diff options
Diffstat (limited to 'extern/draco/dracoenc/src/draco/compression/bit_coders/rans_bit_decoder.cc')
-rw-r--r-- | extern/draco/dracoenc/src/draco/compression/bit_coders/rans_bit_decoder.cc | 77 |
1 files changed, 77 insertions, 0 deletions
diff --git a/extern/draco/dracoenc/src/draco/compression/bit_coders/rans_bit_decoder.cc b/extern/draco/dracoenc/src/draco/compression/bit_coders/rans_bit_decoder.cc new file mode 100644 index 00000000000..023e0dbc192 --- /dev/null +++ b/extern/draco/dracoenc/src/draco/compression/bit_coders/rans_bit_decoder.cc @@ -0,0 +1,77 @@ +// 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/rans_bit_decoder.h" + +#include "draco/compression/config/compression_shared.h" +#include "draco/core/bit_utils.h" +#include "draco/core/varint_decoding.h" + +namespace draco { + +RAnsBitDecoder::RAnsBitDecoder() : prob_zero_(0) {} + +RAnsBitDecoder::~RAnsBitDecoder() { Clear(); } + +bool RAnsBitDecoder::StartDecoding(DecoderBuffer *source_buffer) { + Clear(); + + if (!source_buffer->Decode(&prob_zero_)) + return false; + + uint32_t size_in_bytes; +#ifdef DRACO_BACKWARDS_COMPATIBILITY_SUPPORTED + if (source_buffer->bitstream_version() < DRACO_BITSTREAM_VERSION(2, 2)) { + if (!source_buffer->Decode(&size_in_bytes)) + return false; + + } else +#endif + { + if (!DecodeVarint(&size_in_bytes, source_buffer)) + 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 RAnsBitDecoder::DecodeNextBit() { + const uint8_t bit = rabs_read(&ans_decoder_, prob_zero_); + return bit > 0; +} + +void RAnsBitDecoder::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 RAnsBitDecoder::Clear() { ans_read_end(&ans_decoder_); } + +} // namespace draco |