ostream (3C++std) - Tru64 UNIX
Standard C++ LibraryCopyright 1996, Rogue Wave Software, Inc.
NAME
basic_ostream
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 a number of member function signatures that
assist in formatting and writing output to sequences controlled by a stream
buffer.
Two groups of member function signatures 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
construction, the function tries to perform the requested output. The
sentry object performs exception-safe initialization, such as controlling
the status of the stream or locking it in multithread environment.
Some formatted output functions generate the requested output by converting
a value from some scalar to text form and inserting the converted text in
the output sequence. The conversion behavior is locale dependent, and
directly depend on the locale object imbued in the stream.
INTERFACE
template<class charT, class traits = char_traits<charT> >
class basic_ostream
:virtual public basic_ios<charT, traits> {
public:
typedef basic_ostream<charT, traits> ostream_type;
typedef basic_ios<charT, traits> ios_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_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<<(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();
ostream_type& seekp(pos_type );
ostream_type& seekp(off_type , ios_base::seekdir );
pos_type tellp();
protected:
basic_ostream();
};
//global 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 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>&, unsigned 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>&, const unsigned char*);
template <class traits>
basic_ostream<char,traits>&
operator<<(basic_ostream<char,traits>&, const signed 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;
CONSTRUCTOR
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).
DESTRUCTOR
virtual ~basic_ostream();
Destroys an object of class basic_ostream.
SENTRY CLASS
explicit sentry(basic_ostream<charT,traits>&);
Prepares for formatted or unformatted output. First if the basic_ios
member function 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 function operator bool () will return true. Otherwise it will
return false. In multithread 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 flush the buffer. In 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() will
return true else it will return false.
INSERTORS
ostream_type&
operator<<(ostream_type& (*pf) (ostream_type&));
Calls pf(*this), then return *this. See, for example, the function
signature endl(basic_ostream&).
ostream_type&
operator<<(ios_type& (*pf) (ios_type&));
Calls pf(*this), then return *this.
ostream_type&
operator<<(ios_base& (*pf) (ios_base&));
Calls pf(*this), then return *this. See, for example, the function
signature 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 function numpunct<>::truename() or
numpunct<>::falsename().
ostream_type&
operator<<(short n);
Converts the signed short integer n, and output it into the stream
buffer, then return *this.
ostream_type&
operator<<(unsigned short n);
Converts the unsigned short integer n, and output it into the stream
buffer, then return *this.
ostream_type&
operator<<(int n);
Converts the signed integer n, and output it into the stream buffer,
then return *this.
ostream_type&
operator<<(unsigned int n);
Converts the unsigned integer n, and output it into the stream buffer,
then return *this.
ostream_type&
operator<<(long n);
Converts the signed long integer n, and output it into the stream
buffer, then return *this.
ostream_type&
operator<<(unsigned long n);
Converts the unsigned long integer n, and output it into the stream
buffer, then return *this.
ostream_type&
operator<<(float f);
Converts the float f and output it into the stream buffer, then return
*this.
ostream_type&
operator<<(double f);
Converts the double f and output it into the stream buffer, then return
*this.
ostream_type&
operator<<(long double f);
Converts the long double f and output it into the stream buffer, then
return *this.
ostream_type&
operator<<(void *p);
Converts the pointer p, and output it into the stream buffer, then
return *this.
ostream_type&
operator<<(basic_streambuf<charT,traits> *sb);
If sb is null calls the basic_ios member function setstate(badbit).
Otherwise gets characters from sb and inserts them into the stream
buffer until any of the following occurs:
• end-of-file occurs on the input sequence.
• inserting in the output sequence fails
• an exception occurs 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:
• end-of-file occurs on the input sequence.
• inserting in the output sequence fails
• an exception occurs 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 will position 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 will position the current pointer of
the output sequence at the position designated by off and dir.
pos_type
tellp();
If the basic_ios member function fail() returns true, tellp() returns
pos_type(off_type(-1)) to indicate failure. Otherwise it returns the
current 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
setstate(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 flush 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
buffer. 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
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. 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
buffer. 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
generated floating-point output
boolalpha Insert and extract bool type in alphabetic format
unitbuf Flushes output after each output operation
internal Adds fill characters at a designated internal point in certain
generated output, or identical to right if no such point is
designated
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
resetiosflagss
(ios_base::fmtflags flag) Resets the fmtflags field flag
setiosflags
(ios_base::fmtflags flag) Set 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) Set the character used to pad (fill) an output
conversion to the specified field width
setprecision(int n) Set the precision (number of digits after the decimal
point) to generate on certain output conversions
setw(int n) Set the field with (number of characters) to generate on
certain output conversions
EXAMPLES
//
// 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;
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('0);
// 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;
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++std), ios_base(3C++std), basic_ios(3C++std),
basic_streambuf(3C++std), basic_iostream(3C++std)
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
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