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- /* 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 <algorithm>
- #include <type_traits>
-
- namespace bssl {
-
- 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:
- template <bool B, class V = void>
- using enable_if_t = typename std::enable_if<B, V>::type;
-
- // Heuristically test whether C is a container type that can be converted into
- // a Span by checking for data() and size() member functions.
- template <typename C>
- using EnableIfContainer = enable_if_t<
- std::is_convertible<decltype(std::declval<C>().data()), T *>::value &&
- std::is_integral<decltype(std::declval<C>().size())>::value>;
-
- 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, typename = EnableIfContainer<C>,
- typename = enable_if_t<std::is_const<T>::value, C>>
- Span(const C &container) : data_(container.data()), size_(container.size()) {}
-
- template <typename C, typename = EnableIfContainer<C>,
- typename = enable_if_t<!std::is_const<T>::value, C>>
- explicit Span(C &container)
- : data_(container.data()), size_(container.size()) {}
-
- T *data() const { return data_; }
- size_t size() const { return size_; }
-
- T *begin() const { return data_; }
- const T *cbegin() const { return data_; }
- T *end() const { return data_ + size_; };
- const T *cend() const { return end(); };
-
- T &operator[](size_t i) const { return data_[i]; }
- T &at(size_t i) const { return data_[i]; }
-
- private:
- T *data_;
- size_t size_;
- };
-
- 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());
- }
-
- } // namespace bssl
-
- } // extern C++
-
- #endif // !defined(BORINGSSL_NO_CXX)
-
- #endif /* OPENSSL_HEADER_SSL_SPAN_H */
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