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Containers: add explicit StridedDimension conversion from/to external types #162

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Containers: add explicit StridedDimension conversion from/to external types #162

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27 changes: 25 additions & 2 deletions src/Corrade/Containers/StridedDimensions.h
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Original file line number Diff line number Diff line change
Expand Up @@ -41,6 +41,7 @@ namespace Corrade { namespace Containers {

namespace Implementation {
template<unsigned, class, class> struct StridedDimensionsConverter;
template<unsigned, class, class> struct ExplicitStridedDimensionsConverter;
/* Used by StridedArrayView, needed here to friend them */
template<unsigned, class> struct StridedElement;
template<int> struct ArrayCastFlattenOrInflate;
Expand Down Expand Up @@ -87,7 +88,17 @@ template<unsigned dimensions, class T> class StridedDimensions {
* Conversion from a @ref StaticArrayView of the same type and
* dimension count is builtin.
*/
template<class U, class = decltype(Implementation::StridedDimensionsConverter<dimensions, T, typename std::decay<U&&>::type>::from(std::declval<U&&>()))> constexpr /*implicit*/ StridedDimensions(U&& other) noexcept: StridedDimensions{Implementation::StridedDimensionsConverter<dimensions, T, typename std::decay<U&&>::type>::from(Utility::forward<U>(other))} {}
template<class U, typename std::enable_if<sizeof(decltype(Implementation::StridedDimensionsConverter<dimensions, T, typename std::decay<U&&>::type>::from(std::declval<U&&>()))) != 0, int>::type = 0> constexpr /*implicit*/ StridedDimensions(U&& other) noexcept: StridedDimensions{Implementation::StridedDimensionsConverter<dimensions, T, typename std::decay<U&&>::type>::from(Utility::forward<U>(other))} {}

/**
* @brief Explicitly construct from an external representation
* @m_since_latest
*
* Compared to the above, this conversion is explicit and thus meant to
* be used in scenarios with a potential for data loss, such as
* conversion between signed and unsigned types.
*/
template<class U, typename std::enable_if<sizeof(decltype(Implementation::ExplicitStridedDimensionsConverter<dimensions, T, typename std::decay<U&&>::type>::from(std::declval<U&&>()))) != 0, int>::type = 0> constexpr explicit StridedDimensions(U&& other) noexcept: StridedDimensions{Implementation::ExplicitStridedDimensionsConverter<dimensions, T, typename std::decay<U&&>::type>::from(Utility::forward<U>(other))} {}

/**
* @brief Convert to an external representation
Expand All @@ -96,10 +107,22 @@ template<unsigned dimensions, class T> class StridedDimensions {
* Conversion to a @ref StaticArrayView of the same type and dimension
* count is builtin.
*/
template<class U, class = decltype(Implementation::StridedDimensionsConverter<dimensions, T, U>::to(std::declval<StridedDimensions<dimensions, T>>()))> constexpr /*implicit*/ operator U() const noexcept {
template<class U, typename std::enable_if<sizeof(decltype(Implementation::StridedDimensionsConverter<dimensions, T, U>::to(std::declval<StridedDimensions<dimensions, T>>()))) != 0, int>::type = 0> constexpr /*implicit*/ operator U() const noexcept {
return Implementation::StridedDimensionsConverter<dimensions, T, U>::to(*this);
}

/**
* @brief Explicitly convert to an external representation
* @m_since_latest
*
* Compared to the above, this conversion is explicit and thus meant to
* be used in scenarios with a potential for data loss, such as
* conversion between signed and unsigned types.
*/
template<class U, typename std::enable_if<sizeof(decltype(Implementation::ExplicitStridedDimensionsConverter<dimensions, T, U>::to(std::declval<StridedDimensions<dimensions, T>>()))) != 0, int>::type = 0> constexpr explicit operator U() const noexcept {
return Implementation::ExplicitStridedDimensionsConverter<dimensions, T, U>::to(*this);
}

