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diff --git a/third_party/jpeg-xl/lib/jxl/ans_params.h b/third_party/jpeg-xl/lib/jxl/ans_params.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.
+
+#ifndef LIB_JXL_ANS_PARAMS_H_
+#define LIB_JXL_ANS_PARAMS_H_
+
+// Common parameters that are needed for both the ANS entropy encoding and
+// decoding methods.
+
+#include <stdint.h>
+#include <stdlib.h>
+
+namespace jxl {
+
+// TODO(veluca): decide if 12 is the best constant here (valid range is up to
+// 16). This requires recomputing the Huffman tables in {enc,dec}_ans.cc
+// 14 gives a 0.2% improvement at d1 and makes d8 slightly worse. This is
+// likely not worth the increase in encoder complexity.
+#define ANS_LOG_TAB_SIZE 12u
+#define ANS_TAB_SIZE (1 << ANS_LOG_TAB_SIZE)
+#define ANS_TAB_MASK (ANS_TAB_SIZE - 1)
+
+// Largest possible symbol to be encoded by either ANS or prefix coding.
+#define PREFIX_MAX_ALPHABET_SIZE 4096
+#define ANS_MAX_ALPHABET_SIZE 256
+
+// Max number of bits for prefix coding.
+#define PREFIX_MAX_BITS 15
+
+#define ANS_SIGNATURE 0x13  // Initial state, used as CRC.
+
+}  // namespace jxl
+
+#endif  // LIB_JXL_ANS_PARAMS_H_