Difference between revisions of "cpp/io/basic osyncstream"

Latest revision as of 03:48, 7 December 2023

Defined in header `<syncstream>`
template< class CharT, class Traits = std::char_traits<CharT>, class Allocator = std::allocator<CharT> > class basic_osyncstream : public std::basic_ostream<CharT, Traits>		(since C++20)

The class template std::basic_osyncstream is a convenience wrapper for std::basic_syncbuf. It provides a mechanism to synchronize threads writing to the same stream.

It can be used with a named variable:

{
    std::osyncstream synced_out(std::cout); // synchronized wrapper for std::cout
    synced_out << "Hello, ";
    synced_out << "World!";
    synced_out << std::endl; // flush is noted, but not yet performed
    synced_out << "and more!\n";
} // characters are transferred and std::cout is flushed

as well as with a temporary:

std::osyncstream(std::cout) << "Hello, " << "World!" << '\n';

It provides the guarantee that all output made to the same final destination buffer (std::cout in the examples above) will be free of data races and will not be interleaved or garbled in any way, as long as every write to that final destination buffer is made through (possibly different) instances of std::basic_osyncstream.

Typical implementation of std::basic_osyncstream holds only one member: the wrapped std::basic_syncbuf.

Inheritance diagram

Several typedefs for common character types are provided:

Defined in header `<syncstream>`
Type	Definition
`std::osyncstream`	std::basic_osyncstream<char>
`std::wosyncstream`	std::basic_osyncstream<wchar_t>

[edit] Member types

Member type	Definition
`char_type`	`CharT`[edit]
`traits_type`	`Traits`; the program is ill-formed if `Traits::char_type` is not `CharT`.[edit]
`int_type`	`Traits::int_type`[edit]
`pos_type`	`Traits::pos_type`[edit]
`off_type`	`Traits::off_type`[edit]
`allocator_type`	`Allocator`
`streambuf_type`	std::basic_streambuf<CharT, Traits>
`syncbuf_type`	std::basic_syncbuf<CharT, Traits, Allocator>

[edit] Member functions

(constructor)	constructs a `basic_osyncstream` object (public member function) [edit]
operator=	assigns a `basic_osyncstream` object (public member function) [edit]
(destructor)	destroys the `basic_osyncstream` and emits its internal buffer (public member function) [edit]
rdbuf	obtains a pointer to the underlying `basic_syncbuf` (public member function) [edit]
get_wrapped	obtains a pointer to the final destination stream buffer (public member function) [edit]
emit	calls `emit()` on the underlying `basic_syncbuf` to transmit its internal data to the final destination (public member function) [edit]

Inherited from std::basic_ostream

Member functions

Formatted output
operator<<	inserts formatted data (public member function of `std::basic_ostream<CharT,Traits>`) [edit]
Unformatted output
put	inserts a character (public member function of `std::basic_ostream<CharT,Traits>`) [edit]
write	inserts blocks of characters (public member function of `std::basic_ostream<CharT,Traits>`) [edit]
Positioning
tellp	returns the output position indicator (public member function of `std::basic_ostream<CharT,Traits>`) [edit]
seekp	sets the output position indicator (public member function of `std::basic_ostream<CharT,Traits>`) [edit]
Miscellaneous
flush	synchronizes with the underlying storage device (public member function of `std::basic_ostream<CharT,Traits>`) [edit]

Member classes

sentry

implements basic logic for preparation of the stream for output operations
(public member class of std::basic_ostream<CharT,Traits>) [edit]

Inherited from std::basic_ios

Member types

Member type	Definition
`char_type`	`CharT`
`traits_type`	`Traits`
`int_type`	`Traits::int_type`
`pos_type`	`Traits::pos_type`
`off_type`	`Traits::off_type`

