More C++20 conformance fixes

Signed-off-by: Nick Avramoussis <4256455+Idclip@users.noreply.github.com>

Author: Idclip

openvdb/openvdb/Platform.h

@@ -35,9 +35,12 @@
     #define OPENVDB_CHECK_GCC(MAJOR, MINOR) 0
 #endif
 
-/// OpenVDB now requires C++11
-#define OPENVDB_HAS_CXX11 1
+/// OpenVDB now requires C++17
+#define OPENVDB_HAS_CXX11 1 // kept for backward compatibility
 
+#if __cplusplus >= 202002L
+    #define OPENVDB_HAS_CXX20
+#endif
 
 /// SIMD Intrinsic Headers
 #if defined(OPENVDB_USE_SSE42) || defined(OPENVDB_USE_AVX)

openvdb/openvdb/tools/MultiResGrid.h

@@ -522,8 +522,8 @@ template<Index Order>
 typename TreeType::ValueType MultiResGrid<TreeType>::
 sampleValue(const Coord& in_ijk, size_t in_level, size_t out_level) const
 {
-    assert( in_level  >= 0 && in_level  < mTrees.size() );
-    assert( out_level >= 0 && out_level < mTrees.size() );
+    assert( in_level  < mTrees.size() );
+    assert( out_level < mTrees.size() );
     const ConstAccessor acc(*mTrees[out_level]);// has disabled registration!
     return tools::Sampler<Order>::sample( acc, this->xyz(in_ijk, in_level, out_level) );
 }
@@ -533,8 +533,8 @@ template<Index Order>
 typename TreeType::ValueType MultiResGrid<TreeType>::
 sampleValue(const Vec3R& in_xyz, size_t in_level, size_t out_level) const
 {
-    assert( in_level  >= 0 && in_level  < mTrees.size() );
-    assert( out_level >= 0 && out_level < mTrees.size() );
+    assert( in_level  < mTrees.size() );
+    assert( out_level < mTrees.size() );
     const ConstAccessor acc(*mTrees[out_level]);// has disabled registration!
     return tools::Sampler<Order>::sample( acc, this->xyz(in_xyz, in_level, out_level) );
 }

openvdb/openvdb/tools/ValueTransformer.h

@@ -462,12 +462,13 @@ class SharedOpTransformer
     }
 
     /// Transform each element in the given range.
-    void operator()(IterRange& range) const
+    void operator()(const IterRange& range) const
     {
         if (!mOutputTree) return;
+        IterRange r(range);
         typename tree::ValueAccessor<OutTreeT> outAccessor(*mOutputTree);
-        for ( ; range; ++range) {
-            mOp(range.iterator(), outAccessor);
+        for ( ; r; ++r) {
+            mOp(r.iterator(), outAccessor);
         }
     }
 
@@ -550,12 +551,13 @@ class CopyableOpTransformer
     }
 
     /// Transform each element in the given range.
-    void operator()(IterRange& range)
+    void operator()(const IterRange& range)
     {
         if (!mOutputTree) return;
+        IterRange r(range);
         typename tree::ValueAccessor<OutTreeT> outAccessor(*mOutputTree);
-        for ( ; range; ++range) {
-            mOp(range.iterator(), outAccessor);
+        for ( ; r; ++r) {
+            mOp(r.iterator(), outAccessor);
         }
     }
 

openvdb/openvdb/util/PagedArray.h

@@ -618,6 +618,7 @@ class PagedArray<ValueT, Log2PageSize>::ConstIterator
     ConstIterator operator+(const difference_type &pos) const { return Iterator(*mParent,mPos+pos); }
     ConstIterator operator-(const difference_type &pos) const { return Iterator(*mParent,mPos-pos); }
     difference_type operator-(const ConstIterator& other) const { return mPos - other.pos(); }
+    friend ConstIterator operator+(const difference_type& pos, const ConstIterator& other) { return other + pos; }
     // comparisons
     bool operator==(const ConstIterator& other) const { return mPos == other.mPos; }
     bool operator!=(const ConstIterator& other) const { return mPos != other.mPos; }
@@ -633,6 +634,12 @@ class PagedArray<ValueT, Log2PageSize>::ConstIterator
     const PagedArray* mParent;
 };// Public class PagedArray::ConstIterator
 
+#ifdef OPENVDB_HAS_CXX20
+static_assert(std::random_access_iterator<PagedArray<int, 10UL>::ConstIterator>,
+    "ConstIterator must satisfy random_access_iterator concept");
+#endif
+
+
 ////////////////////////////////////////////////////////////////////////////////
 
 // Non-const std-compliant iterator
@@ -672,6 +679,7 @@ class PagedArray<ValueT, Log2PageSize>::Iterator
     Iterator operator+(const difference_type &pos) const { return Iterator(*mParent, mPos+pos); }
     Iterator operator-(const difference_type &pos) const { return Iterator(*mParent, mPos-pos); }
     difference_type operator-(const Iterator& other) const { return mPos - other.pos(); }
+    friend Iterator operator+(const difference_type& pos, const Iterator& other) { return other + pos; }
     // comparisons
     bool operator==(const Iterator& other) const { return mPos == other.mPos; }
     bool operator!=(const Iterator& other) const { return mPos != other.mPos; }
@@ -687,6 +695,11 @@ class PagedArray<ValueT, Log2PageSize>::Iterator
     PagedArray* mParent;
 };// Public class PagedArray::Iterator
 
+#ifdef OPENVDB_HAS_CXX20
+static_assert(std::random_access_iterator<PagedArray<int, 10UL>::Iterator>,
+    "Iterator must satisfy random_access_iterator concept");
+#endif
+
 ////////////////////////////////////////////////////////////////////////////////
 
 // Private member-class of PagedArray implementing a memory page