chromium/third_party/openscreen/src/platform/base/span.h

// Copyright 2023 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef PLATFORM_BASE_SPAN_H_
#define PLATFORM_BASE_SPAN_H_

#include <stddef.h>
#include <stdint.h>

#include <array>
#include <cassert>
#include <type_traits>
#include <vector>

#include "platform/base/type_util.h"

namespace openscreen {

template <typename T>
class Span;

// In Open Screen code, use these aliases for the most common types of Spans.
// These can be converted to use std::span once the library supports C++20.
ByteView;
ByteBuffer;

// Contains a pointer and length to a span of contiguous data.
//
// The API is a slimmed-down version of a C++20 std::span<T> and is intended to
// be forwards-compatible with very slight modifications.  We don't intend to
// add support for static extents.
//
// NOTES:
// - Although other span implementations allow passing zero to last(), we do
//   not, as the behavior is undefined.  Callers should explicitly create an
//   empty Span instead.
//
// - operator== is not implemented to align with std::span.  For more
//   discussion, this blog post has considerations when implementing operators
//   on types that don't own the data they depend upon:
//   https://abseil.io/blog/20180531-regular-types
//
// - Unit tests that want to compare the bytes behind two ByteViews can use
//   ExpectByteViewsHaveSameBytes().
template <typename T>
class Span { … };

}  // namespace openscreen

#endif  // PLATFORM_BASE_SPAN_H_