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diff --git a/src/utils/bit_reader.h b/src/utils/bit_reader.h
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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_BIT_READER_H_
+#define LIBGAV1_SRC_UTILS_BIT_READER_H_
+
+#include <cstdint>
+
+namespace libgav1 {
+
+class BitReader {
+ public:
+  virtual ~BitReader() = default;
+
+  virtual int ReadBit() = 0;
+  // |num_bits| has to be <= 32. The function returns a value in the range [0,
+  // 2^num_bits - 1] (inclusive) on success and -1 on failure.
+  virtual int64_t ReadLiteral(int num_bits) = 0;
+
+  bool DecodeSignedSubexpWithReference(int low, int high, int reference,
+                                       int control, int* value);  // 5.9.26.
+  // Decodes a nonnegative integer with maximum number of values |n| (i.e.,
+  // output in range 0..n-1) by following the process specified in Section
+  // 4.10.7 ns(n) and Section 4.10.10 NS(n) of the spec.
+  bool DecodeUniform(int n, int* value);
+
+ private:
+  // Helper functions for DecodeSignedSubexpWithReference.
+  bool DecodeUnsignedSubexpWithReference(int mx, int reference, int control,
+                                         int* value);           // 5.9.27.
+  bool DecodeSubexp(int num_symbols, int control, int* value);  // 5.9.28.
+};
+
+}  // namespace libgav1
+
+#endif  // LIBGAV1_SRC_UTILS_BIT_READER_H_