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diff --git a/modules/brotli/enc/backward_references_hq.h b/modules/brotli/enc/backward_references_hq.h
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+++ b/modules/brotli/enc/backward_references_hq.h
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+/* Copyright 2013 Google Inc. All Rights Reserved.
+
+   Distributed under MIT license.
+   See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
+*/
+
+/* Function to find backward reference copies. */
+
+#ifndef BROTLI_ENC_BACKWARD_REFERENCES_HQ_H_
+#define BROTLI_ENC_BACKWARD_REFERENCES_HQ_H_
+
+#include "../common/constants.h"
+#include "../common/dictionary.h"
+#include "../common/platform.h"
+#include <brotli/types.h>
+#include "./command.h"
+#include "./hash.h"
+#include "./memory.h"
+#include "./quality.h"
+
+#if defined(__cplusplus) || defined(c_plusplus)
+extern "C" {
+#endif
+
+BROTLI_INTERNAL void BrotliCreateZopfliBackwardReferences(MemoryManager* m,
+    size_t num_bytes, size_t position, const uint8_t* ringbuffer,
+    size_t ringbuffer_mask, const BrotliEncoderParams* params,
+    HasherHandle hasher, int* dist_cache, size_t* last_insert_len,
+    Command* commands, size_t* num_commands, size_t* num_literals);
+
+BROTLI_INTERNAL void BrotliCreateHqZopfliBackwardReferences(MemoryManager* m,
+    size_t num_bytes, size_t position, const uint8_t* ringbuffer,
+    size_t ringbuffer_mask, const BrotliEncoderParams* params,
+    HasherHandle hasher, int* dist_cache, size_t* last_insert_len,
+    Command* commands, size_t* num_commands, size_t* num_literals);
+
+typedef struct ZopfliNode {
+  /* Best length to get up to this byte (not including this byte itself)
+     highest 7 bit is used to reconstruct the length code. */
+  uint32_t length;
+  /* Distance associated with the length. */
+  uint32_t distance;
+  /* Number of literal inserts before this copy; highest 5 bits contain
+     distance short code + 1 (or zero if no short code). */
+  uint32_t dcode_insert_length;
+
+  /* This union holds information used by dynamic-programming. During forward
+     pass |cost| it used to store the goal function. When node is processed its
+     |cost| is invalidated in favor of |shortcut|. On path back-tracing pass
+     |next| is assigned the offset to next node on the path. */
+  union {
+    /* Smallest cost to get to this byte from the beginning, as found so far. */
+    float cost;
+    /* Offset to the next node on the path. Equals to command_length() of the
+       next node on the path. For last node equals to BROTLI_UINT32_MAX */
+    uint32_t next;
+    /* Node position that provides next distance for distance cache. */
+    uint32_t shortcut;
+  } u;
+} ZopfliNode;
+
+BROTLI_INTERNAL void BrotliInitZopfliNodes(ZopfliNode* array, size_t length);
+
+/* Computes the shortest path of commands from position to at most
+   position + num_bytes.
+
+   On return, path->size() is the number of commands found and path[i] is the
+   length of the i-th command (copy length plus insert length).
+   Note that the sum of the lengths of all commands can be less than num_bytes.
+
+   On return, the nodes[0..num_bytes] array will have the following
+   "ZopfliNode array invariant":
+   For each i in [1..num_bytes], if nodes[i].cost < kInfinity, then
+     (1) nodes[i].copy_length() >= 2
+     (2) nodes[i].command_length() <= i and
+     (3) nodes[i - nodes[i].command_length()].cost < kInfinity */
+BROTLI_INTERNAL size_t BrotliZopfliComputeShortestPath(
+    MemoryManager* m, size_t num_bytes,
+    size_t position, const uint8_t* ringbuffer, size_t ringbuffer_mask,
+    const BrotliEncoderParams* params,
+    const int* dist_cache, HasherHandle hasher, ZopfliNode* nodes);
+
+BROTLI_INTERNAL void BrotliZopfliCreateCommands(
+    const size_t num_bytes, const size_t block_start, const ZopfliNode* nodes,
+    int* dist_cache, size_t* last_insert_len, const BrotliEncoderParams* params,
+    Command* commands, size_t* num_literals);
+
+#if defined(__cplusplus) || defined(c_plusplus)
+}  /* extern "C" */
+#endif
+
+#endif  /* BROTLI_ENC_BACKWARD_REFERENCES_HQ_H_ */