ref: 94f2907dc40a6415a10c252cb9ba3971f1f7e838
dir: /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.
template <typename T>
inline constexpr bool std::ranges::enable_view<bssl::Span<T>> = true;
template <typename T>
inline constexpr bool std::ranges::enable_borrowed_range<bssl::Span<T>> = true;
#endif
BSSL_NAMESPACE_BEGIN
template <typename T>
class Span;
namespace internal {
template <typename T>
class SpanBase {
// Put comparison operator implementations into a base class with const T, so
// they can be used with any type that implicitly converts into a Span.
static_assert(std::is_const<T>::value,
"Span<T> must be derived from SpanBase<const T>");
friend bool operator==(Span<T> lhs, Span<T> rhs) {
return std::equal(lhs.begin(), lhs.end(), rhs.begin(), rhs.end());
}
friend bool operator!=(Span<T> lhs, Span<T> rhs) { return !(lhs == rhs); }
};
// 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.
template <typename C, typename T>
using EnableIfContainer = std::enable_if_t<
std::is_convertible<decltype(std::declval<C>().data()), T *>::value &&
std::is_integral<decltype(std::declval<C>().size())>::value>;
} // 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> {
public:
static const size_t npos = static_cast<size_t>(-1);
using element_type = T;
using value_type = std::remove_cv_t<T>;
using size_type = size_t;
using difference_type = ptrdiff_t;
using pointer = T *;
using const_pointer = const T *;
using reference = T &;
using const_reference = const T &;
using iterator = T *;
using const_iterator = const T *;
constexpr Span() : Span(nullptr, 0) {}
constexpr Span(T *ptr, size_t len) : data_(ptr), size_(len) {}
template <size_t N>
constexpr Span(T (&array)[N]) : Span(array, N) {}
template <typename C, typename = internal::EnableIfContainer<C, T>,
typename = std::enable_if_t<std::is_const<T>::value, C>>
constexpr Span(const C &container)
: data_(container.data()), size_(container.size()) {}
template <typename C, typename = internal::EnableIfContainer<C, T>,
typename = std::enable_if_t<!std::is_const<T>::value, C>>
constexpr explicit Span(C &container)
: data_(container.data()), size_(container.size()) {}
constexpr T *data() const { return data_; }
constexpr size_t size() const { return size_; }
constexpr bool empty() const { return size_ == 0; }
constexpr iterator begin() const { return data_; }
constexpr const_iterator cbegin() const { return data_; }
constexpr iterator end() const { return data_ + size_; }
constexpr const_iterator cend() const { return end(); }
constexpr T &front() const {
if (size_ == 0) {
abort();
}
return data_[0];
}
constexpr T &back() const {
if (size_ == 0) {
abort();
}
return data_[size_ - 1];
}
constexpr T &operator[](size_t i) const {
if (i >= size_) {
abort();
}
return data_[i];
}
T &at(size_t i) const { return (*this)[i]; }
constexpr Span subspan(size_t pos = 0, size_t len = npos) const {
if (pos > size_) {
// absl::Span throws an exception here. Note std::span and Chromium
// base::span additionally forbid pos + len being out of range, with a
// special case at npos/dynamic_extent, while absl::Span::subspan clips
// the span. For now, we align with absl::Span in case we switch to it in
// the future.
abort();
}
return Span(data_ + pos, std::min(size_ - pos, len));
}
constexpr Span first(size_t len) const {
if (len > size_) {
abort();
}
return Span(data_, len);
}
constexpr Span last(size_t len) const {
if (len > size_) {
abort();
}
return Span(data_ + size_ - len, len);
}
private:
T *data_;
size_t size_;
};
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) {
return Span<T>(ptr, size);
}
template <typename C>
constexpr auto MakeSpan(C &c) -> decltype(MakeSpan(c.data(), c.size())) {
return MakeSpan(c.data(), c.size());
}
template <typename T>
constexpr Span<const T> MakeConstSpan(T *ptr, size_t size) {
return Span<const T>(ptr, size);
}
template <typename C>
constexpr auto MakeConstSpan(const C &c)
-> decltype(MakeConstSpan(c.data(), c.size())) {
return MakeConstSpan(c.data(), c.size());
}
template <typename T, size_t size>
constexpr Span<const T> MakeConstSpan(T (&array)[size]) {
return array;
}
#if __cplusplus >= 201703L
inline Span<const uint8_t> StringAsBytes(std::string_view s) {
return MakeConstSpan(reinterpret_cast<const uint8_t *>(s.data()), s.size());
}
inline std::string_view BytesAsStringView(bssl::Span<const uint8_t> b) {
return std::string_view(reinterpret_cast<const char *>(b.data()), b.size());
}
#endif
BSSL_NAMESPACE_END
} // extern C++
#endif // !defined(BORINGSSL_NO_CXX)
#endif // OPENSSL_HEADER_SSL_SPAN_H