MeshTools: make a version of duplicate() not dependent on std::vector.

Provide a version taking StridedArrayView instead, taking an arbitrary
view and also arbitrary index type. Also introduce duplicateInto() which
doesn't even allocate, but rather writes the output to pre-existing
location.

doc/changelog.dox

@@ -133,6 +133,11 @@ See also:
     @ref Math::UnderlyingTypeOf utility
 -   Added batch versions of @ref Math::isInf() and @ref Math::isNan()
 
+@subsubsection changelog-latest-new-meshtools MeshTools library
+
+-   @ref MeshTools::duplicateInto() alternative to @ref MeshTools::duplicate()
+    that writes the output to an existing location
+
 @subsubsection changelog-latest-new-platform Platform libraries
 
 -   @ref Platform::Sdl2Application and @ref Platform::GlfwApplication are now

src/Magnum/MeshTools/Duplicate.h

@@ -26,30 +26,70 @@
 */
 
 /** @file
- * @brief Function @ref Magnum::MeshTools::duplicate()
+ * @brief Function @ref Magnum::MeshTools::duplicate(), @ref Magnum::MeshTools::duplicateInto()
  */
 
 #include <vector>
+#include <Corrade/Containers/Array.h>
+#include <Corrade/Containers/ArrayViewStl.h>
+#include <Corrade/Containers/StridedArrayView.h>
 #include <Corrade/Utility/Assert.h>
 
-#include "Magnum/Types.h"
+#include "Magnum/Magnum.h"
 
 namespace Magnum { namespace MeshTools {
 
+#ifndef DOXYGEN_GENERATING_OUTPUT
+/* Fwdecl so we can have duplicateInto() ordered after duplicate() */
+template<class IndexType, class T> void duplicateInto(const Containers::StridedArrayView1D<const IndexType>&, const Containers::StridedArrayView1D<const T>&, const Containers::StridedArrayView1D<T>&);
+#endif
+
 /**
-@brief Duplicate data using index array
+@brief Duplicate data using given index array
 
 Converts indexed array to non-indexed, for example data `{a, b, c, d}` with
 index array `{1, 1, 0, 3, 2, 2}` will be converted to `{b, b, a, d, c, c}`.
+The resulting array size is the same as size of @p indices, expects that all
+indices are in range for the @p data array.
+
+If you want to fill an existing memory (or, for example a @ref std::vector),
+use @ref duplicateInto().
 @see @ref removeDuplicates(), @ref combineIndexedArrays()
 */
-template<class T> std::vector<T> duplicate(const std::vector<UnsignedInt>& indices, const std::vector<T>& data) {
-    std::vector<T> out;
-    out.reserve(indices.size());
-    for(const UnsignedInt index: indices) {
-        CORRADE_ASSERT(index < data.size(), "MeshTools::duplicate(): index out of range", out);
-        out.push_back(data[index]);
+template<class IndexType, class T> Containers::Array<T> duplicate(const Containers::StridedArrayView1D<const IndexType>& indices, const Containers::StridedArrayView1D<const T>& data) {
+    Containers::Array<T> out{Containers::NoInit, indices.size()};
+    duplicateInto<IndexType, T>(indices, data, out);
+    return out;
+}
+
+/**
+@brief Duplicate data using an index array into given output array
+@param[in]  indices Index array to use
+@param[in]  data    Input data
+@param[out] out     Where to store the output
+
+A variant of @ref duplicate() that fills existing memory instead of allocating
+a new array.
+*/
+template<class IndexType, class T> void duplicateInto(const Containers::StridedArrayView1D<const IndexType>& indices, const Containers::StridedArrayView1D<const T>& data, const Containers::StridedArrayView1D<T>& out) {
+    CORRADE_ASSERT(out.size() == indices.size(),
+        "MeshTools::duplicateInto(): bad output size, expected" << indices.size() << "but got" << out.size(), );
+    for(std::size_t i = 0; i != indices.size(); ++i) {
+        const std::size_t index = indices[i];
+        CORRADE_ASSERT(index < data.size(), "MeshTools::duplicateInto(): index" << index << "out of bounds for" << data.size() << "elements", );
+        out[i] = data[index];
     }
+}
+
+/**
+@brief Duplicate data using given index array
+
+Like @ref duplicate(const Containers::StridedArrayView1D<const IndexType>&, const Containers::StridedArrayView1D<const T>&),
+but putting the result into a @ref std::vector.
+*/
+template<class T> std::vector<T> duplicate(const std::vector<UnsignedInt>& indices, const std::vector<T>& data) {
+    std::vector<T> out(indices.size());
+    duplicateInto<UnsignedInt, T>(indices, data, out);
     return out;
 }
 

