std::basic_spanbuf
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Defined in header
<spanstream> |
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template<
class CharT, |
(since C++23) | |
std::basic_spanbuf is a std::basic_streambuf whose associated character sequence is a memory-resident sequence of arbitrary characters, which can be initialized from or made available as an instance of std::span<CharT>.
std::basic_spanbuf performs I/O on a fixed buffer, and therefore it does not attempt to obtain a new buffer when the underlying buffer is exhausted.
Typical implementations of std::basic_spanbuf add two member subobjects: a std::ios_base::openmode recording the open mode, and a std::span<CharT> referencing the underlying buffer.
Several typedefs for common character types are provided:
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Defined in header
<spanstream> |
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| Type | Definition |
std::spanbuf |
std::basic_spanbuf<char> |
std::wspanbuf |
std::basic_spanbuf<wchar_t> |
Member types
| Member type | Definition |
char_type |
CharT |
traits_type |
Traits; the program is ill-formed if Traits::char_type is not CharT. |
int_type |
Traits::int_type |
pos_type |
Traits::pos_type |
off_type |
Traits::off_type |
Member functions
Public member functions |
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(C++23)
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constructs a basic_spanbuf object(public member function) |
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(destructor)
[virtual] (C++23)
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destroys the basic_spanbuf object(virtual public member function) |
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(C++23)
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assigns a basic_spanbuf object(public member function) |
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(C++23)
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swaps two basic_spanbuf objects(public member function) |
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(C++23)
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obtains or initializes an underlying buffer according to mode (public member function) |
Protected member functions |
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[virtual] (C++23)
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attempts to replace the controlled character sequence with an array (virtual protected member function) |
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[virtual] (C++23)
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repositions the next pointer in the input sequence, output sequence, or both, using relative addressing (virtual protected member function) |
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[virtual] (C++23)
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repositions the next pointer in the input sequence, output sequence, or both using absolute addressing (virtual protected member function) |
Non-member functions
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(C++23)
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specializes the std::swap algorithm (function template) |
Inherited from std::basic_streambuf
Member types
| Member type | Definition |
char_type |
CharT |
traits_type |
Traits; the program is ill-formed if Traits::char_type is not CharT. |
int_type |
Traits::int_type |
pos_type |
Traits::pos_type |
off_type |
Traits::off_type |
Member functions
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[virtual]
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destructs the basic_streambuf object(virtual public member function of std::basic_streambuf<CharT,Traits>) |
Locales |
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| invokes imbue() (public member function of std::basic_streambuf<CharT,Traits>) |
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| obtains a copy of the associated locale (public member function of std::basic_streambuf<CharT,Traits>) |
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Positioning |
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| invokes setbuf() (public member function of std::basic_streambuf<CharT,Traits>) |
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| invokes seekoff() (public member function of std::basic_streambuf<CharT,Traits>) |
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| invokes seekpos() (public member function of std::basic_streambuf<CharT,Traits>) |
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| invokes sync() (public member function of std::basic_streambuf<CharT,Traits>) |
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Get area |
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| obtains the number of characters immediately available in the get area (public member function of std::basic_streambuf<CharT,Traits>) |
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| advances the input sequence, then reads one character without advancing again (public member function of std::basic_streambuf<CharT,Traits>) |
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(removed in C++17)
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reads one character from the input sequence and advances the sequence (public member function of std::basic_streambuf<CharT,Traits>) |
| reads one character from the input sequence without advancing the sequence (public member function of std::basic_streambuf<CharT,Traits>) |
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| invokes xsgetn() (public member function of std::basic_streambuf<CharT,Traits>) |
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Put area |
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| writes one character to the put area and advances the next pointer (public member function of std::basic_streambuf<CharT,Traits>) |
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| invokes xsputn() (public member function of std::basic_streambuf<CharT,Traits>) |
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Putback |
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| puts one character back in the input sequence (public member function of std::basic_streambuf<CharT,Traits>) |
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| moves the next pointer in the input sequence back by one (public member function of std::basic_streambuf<CharT,Traits>) |
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Protected member functions
constructs a basic_streambuf object(protected member function) |
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(C++11)
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replaces a basic_streambuf object(protected member function) |
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(C++11)
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swaps two basic_streambuf objects(protected member function) |
Locales |
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[virtual]
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changes the associated locale (virtual protected member function of std::basic_streambuf<CharT,Traits>) |
Positioning |
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[virtual]
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replaces the buffer with user-defined array, if permitted (virtual protected member function of std::basic_streambuf<CharT,Traits>) |
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[virtual]
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repositions the next pointer in the input sequence, output sequence, or both, using relative addressing (virtual protected member function of std::basic_streambuf<CharT,Traits>) |
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[virtual]
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repositions the next pointer in the input sequence, output sequence, or both using absolute addressing (virtual protected member function of std::basic_streambuf<CharT,Traits>) |
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[virtual]
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synchronizes the buffers with the associated character sequence (virtual protected member function of std::basic_streambuf<CharT,Traits>) |
Get area |
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[virtual]
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obtains the number of characters available for input in the associated input sequence, if known (virtual protected member function of std::basic_streambuf<CharT,Traits>) |
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[virtual]
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reads characters from the associated input sequence to the get area (virtual protected member function of std::basic_streambuf<CharT,Traits>) |
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[virtual]
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reads characters from the associated input sequence to the get area and advances the next pointer (virtual protected member function of std::basic_streambuf<CharT,Traits>) |
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[virtual]
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reads multiple characters from the input sequence (virtual protected member function of std::basic_streambuf<CharT,Traits>) |
| returns a pointer to the beginning, current character and the end of the get area (protected member function) |
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| advances the next pointer in the input sequence (protected member function) |
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| repositions the beginning, next, and end pointers of the input sequence (protected member function) |
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Put area |
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[virtual]
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writes multiple characters to the output sequence (virtual protected member function of std::basic_streambuf<CharT,Traits>) |
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[virtual]
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writes characters to the associated output sequence from the put area (virtual protected member function of std::basic_streambuf<CharT,Traits>) |
| returns a pointer to the beginning, current character and the end of the put area (protected member function) |
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| advances the next pointer of the output sequence (protected member function) |
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| repositions the beginning, next, and end pointers of the output sequence (protected member function) |
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Putback |
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[virtual]
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puts a character back into the input sequence, possibly modifying the input sequence (virtual protected member function of std::basic_streambuf<CharT,Traits>) |
Notes
std::basic_spanbuf does not own the underlying buffer.
It is the responsibility of programmers to ensure the underlying buffer is in its lifetime when used by a std::basic_spanbuf object. Additional synchronization may be needed if more than one thread operates the same underlying buffer through different std::basic_spanbuf objects.
| Feature-test macro | Value | Std | Comment |
|---|---|---|---|
__cpp_lib_spanstream |
202106L | (C++23) | std::spanbuf, std::spanstream |
See also
| implements raw string device (class template) |
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(deprecated in C++98)
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implements raw character array device (class) |