std::basic_ostringstream<CharT,Traits,Allocator>::basic_ostringstream
From cppreference.com
< cpp | io | basic ostringstream
C++
Feature test macros (C++20)
Concepts library (C++20)
Metaprogramming library (C++11)
Ranges library (C++20)
Filesystem library (C++17)
Concurrency support library (C++11)
Execution control library (C++26)
Input/output library
Print functions (C++23)
Buffers
(C++23)
(C++98/26*)
(C++20)
Streams
Abstractions
File I/O
String I/O
Array I/O
(C++23)
(C++23)
(C++23)
(C++98/26*)
(C++98/26*)
(C++98/26*)
Synchronized Output
(C++20)
Types
Error category interface
(C++11)
(C++11)
std::basic_ostringstream
Member functions
basic_ostringstream::basic_ostringstream
(C++11)
String operations
(C++20)
Non-member functions
(C++11)
(1)
explicit basic_ostringstream( std::ios_base::openmode mode =
std::ios_base::out );
(until C++11)
std::ios_base::out );
explicit basic_ostringstream( std::ios_base::openmode mode );
(since C++11)
basic_ostringstream()
: basic_ostringstream(std::ios_base::out ) {}
(2)
(since C++11)
: basic_ostringstream(std::ios_base::out ) {}
explicit basic_ostringstream
(3)
( const std::basic_string <CharT, Traits, Allocator>& str,
std::ios_base::openmode mode =
explicit basic_ostringstream
(4)
(since C++20)
( std::basic_string <CharT, Traits, Allocator>&& str,
std::ios_base::openmode mode =
basic_ostringstream( std::ios_base::openmode mode, const Allocator& a );
(5)
(since C++20)
template< class SAlloc >
(6)
(since C++20)
basic_ostringstream( const std::basic_string <CharT, Traits, SAlloc>& str,
template< class SAlloc >
(7)
(since C++20)
basic_ostringstream( const std::basic_string <CharT, Traits, SAlloc>& str,
const Allocator& a )
template< class SAlloc >
(8)
(since C++20)
explicit basic_ostringstream
( const std::basic_string <CharT, Traits, SAlloc>& str,
std::ios_base::openmode mode =
template< class StringViewLike >
(9)
(since C++26)
explicit basic_ostringstream
( const StringViewLike& t,
std::ios_base::openmode mode =
template< class StringViewLike >
(10)
(since C++26)
basic_ostringstream( const StringViewLike& t,
template< class StringViewLike >
basic_ostringstream( const StringViewLike& t, const Allocator& a );
(11)
(since C++26)
basic_ostringstream( const StringViewLike& t, const Allocator& a );
basic_ostringstream( basic_ostringstream&& other );
(12)
(since C++11)
Constructs new string stream.
Given
-
base_typeas std::basic_ostream <CharT, Traits>, and -
buf_typeas std::basic_stringbuf <CharT, Traits, Allocator>,
the std::basic_ostream base and the exposition-only data member sb are initialized as follows.
| Over load |
std::basic_ostream base | sb
|
|---|---|---|
| (1) | base_type(std::addressof (sb))[1] | buf_type(mode | std::ios_base::out ) |
| (2) | buf_type(std::ios_base::out ) | |
| (3) | buf_type(str, mode | std::ios_base::out ) | |
| (4) | buf_type(std::move(str), mode | std::ios_base::out ) | |
| (5) | buf_type(mode | std::ios_base::out, a) | |
| (6) | buf_type(str, mode | std::ios_base::out, a) | |
| (7) | buf_type(str, std::ios_base::out, a) | |
| (8) | buf_type(str, mode | std::ios_base::out ) | |
| (9) | std::addressof (sb) | {t, mode | std::ios_base::out, Allocator()} |
| (10) | {t, mode | std::ios_base::out, a} | |
| (11) | {t, std::ios_base::out, a} | |
| (12) | move constructed from other's std::basic_ostream base | move constructed from other.sb |
- ↑ The std::basic_iostream base was intialized with base_type(&sb) (for overloads (1,3)) until C++11.
8) This overload participates in overload resolution only if std::is_same_v <SAlloc, Allocator> is false.
9-11) These overloads participate in overload resolution only if std::is_convertible_v <const StringViewLike&, std::basic_string_view <CharT, Traits>> is true.
[edit] Parameters
str
-
string to use as initial contents of the string stream
t
-
an object (convertible to std::basic_string_view ) to use as initial contents of the string stream
a
-
allocator used for allocating the contents of the string stream
mode
-
specifies stream open mode. It is a BitmaskType, the following constants are defined:
other
-
another string stream to use as source
Constant
Explanation
app
seek to the end of stream before each write
binary
open in binary mode
in
open for reading
out
open for writing
trunc
discard the contents of the stream when opening
ate
seek to the end of stream immediately after open
noreplace (C++23)
open in exclusive mode
[edit] Notes
Construction of one-off basic_ostringstream objects in a tight loop, such as when used for string conversion, may be significantly more costly than calling str() to reuse the same object.
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_sstream_from_string_view |
202306L |
(C++26) | Interfacing std::stringstream s with std::string_view , (9-11) |
[edit] Example
Run this code
#include <iostream> #include <sstream> int main() { // default constructor (input/output stream) std::stringstream buf1; buf1 << 7; int n = 0; buf1 >> n; std::cout << "buf1 = " << buf1.str() << " n = " << n << '\n'; // input stream std::istringstream inbuf("-10"); inbuf >> n; std::cout << "n = " << n << '\n'; // output stream in append mode (C++11) std::ostringstream buf2("test", std::ios_base::ate ); buf2 << '1'; std::cout << buf2.str() << '\n'; }
Output:
buf1 = 7 n = 7 n = -10 test1
[edit] Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| P0935R0 | C++11 | the default constructor was explicit | made implicit |
[edit] See also
constructs a
(public member function of
basic_stringbuf object (public member function of
std::basic_stringbuf<CharT,Traits,Allocator>) [edit]