Functions: add MutableAttributesRef data structure

This will be used to reference the content of a CustomData structure
in C++ code, that does not need to know who owns the data but only
works with it.

3 files changed, 320 insertions, 0 deletions

diff --git a/source/blender/functions/CMakeLists.txt b/source/blender/functions/CMakeLists.txt
index acaef1d146a..5b18dd4258e 100644
--- a/source/blender/functions/CMakeLists.txt
+++ b/source/blender/functions/CMakeLists.txt
@@ -27,11 +27,13 @@ set(INC_SYS
 )
 
 set(SRC
+  intern/attributes_ref.cc
   intern/cpp_types.cc
   intern/multi_function_network.cc
   intern/multi_function_network_evaluation.cc
 
   FN_array_spans.hh
+  FN_attributes_ref.hh
   FN_cpp_type.hh
   FN_cpp_types.hh
   FN_multi_function.hh
diff --git a/source/blender/functions/FN_attributes_ref.hh b/source/blender/functions/FN_attributes_ref.hh
new file mode 100644
index 00000000000..1a4c1d2aadc
--- /dev/null
+++ b/source/blender/functions/FN_attributes_ref.hh
@@ -0,0 +1,246 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#ifndef __FN_ATTRIBUTES_REF_HH__
+#define __FN_ATTRIBUTES_REF_HH__
+
+/** \file
+ * \ingroup fn
+ *
+ * An AttributesRef references multiple arrays of equal length. Each array has a corresponding name
+ * and index.
+ */
+
+#include "FN_spans.hh"
+
+#include "BLI_linear_allocator.hh"
+#include "BLI_map.hh"
+#include "BLI_utility_mixins.hh"
+#include "BLI_vector_set.hh"
+
+namespace blender {
+namespace fn {
+
+class AttributesInfo;
+
+class AttributesInfoBuilder : NonCopyable, NonMovable {
+ private:
+  LinearAllocator<> m_allocator;
+  VectorSet<std::string> m_names;
+  Vector<const CPPType *> m_types;
+  Vector<void *> m_defaults;
+
+  friend AttributesInfo;
+
+ public:
+  AttributesInfoBuilder() = default;
+  ~AttributesInfoBuilder();
+
+  template<typename T> void add(StringRef name, const T &default_value)
+  {
+    this->add(name, CPPType::get<T>(), (const void *)&default_value);
+  }
+
+  void add(StringRef name, const CPPType &type, const void *default_value = nullptr);
+};
+
+/**
+ * Stores which attributes are in an AttributesRef. Every attribute has a unique index, a unique
+ * name, a type and a default value.
+ */
+class AttributesInfo : NonCopyable, NonMovable {
+ private:
+  LinearAllocator<> m_allocator;
+  Map<StringRefNull, uint> m_index_by_name;
+  Vector<StringRefNull> m_name_by_index;
+  Vector<const CPPType *> m_type_by_index;
+  Vector<void *> m_defaults;
+
+ public:
+  AttributesInfo() = default;
+  AttributesInfo(const AttributesInfoBuilder &builder);
+  ~AttributesInfo();
+
+  uint size() const
+  {
+    return m_name_by_index.size();
+  }
+
+  IndexRange index_range() const
+  {
+    return m_name_by_index.index_range();
+  }
+
+  StringRefNull name_of(uint index) const
+  {
+    return m_name_by_index[index];
+  }
+
+  uint index_of(StringRef name) const
+  {
+    return m_index_by_name.lookup_as(name);
+  }
+
+  const void *default_of(uint index) const
+  {
+    return m_defaults[index];
+  }
+
+  const void *default_of(StringRef name) const
+  {
+    return this->default_of(this->index_of(name));
+  }
+
+  template<typename T> const T &default_of(uint index) const
+  {
+    BLI_assert(m_type_by_index[index]->is<T>());
+    return *(T *)m_defaults[index];
+  }
+
+  template<typename T> const T &default_of(StringRef name) const
+  {
+    return this->default_of<T>(this->index_of(name));
+  }
+
+  const CPPType &type_of(uint index) const
+  {
+    return *m_type_by_index[index];
+  }
+
+  const CPPType &type_of(StringRef name) const
+  {
+    return this->type_of(this->index_of(name));
+  }
+
+  bool has_attribute(StringRef name, const CPPType &type) const
+  {
+    return this->try_index_of(name, type) >= 0;
+  }
+
+  int try_index_of(StringRef name) const
+  {
+    return (int)m_index_by_name.lookup_default_as(name, -1);
+  }
+
+  int try_index_of(StringRef name, const CPPType &type) const
+  {
+    int index = this->try_index_of(name);
+    if (index == -1) {
+      return -1;
+    }
+    else if (this->type_of((uint)index) == type) {
+      return index;
+    }
+    else {
+      return -1;
+    }
+  }
+};
+
+/**
+ * References multiple arrays that match the description of an AttributesInfo instance. This class
