Function DecompressBuffers

cpp/src/arrow/ipc/reader.cc:580–615

}

Status DecompressBuffers(Compression::type compression, const IpcReadOptions& options,
                         ArrayDataVector* fields) {
  struct BufferAccumulator {
    using BufferPtrVector = std::vector<std::shared_ptr<Buffer>*>;

    void AppendFrom(const ArrayDataVector& fields) {
      for (const auto& field : fields) {
        for (auto& buffer : field->buffers) {
          buffers_.push_back(&buffer);
        }
        AppendFrom(field->child_data);
      }
      // Dictionary buffers are decompressed separately (see ReadDictionary).
    }

    BufferPtrVector Get(const ArrayDataVector& fields) && {
      AppendFrom(fields);
      return std::move(buffers_);
    }

    BufferPtrVector buffers_;
  };

  // Flatten all buffers
  auto buffers = BufferAccumulator{}.Get(*fields);

  std::unique_ptr<util::Codec> codec;
  ARROW_ASSIGN_OR_RAISE(codec, util::Codec::Create(compression));

  return ::arrow::internal::OptionalParallelFor(
      options.use_threads, static_cast<int>(buffers.size()), [&](int i) {
        ARROW_ASSIGN_OR_RAISE(*buffers[i],
                              DecompressBuffer(*buffers[i], options, codec.get()));
        return Status::OK();
      });
}

// Helper class to run post-ArrayLoader steps:
// buffer decompression, dictionary resolution, buffer re-alignment.