chromium/third_party/boringssl/src/include/openssl/span.h

/* Copyright (c) 2017, Google Inc.
 *
 * Permission to use, copy, modify, and/or distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
 * SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
 * OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
 * CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */

#ifndef OPENSSL_HEADER_SSL_SPAN_H
#define OPENSSL_HEADER_SSL_SPAN_H

#include <openssl/base.h>

#if !defined(BORINGSSL_NO_CXX)

extern "C++" {

#include <stdlib.h>

#include <algorithm>
#include <type_traits>

#if __cplusplus >= 201703L
#include <string_view>
#endif

#if defined(__has_include)
#if __has_include(<version>)
#include <version>
#endif
#endif

#if defined(__cpp_lib_ranges) && __cpp_lib_ranges >= 201911L
#include <ranges>
BSSL_NAMESPACE_BEGIN
template <typename T>
class Span;
BSSL_NAMESPACE_END

// Mark `Span` as satisfying the `view` and `borrowed_range` concepts. This
// should be done before the definition of `Span`, so that any inlined calls to
// range functionality use the correct specializations.
enable_view;
enable_borrowed_range;
#endif

BSSL_NAMESPACE_BEGIN

template <typename T>
class Span;

namespace internal {
template <typename T>
class SpanBase { … };

// Heuristically test whether C is a container type that can be converted into
// a Span<T> by checking for data() and size() member functions.
//
// TODO(davidben): Require C++17 support for std::is_convertible_v, etc.
EnableIfContainer;

}  // namespace internal

// A Span<T> is a non-owning reference to a contiguous array of objects of type
// |T|. Conceptually, a Span is a simple a pointer to |T| and a count of
// elements accessible via that pointer. The elements referenced by the Span can
// be mutated if |T| is mutable.
//
// A Span can be constructed from container types implementing |data()| and
// |size()| methods. If |T| is constant, construction from a container type is
// implicit. This allows writing methods that accept data from some unspecified
// container type:
//
// // Foo views data referenced by v.
// void Foo(bssl::Span<const uint8_t> v) { ... }
//
// std::vector<uint8_t> vec;
// Foo(vec);
//
// For mutable Spans, conversion is explicit:
//
// // FooMutate mutates data referenced by v.
// void FooMutate(bssl::Span<uint8_t> v) { ... }
//
// FooMutate(bssl::Span<uint8_t>(vec));
//
// You can also use the |MakeSpan| and |MakeConstSpan| factory methods to
// construct Spans in order to deduce the type of the Span automatically.
//
// FooMutate(bssl::MakeSpan(vec));
//
// Note that Spans have value type sematics. They are cheap to construct and
// copy, and should be passed by value whenever a method would otherwise accept
// a reference or pointer to a container or array.
template <typename T>
class Span : private internal::SpanBase<const T> { … };

template <typename T>
const size_t Span<T>::npos;

#if __cplusplus >= 201703L
template <typename T>
Span(T *, size_t) -> Span<T>;
template <typename T, size_t size>
Span(T (&array)[size]) -> Span<T>;
template <
    typename C,
    typename T = std::remove_pointer_t<decltype(std::declval<C>().data())>,
    typename = internal::EnableIfContainer<C, T>>
Span(C &) -> Span<T>;
#endif

// C++17 callers can instead rely on CTAD and the deduction guides defined
// above.
template <typename T>
constexpr Span<T> MakeSpan(T *ptr, size_t size) { … }

template <typename C>
constexpr auto MakeSpan(C &c) -> decltype(MakeSpan(c.data(), c.size())) { … }

template <typename T>
constexpr Span<const T> MakeConstSpan(T *ptr, size_t size) { … }

template <typename C>
constexpr auto MakeConstSpan(const C &c)
    -> decltype(MakeConstSpan(c.data(), c.size())) { … }

template <typename T, size_t size>
constexpr Span<const T> MakeConstSpan(T (&array)[size]) { … }

#if __cplusplus >= 201703L
inline Span<const uint8_t> StringAsBytes(std::string_view s) { … }

inline std::string_view BytesAsStringView(bssl::Span<const uint8_t> b) { … }
#endif

BSSL_NAMESPACE_END

}  // extern C++

#endif  // !defined(BORINGSSL_NO_CXX)

#endif  // OPENSSL_HEADER_SSL_SPAN_H