs a newline character and flushes the buffer, then returns os.
template<class charT, class traits>
basic_ostream<charT, traits>&
ends(basic_ostream<charT, traits>& os);
Inserts a null character into the output sequence, then returns os.
template<class charT, class traits>
basic_ostream<charT, traits>&
flush(basic_ostream<charT, traits>& os);
Flushes the buffer, then returns os.
template<class charT, class traits>
basic_ostream<charT, traits>&
operator<<(basic_ostream<charT, traits>& os, charT c);
Outputs the character c of type charT into the basic_ostream object's buf‐
fer. Both the stream and the stream buffer are instantiated on type charT.
Padding is not ignored.
template<class charT, class traits>
basic_ostream<charT, traits>&
operator<<(basic_ostream<charT, traits>& os, char c);
Outputs the character c of type char into the basic_ostream object's buf‐
fer. Both the stream and the stream buffer are instantiated on type charT.
Conversion from characters of type char to characters of type charT is per‐
formed by the basic_ios member function widen. Padding is not ignored.
template<class traits>
basic_ostream<char, traits>&
operator<<(basic_ostream<char, traits>& os, char c);
Outputs the character c of type char into the basic_ostream object's buf‐
fer. Both the stream and the stream buffer are instantiated on type char.
Padding is not ignored.
template<class charT, class traits>
basic_ostream<charT, traits>&
operator<<(basic_ostream<charT, traits>& os,
const charT* s);
Outputs the null-terminated-byte-string s of type charT* into the
basic_ostream object's buffer. Both the stream and the stream buffer are
instantiated on type charT.
template<class charT, class traits>
basic_ostream<charT, traits>&
operator<<(basic_ostream<charT, traits>& os,
const char* s);
Outputs the null-terminated-byte-string s of type char* into the
basic_ostream object's buffer. Both the stream and the stream buffer are
instantiated on type charT. Conversion from characters of type char to
characters of type charT is performed by the basic_ios member function
widen.
template<class traits>
basic_ostream<char, traits>&
operator<<(basic_ostream<char, traits>& os, const char* s);
Outputs the null-terminated-byte-string s of type char* into the
basic_ostream object's buffer. Both the stream and the stream buffer are
instantiated on type char.
template<class traits>
basic_ostream<char, traits>&
operator<<(basic_ostream<char, traits>& os,
unsigned char c);
Returns os << (char)c.
template<class traits>
basic_ostream<char, traits>&
operator<<(basic_ostream<char, traits>& os, signed char c);
Returns os << (char)c.
template<class traits>
basic_ostream<char, traits>&
operator<<(basic_ostream<char, traits>& os,
unsigned char* c);
Returns os << (char*)c.
template<class traits>
basic_ostream<char, traits>&
operator<<(basic_ostream<char, traits>& os,
signed char* c);
Returns os << (char*)c.
FORMATTING
The formatting is done through member functions or manipulators.
Manipulators Member Functions
showpos setf(ios_base::showpos)
noshowpos unsetf(ios_base::showpos)
showbase setf(ios_base::showbase)
noshowbase unsetf(ios_base::showbase)
uppercase setf(ios_base::uppercase)
nouppercase unsetf(ios_base::uppercase)
showpoint setf(ios_base::showpoint)
noshowpoint unsetf(ios_base::showpoint)
boolalpha setf(ios_base::boolalpha)
noboolalpha unsetf(ios_base::boolalpha)
unitbuf setf(ios_base::unitbuf)
nounitbuf unsetf(ios_base::unitbuf)
internal setf(ios_base::internal,
ios_base::adjustfield)
left setf(ios_base::left,
ios_base::adjustfield)
right setf(ios_base::right,
ios_base::adjustfield)
dec setf(ios_base::dec,
ios_base::basefield)
hex setf(ios_base::hex,
ios_base::basefield)
oct setf(ios_base::oct,
ios_base::basefield)
fixed setf(ios_base::fixed,
ios_base::floatfield)
scientific setf(ios_base::scientific,
ios_base::floatfield)
resetiosflags
(ios_base::fmtflags flag) setf(0,flag)
setiosflags
(ios_base::fmtflags flag) setf(flag)
setbase(int base) see above
setfill(char_type c) fill(c)
setprecision(int n) precision(n)
setw(int n) width(n)DESCRIPTION
showpos Generates a + sign in non-negative generated numeric output.
