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+/*
+ * Copyright 2019 The libgav1 Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LIBGAV1_SRC_UTILS_PARAMETER_TREE_H_
+#define LIBGAV1_SRC_UTILS_PARAMETER_TREE_H_
+
+#include <cassert>
+#include <memory>
+
+#include "src/utils/common.h"
+#include "src/utils/compiler_attributes.h"
+#include "src/utils/constants.h"
+#include "src/utils/memory.h"
+#include "src/utils/types.h"
+
+namespace libgav1 {
+
+class ParameterTree : public Allocable {
+ public:
+  // Creates a parameter tree to store the parameters of a block of size
+  // |block_size| starting at coordinates |row4x4| and |column4x4|. If |is_leaf|
+  // is set to true, the memory will be allocated for the BlockParameters for
+  // this node. Otherwise, no memory will be allocated. If |is_leaf| is set to
+  // false, |block_size| must be a square block, i.e.,
+  // kBlockWidthPixels[block_size] must be equal to
+  // kBlockHeightPixels[block_size].
+  static std::unique_ptr<ParameterTree> Create(int row4x4, int column4x4,
+                                               BlockSize block_size,
+                                               bool is_leaf = false);
+
+  // Move only (not Copyable).
+  ParameterTree(ParameterTree&& other) = default;
+  ParameterTree& operator=(ParameterTree&& other) = default;
+  ParameterTree(const ParameterTree&) = delete;
+  ParameterTree& operator=(const ParameterTree&) = delete;
+
+  // Set the partition type of the current node to |partition|.
+  // if (partition == kPartitionNone) {
+  //   Memory will be allocated for the BlockParameters for this node.
+  // } else if (partition != kPartitionSplit) {
+  //   The appropriate child nodes will be populated and memory will be
+  //   allocated for the BlockParameters of the children.
+  // } else {
+  //   The appropriate child nodes will be populated but they are considered to
+  //   be hanging, i.e., future calls to SetPartitionType() on the child nodes
+  //   will have to set them or their descendants to a terminal type.
+  // }
+  // This function must be called only once per node.
+  LIBGAV1_MUST_USE_RESULT bool SetPartitionType(Partition partition);
+
+  // Basic getters.
+  int row4x4() const { return row4x4_; }
+  int column4x4() const { return column4x4_; }
+  BlockSize block_size() const { return block_size_; }
+  Partition partition() const { return partition_; }
+  ParameterTree* children(int index) const {
+    assert(index < 4);
+    return children_[index].get();
+  }
+  // Returns the BlockParameters object of the current node if one exists.
+  // Otherwise returns nullptr. This function will return a valid
+  // BlockParameters object only for leaf nodes.
+  BlockParameters* parameters() const { return parameters_.get(); }
+
+ private:
+  ParameterTree(int row4x4, int column4x4, BlockSize block_size)
+      : row4x4_(row4x4), column4x4_(column4x4), block_size_(block_size) {}
+
+  Partition partition_ = kPartitionNone;
+  std::unique_ptr<BlockParameters> parameters_ = nullptr;
+  int row4x4_ = -1;
+  int column4x4_ = -1;
+  BlockSize block_size_ = kBlockInvalid;
+  bool partition_type_set_ = false;
+
+  // Child values are defined as follows for various partition types:
+  //  * Horizontal: 0 top partition; 1 bottom partition; 2 nullptr; 3 nullptr;
+  //  * Vertical: 0 left partition; 1 right partition; 2 nullptr; 3 nullptr;
+  //  * Split: 0 top-left partition; 1 top-right partition; 2; bottom-left
+  //    partition; 3 bottom-right partition;
+  //  * HorizontalWithTopSplit: 0 top-left partition; 1 top-right partition; 2
+  //    bottom partition; 3 nullptr;
+  //  * HorizontalWithBottomSplit: 0 top partition; 1 bottom-left partition; 2
+  //    bottom-right partition; 3 nullptr;
+  //  * VerticalWithLeftSplit: 0 top-left partition; 1 bottom-left partition; 2
+  //    right partition; 3 nullptr;
+  //  * VerticalWithRightSplit: 0 left-partition; 1 top-right partition; 2
+  //    bottom-right partition; 3 nullptr;
+  //  * Horizontal4: 0 top partition; 1 second top partition; 2 third top
+  //    partition; 3 bottom partition;
+  //  * Vertical4: 0 left partition; 1 second left partition; 2 third left
+  //    partition; 3 right partition;
+  std::unique_ptr<ParameterTree> children_[4] = {};
+
+  friend class ParameterTreeTest;
+};
+
+}  // namespace libgav1
+
+#endif  // LIBGAV1_SRC_UTILS_PARAMETER_TREE_H_