diff options
Diffstat (limited to 'absl/types/span.h')
| -rw-r--r-- | absl/types/span.h | 221 |
1 files changed, 85 insertions, 136 deletions
diff --git a/absl/types/span.h b/absl/types/span.h index 99b6765b..98c6cdc8 100644 --- a/absl/types/span.h +++ b/absl/types/span.h @@ -5,7 +5,7 @@ // you may not use this file except in compliance with the License. // You may obtain a copy of the License at // -// http://www.apache.org/licenses/LICENSE-2.0 +// https://www.apache.org/licenses/LICENSE-2.0 // // Unless required by applicable law or agreed to in writing, software // distributed under the License is distributed on an "AS IS" BASIS, @@ -60,115 +60,18 @@ #include <cstddef> #include <initializer_list> #include <iterator> -#include <string> #include <type_traits> #include <utility> -#include "absl/algorithm/algorithm.h" #include "absl/base/internal/throw_delegate.h" #include "absl/base/macros.h" #include "absl/base/optimization.h" -#include "absl/base/port.h" +#include "absl/base/port.h" // TODO(strel): remove this include #include "absl/meta/type_traits.h" +#include "absl/types/internal/span.h" namespace absl { -inline namespace lts_2018_12_18 { - -template <typename T> -class Span; - -namespace span_internal { -// A constexpr min function -constexpr size_t Min(size_t a, size_t b) noexcept { return a < b ? a : b; } - -// Wrappers for access to container data pointers. -template <typename C> -constexpr auto GetDataImpl(C& c, char) noexcept // NOLINT(runtime/references) - -> decltype(c.data()) { - return c.data(); -} - -// Before C++17, string::data returns a const char* in all cases. -inline char* GetDataImpl(std::string& s, // NOLINT(runtime/references) - int) noexcept { - return &s[0]; -} - -template <typename C> -constexpr auto GetData(C& c) noexcept // NOLINT(runtime/references) - -> decltype(GetDataImpl(c, 0)) { - return GetDataImpl(c, 0); -} - -// Detection idioms for size() and data(). -template <typename C> -using HasSize = - std::is_integral<absl::decay_t<decltype(std::declval<C&>().size())>>; - -// We want to enable conversion from vector<T*> to Span<const T* const> but -// disable conversion from vector<Derived> to Span<Base>. Here we use -// the fact that U** is convertible to Q* const* if and only if Q is the same -// type or a more cv-qualified version of U. We also decay the result type of -// data() to avoid problems with classes which have a member function data() -// which returns a reference. -template <typename T, typename C> -using HasData = - std::is_convertible<absl::decay_t<decltype(GetData(std::declval<C&>()))>*, - T* const*>; - -// Extracts value type from a Container -template <typename C> -struct ElementType { - using type = typename absl::remove_reference_t<C>::value_type; -}; - -template <typename T, size_t N> -struct ElementType<T (&)[N]> { - using type = T; -}; - -template <typename C> -using ElementT = typename ElementType<C>::type; - -template <typename T> -using EnableIfMutable = - typename std::enable_if<!std::is_const<T>::value, int>::type; - -template <typename T> -bool EqualImpl(Span<T> a, Span<T> b) { - static_assert(std::is_const<T>::value, ""); - return absl::equal(a.begin(), a.end(), b.begin(), b.end()); -} - -template <typename T> -bool LessThanImpl(Span<T> a, Span<T> b) { - static_assert(std::is_const<T>::value, ""); - return std::lexicographical_compare(a.begin(), a.end(), b.begin(), b.end()); -} - -// The `IsConvertible` classes here are needed because of the -// `std::is_convertible` bug in libcxx when compiled with GCC. This build -// configuration is used by Android NDK toolchain. Reference link: -// https://bugs.llvm.org/show_bug.cgi?id=27538. -template <typename From, typename To> -struct IsConvertibleHelper { - private: - static std::true_type testval(To); - static std::false_type