16 Buffers [buffer]

16.13 Class template dynamic_string_buffer [buffer.dynamic.string]

1

Class template dynamic_string_buffer is an adaptor used to automatically grow or shrink a basic_string object, to reflect the data successfully transferred in an I/O operation.

namespace std {
namespace experimental {
namespace net {
inline namespace v1 {

  template<class CharT, class Traits, class Allocator>
  class dynamic_string_buffer
  {
  public:
    // types:
    using const_buffers_type = const_buffer;
    using mutable_buffers_type = mutable_buffer;

    // constructors:
    explicit dynamic_string_buffer(basic_string<CharT, Traits, Allocator>& str) noexcept;
    dynamic_string_buffer(basic_string<CharT, Traits, Allocator>& str,
                          size_t maximum_size) noexcept;
    dynamic_string_buffer(dynamic_string_buffer&&) = default;

    // members:
    size_t size() const noexcept;
    size_t max_size() const noexcept;
    size_t capacity() const noexcept;
    const_buffers_type data() const noexcept;
    mutable_buffers_type prepare(size_t n);
    void commit(size_t n) noexcept;
    void consume(size_t n);

  private:
    basic_string<CharT, Traits, Allocator>& str_; // exposition only
    size_t size_; // exposition only
    const size_t max_size_; // exposition only
  };

} // inline namespace v1
} // namespace net
} // namespace experimental
} // namespace std
2

The dynamic_string_buffer class template meets the requirements of DynamicBuffer ([buffer.reqmts.dynamicbuffer]).

3

The dynamic_string_buffer class template requires that sizeof(CharT) == 1.

explicit dynamic_string_buffer(basic_string<CharT, Traits, Allocator>& str) noexcept;

4

Effects: Initializes str_ with str, size_ with str.size(), and max_size_ with str.max_size().

dynamic_string_buffer(basic_string<CharT, Traits, Allocator>& str, size_t maximum_size) noexcept;

5

Requires: str.size() <= maximum_size.

6

Effects: Initializes str_ with str, size_ with str.size(), and max_size_ with maximum_size.

size_t size() const noexcept;

7

Returns: size_.

size_t max_size() const noexcept;

8

Returns: max_size_.

size_t capacity() const noexcept;

9

Returns: str_.capacity().

const_buffers_type data() const noexcept;

10

Returns: buffer(str_, size_).

mutable_buffers_type prepare(size_t n);

11

Effects: Performs str_.resize(size_ + n).

12

Returns: buffer(buffer(str_) + size_, n).

13

Remarks: length_error if size() + n exceeds max_size().

void commit(size_t n) noexcept;

14

Effects: Performs: 

size_ += min(n, str_.size() - size_);
str_.resize(size_);

void consume(size_t n);

15

Effects: Performs: 

size_t m = min(n, size_);
str_.erase(0, m);
size_ -= m;