Member functions

State functions
good	checks if no error has occurred i.e. I/O operations are available (public member function of `std::basic_ios<CharT,Traits>`) [edit]
eof	checks if end-of-file has been reached (public member function of `std::basic_ios<CharT,Traits>`) [edit]
fail	checks if an error has occurred (public member function of `std::basic_ios<CharT,Traits>`) [edit]
bad	checks if a non-recoverable error has occurred (public member function of `std::basic_ios<CharT,Traits>`) [edit]
operator!	checks if an error has occurred (synonym of fail()) (public member function of `std::basic_ios<CharT,Traits>`) [edit]
operator bool	checks if no error has occurred (synonym of `!`fail()) (public member function of `std::basic_ios<CharT,Traits>`) [edit]
rdstate	returns state flags (public member function of `std::basic_ios<CharT,Traits>`) [edit]
setstate	sets state flags (public member function of `std::basic_ios<CharT,Traits>`) [edit]
clear	modifies state flags (public member function of `std::basic_ios<CharT,Traits>`) [edit]
Formatting
copyfmt	copies formatting information (public member function of `std::basic_ios<CharT,Traits>`) [edit]
fill	manages the fill character (public member function of `std::basic_ios<CharT,Traits>`) [edit]
Miscellaneous
exceptions	manages exception mask (public member function of `std::basic_ios<CharT,Traits>`) [edit]
imbue	sets the locale (public member function of `std::basic_ios<CharT,Traits>`) [edit]
rdbuf	manages associated stream buffer (public member function of `std::basic_ios<CharT,Traits>`) [edit]
tie	manages tied stream (public member function of `std::basic_ios<CharT,Traits>`) [edit]
narrow	narrows characters (public member function of `std::basic_ios<CharT,Traits>`) [edit]
widen	widens characters (public member function of `std::basic_ios<CharT,Traits>`) [edit]

Inherited from std::ios_base

Member functions

Formatting
flags	manages format flags (public member function of `std::ios_base`) [edit]
setf	sets specific format flag (public member function of `std::ios_base`) [edit]
unsetf	clears specific format flag (public member function of `std::ios_base`) [edit]
precision	manages decimal precision of floating point operations (public member function of `std::ios_base`) [edit]
width	manages field width (public member function of `std::ios_base`) [edit]
Locales
imbue	sets locale (public member function of `std::ios_base`) [edit]
getloc	returns current locale (public member function of `std::ios_base`) [edit]
Internal extensible array
xalloc [static]	returns a program-wide unique integer that is safe to use as index to `pword()` and `iword()` (public static member function of `std::ios_base`) [edit]
iword	resizes the private storage if necessary and access to the long element at the given index (public member function of `std::ios_base`) [edit]
pword	resizes the private storage if necessary and access to the void* element at the given index (public member function of `std::ios_base`) [edit]
Miscellaneous
register_callback	registers event callback function (public member function of `std::ios_base`) [edit]
sync_with_stdio [static]	sets whether C++ and C I/O libraries are interoperable (public static member function of `std::ios_base`) [edit]
Member classes
failure	stream exception (public member class of `std::ios_base`) [edit]
Init	initializes standard stream objects (public member class of `std::ios_base`) [edit]

Member types and constants

Type Explanation

openmode

stream open mode type

The following constants are also defined:

Constant	Explanation[edit]
`app`	seek to the end of stream before each write[edit]
`binary`	open in binary mode[edit]
`in`	open for reading[edit]
`out`	open for writing[edit]
`trunc`	discard the contents of the stream when opening[edit]
`ate`	seek to the end of stream immediately after open[edit]
`noreplace` (C++23)	open in exclusive mode[edit]

(typedef) [edit]

fmtflags

formatting flags type

The following constants are also defined:

Constant	Explanation[edit]
`dec`	use decimal base for integer I/O: see std::dec[edit]
`oct`	use octal base for integer I/O: see std::oct[edit]
`hex`	use hexadecimal base for integer I/O: see std::hex[edit]
`basefield`	dec \| oct \| hex. Useful for masking operations[edit]
`left`	left adjustment (adds fill characters to the right): see std::left[edit]
`right`	right adjustment (adds fill characters to the left): see std::right[edit]
`internal`	internal adjustment (adds fill characters to the internal designated point): see std::internal[edit]
`adjustfield`	left \| right \| internal. Useful for masking operations[edit]
`scientific`	generate floating point types using scientific notation, or hex notation if combined with fixed: see std::scientific[edit]
`fixed`	generate floating point types using fixed notation, or hex notation if combined with scientific: see std::fixed[edit]
`floatfield`	scientific \| fixed. Useful for masking operations[edit]
`boolalpha`	insert and extract bool type in alphanumeric format: see std::boolalpha[edit]
`showbase`	generate a prefix indicating the numeric base for integer output, require the currency indicator in monetary I/O: see std::showbase[edit]
`showpoint`	generate a decimal-point character unconditionally for floating-point number output: see std::showpoint[edit]
`showpos`	generate a + character for non-negative numeric output: see std::showpos[edit]
`skipws`	skip leading whitespace before certain input operations: see std::skipws[edit]
`unitbuf`	flush the output after each output operation: see std::unitbuf[edit]
`uppercase`	replace certain lowercase letters with their uppercase equivalents in certain output operations: see std::uppercase[edit]