+ * is supposed to be relatively cheap to copy. It does not own any of the arrays itself.
+ */
+class MutableAttributesRef {
+ private:
+  const AttributesInfo *m_info;
+  Span<void *> m_buffers;
+  IndexRange m_range;
+
+ public:
+  MutableAttributesRef(const AttributesInfo &info, Span<void *> buffers, uint size)
+      : MutableAttributesRef(info, buffers, IndexRange(size))
+  {
+  }
+
+  MutableAttributesRef(const AttributesInfo &info, Span<void *> buffers, IndexRange range)
+      : m_info(&info), m_buffers(buffers), m_range(range)
+  {
+  }
+
+  uint size() const
+  {
+    return m_range.size();
+  }
+
+  const AttributesInfo &info() const
+  {
+    return *m_info;
+  }
+
+  GMutableSpan get(uint index) const
+  {
+    const CPPType &type = m_info->type_of(index);
+    void *ptr = POINTER_OFFSET(m_buffers[index], type.size() * m_range.start());
+    return GMutableSpan(type, ptr, m_range.size());
+  }
+
+  GMutableSpan get(StringRef name) const
+  {
+    return this->get(m_info->index_of(name));
+  }
+
+  template<typename T> MutableSpan<T> get(uint index) const
+  {
+    BLI_assert(m_info->type_of(index).is<T>());
+    return MutableSpan<T>((T *)m_buffers[index] + m_range.start(), m_range.size());
+  }
+
+  template<typename T> MutableSpan<T> get(StringRef name) const
+  {
+    return this->get<T>(m_info->index_of(name));
+  }
+
+  Optional<GMutableSpan> try_get(StringRef name, const CPPType &type) const
+  {
+    int index = m_info->try_index_of(name, type);
+    if (index == -1) {
+      return {};
+    }
+    else {
+      return this->get((uint)index);
+    }
+  }
+
+  template<typename T> Optional<MutableSpan<T>> try_get(StringRef name) const
+  {
+    int index = m_info->try_index_of(name);
+    if (index == -1) {
+      return {};
+    }
+    else if (m_info->type_of((uint)index).is<T>()) {
+      return this->get<T>((uint)index);
+    }
+    else {
+      return {};
+    }
+  }
+
+  MutableAttributesRef slice(IndexRange range) const
+  {
+    return this->slice(range.start(), range.size());
+  }
+
+  MutableAttributesRef slice(uint start, uint size) const
+  {
+    return MutableAttributesRef(*m_info, m_buffers, m_range.slice(start, size));
+  }
+};
+
+}  // namespace fn
+}  // namespace blender
+
+#endif /* __FN_ATTRIBUTES_REF_HH__ */
diff --git a/source/blender/functions/intern/attributes_ref.cc b/source/blender/functions/intern/attributes_ref.cc
new file mode 100644
index 00000000000..dc64f571596
--- /dev/null
+++ b/source/blender/functions/intern/attributes_ref.cc
@@ -0,0 +1,72 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#include "FN_attributes_ref.hh"
+
+namespace blender {
+namespace fn {
+
+AttributesInfoBuilder::~AttributesInfoBuilder()
+{
+  for (uint i : m_defaults.index_range()) {
+    m_types[i]->destruct(m_defaults[i]);
+  }
+}
+
+void AttributesInfoBuilder::add(StringRef name, const CPPType &type, const void *default_value)
+{
+  if (m_names.add_as(name)) {
+    m_types.append(&type);
+
+    if (default_value == nullptr) {
+      default_value = type.default_value();
+    }
+    void *dst = m_allocator.allocate(type.size(), type.alignment());
+    type.copy_to_uninitialized(default_value, dst);
+    m_defaults.append(dst);
+  }
+  else {
+    /* The same name can be added more than once as long as the type is always the same. */
+    BLI_assert(m_types[m_names.index_of_as(name)] == &type);
+  }
+}
+
+AttributesInfo::AttributesInfo(const AttributesInfoBuilder &builder)
+{
+  for (uint i : builder.m_types.index_range()) {
+    StringRefNull name = m_allocator.copy_string(builder.m_names[i]);
+    const CPPType &type = *builder.m_types[i];
+    const void *default_value = builder.m_defaults[i];
+
+    m_index_by_name.add_new(name, i);
+    m_name_by_index.append(name);
+    m_type_by_index.append(&type);
+
+    void *dst = m_allocator.allocate(type.size(), type.alignment());
+    type.copy_to_uninitialized(default_value, dst);
+    m_defaults.append(dst);
+  }
+}
+
+AttributesInfo::~AttributesInfo()
+{
+  for (uint i : m_defaults.index_range()) {
+    m_type_by_index[i]->destruct(m_defaults[i]);
+  }
+}
+
+}  // namespace fn
+}  // namespace blender