testval(...); - - public: - using type = decltype(testval(std::declval<From>())); -}; - -template <typename From, typename To> -struct IsConvertible : IsConvertibleHelper<From, To>::type {}; - -// TODO(zhangxy): replace `IsConvertible` with `std::is_convertible` once the -// older version of libcxx is not supported. -template <typename From, typename To> -using EnableIfConvertibleToSpanConst = - typename std::enable_if<IsConvertible<From, Span<const To>>::value>::type; -} // namespace span_internal +inline namespace lts_2019_08_08 { //------------------------------------------------------------------------------ // Span @@ -486,6 +389,40 @@ class Span { : (base_internal::ThrowStdOutOfRange("pos > size()"), Span()); } + // Span::first() + // + // Returns a `Span` containing first `len` elements. Parameter `len` is of + // type `size_type` and thus non-negative. `len` value must be <= size(). + // + // Examples: + // + // std::vector<int> vec = {10, 11, 12, 13}; + // absl::MakeSpan(vec).first(1); // {10} + // absl::MakeSpan(vec).first(3); // {10, 11, 12} + // absl::MakeSpan(vec).first(5); // throws std::out_of_range + constexpr Span first(size_type len) const { + return (len <= size()) + ? Span(data(), len) + : (base_internal::ThrowStdOutOfRange("len > size()"), Span()); + } + + // Span::last() + // + // Returns a `Span` containing last `len` elements. Parameter `len` is of + // type `size_type` and thus non-negative. `len` value must be <= size(). + // + // Examples: + // + // std::vector<int> vec = {10, 11, 12, 13}; + // absl::MakeSpan(vec).last(1); // {13} + // absl::MakeSpan(vec).last(3); // {11, 12, 13} + // absl::MakeSpan(vec).last(5); // throws std::out_of_range + constexpr Span last(size_type len) const { + return (len <= size()) + ? Span(size() - len + data(), len) + : (base_internal::ThrowStdOutOfRange("len > size()"), Span()); + } + // Support for absl::Hash. template <typename H> friend H AbslHashValue(H h, Span v) { @@ -518,25 +455,27 @@ const typename Span<T>::size_type Span<T>::npos; // operator== template <typename T> bool operator==(Span<T> a, Span<T> b) { - return span_internal::EqualImpl<const T>(a, b); + return span_internal::EqualImpl<Span, const T>(a, b); } template <typename T> bool operator==(Span<const T> a, Span<T> b) { - return span_internal::EqualImpl<const T>(a, b); + return span_internal::EqualImpl<Span, const T>(a, b); } template <typename T> bool operator==(Span<T> a, Span<const T> b) { - return span_internal::EqualImpl<const T>(a, b); + return span_internal::EqualImpl<Span, const T>(a, b); } -template <typename T, typename U, - typename = span_internal::EnableIfConvertibleToSpanConst<U, T>> +template < + typename T, typename U, + typename = span_internal::EnableIfConvertibleTo<U, absl::Span<const T>>> bool operator==(const U& a, Span<T> b) { - return span_internal::EqualImpl<const T>(a, b); + return span_internal::EqualImpl<Span, const T>(a, b); } -template <typename T, typename U, - typename = span_internal::EnableIfConvertibleToSpanConst<U, T>> +template < + typename T, typename U, + typename = span_internal::EnableIfConvertibleTo<U, absl::Span<const T>>> bool operator==(Span<T> a, const U& b) { - return span_internal::EqualImpl<const T>(a, b); + return span_internal::EqualImpl<Span, const T>(a, b); } // operator!= @@ -552,13 +491,15 @@ template <typename T> bool operator!=(Span<T> a, Span<const T> b) { return !(a == b); } -template <typename T, typename U, - typename = span_internal::EnableIfConvertibleToSpanConst<U, T>> +template < + typename T, typename U, + typename = span_internal::EnableIfConvertibleTo<U, absl::Span<const T>>> bool operator!=(const U& a, Span<T> b) { return !(a == b); } -template <typename T, typename U, - typename = span_internal::EnableIfConvertibleToSpanConst<U, T>> +template < + typename T, typename U, + typename = span_internal::EnableIfConvertibleTo<U, absl::Span<const T>>> bool operator!