blob: 64dad43b2d0bf0111ef55060abd82e044237b1dd [file] [log] [blame]
.. _chapter-pw-span:
.. default-domain:: cpp
.. highlight:: sh
The ``pw_span`` module provides an implementation of C++20's
`std::span <>`_, which is a
non-owning view of an array of values. The intent is for this implementation of
``std::span`` is to exactly match the C++20 standard.
The only header provided by the ``pw_span`` module is ``<span>``. It is included
as if it were coming from the C++ Standard Library. If the C++ library provides
``<span>``, the library's version of ``std::span`` is used in place of
``pw_span`` requires two include paths -- ``public/`` and ``public_overrides/``.
The internal implementation header is in ``public/``, and the ``<span>`` header
that mimics the C++ Standard Library is in ``public_overrides/``.
Using std::span
``std::span`` is a convenient abstraction that wraps a pointer and a size.
``std::span`` is especially useful in APIs. Spans support implicit conversions
from C arrays, ``std::array``, or any STL-style container, such as
Functions operating on an array of bytes typically accept pointer and size
.. code-block:: cpp
bool ProcessBuffer(char* buffer, size_t buffer_size);
bool DoStuff() {
ProcessBuffer(c_array, sizeof(c_array));
ProcessBuffer(, array_object.size());
ProcessBuffer(data_pointer, data_size);
Pointer and size arguments can be replaced with a ``std::span``:
.. code-block:: cpp
#include <span>
// With std::span, the buffer is passed as a single argument.
bool ProcessBuffer(std::span<uint8_t> buffer);
bool DoStuff() {
ProcessBuffer(std::span(data_pointer, data_size));
.. tip::
Use ``std::span<std::byte>`` or ``std::span<const std::byte>`` to represent
spans of binary data. Use ``std::as_bytes`` or ``std::as_writeable_bytes``
to convert any span to a byte span.
.. code-block:: cpp
void ProcessData(std::span<const std::byte> data);
void DoStuff() {
std::array<AnyType, 7> data = { ... };
Works with C++11, but some features require C++17.