/**
* @brief Conversion to a scalar
*
Expand Down
65 changes: 56 additions & 9 deletions src/Corrade/Containers/Test/StridedDimensionsTest.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -33,8 +33,15 @@

namespace {

struct Rectangle {
constexpr Rectangle(int rows, int cols): rows{rows}, cols{cols} {}
struct Rectangleu {
constexpr Rectangleu(unsigned rows, unsigned cols): rows{rows}, cols{cols} {}

unsigned rows;
unsigned cols;
};

struct Rectanglei {
constexpr Rectanglei(int rows, int cols): rows{rows}, cols{cols} {}

int rows;
int cols;
Expand All @@ -46,11 +53,20 @@ namespace Corrade { namespace Containers {

namespace Implementation {

template<> struct StridedDimensionsConverter<2, std::size_t, Rectangle> {
constexpr static Size2D from(const Rectangle& other) {
template<> struct StridedDimensionsConverter<2, std::size_t, Rectangleu> {
constexpr static Size2D from(const Rectangleu& other) {
return {std::size_t(other.rows), std::size_t(other.cols)};
}
constexpr static Rectangle to(const Size2D& to) {
constexpr static Rectangleu to(const Size2D& to) {
return {unsigned(to[0]), unsigned(to[1])};
}
};

template<> struct ExplicitStridedDimensionsConverter<2, std::size_t, Rectanglei> {
constexpr static Size2D from(const Rectanglei& other) {
return {std::size_t(other.rows), std::size_t(other.cols)};
}
constexpr static Rectanglei to(const Size2D& to) {
return {int(to[0]), int(to[1])};
}
};
Expand All @@ -71,6 +87,7 @@ struct StridedDimensionsTest: TestSuite::Tester {
void convertScalar();
void convertScalar3D();
void convertExternal();
void convertExternalExplicit();
void convertExternalStaticArrayView();

void compare();
Expand All @@ -90,6 +107,7 @@ StridedDimensionsTest::StridedDimensionsTest() {
&StridedDimensionsTest::convertScalar,
&StridedDimensionsTest::convertScalar3D,
&StridedDimensionsTest::convertExternal,
&StridedDimensionsTest::convertExternalExplicit,
&StridedDimensionsTest::convertExternalStaticArrayView,

&StridedDimensionsTest::compare,
Expand Down Expand Up @@ -231,24 +249,53 @@ constexpr Size2D Sizes{34, 67};
void StridedDimensionsTest::convertExternal() {
Size2D a{12, 37};

Rectangle b = a;
Rectangleu b = a;
CORRADE_COMPARE(b.rows, 12);
CORRADE_COMPARE(b.cols, 37);

Size2D c = b;
CORRADE_COMPARE(c[0], 12);
CORRADE_COMPARE(c[1], 37);

constexpr Rectangle cb = Sizes;
constexpr Rectangleu cb = Sizes;
CORRADE_COMPARE(cb.rows, 34);
CORRADE_COMPARE(cb.cols, 67);

constexpr Size2D cc = cb;
CORRADE_COMPARE(cc[0], 34);
CORRADE_COMPARE(cc[1], 67);

CORRADE_VERIFY(std::is_nothrow_constructible<Size2D, Rectangle>::value);
CORRADE_VERIFY(std::is_nothrow_constructible<Rectangle, Size2D>::value);
CORRADE_VERIFY(std::is_nothrow_constructible<Size2D, Rectangleu>::value);
CORRADE_VERIFY(std::is_nothrow_constructible<Rectangleu, Size2D>::value);
}

void StridedDimensionsTest::convertExternalExplicit() {
Size2D a{12, 37};

Rectanglei b{a};
CORRADE_COMPARE(b.rows, 12);
CORRADE_COMPARE(b.cols, 37);

Size2D c{b};
CORRADE_COMPARE(c[0], 12);
CORRADE_COMPARE(c[1], 37);

constexpr Rectanglei cb{Sizes};
CORRADE_COMPARE(cb.rows, 34);
CORRADE_COMPARE(cb.cols, 67);

constexpr Size2D cc{cb};
CORRADE_COMPARE(cc[0], 34);
CORRADE_COMPARE(cc[1], 67);

/* Shouldn't be implicitly convertible */
CORRADE_VERIFY(std::is_convertible<Rectangleu, Size2D>::value);
CORRADE_VERIFY(std::is_convertible<Size2D, Rectangleu>::value);
CORRADE_VERIFY(!std::is_convertible<Rectanglei, Size2D>::value);
CORRADE_VERIFY(!std::is_convertible<Size2D, Rectanglei>::value);

CORRADE_VERIFY(std::is_nothrow_constructible<Size2D, Rectanglei>::value);
CORRADE_VERIFY(std::is_nothrow_constructible<Rectanglei, Size2D>::value);
}

void StridedDimensionsTest::convertExternalStaticArrayView() {
Expand Down