=(Span<T> a, const U& b) { return !(a == b); } @@ -566,25 +507,27 @@ bool operator!=(Span<T> a, const U& b) { // operator< template <typename T> bool operator<(Span<T> a, Span<T> b) { - return span_internal::LessThanImpl<const T>(a, b); + return span_internal::LessThanImpl<Span, const T>(a, b); } template <typename T> bool operator<(Span<const T> a, Span<T> b) { - return span_internal::LessThanImpl<const T>(a, b); + return span_internal::LessThanImpl<Span, const T>(a, b); } template <typename T> bool operator<(Span<T> a, Span<const T> b) { - return span_internal::LessThanImpl<const T>(a, b); + return span_internal::LessThanImpl<Span, const T>(a, b); } -template <typename T, typename U, - typename = span_internal::EnableIfConvertibleToSpanConst<U, T>> +template < + typename T, typename U, + typename = span_internal::EnableIfConvertibleTo<U, absl::Span<const T>>> bool operator<(const U& a, Span<T> b) { - return span_internal::LessThanImpl<const T>(a, b); + return span_internal::LessThanImpl<Span, const T>(a, b); } -template <typename T, typename U, - typename = span_internal::EnableIfConvertibleToSpanConst<U, T>> +template < + typename T, typename U, + typename = span_internal::EnableIfConvertibleTo<U, absl::Span<const T>>> bool operator<(Span<T> a, const U& b) { - return span_internal::LessThanImpl<const T>(a, b); + return span_internal::LessThanImpl<Span, const T>(a, b); } // operator> @@ -600,13 +543,15 @@ template <typename T> bool operator>(Span<T> a, Span<const T> b) { return b < a; } -template <typename T, typename U, - typename = span_internal::EnableIfConvertibleToSpanConst<U, T>> +template < + typename T, typename U, + typename = span_internal::EnableIfConvertibleTo<U, absl::Span<const T>>> bool operator>(const U& a, Span<T> b) { return b < a; } -template <typename T, typename U, - typename = span_internal::EnableIfConvertibleToSpanConst<U, T>> +template < + typename T, typename U, + typename = span_internal::EnableIfConvertibleTo<U, absl::Span<const T>>> bool operator>(Span<T> a, const U& b) { return b < a; } @@ -624,13 +569,15 @@ template <typename T> bool operator<=(Span<T> a, Span<const T> b) { return !(b < a); } -template <typename T, typename U, - typename = span_internal::EnableIfConvertibleToSpanConst<U, T>> +template < + typename T, typename U, + typename = span_internal::EnableIfConvertibleTo<U, absl::Span<const T>>> bool operator<=(const U& a, Span<T> b) { return !(b < a); } -template <typename T, typename U, - typename = span_internal::EnableIfConvertibleToSpanConst<U, T>> +template < + typename T, typename U, + typename = span_internal::EnableIfConvertibleTo<U, absl::Span<const T>>> bool operator<=(Span<T> a, const U& b) { return !(b < a); } @@ -648,13 +595,15 @@ template <typename T> bool operator>=(Span<T> a, Span<const T> b) { return !(a < b); } -template <typename T, typename U, - typename = span_internal::EnableIfConvertibleToSpanConst<U, T>> +template < + typename T, typename U, + typename = span_internal::EnableIfConvertibleTo<U, absl::Span<const T>>> bool operator>=(const U& a, Span<T> b) { return !(a < b); } -template <typename T, typename U, - typename = span_internal::EnableIfConvertibleToSpanConst<U, T>> +template < + typename T, typename U, + typename = span_internal::EnableIfConvertibleTo<U, absl::Span<const T>>> bool operator>=(Span<T> a, const U& b) { return !(a < b); } @@ -759,6 +708,6 @@ template <int&... ExplicitArgumentBarrier, typename T, size_t N> constexpr Span<const T> MakeConstSpan(const T (&array)[N]) noexcept { return Span<const T>(array, N); } -} // inline namespace lts_2018_12_18 +} // inline namespace lts_2019_08_08 } // namespace absl #endif // ABSL_TYPES_SPAN_H_ |