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// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0
#pragma once
// IWYU pragma: private, include "opentelemetry/nostd/span.h"
#include "opentelemetry/version.h"
// Standard library implementation requires at least C++17 compiler.
// Older C++14 compilers may provide support for __has_include as a
// conforming extension.
#if defined __has_include
# if __has_include(<version>) // Check for __cpp_{feature}
# include <version>
# if defined(__cpp_lib_span) && __cplusplus > 201703L
# define OPENTELEMETRY_HAVE_SPAN
# endif
# endif
# if !defined(OPENTELEMETRY_HAVE_SPAN)
# // Check for Visual Studio span
# if defined(_MSVC_LANG) && _HAS_CXX20
# define OPENTELEMETRY_HAVE_SPAN
# endif
# // Check for other compiler span implementation
# if !defined(_MSVC_LANG) && __has_include(<span>) && __cplusplus > 201703L
// This works as long as compiler standard is set to C++20
# define OPENTELEMETRY_HAVE_SPAN
# endif
# endif
# if !__has_include(<gsl/gsl>)
# undef HAVE_GSL
# endif
#endif
#if !defined(OPENTELEMETRY_HAVE_SPAN)
# if defined(HAVE_GSL)
# include <type_traits>
// Guidelines Support Library provides an implementation of std::span
# include <gsl/gsl>
OPENTELEMETRY_BEGIN_NAMESPACE
namespace nostd
{
using gsl::dynamic_extent;
template <class ElementType, std::size_t Extent = gsl::dynamic_extent>
using span = gsl::span<ElementType, Extent>;
} // namespace nostd
OPENTELEMETRY_END_NAMESPACE
# define OPENTELEMETRY_HAVE_SPAN
# else
// No `gsl::span`, no `std::span`, fallback to `nostd::span`
# endif
#else // OPENTELEMETRY_HAVE_SPAN
// Using std::span (https://wg21.link/P0122R7) from Standard Library available in C++20 :
// - GCC libstdc++ 10+
// - Clang libc++ 7
// - MSVC Standard Library 19.26*
// - Apple Clang 10.0.0*
# include <limits>
# include <span>
OPENTELEMETRY_BEGIN_NAMESPACE
namespace nostd
{
constexpr std::size_t dynamic_extent = (std::numeric_limits<std::size_t>::max)();
template <class ElementType, std::size_t Extent = nostd::dynamic_extent>
using span = std::span<ElementType, Extent>;
} // namespace nostd
OPENTELEMETRY_END_NAMESPACE
#endif // if OPENTELEMETRY_HAVE_SPAN
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