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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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