emkornfield commented on code in PR #48345:
URL: https://github.com/apache/arrow/pull/48345#discussion_r2722319470
##########
cpp/src/parquet/decoder.cc:
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@@ -2323,6 +2327,121 @@ class ByteStreamSplitDecoder<FLBAType> : public
ByteStreamSplitDecoderBase<FLBAT
}
};
+// ----------------------------------------------------------------------
+// ALP decoder (Adaptive Lossless floating-Point)
+
+template <typename DType>
+class AlpDecoder : public TypedDecoderImpl<DType> {
+ public:
+ using Base = TypedDecoderImpl<DType>;
+ using T = typename DType::c_type;
+
+ explicit AlpDecoder(const ColumnDescriptor* descr)
+ : Base(descr, Encoding::ALP), current_offset_{0}, needs_decode_{false} {
+ static_assert(std::is_same<T, float>::value || std::is_same<T,
double>::value,
+ "ALP only supports float and double types");
+ }
+
+ void SetData(int num_values, const uint8_t* data, int len) final {
+ Base::SetData(num_values, data, len);
+ current_offset_ = 0;
+ needs_decode_ = (len > 0 && num_values > 0);
+ decoded_buffer_.clear();
+ }
+
+ int Decode(T* buffer, int max_values) override {
+ // Fast path: decode directly into output buffer if requesting all values
+ if (needs_decode_ && max_values >= this->num_values_) {
+ ::arrow::util::alp::AlpWrapper<T>::Decode(
Review Comment:
Follow up? this should almost certainly return a status, indicating a
problem with decoding?
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