From 3e16f3b3ef4b8f385b30fe4a1e00860620f610ee Mon Sep 17 00:00:00 2001
From: Jacques Lucke <jacques@blender.org>
Date: Sat, 19 Mar 2022 08:26:29 +0100
Subject: BLI: move generic data structures to blenlib

This is a follow up to rB2252bc6a5527cd7360d1ccfe7a2d1bc640a8dfa6.
---
 source/blender/blenlib/BLI_generic_vector_array.hh | 147 +++++++++++++++++++++
 1 file changed, 147 insertions(+)
 create mode 100644 source/blender/blenlib/BLI_generic_vector_array.hh

(limited to 'source/blender/blenlib/BLI_generic_vector_array.hh')

diff --git a/source/blender/blenlib/BLI_generic_vector_array.hh b/source/blender/blenlib/BLI_generic_vector_array.hh
new file mode 100644
index 00000000000..c98817df4e3
--- /dev/null
+++ b/source/blender/blenlib/BLI_generic_vector_array.hh
@@ -0,0 +1,147 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#pragma once
+
+/** \file
+ * \ingroup bli
+ *
+ * A`GVectorArray` is a container for a fixed amount of dynamically growing vectors with a generic
+ * data 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 vector separately.
+ */
+
+#include "BLI_array.hh"
+#include "BLI_generic_virtual_vector_array.hh"
+#include "BLI_linear_allocator.hh"
+
+namespace blender {
+
+/* An array of vectors containing elements of a generic type. */
+class GVectorArray : NonCopyable, NonMovable {
+ private:
+  struct Item {
+    void *start = nullptr;
+    int64_t length = 0;
+    int64_t capacity = 0;
+  };
+
+  /* Use a linear allocator to pack many small vectors together. Currently, memory from reallocated
+   * vectors is not reused. This can be improved in the future. */
+  LinearAllocator<> allocator_;
+  /* The data type of individual elements. */
+  const CPPType &type_;
+  /* The size of an individual element. This is inlined from `type_.size()` for easier access. */
+  const int64_t element_size_;
+  /* The individual vectors. */
+  Array<Item> items_;
+
+ public:
+  GVectorArray() = delete;
+
+  GVectorArray(const CPPType &type, int64_t array_size);
+
+  ~GVectorArray();
+
+  int64_t size() const
+  {
+    return items_.size();
+  }
+
+  bool is_empty() const
+  {
+    return items_.is_empty();
+  }
+
+  const CPPType &type() const
+  {
+    return type_;
+  }
+
+  void append(int64_t index, const void *value);
+
+  /* Add multiple elements to a single vector. */
+  void extend(int64_t index, const GVArray &values);
+  void extend(int64_t index, GSpan values);
+
+  /* Add multiple elements to multiple vectors. */
+  void extend(IndexMask mask, const GVVectorArray &values);
+  void extend(IndexMask mask, const GVectorArray &values);
+
+  void clear(IndexMask mask);
+
+  GMutableSpan operator[](int64_t index);
+  GSpan operator[](int64_t index) const;
+
+ private:
+  void realloc_to_at_least(Item &item, int64_t min_capacity);
+};
+
+/* A non-owning typed mutable reference to an `GVectorArray`. It simplifies access when the type of
+ * the data is known at compile time. */
+template<typename T> class GVectorArray_TypedMutableRef {
+ private:
+  GVectorArray *vector_array_;
+
+ public:
+  GVectorArray_TypedMutableRef(GVectorArray &vector_array) : vector_array_(&vector_array)
+  {
+    BLI_assert(vector_array_->type().is<T>());
+  }
+
+  int64_t size() const
+  {
+    return vector_array_->size();
+  }
+
+  bool is_empty() const
+  {
+    return vector_array_->is_empty();
+  }
+
+  void append(const int64_t index, const T &value)
+  {
+    vector_array_->append(index, &value);
+  }
+
+  void extend(const int64_t index, const Span<T> values)
+  {
+    vector_array_->extend(index, values);
+  }
+
+  void extend(const int64_t index, const VArray<T> &values)
+  {
+    vector_array_->extend(index, values);
+  }
+
+  MutableSpan<T> operator[](const int64_t index)
+  {
+    return (*vector_array_)[index].typed<T>();
+  }
+};
+
+/* A generic virtual vector array implementation for a `GVectorArray`. */
+class GVVectorArray_For_GVectorArray : public GVVectorArray {
+ private:
+  const GVectorArray &vector_array_;
+
+ public:
+  GVVectorArray_For_GVectorArray(const GVectorArray &vector_array)
+      : GVVectorArray(vector_array.type(), vector_array.size()), vector_array_(vector_array)
+  {
+  }
+
+ protected:
+  int64_t get_vector_size_impl(const int64_t index) const override
+  {
+    return vector_array_[index].size();
+  }
+
+  void get_vector_element_impl(const int64_t index,
+                               const int64_t index_in_vector,
+                               void *r_value) const override
+  {
+    type_->copy_assign(vector_array_[index][index_in_vector], r_value);
+  }
+};
+
+}  // namespace blender
-- 
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