(typedef) [edit]

iostate

state of the stream type

The following constants are also defined:

Constant	Explanation[edit]
`goodbit`	no error[edit]
`badbit`	irrecoverable stream error[edit]
`failbit`	input/output operation failed (formatting or extraction error)[edit]
`eofbit`	associated input sequence has reached end-of-file[edit]

(typedef) [edit]

seekdir

seeking direction type

The following constants are also defined:

Constant	Explanation[edit]
`beg`	the beginning of a stream[edit]
`end`	the ending of a stream[edit]
`cur`	the current position of stream position indicator[edit]

(typedef) [edit]

event

specifies event type
(enum) [edit]

event_callback

callback function type
(typedef) [edit]

[edit] Notes

Feature-test macro	Value	Std	Feature
`__cpp_lib_syncbuf`	201803L	(C++20)	Synchronized buffered ostream (`std::osyncstream`, std::syncbuf) and manipulators

@@ Line 2: / Line 2: @@
 {{cpp/io/basic_osyncstream/navbar}}
 {{dcl begin}}
-{{dcl header | syncstream}}
+{{dcl header|syncstream}}
-{{dcl | since=c++20 | 1=
+{{dcl|since=c++20|1=
 template<
      class CharT,
      class Traits = std::char_traits<CharT>,
      class Allocator = std::allocator<CharT>
-> class basic_osyncstream: public std::basic_ostream<CharT, Traits>
+> class basic_osyncstream : public std::basic_ostream<CharT, Traits>
 }}
 {{dcl end}}
@@ Line 15: / Line 15: @@
 It can be used with a named variable:
 {{source|1=
 {
-  std::osyncstream bout(std::cout); // synchronized wrapper for std::cout
+    std::osyncstream synced_out(std::cout); // synchronized wrapper for std::cout
-  bout << "Hello, ";
+    synced_out << "Hello, ";
-  bout << "World!";
+    synced_out << "World!";
-  bout << std::endl; // flush is noted, but not yet performed
+    synced_out << std::endl; // flush is noted, but not yet performed
-  bout << "and more!\n";
+    synced_out << "and more!\n";
 } // characters are transferred and std::cout is flushed
 }}
 as well as with a temporary:
 {{source|1=
 std::osyncstream(std::cout) << "Hello, " << "World!" << '\n';
 }}
-It provides the guarantee that all output made to the same final destination buffer (std::cout in the examples above) will be free of data races and will not be interleaved or garbled in any way, as long as every write to the that final destination buffer is made through (possibly different) instances of {{tt|std::basic_osyncstream}}.
+It provides the guarantee that all output made to the same final destination buffer ({{lc|std::cout}} in the examples above) will be free of data races and will not be interleaved or garbled in any way, as long as every write to that final destination buffer is made through (possibly different) instances of {{tt|std::basic_osyncstream}}.
-Typical implementation of {{tt|std::basic_osyncstream}} holds only one member: the wrapped {{lc|std::basic_syncbuf}}
+Typical implementation of {{tt|std::basic_osyncstream}} holds only one member: the wrapped {{lc|std::basic_syncbuf}}.
-Two specializations for common character types are also defined:
+{{inheritance diagram/std-basic_osyncstream}}
-{{dsc begin}}
+{{cpp/basic char typedefs|osyncstream|syncstream}}
-{{dsc header | syncstream}}
-{{dsc hitem | Type | Definition}}
-{{dsc | {{tt|osyncstream}} | {{c|basic_osyncstream<char>}}}}
-{{dsc | {{tt|wosyncstream}} | {{c|basic_osyncstream<wchar_t>}}}}
-{{dsc end}}
 ===Member types===
 {{dsc begin}}
-{{dsc hitem | Member type | Definition}}
+{{dsc hitem|Member type|Definition}}
-{{dsc inc | cpp/io/dsc char_type}}
+{{dsc inc|cpp/io/dsc char_type}}
-{{dsc inc | cpp/io/dsc traits_type}}
+{{dsc inc|cpp/io/dsc traits_type}}
-{{dsc inc | cpp/io/dsc int_type}}
+{{dsc inc|cpp/io/dsc int_type}}
-{{dsc inc | cpp/io/dsc pos_type}}
+{{dsc inc|cpp/io/dsc pos_type}}
-{{dsc inc | cpp/io/dsc off_type}}
+{{dsc inc|cpp/io/dsc off_type}}
-{{dsc | {{tt|allocator_type}} | {{c|Allocator}}}}
+{{dsc|{{tt|allocator_type}}|{{tt|Allocator}}}}
-{{dsc | {{tt|streambuf_type }} | {{c|std::basic_streambuf<CharT, Traits>}}}}
+{{dsc|{{tt|streambuf_type }}|{{c/core|std::basic_streambuf<CharT, Traits>}}}}
-{{dsc | {{tt|syncbuf_type }} | {{c|std::basic_syncbuf<CharT, Traits, Allocator>}}}}
+{{dsc|{{tt|syncbuf_type }}|{{c/core|std::basic_syncbuf<CharT, Traits, Allocator>}}}}
 {{dsc end}}
 ===Member functions===
 {{dsc begin}}
-{{dsc inc | cpp/io/basic_osyncstream/dsc constructor}}
+{{dsc inc|cpp/io/basic_osyncstream/dsc constructor}}
-{{dsc inc | cpp/io/basic_osyncstream/dsc operator{{=}}}}
+{{dsc inc|1=cpp/io/basic_osyncstream/dsc operator=}}
-{{dsc inc | cpp/io/basic_osyncstream/dsc destructor}}
+{{dsc inc|cpp/io/basic_osyncstream/dsc destructor}}
-{{dsc inc | cpp/io/basic_osyncstream/dsc rdbuf}}
+{{dsc inc|cpp/io/basic_osyncstream/dsc rdbuf}}
-{{dsc inc | cpp/io/basic_osyncstream/dsc get_wrapped}}
+{{dsc inc|cpp/io/basic_osyncstream/dsc get_wrapped}}
-{{dsc inc | cpp/io/basic_osyncstream/dsc emit}}
+{{dsc inc|cpp/io/basic_osyncstream/dsc emit}}
 {{dsc end}}
@@ Line 71: / Line 64: @@
 {{cpp/io/basic_ios/inherit}}
 {{cpp/io/ios_base/inherit}}
+===Notes===
+{{feature test macro|__cpp_lib_syncbuf|std=C++20|value=201803L|Synchronized buffered ostream ([[#Top|{{tt|std::osyncstream}}]], {{lc|std::syncbuf}}) and manipulators}}
 {{langlinks|de|es|fr|it|ja|pt|ru|zh}}

