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diff --git a/extern/draco/draco/src/draco/compression/bit_coders/adaptive_rans_bit_encoder.h b/extern/draco/draco/src/draco/compression/bit_coders/adaptive_rans_bit_encoder.h
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+++ b/extern/draco/draco/src/draco/compression/bit_coders/adaptive_rans_bit_encoder.h
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+// Copyright 2016 The Draco 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.
+//
+// File provides basic classes and functions for rANS bit encoding.
+#ifndef DRACO_COMPRESSION_BIT_CODERS_ADAPTIVE_RANS_BIT_ENCODER_H_
+#define DRACO_COMPRESSION_BIT_CODERS_ADAPTIVE_RANS_BIT_ENCODER_H_
+
+#include <vector>
+
+#include "draco/compression/entropy/ans.h"
+#include "draco/core/encoder_buffer.h"
+
+namespace draco {
+
+// Class for adaptive encoding a sequence of bits using rANS.
+class AdaptiveRAnsBitEncoder {
+ public:
+  AdaptiveRAnsBitEncoder();
+  ~AdaptiveRAnsBitEncoder();
+
+  // Must be called before any Encode* function is called.
+  void StartEncoding();
+
+  // Encode one bit. If |bit| is true encode a 1, otherwise encode a 0.
+  void EncodeBit(bool bit) { bits_.push_back(bit); }
+
+  // Encode |nbits| of |value|, starting from the least significant bit.
+  // |nbits| must be > 0 and <= 32.
+  void EncodeLeastSignificantBits32(int nbits, uint32_t value) {
+    DRACO_DCHECK_EQ(true, nbits <= 32);
+    DRACO_DCHECK_EQ(true, nbits > 0);
+    uint32_t selector = (1 << (nbits - 1));
+    while (selector) {
+      EncodeBit(value & selector);
+      selector = selector >> 1;
+    }
+  }
+
+  // Ends the bit encoding and stores the result into the target_buffer.
+  void EndEncoding(EncoderBuffer *target_buffer);
+
+ private:
+  void Clear();
+
+  std::vector<bool> bits_;
+};
+
+}  // namespace draco
+
+#endif  // DRACO_COMPRESSION_BIT_CODERS_ADAPTIVE_RANS_BIT_ENCODER_H_