AntoinePrv commented on code in PR #50629:
URL: https://github.com/apache/arrow/pull/50629#discussion_r4334773292
##########
cpp/src/parquet/column_reader.cc:
##########
@@ -91,137 +83,100 @@ inline void CheckNumberDecoded(int64_t number_decoded,
int64_t expected) {
}
}
-constexpr std::string_view kErrorRepDefLevelNotMatchesNumValues =
- "Number of decoded rep / def levels do not match num_values in page
header";
+/// True if a T can hold a U.
+template <typename T, typename U>
+inline constexpr bool can_hold_v =
std::in_range<T>(std::numeric_limits<U>::min()) &&
+
std::in_range<T>(std::numeric_limits<U>::max());
+
+/// Clamp to a given type.
+template <typename T, typename U>
+constexpr T clamp_to(U val) {
+ if constexpr (can_hold_v<T, U>) {
+ return static_cast<T>(val);
+ }
+ constexpr U kMax = std::numeric_limits<T>::max();
+ constexpr U kMin = std::numeric_limits<T>::min();
+ return static_cast<T>(std::clamp<U>(val, kMin, kMax));
+}
+
+/// Return the int that can be represented by the other.
+template <typename T, typename U>
+using smallest_int_t = std::conditional_t<can_hold_v<T, U>, U, T>;
+
+/// Return the min in the smallest integer size of its inputs.
+template <typename T, typename U>
+constexpr auto narrow_min(T x, U y) -> smallest_int_t<T, U> {
+ using V = smallest_int_t<T, U>;
+ return std::min<V>(clamp_to<V>(x), clamp_to<V>(y));
+}
+
+/// Whether values of type T can be printed to `std::cout`.
+template <typename T>
+concept can_cout = requires(std::ostream& os, const T& value) {
+ os << value;
+}; // NOLINT(readability/braces)
} // namespace
/******************
* LevelDecoder *
******************/
-struct LevelDecoder::Impl {
- using RleBitPackedDecoder = ::arrow::util::RleBitPackedDecoder<int16_t>;
- using BitPackedDecoder = ::arrow::util::BitPackedDecoder<int16_t>;
-
- std::variant<RleBitPackedDecoder, BitPackedDecoder> decoder = {};
-
- [[nodiscard]] int GetBatch(int16_t* out, int batch_size) {
- return std::visit([&](auto& dec) { return dec.GetBatch(out, batch_size);
}, decoder);
- }
+// Replacement for legacy LevelDecoder
+using NewLevelDecoder = PageLevelDecoder<>;
Review Comment:
Went with `PageLevelToIntDecoder` to mirror `PageLevelToBitmapDecoder`.
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