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diff --git a/third_party/jpeg-xl/lib/jxl/enc_huffman_tree.h b/third_party/jpeg-xl/lib/jxl/enc_huffman_tree.h
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+// Copyright (c) the JPEG XL Project Authors. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Library for creating Huffman codes from population counts.
+
+#ifndef LIB_JXL_HUFFMAN_TREE_H_
+#define LIB_JXL_HUFFMAN_TREE_H_
+
+#include <stdint.h>
+#include <stdlib.h>
+
+namespace jxl {
+
+// A node of a Huffman tree.
+struct HuffmanTree {
+  HuffmanTree(uint32_t count, int16_t left, int16_t right)
+      : total_count(count), index_left(left), index_right_or_value(right) {}
+  uint32_t total_count;
+  int16_t index_left;
+  int16_t index_right_or_value;
+};
+
+void SetDepth(const HuffmanTree& p, HuffmanTree* pool, uint8_t* depth,
+              uint8_t level);
+
+// This function will create a Huffman tree.
+//
+// The (data,length) contains the population counts.
+// The tree_limit is the maximum bit depth of the Huffman codes.
+//
+// The depth contains the tree, i.e., how many bits are used for
+// the symbol.
+//
+// See http://en.wikipedia.org/wiki/Huffman_coding
+void CreateHuffmanTree(const uint32_t* data, size_t length, int tree_limit,
+                       uint8_t* depth);
+
+// Write a Huffman tree from bit depths into the bitstream representation
+// of a Huffman tree. The generated Huffman tree is to be compressed once
+// more using a Huffman tree
+void WriteHuffmanTree(const uint8_t* depth, size_t length, size_t* tree_size,
+                      uint8_t* tree, uint8_t* extra_bits_data);
+
+// Get the actual bit values for a tree of bit depths.
+void ConvertBitDepthsToSymbols(const uint8_t* depth, size_t len,
+                               uint16_t* bits);
+
+}  // namespace jxl
+
+#endif  // LIB_JXL_HUFFMAN_TREE_H_