ref: 127dfcfefaec2397cb462ef797befd0b3611864e
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> 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) { // MSVC issues warning C4996 because std::equal is unsafe. The pragma to // suppress the warning mysteriously has no effect, hence this // implementation. See // https://msdn.microsoft.com/en-us/library/aa985974.aspx. if (lhs.size() != rhs.size()) { return false; } for (T *l = lhs.begin(), *r = rhs.begin(); l != lhs.end() && r != rhs.end(); ++l, ++r) { if (*l != *r) { return false; } } return true; } friend bool operator!=(Span<T> lhs, Span<T> rhs) { return !(lhs == rhs); } }; } // 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> { private: static const size_t npos = static_cast<size_t>(-1); public: 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, // TODO(davidben): Switch everything to std::enable_if_t when we remove // support for MSVC 2015. Although we could write our own enable_if_t and // MSVC 2015 has std::enable_if_t anyway, MSVC 2015's SFINAE // implementation is problematic and does not work below unless we write // the ::type at use. // // TODO(davidben): Move this and the identical copy below into an // EnableIfContainer alias when we drop MSVC 2015 support. MSVC 2015's // SFINAE support cannot handle type aliases. typename = typename std::enable_if< std::is_convertible<decltype(std::declval<C>().data()), T *>::value && std::is_integral<decltype(std::declval<C>().size())>::value>::type, typename = typename std::enable_if<std::is_const<T>::value, C>::type> Span(const C &container) : data_(container.data()), size_(container.size()) {} template < typename C, typename = typename std::enable_if< std::is_convertible<decltype(std::declval<C>().data()), T *>::value && std::is_integral<decltype(std::declval<C>().size())>::value>::type, typename = typename std::enable_if<!std::is_const<T>::value, C>::type> explicit Span(C &container) : data_(container.data()), size_(container.size()) {} T *data() const { return data_; } size_t size() const { return size_; } bool empty() const { return size_ == 0; } T *begin() const { return data_; } const T *cbegin() const { return data_; } T *end() const { return data_ + size_; } const T *cend() const { return end(); } T &front() const { if (size_ == 0) { abort(); } return data_[0]; } T &back() const { if (size_ == 0) { abort(); } return data_[size_ - 1]; } T &operator[](size_t i) const { if (i >= size_) { abort(); } return data_[i]; } T &at(size_t i) const { return (*this)[i]; } 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)); } Span first(size_t len) { if (len > size_) { abort(); } return Span(data_, len); } Span last(size_t len) { 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; template <typename T> Span<T> MakeSpan(T *ptr, size_t size) { return Span<T>(ptr, size); } template <typename C> auto MakeSpan(C &c) -> decltype(MakeSpan(c.data(), c.size())) { return MakeSpan(c.data(), c.size()); } template <typename T> Span<const T> MakeConstSpan(T *ptr, size_t size) { return Span<const T>(ptr, size); } template <typename C> auto MakeConstSpan(const C &c) -> decltype(MakeConstSpan(c.data(), c.size())) { return MakeConstSpan(c.data(), c.size()); } BSSL_NAMESPACE_END } // extern C++ #endif // !defined(BORINGSSL_NO_CXX) #endif // OPENSSL_HEADER_SSL_SPAN_H