From 40a5b898a2db9d4dbc0f410246d8ff493aeeb5e2 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Vladim=C3=ADr=20Vondru=C5=A1?= <mosra@centrum.cz>
Date: Thu, 31 May 2018 16:38:04 +0200
Subject: [PATCH] Math: ability to convert BoolVector from/to external
 representation.

---
 doc/changelog.dox                       |  2 ++
 src/Magnum/Math/BoolVector.h            | 10 ++++++
 src/Magnum/Math/Test/BoolVectorTest.cpp | 43 ++++++++++++++++++++++++-
 3 files changed, 54 insertions(+), 1 deletion(-)

diff --git a/doc/changelog.dox b/doc/changelog.dox
index 9dea725db..737aae7de 100644
--- a/doc/changelog.dox
+++ b/doc/changelog.dox
@@ -43,6 +43,8 @@ See also:
 @subsubsection changelog-lates-new-math Math library
 
 -   Added @ref Math::Constants::piQuarter()
+-   Ability to convert @ref Math::BoolVector from and to external
+    representation
 
 @subsection changelog-latest-changes Changes and improvements
 
diff --git a/src/Magnum/Math/BoolVector.h b/src/Magnum/Math/BoolVector.h
index b8044f020..ad133882a 100644
--- a/src/Magnum/Math/BoolVector.h
+++ b/src/Magnum/Math/BoolVector.h
@@ -38,6 +38,8 @@
 namespace Magnum { namespace Math {
 
 namespace Implementation {
+    template<std::size_t, class> struct BoolVectorConverter;
+
     /** @todo C++14: use std::make_index_sequence and std::integer_sequence */
     template<std::size_t ...> struct Sequence {};
 
@@ -100,9 +102,17 @@ template<std::size_t size> class BoolVector {
         template<class T, class U = typename std::enable_if<std::is_same<bool, T>::value && size != 1, bool>::type> constexpr explicit BoolVector(T value) noexcept: BoolVector(typename Implementation::GenerateSequence<DataSize>::Type(), value ? FullSegmentMask : 0) {}
         #endif
 
+        /** @brief Construct boolean vector from external representation */
+        template<class U, class V = decltype(Implementation::BoolVectorConverter<size, U>::from(std::declval<U>()))> constexpr explicit BoolVector(const U& other) noexcept: BoolVector{Implementation::BoolVectorConverter<size, U>::from(other)} {}
+
         /** @brief Copy constructor */
         constexpr /*implicit*/ BoolVector(const BoolVector<size>&) noexcept = default;
 
+        /** @brief Convert boolean vector to external representation */
+        template<class U, class V = decltype(Implementation::BoolVectorConverter<size, U>::to(std::declval<BoolVector<size>>()))> constexpr explicit operator U() const {
+            return Implementation::BoolVectorConverter<size, U>::to(*this);
+        }
+
         /**
          * @brief Raw data
          * @return Array of DataSize length
diff --git a/src/Magnum/Math/Test/BoolVectorTest.cpp b/src/Magnum/Math/Test/BoolVectorTest.cpp
index cdf9618d7..e4e8d72ba 100644
--- a/src/Magnum/Math/Test/BoolVectorTest.cpp
+++ b/src/Magnum/Math/Test/BoolVectorTest.cpp
@@ -28,7 +28,27 @@
 
 #include "Magnum/Math/BoolVector.h"
 
-namespace Magnum { namespace Math { namespace Test {
+struct BVec3 {
+    bool x, y, z;
+};
+
+namespace Magnum { namespace Math {
+
+namespace Implementation {
+
+template<> struct BoolVectorConverter<3, BVec3> {
+    constexpr static BoolVector<3> from(const BVec3& other) {
+        return (other.x << 0)|(other.y << 1)|(other.z << 2);
+    }
+
+    constexpr static BVec3 to(const BoolVector<3>& other) {
+        return {other[0], other[1], other[2]};
+    }
+};
+
+}
+
+namespace Test {
 
 struct BoolVectorTest: Corrade::TestSuite::Tester {
     explicit BoolVectorTest();
@@ -39,6 +59,8 @@ struct BoolVectorTest: Corrade::TestSuite::Tester {
     void constructOneValue();
     void constructOneElement();
     void constructCopy();
+    void convert();
+
     void data();
 
     void compare();
@@ -67,6 +89,8 @@ BoolVectorTest::BoolVectorTest() {
               &BoolVectorTest::constructOneValue,
               &BoolVectorTest::constructOneElement,
               &BoolVectorTest::constructCopy,
+              &BoolVectorTest::convert,
+
               &BoolVectorTest::data,
 
               &BoolVectorTest::compare,
@@ -145,6 +169,23 @@ void BoolVectorTest::constructCopy() {
     CORRADE_VERIFY(std::is_nothrow_copy_assignable<BoolVector19>::value);
 }
 
+void BoolVectorTest::convert() {
+    constexpr BVec3 a{false, true, true};
+    constexpr BoolVector<3> b{0x6};
+
+    constexpr BoolVector<3> c{a};
+    CORRADE_COMPARE(c, b);
+
+    constexpr BVec3 d(b);
+    CORRADE_COMPARE(d.x, a.x);
+    CORRADE_COMPARE(d.y, a.y);
+    CORRADE_COMPARE(d.z, a.z);
+
+    /* Implicit conversion is not allowed */
+    CORRADE_VERIFY(!(std::is_convertible<BVec3, BoolVector<3>>::value));
+    CORRADE_VERIFY(!(std::is_convertible<BoolVector<3>, BVec3>::value));
+}
+
 void BoolVectorTest::data() {
     constexpr BoolVector19 a(0x08, 0x03, 0x04);