pitrou commented on code in PR #40094:
URL: https://github.com/apache/arrow/pull/40094#discussion_r1494375511
##########
cpp/src/parquet/encoding.cc:
##########
@@ -3559,136 +3618,162 @@ class DeltaByteArrayFLBADecoder : public
DeltaByteArrayDecoderImpl<FLBAType>,
};
// ----------------------------------------------------------------------
-// BYTE_STREAM_SPLIT
+// BYTE_STREAM_SPLIT decoders
template <typename DType>
-class ByteStreamSplitDecoder : public DecoderImpl, virtual public
TypedDecoder<DType> {
+class ByteStreamSplitDecoderBase : public DecoderImpl,
+ virtual public TypedDecoder<DType> {
public:
using T = typename DType::c_type;
- explicit ByteStreamSplitDecoder(const ColumnDescriptor* descr);
- int Decode(T* buffer, int max_values) override;
+ ByteStreamSplitDecoderBase(const ColumnDescriptor* descr, int byte_width)
+ : DecoderImpl(descr, Encoding::BYTE_STREAM_SPLIT),
byte_width_(byte_width) {}
- int DecodeArrow(int num_values, int null_count, const uint8_t* valid_bits,
- int64_t valid_bits_offset,
- typename EncodingTraits<DType>::Accumulator* builder)
override;
+ void SetData(int num_values, const uint8_t* data, int len) override {
+ if (static_cast<int64_t>(num_values) * byte_width_ != len) {
+ throw ParquetException(
+ "Data size does not match number of values in BYTE_STREAM_SPLIT");
+ }
+ DecoderImpl::SetData(num_values, data, len);
+ stride_ = num_values_;
+ }
int DecodeArrow(int num_values, int null_count, const uint8_t* valid_bits,
int64_t valid_bits_offset,
- typename EncodingTraits<DType>::DictAccumulator* builder)
override;
-
- void SetData(int num_values, const uint8_t* data, int len) override;
+ typename EncodingTraits<DType>::DictAccumulator* builder)
override {
+ ParquetException::NYI("DecodeArrow to DictAccumulator for
BYTE_STREAM_SPLIT");
+ }
- T* EnsureDecodeBuffer(int64_t min_values) {
- const int64_t size = sizeof(T) * min_values;
+ protected:
+ int DecodeRaw(uint8_t* out_buffer, int max_values) {
+ const int values_to_decode = std::min(num_values_, max_values);
+ ::arrow::util::internal::ByteStreamSplitDecode(data_, byte_width_,
values_to_decode,
+ stride_, out_buffer);
+ data_ += values_to_decode;
+ num_values_ -= values_to_decode;
+ len_ -= byte_width_ * values_to_decode;
+ return values_to_decode;
+ }
+
+ uint8_t* EnsureDecodeBuffer(int64_t min_values) {
+ const int64_t size = byte_width_ * min_values;
if (!decode_buffer_ || decode_buffer_->size() < size) {
- PARQUET_ASSIGN_OR_THROW(decode_buffer_, ::arrow::AllocateBuffer(size));
+ const auto alloc_size = ::arrow::bit_util::NextPower2(size);
+ PARQUET_ASSIGN_OR_THROW(decode_buffer_,
::arrow::AllocateBuffer(alloc_size));
}
- return decode_buffer_->mutable_data_as<T>();
+ return decode_buffer_->mutable_data();
}
- private:
- int num_values_in_buffer_{0};
+ const int byte_width_;
+ int stride_{0};
std::shared_ptr<Buffer> decode_buffer_;
-
- static constexpr int kNumStreams = sizeof(T);
+ const uint8_t* decode_data_;
Review Comment:
Indeed, thank you.
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