pitrou commented on a change in pull request #7507:
URL: https://github.com/apache/arrow/pull/7507#discussion_r576998571
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File path: cpp/src/arrow/array/util.cc
##########
@@ -74,11 +75,222 @@ class ArrayDataWrapper {
std::shared_ptr<Array>* out_;
};
+class ArrayDataEndianSwapper {
+ public:
+ ArrayDataEndianSwapper(const std::shared_ptr<ArrayData>& data, int64_t
length)
+ : data_(data), length_(length) {
+ const std::shared_ptr<DataType>& type = data->type;
+ std::vector<std::shared_ptr<Buffer>> buffers(data->buffers.size(),
nullptr);
+ std::vector<std::shared_ptr<ArrayData>>
child_data(data->child_data.size(), nullptr);
+ out_ = ArrayData::Make(type, data->length, buffers, child_data,
data->null_count, 0);
+ }
+
+ Status SwapType(const DataType& type) {
+ RETURN_NOT_OK(VisitTypeInline(type, this));
+ RETURN_NOT_OK(SwapChildren(type.fields()));
+ return Status::OK();
+ }
+
+ Status SwapChildren(const std::vector<std::shared_ptr<Field>>& child_fields)
{
+ for (size_t i = 0; i < child_fields.size(); i++) {
+ ARROW_ASSIGN_OR_RAISE(out_->child_data[i],
+
internal::SwapEndianArrayData(data_->child_data[i]));
+ }
+ return Status::OK();
+ }
+
+ template <typename T>
+ Result<std::shared_ptr<Buffer>> ByteSwapBuffer(
+ const std::shared_ptr<Buffer>& in_buffer) {
+ if (sizeof(T) == 1) {
+ // if data size is 1, element is not swapped. We can use the original
buffer
+ return in_buffer;
+ }
+ auto in_data = reinterpret_cast<const T*>(in_buffer->data());
+ ARROW_ASSIGN_OR_RAISE(auto out_buffer, AllocateBuffer(in_buffer->size()));
+ auto out_data = reinterpret_cast<T*>(out_buffer->mutable_data());
+ int64_t length = in_buffer->size() / sizeof(T);
+ for (int64_t i = 0; i < length; i++) {
+ out_data[i] = BitUtil::ByteSwap(in_data[i]);
+ }
+ return std::move(out_buffer);
+ }
+
+ template <typename VALUE_TYPE>
+ Status SwapOffsets(int index) {
+ if (data_->buffers[index] == nullptr || data_->buffers[index]->size() ==
0) {
+ out_->buffers[index] = data_->buffers[index];
+ return Status::OK();
+ }
+ // Except union, offset has one more element rather than data->length
+ ARROW_ASSIGN_OR_RAISE(out_->buffers[index],
+ ByteSwapBuffer<VALUE_TYPE>(data_->buffers[index]));
+ return Status::OK();
+ }
+
+ template <typename T>
+ enable_if_t<std::is_base_of<FixedWidthType, T>::value &&
+ !std::is_base_of<FixedSizeBinaryType, T>::value &&
+ !std::is_base_of<DictionaryType, T>::value,
+ Status>
+ Visit(const T& type) {
+ using value_type = typename T::c_type;
+ ARROW_ASSIGN_OR_RAISE(out_->buffers[1],
+ ByteSwapBuffer<value_type>(data_->buffers[1]));
+ return Status::OK();
+ }
+
+ Status Visit(const Decimal128Type& type) {
+ auto data = reinterpret_cast<const uint64_t*>(data_->buffers[1]->data());
+ ARROW_ASSIGN_OR_RAISE(auto new_buffer,
AllocateBuffer(data_->buffers[1]->size()));
+ auto new_data = reinterpret_cast<uint64_t*>(new_buffer->mutable_data());
+ int64_t length = length_;
+ length = data_->buffers[1]->size() / (sizeof(uint64_t) * 2);
+ for (int64_t i = 0; i < length; i++) {
+ uint64_t tmp;
+ auto idx = i * 2;
+#if ARROW_LITTLE_ENDIAN
+ tmp = BitUtil::FromBigEndian(data[idx]);
+ new_data[idx] = BitUtil::FromBigEndian(data[idx + 1]);
+ new_data[idx + 1] = tmp;
+#else
+ tmp = BitUtil::FromLittleEndian(data[idx]);
+ new_data[idx] = BitUtil::FromLittleEndian(data[idx + 1]);
+ new_data[idx + 1] = tmp;
+#endif
+ }
+ out_->buffers[1] = std::move(new_buffer);
+ return Status::OK();
+ }
+
+ Status Visit(const Decimal256Type& type) {
+ auto data = reinterpret_cast<const uint64_t*>(data_->buffers[1]->data());
+ ARROW_ASSIGN_OR_RAISE(auto new_buffer,
AllocateBuffer(data_->buffers[1]->size()));
+ auto new_data = reinterpret_cast<uint64_t*>(new_buffer->mutable_data());
+ int64_t length = length_;
+ length = data_->buffers[1]->size() / (sizeof(uint64_t) * 4);
+ for (int64_t i = 0; i < length; i++) {
+ uint64_t tmp0, tmp1, tmp2;
+ auto idx = i * 4;
+#if ARROW_LITTLE_ENDIAN
+ tmp0 = BitUtil::FromBigEndian(data[idx]);
+ tmp1 = BitUtil::FromBigEndian(data[idx + 1]);
+ tmp2 = BitUtil::FromBigEndian(data[idx + 2]);
+ new_data[idx] = BitUtil::FromBigEndian(data[idx + 3]);
+ new_data[idx + 1] = tmp2;
+ new_data[idx + 2] = tmp1;
+ new_data[idx + 3] = tmp0;
+#else
+ tmp0 = BitUtil::FromLittleEndian(data[idx]);
+ tmp1 = BitUtil::FromLittleEndian(data[idx + 1]);
+ tmp2 = BitUtil::FromLittleEndian(data[idx + 2]);
+ new_data[idx] = BitUtil::FromLittleEndian(data[idx + 3]);
+ new_data[idx + 1] = tmp2;
+ new_data[idx + 2] = tmp1;
+ new_data[idx + 3] = tmp0;
+#endif
+ }
+ out_->buffers[1] = std::move(new_buffer);
+ return Status::OK();
+ }
+
+ Status Visit(const DayTimeIntervalType& type) {
+ ARROW_ASSIGN_OR_RAISE(out_->buffers[1],
ByteSwapBuffer<uint32_t>(data_->buffers[1]));
+ return Status::OK();
+ }
+
+ Status ReuseDataBuffer() {
+ out_->buffers[1] = data_->buffers[1];
Review comment:
Isn't this automatically the case? (since `out_` is initialized from
`data_`)
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