std::basic_spanbuf

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< cpp‎ | io
 
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Input/output library
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basic_spanbuf
(C++23)
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(C++20)
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(C++20)
Types
Error category interface
(C++11)
(C++11)
 
std::basic_spanbuf
Public member functions
(C++23)
(C++23)
(C++23)
(C++23)
Protected member functions
(C++23)
(C++23)
(C++23)
Non-member functions
(C++23)
 
Defined in header <spanstream>
template<

    class CharT,
    class Traits = std::char_traits<CharT>

> class basic_spanbuf : public std::basic_streambuf<CharT, Traits>
 (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:

Defined in header <spanstream>
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
(C++23)
 constructs a basic_spanbuf object
(public member function)
(destructor)
[virtual] (C++23)
 destroys the basic_spanbuf object
(virtual public member function)
(C++23)
 assigns a basic_spanbuf object
(public member function)
(C++23)
 swaps two basic_spanbuf objects
(public member function)
(C++23)
 obtains or initializes an underlying buffer according to mode
(public member function)
Protected member functions
[virtual] (C++23)
 attempts to replace the controlled character sequence with an array
(virtual protected member function)
[virtual] (C++23)
 repositions the next pointer in the input sequence, output sequence, or both, using relative addressing
(virtual protected member function)
[virtual] (C++23)
 repositions the next pointer in the input sequence, output sequence, or both using absolute addressing
(virtual protected member function)

Non-member functions

(C++23)
 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

[virtual]
 destructs the basic_streambuf object
(virtual public member function of std::basic_streambuf<CharT,Traits>)
Locales
invokes imbue()
(public member function of std::basic_streambuf<CharT,Traits>)
obtains a copy of the associated locale
(public member function of std::basic_streambuf<CharT,Traits>)
Positioning
invokes setbuf()
(public member function of std::basic_streambuf<CharT,Traits>)
invokes seekoff()
(public member function of std::basic_streambuf<CharT,Traits>)
invokes seekpos()
(public member function of std::basic_streambuf<CharT,Traits>)
invokes sync()
(public member function of std::basic_streambuf<CharT,Traits>)
Get area
obtains the number of characters immediately available in the get area
(public member function of std::basic_streambuf<CharT,Traits>)
advances the input sequence, then reads one character without advancing again
(public member function of std::basic_streambuf<CharT,Traits>)
(removed in C++17)
 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>)
invokes xsgetn()
(public member function of std::basic_streambuf<CharT,Traits>)
Put area
writes one character to the put area and advances the next pointer
(public member function of std::basic_streambuf<CharT,Traits>)
invokes xsputn()
(public member function of std::basic_streambuf<CharT,Traits>)
Putback
puts one character back in the input sequence
(public member function of std::basic_streambuf<CharT,Traits>)
moves the next pointer in the input sequence back by one
(public member function of std::basic_streambuf<CharT,Traits>)

Protected member functions

 constructs a basic_streambuf object
(protected member function)
(C++11)
 replaces a basic_streambuf object
(protected member function)
(C++11)
 swaps two basic_streambuf objects
(protected member function)
Locales
[virtual]
 changes the associated locale
(virtual protected member function of std::basic_streambuf<CharT,Traits>)
Positioning
[virtual]
 replaces the buffer with user-defined array, if permitted
(virtual protected member function of std::basic_streambuf<CharT,Traits>)
[virtual]
 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>)
[virtual]
 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>)
[virtual]
 synchronizes the buffers with the associated character sequence
(virtual protected member function of std::basic_streambuf<CharT,Traits>)
Get area
[virtual]
 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>)
[virtual]
 reads characters from the associated input sequence to the get area
(virtual protected member function of std::basic_streambuf<CharT,Traits>)
[virtual]
 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>)
[virtual]
 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)
advances the next pointer in the input sequence
(protected member function)
repositions the beginning, next, and end pointers of the input sequence
(protected member function)
Put area
[virtual]
 writes multiple characters to the output sequence
(virtual protected member function of std::basic_streambuf<CharT,Traits>)
[virtual]
 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)
advances the next pointer of the output sequence
(protected member function)
repositions the beginning, next, and end pointers of the output sequence
(protected member function)
Putback
[virtual]
 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)
(deprecated in C++98)
 implements raw character array device
(class)
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