1 files changed, 70 insertions, 0 deletions
diff --git a/extern/draco/draco/src/draco/compression/bit_coders/adaptive_rans_bit_decoder.cc b/extern/draco/draco/src/draco/compression/bit_coders/adaptive_rans_bit_decoder.cc
new file mode 100644
index 00000000000..056842c4a99
--- /dev/null
+++ b/extern/draco/draco/src/draco/compression/bit_coders/adaptive_rans_bit_decoder.cc
@@ -0,0 +1,70 @@
+// 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.
+//
+#include "draco/compression/bit_coders/adaptive_rans_bit_decoder.h"
+
+#include "draco/compression/bit_coders/adaptive_rans_bit_coding_shared.h"
+
+namespace draco {
+
+AdaptiveRAnsBitDecoder::AdaptiveRAnsBitDecoder() : p0_f_(0.5) {}
+
+AdaptiveRAnsBitDecoder::~AdaptiveRAnsBitDecoder() { Clear(); }
+
+bool AdaptiveRAnsBitDecoder::StartDecoding(DecoderBuffer *source_buffer) {
+  Clear();
+
+  uint32_t size_in_bytes;
+  if (!source_buffer->Decode(&size_in_bytes)) {
+    return false;
+  }
+  if (size_in_bytes > source_buffer->remaining_size()) {
+    return false;
+  }
+  if (ans_read_init(&ans_decoder_,
+                    reinterpret_cast<uint8_t *>(
+                        const_cast<char *>(source_buffer->data_head())),
+                    size_in_bytes) != 0) {
+    return false;
+  }
+  source_buffer->Advance(size_in_bytes);
+  return true;
+}
+
+bool AdaptiveRAnsBitDecoder::DecodeNextBit() {
+  const uint8_t p0 = clamp_probability(p0_f_);
+  const bool bit = static_cast<bool>(rabs_read(&ans_decoder_, p0));
+  p0_f_ = update_probability(p0_f_, bit);
+  return bit;
+}
+
+void AdaptiveRAnsBitDecoder::DecodeLeastSignificantBits32(int nbits,
+                                                          uint32_t *value) {
+  DRACO_DCHECK_EQ(true, nbits <= 32);
+  DRACO_DCHECK_EQ(true, nbits > 0);
+
+  uint32_t result = 0;
+  while (nbits) {
+    result = (result << 1) + DecodeNextBit();
+    --nbits;
+  }
+  *value = result;
+}
+
+void AdaptiveRAnsBitDecoder::Clear() {
+  ans_read_end(&ans_decoder_);
+  p0_f_ = 0.5;
+}
+
+}  // namespace draco