BLI: new C++ ArrayRef, Vector, Stack, ... data structures

Many generic C++ data structures have been developed in the
functions branch. This commit merges a first chunk of them into
master. The following new data structures are included:

Array: Owns a memory buffer with a fixed size. It is different
  from std::array in that the size is not part of the type.

ArrayRef: References an array owned by someone else. All elements
  in the referenced array are considered to be const. This should
  be the preferred parameter type for functions that take arrays
  as input.

MutableArrayRef: References an array owned by someone else. The
  elements in the referenced array can be changed.

IndexRange: Specifies a continuous range of integers with a start
  and end index.

IntrusiveListBaseWrapper: A utility class that allows iterating
  over ListBase instances where the prev and next pointer are
  stored in the objects directly.

Stack: A stack implemented on top of a vector.

Vector: An array that can grow dynamically.

Allocators: Three allocator types are included that can be used
  by the container types to support different use cases.

The Stack and Vector support small object optimization. So when
the amount of elements in them is below a certain threshold, no
memory allocation is performed.

Additionally, most methods have unit tests.

I'm merging this without normal code review, after I checked the
code roughly with Sergey, and after we talked about it with Brecht.

1 files changed, 193 insertions, 0 deletions

diff --git a/source/blender/blenlib/BLI_index_range.h b/source/blender/blenlib/BLI_index_range.h
new file mode 100644
index 00000000000..96c3d22c4e5
--- /dev/null
+++ b/source/blender/blenlib/BLI_index_range.h
@@ -0,0 +1,193 @@
+/*
+ * 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.
+ */
+
+/** \file
+ * \ingroup bli
+ *
+ * Allows passing iterators over ranges of integers without actually allocating an array or passing
+ * separate values. A range always has a step of one. If other step sizes are required in some
+ * cases, a separate data structure should be used.
+ */
+
+#pragma once
+
+#include <cmath>
+#include <algorithm>
+#include <iostream>
+
+#include "BLI_utildefines.h"
+
+namespace BLI {
+
+template<typename T> class ArrayRef;
+
+class IndexRange {
+ private:
+  uint m_start = 0;
+  uint m_size = 0;
+
+ public:
+  IndexRange() = default;
+
+  explicit IndexRange(uint size) : m_start(0), m_size(size)
+  {
+  }
+
+  IndexRange(uint start, uint size) : m_start(start), m_size(size)
+  {
+  }
+
+  class Iterator {
+   private:
+    uint m_current;
+
+   public:
+    Iterator(uint current) : m_current(current)
+    {
+    }
+
+    Iterator &operator++()
+    {
+      m_current++;
+      return *this;
+    }
+
+    bool operator!=(const Iterator &iterator) const
+    {
+      return m_current != iterator.m_current;
+    }
+
+    uint operator*() const
+    {
+      return m_current;
+    }
+  };
+
+  Iterator begin() const
+  {
+    return Iterator(m_start);
+  }
+
+  Iterator end() const
+  {
+    return Iterator(m_start + m_size);
+  }
+
+  /**
+   * Access an element in the range.
+   */
+  uint operator[](uint index) const
+  {
+    BLI_assert(index < this->size());
+    return m_start + index;
+  }
+
+  /**
+   * Two ranges compare equal when they contain the same numbers.
+   */
+  friend bool operator==(IndexRange a, IndexRange b)
+  {
+    return (a.m_size == b.m_size) && (a.m_start == b.m_start || a.m_size == 0);
+  }
+
+  /**
+   * Get the amount of numbers in the range.
+   */
+  uint size() const
+  {
+    return m_size;
+  }
+
+  /**
+   * Create a new range starting at the end of the current one.
+   */
+  IndexRange after(uint n) const
+  {
+    return IndexRange(m_start + m_size, n);
+  }
+
+  /**
+   * Create a new range that ends at the start of the current one.
+   */
+  IndexRange before(uint n) const
+  {
+    return IndexRange(m_start - n, n);
+  }
+
+  /**
+   * Get the first element in the range.
+   * Asserts when the range is empty.
+   */
+  uint first() const
+  {
+    BLI_assert(this->size() > 0);
+    return m_start;
+  }
+
+  /**
+   * Get the last element in the range.
+   * Asserts when the range is empty.
+   */
+  uint last() const
+  {
+    BLI_assert(this->size() > 0);
+    return m_start + m_size - 1;
+  }
+
+  /**
+   * Get the element one after the end. The returned value is undefined when the range is empty.
+   */
+  uint one_after_last() const
+  {
+    return m_start + m_size;
+  }
+
+  /**
+   * Get the first element in the range. The returned value is undefined when the range is empty.
+   */
+  uint start() const
+  {
+    return m_start;
+  }
+
+  /**
+   * Returns true when the range contains a certain number, otherwise false.
+   */
+  bool contains(uint value) const
+  {
+    return value >= m_start && value < m_start + m_size;
+  }
+
+  IndexRange slice(uint start, uint size) const
+  {
+    uint new_start = m_start + start;
+    BLI_assert(new_start + size <= m_start + m_size || size == 0);
+    return IndexRange(new_start, size);
+  }
+
+  /**
+   * Get read-only access to a memory buffer that contains the range as actual numbers.
+   */
+  ArrayRef<uint> as_array_ref() const;
+
+  friend std::ostream &operator<<(std::ostream &stream, IndexRange range)
+  {
+    stream << "[" << range.start() << ", " << range.one_after_last() << ")";
+    return stream;
+  }
+};
+
+}  // namespace BLI