|
VMS Help CXXLSTD, IOStreams, basic_ostream *Conan The Librarian |
Standard C++ Library
Copyright 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 gen-
erated 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, ios_base, basic_ios,
basic_streambuf, basic_iostream
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
|
|