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