src/Magnum/MeshTools/Test/CMakeLists.txt

@@ -37,6 +37,7 @@ corrade_add_test(MeshToolsTransformTest TransformTest.cpp LIBRARIES MagnumMeshTo
 # Graceful assert for testing
 set_property(TARGET
     MeshToolsCombineIndexedArraysTest
+    MeshToolsDuplicateTest
     MeshToolsInterleaveTest
     MeshToolsSubdivideTest
     APPEND PROPERTY COMPILE_DEFINITIONS "CORRADE_GRACEFUL_ASSERT")

src/Magnum/MeshTools/Test/DuplicateTest.cpp

@@ -23,7 +23,10 @@
     DEALINGS IN THE SOFTWARE.
 */
 
+#include <sstream>
 #include <Corrade/TestSuite/Tester.h>
+#include <Corrade/TestSuite/Compare/Container.h>
+#include <Corrade/Utility/DebugStl.h>
 
 #include "Magnum/Magnum.h"
 #include "Magnum/MeshTools/Duplicate.h"
@@ -34,17 +37,74 @@ struct DuplicateTest: TestSuite::Tester {
     explicit DuplicateTest();
 
     void duplicate();
+    void duplicateOutOfBounds();
+    void duplicateStl();
+
+    void duplicateInto();
+    void duplicateIntoWrongSize();
 };
 
 DuplicateTest::DuplicateTest() {
-    addTests({&DuplicateTest::duplicate});
+    addTests({&DuplicateTest::duplicate,
+              &DuplicateTest::duplicateOutOfBounds,
+              &DuplicateTest::duplicateStl,
+
+              &DuplicateTest::duplicateInto,
+              &DuplicateTest::duplicateIntoWrongSize});
 }
 
 void DuplicateTest::duplicate() {
+    constexpr UnsignedByte indices[]{1, 1, 0, 3, 2, 2};
+    constexpr Int data[]{-7, 35, 12, -18};
+
+    CORRADE_COMPARE_AS((MeshTools::duplicate<UnsignedByte, Int>(indices, data)),
+        (Containers::Array<Int>{Containers::InPlaceInit, {
+            35, 35, -7, -18, 12, 12
+        }}), TestSuite::Compare::Container);
+}
+
+void DuplicateTest::duplicateOutOfBounds() {
+    constexpr UnsignedByte indices[]{1, 1, 0, 4, 2, 2};
+    constexpr Int data[]{-7, 35, 12, -18};
+
+    std::ostringstream out;
+    Error redirectError{&out};
+
+    MeshTools::duplicate<UnsignedByte, Int>(indices, data);
+    CORRADE_COMPARE(out.str(),
+        "MeshTools::duplicateInto(): index 4 out of bounds for 4 elements\n");
+}
+
+void DuplicateTest::duplicateStl() {
     CORRADE_COMPARE(MeshTools::duplicate({1, 1, 0, 3, 2, 2}, std::vector<int>{-7, 35, 12, -18}),
         (std::vector<Int>{35, 35, -7, -18, 12, 12}));
 }
 
+void DuplicateTest::duplicateInto() {
+    constexpr UnsignedByte indices[]{1, 1, 0, 3, 2, 2};
+    constexpr Int data[]{-7, 35, 12, -18};
+    Int output[6];
+
+    MeshTools::duplicateInto<UnsignedByte, Int>(indices, data, output);
+    CORRADE_COMPARE_AS(Containers::arrayView<const Int>(output),
+        (Containers::Array<Int>{Containers::InPlaceInit, {
+            35, 35, -7, -18, 12, 12
+        }}), TestSuite::Compare::Container);
+}
+
+void DuplicateTest::duplicateIntoWrongSize() {
+    constexpr UnsignedByte indices[]{1, 1, 0, 3, 2, 2};
+    constexpr Int data[]{-7, 35, 12, -18};
+    Int output[5];
+
+    std::ostringstream out;
+    Error redirectError{&out};
+
+    MeshTools::duplicateInto<UnsignedByte, Int>(indices, data, output);
+    CORRADE_COMPARE(out.str(),
+        "MeshTools::duplicateInto(): bad output size, expected 6 but got 5\n");
+}
+
 }}}}
 
 CORRADE_TEST_MAIN(Magnum::MeshTools::Test::DuplicateTest)