showbase Generates a prefix indicating the numeric base of generated
integer output
uppercase Replaces certain lowercase letters with their uppercase
equivalents in generated output
showpoint Generates a decimal-point character unconditionally in gen‐
erated floating-point output
boolalpha Inserts and extracts bool type in alphabetic format
unitbuf Flushes output after each output operation
internal Adds fill characters at a designated internal point in cer‐
tain generated output. If no such point is designated, it's
identical to right.
left Adds fill characters on the right (final positions) of certain
generated output
right Adds fill characters on the left (initial positions) of certain
generated output
dec Converts integer input or generates integer output in decimal
base
hex Converts integer input or generates integer output in hexadecimal
base
oct Converts integer input or generates integer output in octal base
fixed Generates floating-point output in fixed-point notation
scientific Generates floating-point output in scientific notation
resetiosflags
(ios_base::fmtflags flag) Resets the fmtflags field flag
setiosflags
(ios_base::fmtflags flag) Sets up the flag flag
setbase(int base) Converts integer input or generates integer output
in base base. The parameter base can be 8, 10 or
16.
setfill(char_type c) Sets the character used to pad (fill) an output
conversion to the specified field width
setprecision(int n) Sets the precision (number of digits after the
decimal point) to generate on certain output con‐
versions
setw(int n) Sets the field with (number of characters) to generate on
certain output conversions
EXAMPLE
//
// stdlib/examples/manual/ostream1.cpp
//
#include<iostream>
#include<ostream>
#include<sstream>
#include<iomanip>
void main ( )
{
using namespace std;
float f= 3.14159;
int i= 22;
const char* s= "Randy is the king of stdlib";
// create a read/write stringbuf object on tiny char
// and attach it to an istringstream object
istringstream in( ios_base::in | ios_base::out );
// tie the ostream object to the istringstream object
ostream out(in.rdbuf());
out << "test beginning !" << endl;
// output i in hexadecimal
out << hex << i <<endl;
// set the field width to 10
// set the padding character to '@'
// and output i in octal
out << setw(10) << oct << setfill('@') << i << endl;
// set the precision to 2 digits after the separator
// output f
out << setprecision(3) << f << endl;
// output the 17 first characters of s
out.write(s,17);
// output a newline character
out.put('\n');
// output s
out << s << endl;
// output the all buffer to standard output
cout << in.rdbuf();
}
//
// stdlib/examples/manual/ostream2.cpp
//
#include<iostream>
#include<ostream>
#include<sstream>
void main ( )
{
using namespace std;
float f= 3.14159;
const wchar_t* s= L"Kenavo !";
// create a read/write stringbuf object on wide char
// and attach it to an wistringstream object
wistringstream in( ios_base::in | ios_base::out );
// tie the wostream object to the wistringstream object
wostream out(in.rdbuf());
out << L"test beginning !" << endl;
// output f in scientific format
out << scientific << f <<endl;
// store the current put-pointer position
wostream::pos_type pos = out.tellp();
// output s
out << s << endl;
// output the all buffer to standard output
wcout << in.rdbuf() << endl;
// position the get-pointer
in.seekg(pos);
// output s
wcout << in.rdbuf() << endl;
}
SEE ALSO
char_traits(3C++), ios_base(3C++), basic_ios(3C++), basic_stream‐
buf(3C++), basic_iostream(3C++)
Working Paper for Draft Proposed International Standard for Information
Systems--Programming Language C++, Section 27.6.2.1
STANDARDS CONFORMANCE
ANSI X3J16/ISO WG21 Joint C++ Committee
Rogue Wave Software 02 Apr 1998 basic_ostream(3C++)