/* Copyright (c) 2017, Google Inc.
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*
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* Permission to use, copy, modify, and/or distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
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* SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
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* OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
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* CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */
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#ifndef OPENSSL_HEADER_SSL_SPAN_H
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#define OPENSSL_HEADER_SSL_SPAN_H
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#include <openssl/base.h>
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#if !defined(BORINGSSL_NO_CXX)
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extern "C++" {
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#include <algorithm>
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#include <type_traits>
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namespace bssl {
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template <typename T>
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class Span;
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namespace internal {
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template <typename T>
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class SpanBase {
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// Put comparison operator implementations into a base class with const T, so
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// they can be used with any type that implicitly converts into a Span.
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static_assert(std::is_const<T>::value,
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"Span<T> must be derived from SpanBase<const T>");
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friend bool operator==(Span<T> lhs, Span<T> rhs) {
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// MSVC issues warning C4996 because std::equal is unsafe. The pragma to
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// suppress the warning mysteriously has no effect, hence this
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// implementation. See
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// https://msdn.microsoft.com/en-us/library/aa985974.aspx.
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if (lhs.size() != rhs.size()) {
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return false;
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}
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for (T *l = lhs.begin(), *r = rhs.begin(); l != lhs.end() && r != rhs.end();
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++l, ++r) {
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if (*l != *r) {
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return false;
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}
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}
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return true;
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}
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friend bool operator!=(Span<T> lhs, Span<T> rhs) { return !(lhs == rhs); }
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};
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} // namespace internal
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// A Span<T> is a non-owning reference to a contiguous array of objects of type
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// |T|. Conceptually, a Span is a simple a pointer to |T| and a count of
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// elements accessible via that pointer. The elements referenced by the Span can
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// be mutated if |T| is mutable.
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//
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// A Span can be constructed from container types implementing |data()| and
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// |size()| methods. If |T| is constant, construction from a container type is
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// implicit. This allows writing methods that accept data from some unspecified
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// container type:
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//
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// // Foo views data referenced by v.
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// void Foo(bssl::Span<const uint8_t> v) { ... }
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//
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// std::vector<uint8_t> vec;
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// Foo(vec);
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//
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// For mutable Spans, conversion is explicit:
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//
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// // FooMutate mutates data referenced by v.
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// void FooMutate(bssl::Span<uint8_t> v) { ... }
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//
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// FooMutate(bssl::Span<uint8_t>(vec));
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//
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// You can also use the |MakeSpan| and |MakeConstSpan| factory methods to
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// construct Spans in order to deduce the type of the Span automatically.
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//
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// FooMutate(bssl::MakeSpan(vec));
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//
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// Note that Spans have value type sematics. They are cheap to construct and
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// copy, and should be passed by value whenever a method would otherwise accept
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// a reference or pointer to a container or array.
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template <typename T>
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class Span : private internal::SpanBase<const T> {
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private:
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// Heuristically test whether C is a container type that can be converted into
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// a Span by checking for data() and size() member functions.
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//
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// TODO(davidben): Switch everything to std::enable_if_t when we remove
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// support for MSVC 2015. Although we could write our own enable_if_t and MSVC
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// 2015 has std::enable_if_t anyway, MSVC 2015's SFINAE implementation is
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// problematic and does not work below unless we write the ::type at use.
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template <typename C>
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using EnableIfContainer = std::enable_if<
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std::is_convertible<decltype(std::declval<C>().data()), T *>::value &&
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std::is_integral<decltype(std::declval<C>().size())>::value>;
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public:
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constexpr Span() : Span(nullptr, 0) {}
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constexpr Span(T *ptr, size_t len) : data_(ptr), size_(len) {}
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template <size_t N>
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constexpr Span(T (&array)[N]) : Span(array, N) {}
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template <
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typename C, typename = typename EnableIfContainer<C>::type,
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typename = typename std::enable_if<std::is_const<T>::value, C>::type>
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Span(const C &container) : data_(container.data()), size_(container.size()) {}
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template <
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typename C, typename = typename EnableIfContainer<C>::type,
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typename = typename std::enable_if<!std::is_const<T>::value, C>::type>
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explicit Span(C &container)
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: data_(container.data()), size_(container.size()) {}
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T *data() const { return data_; }
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size_t size() const { return size_; }
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T *begin() const { return data_; }
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const T *cbegin() const { return data_; }
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T *end() const { return data_ + size_; };
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const T *cend() const { return end(); };
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T &operator[](size_t i) const { return data_[i]; }
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T &at(size_t i) const { return data_[i]; }
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private:
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T *data_;
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size_t size_;
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};
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template <typename T>
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Span<T> MakeSpan(T *ptr, size_t size) {
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return Span<T>(ptr, size);
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}
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template <typename C>
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auto MakeSpan(C &c) -> decltype(MakeSpan(c.data(), c.size())) {
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return MakeSpan(c.data(), c.size());
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}
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template <typename T>
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Span<const T> MakeConstSpan(T *ptr, size_t size) {
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return Span<const T>(ptr, size);
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}
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template <typename C>
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auto MakeConstSpan(const C &c) -> decltype(MakeConstSpan(c.data(), c.size())) {
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return MakeConstSpan(c.data(), c.size());
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}
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} // namespace bssl
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} // extern C++
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#endif // !defined(BORINGSSL_NO_CXX)
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#endif // OPENSSL_HEADER_SSL_SPAN_H
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