Compiler support
Freestanding and hosted
Language
Standard library
Standard library headers
Named requirements
Feature test macros (C++20)
Language support library
Concepts library (C++20)
Metaprogramming library (C++11)
Diagnostics library
General utilities library
Strings library
Containers library
Iterators library
Ranges library (C++20)
Algorithms library
Numerics library
Localizations library
Input/output library
Filesystem library (C++17)
Regular expressions library (C++11)
Concurrency support library (C++11)
Execution support library (C++26)
Technical specifications
Symbols index
External libraries

I/O manipulators
Print functions (C++23)
C-style I/O
Buffers
basic_streambuf
basic_filebuf
basic_stringbuf
basic_spanbuf (C++23)
strstreambuf (C++98/26*)
basic_syncbuf (C++20)
Streams
Abstractions
ios_base
basic_ios
basic_istream
basic_ostream
basic_iostream
File I/O
basic_ifstream
basic_ofstream
basic_fstream
String I/O
basic_istringstream
basic_ostringstream
basic_stringstream
Array I/O
basic_ispanstream (C++23)
basic_ospanstream (C++23)
basic_spanstream (C++23)
istrstream (C++98/26*)
ostrstream (C++98/26*)
strstream (C++98/26*)
Synchronized Output
basic_osyncstream (C++20)
Types
streamoff
streamsize
fpos
Error category interface
iostream_category (C++11)
io_errc (C++11)

Public member functions
basic_osyncstream::basic_osyncstream (C++20)
basic_osyncstream::operator= (C++20)
basic_osyncstream::~basic_osyncstream (C++20)
basic_osyncstream::rdbuf (C++20)
basic_osyncstream::get_wrapped (C++20)
basic_osyncstream::emit (C++20)

cppreference.com

Namespaces

Variants

Views

Actions

Difference between revisions of "cpp/io/basic osyncstream"

Latest revision as of 03:48, 7 December 2023

Contents

[edit] Member types

[edit] Member functions

Inherited from std::basic_ostream

Member functions

Formatted output

Unformatted output

Positioning

Miscellaneous

Member classes

Inherited from std::basic_ios

Member types

Member functions

State functions

Formatting

Miscellaneous

Inherited from std::ios_base

Member functions

Formatting

Locales

Internal extensible array

Miscellaneous

Member classes

Member types and constants

[edit] Notes

Navigation

Toolbox