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BLI: improve implicit conversions of spans

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Some conversions that should work did not work before.
For example, `MutableSpan<int *> -> MutableSpan<const int *>`.
This commit is contained in:
Jacques Lucke
2021-03-17 15:26:17 +01:00
parent 256da1c4b9
commit bf620020f1
2 changed files with 32 additions and 4 deletions
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24
source/blender/blenlib/BLI_span.hh
View File

@@ -132,12 +132,11 @@ template<typename T> class Span {
}
/**
* Support implicit conversions like the ones below:
* Support implicit conversions like the one below:
* Span<T *> -> Span<const T *>
*/
template<typename U, typename std::enable_if_t<is_span_convertible_pointer_v<U, T>> * = nullptr>
constexpr Span(Span<U> array) : data_(static_cast<const T *>(array.data())), size_(array.size())
constexpr Span(Span<U> span) : data_(static_cast<const T *>(span.data())), size_(span.size())
{
}
@@ -467,11 +466,27 @@ template<typename T> class MutableSpan {
{
}
/**
* Support implicit conversions like the one below:
* MutableSpan<T *> -> MutableSpan<const T *>
*/
template<typename U, typename std::enable_if_t<is_span_convertible_pointer_v<U, T>> * = nullptr>
constexpr MutableSpan(MutableSpan<U> span)
: data_(static_cast<T *>(span.data())), size_(span.size())
{
}
constexpr operator Span<T>() const
{
return Span<T>(data_, size_);
}
template<typename U, typename std::enable_if_t<is_span_convertible_pointer_v<T, U>> * = nullptr>
constexpr operator Span<U>() const
{
return Span<U>(static_cast<const U *>(data_), size_);
}
/**
* Returns the number of elements in the array.
*/
@@ -653,12 +668,13 @@ template<typename T> class MutableSpan {
/**
* Returns a new span to the same underlying memory buffer. No conversions are done.
* The caller is responsible for making sure that the type cast is valid.
*/
template<typename NewT> constexpr MutableSpan<NewT> cast() const
{
BLI_assert((size_ * sizeof(T)) % sizeof(NewT) == 0);
int64_t new_size = size_ * sizeof(T) / sizeof(NewT);
return MutableSpan<NewT>(reinterpret_cast<NewT *>(data_), new_size);
return MutableSpan<NewT>((NewT *)data_, new_size);
}
};

12
source/blender/blenlib/tests/BLI_span_test.cc
View File

@@ -392,4 +392,16 @@ TEST(span, Constexpr)
EXPECT_EQ(span.slice(1, 2).size(), 2);
}
TEST(span, ImplicitConversions)
{
BLI_STATIC_ASSERT((std::is_convertible_v<MutableSpan<int>, Span<int>>), "");
BLI_STATIC_ASSERT((std::is_convertible_v<Span<int *>, Span<const int *>>), "");
BLI_STATIC_ASSERT((std::is_convertible_v<MutableSpan<int *>, Span<int *>>), "");
BLI_STATIC_ASSERT((std::is_convertible_v<MutableSpan<int *>, Span<const int *>>), "");
BLI_STATIC_ASSERT((std::is_convertible_v<MutableSpan<int *>, MutableSpan<const int *>>), "");
BLI_STATIC_ASSERT((!std::is_convertible_v<MutableSpan<const int *>, MutableSpan<int *>>), "");
BLI_STATIC_ASSERT((!std::is_convertible_v<Span<const int *>, Span<int *>>), "");
BLI_STATIC_ASSERT((!std::is_convertible_v<Span<int *>, MutableSpan<const int *>>), "");
}
} // namespace blender::tests