Functions: Multi Function

This adds the `MultiFunction` type and some smallish utility types that it uses.
A `MultiFunction` encapsulates a function that is optimized for throughput by
always processing many elements at once.

This is an important part of the new particle system, because it allows us to
execute user generated node trees for many particles efficiently.

Reviewers: brecht

Differential Revision: https://developer.blender.org/D8030

1 files changed, 181 insertions, 0 deletions

diff --git a/source/blender/functions/FN_generic_vector_array.hh b/source/blender/functions/FN_generic_vector_array.hh
new file mode 100644
index 00000000000..90c0fbad136
--- /dev/null
+++ b/source/blender/functions/FN_generic_vector_array.hh
@@ -0,0 +1,181 @@
+/*
+ * 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_GENERIC_VECTOR_ARRAY_HH__
+#define __FN_GENERIC_VECTOR_ARRAY_HH__
+
+/** \file
+ * \ingroup fn
+ *
+ * A `GVectorArray` is a container for a fixed amount of dynamically growing arrays with a generic
+ * type. Its main use case is to store many small vectors with few separate allocations. Using this
+ * structure is generally more efficient than allocating each small vector separately.
+ *
+ * `GVectorArrayRef<T>` is a typed reference to a GVectorArray and makes it easier and safer to
+ * work with the class when the type is known at compile time.
+ */
+
+#include "FN_array_spans.hh"
+#include "FN_cpp_type.hh"
+
+#include "BLI_array.hh"
+#include "BLI_linear_allocator.hh"
+#include "BLI_utility_mixins.hh"
+
+namespace blender {
+namespace fn {
+
+template<typename T> class GVectorArrayRef;
+
+class GVectorArray : NonCopyable, NonMovable {
+ private:
+  const CPPType &m_type;
+  uint m_element_size;
+  Array<void *, 1> m_starts;
+  Array<uint, 1> m_lengths;
+  Array<uint, 1> m_capacities;
+  LinearAllocator<> m_allocator;
+
+  template<typename T> friend class GVectorArrayRef;
+
+ public:
+  GVectorArray() = delete;
+
+  GVectorArray(const CPPType &type, uint array_size)
+      : m_type(type),
+        m_element_size(type.size()),
+        m_starts(array_size),
+        m_lengths(array_size),
+        m_capacities(array_size)
+  {
+    m_starts.fill(nullptr);
+    m_lengths.fill(0);
+    m_capacities.fill(0);
+  }
+
+  ~GVectorArray()
+  {
+    if (m_type.is_trivially_destructible()) {
+      return;
+    }
+
+    for (uint i : m_starts.index_range()) {
+      m_type.destruct_n(m_starts[i], m_lengths[i]);
+    }
+  }
+
+  operator GVArraySpan() const
+  {
+    return GVArraySpan(m_type, m_starts.as_span(), m_lengths);
+  }
+
+  bool is_empty() const
+  {
+    return m_starts.size() == 0;
+  }
+
+  uint size() const
+  {
+    return m_starts.size();
+  }
+
+  const CPPType &type() const
+  {
+    return m_type;
+  }
+
+  Span<const void *> starts() const
+  {
+    return m_starts.as_span();
+  }
+
+  Span<uint> lengths() const
+  {
+    return m_lengths;
+  }
+
+  void append(uint index, const void *src)
+  {
+    uint old_length = m_lengths[index];
+    if (old_length == m_capacities[index]) {
+      this->grow_at_least_one(index);
+    }
+
+    void *dst = POINTER_OFFSET(m_starts[index], m_element_size * old_length);
+    m_type.copy_to_uninitialized(src, dst);
+    m_lengths[index]++;
+  }
+
+  GMutableSpan operator[](uint index)
+  {
+    BLI_assert(index < m_starts.size());
+    return GMutableSpan(m_type, m_starts[index], m_lengths[index]);
+  }
+  template<typename T> GVectorArrayRef<T> typed()
+  {
+    return GVectorArrayRef<T>(*this);
+  }
+
+ private:
+  void grow_at_least_one(uint index)
+  {
+    BLI_assert(m_lengths[index] == m_capacities[index]);
+    uint new_capacity = m_lengths[index] * 2 + 1;
+
+    void *new_buffer = m_allocator.allocate(m_element_size * new_capacity, m_type.alignment());
+    m_type.relocate_to_uninitialized_n(m_starts[index], new_buffer, m_lengths[index]);
+
+    m_starts[index] = new_buffer;
+    m_capacities[index] = new_capacity;
+  }
+};
+
+template<typename T> class GVectorArrayRef {
+ private:
+  GVectorArray *m_vector_array;
+
+ public:
+  GVectorArrayRef(GVectorArray &vector_array) : m_vector_array(&vector_array)
+  {
+    BLI_assert(vector_array.m_type == CPPType::get<T>());
+  }
+
+  void append(uint index, const T &value)
+  {
+    m_vector_array->append(index, &value);
+  }
+
+  MutableSpan<T> operator[](uint index)
+  {
+    BLI_assert(index < m_vector_array->m_starts.size());
+    return MutableSpan<T>((T *)m_vector_array->m_starts[index], m_vector_array->m_lengths[index]);
+  }
+
+  uint size() const
+  {
+    return m_vector_array->size();
+  }
+
+  bool is_empty() const
+  {
+    return m_vector_array->is_empty();
+  }
+};
+
+}  // namespace fn
+}  // namespace blender
+
+#endif /* __FN_GENERIC_VECTOR_ARRAY_HH__ */