Dynamic buffer requirements (version 2)

A dynamic buffer encapsulates memory storage that may be automatically resized as required.

A dynamic buffer type X shall satisfy the requirements of CopyConstructible (C++ Std, [copyconstructible]) types in addition to those listed below.

In the table below, X denotes a dynamic buffer class, x denotes a value of type X&, x1 denotes values of type const X&, pos and n denote values of type size_t, and u denotes an identifier.

Table 13. DynamicBuffer_v2 requirements

expression	type	assertion/note pre/post-conditions
`X::const_buffers_type`	type meeting ConstBufferSequence requirements.	This type represents the underlying memory as a sequence of @c const_buffer objects.
`X::mutable_buffers_type`	type meeting MutableBufferSequence requirements.	This type represents the underlying memory as a sequence of @c mutable_buffer objects.
`x1.size()`	`size_t`	Returns the size, in bytes, of the underlying memory.
`x1.max_size()`	`size_t`	Returns the permitted maximum size of the underlying memory.
`x1.capacity()`	`size_t`	Returns the maximum size to which the underlying memory can grow without requiring reallocation.
`x1.data(pos, n)`	`X::const_buffers_type`	Returns a constant buffer sequence `u` that represents the underlying memory beginning at offset `pos`, and where `buffer_size(u) <= n`.
`x.data(pos, n)`	`X::mutable_buffers_type`	Returns a mutable buffer sequence `u` that represents the underlying memory beginning at offset `pos`, and where `buffer_size(u) <= n`.
`x.grow(n)`		Requires: `size() + n <= max_size()`. Extends the underlying memory to accommodate `n` additional bytes at the end. The dynamic buffer reallocates memory as required. All constant or mutable buffer sequences previously obtained using `data()` are invalidated. Throws: `length_error` if `size() + n > max_size()`.
`x.shrink(n)`		Removes `n` bytes from the end of the underlying memory. If `n` is greater than the size of the underlying memory, the entire underlying memory is emptied. All constant or mutable buffer sequences previously obtained using `data()` are invalidated.
`x.consume(n)`		Removes `n` bytes from the beginning of the underlying memory. If `n` is greater than the size of the underlying memory, the entire underlying memory is emptied. All constant or mutable buffer sequences previously obtained using `data()` are invalidated.