AntoinePrv commented on code in PR #50422:
URL: https://github.com/apache/arrow/pull/50422#discussion_r3550170599
##########
cpp/src/arrow/util/rle_encoding_internal.h:
##########
@@ -515,6 +573,71 @@ class RleBitPackedDecoder {
int64_t valid_bits_offset, rle_size_t
null_count);
};
+/// Minimal decoder for legacy bit packed encoding (BIT_PACKED = 4).
+///
+/// The number of values that the decoder can represent is up to 2^31 - 1.
+template <typename T>
+class BitPackedDecoder : private BitPackedRunDecoder<T> {
+ private:
+ using Base = BitPackedRunDecoder<T>;
+
+ public:
+ /// The type in which the data should be decoded.
+ using value_type = T;
+
+ using Base::Advance;
+
+ BitPackedDecoder() noexcept = default;
+
+ /// Create a decoder object.
+ ///
+ /// data and data_size are the raw bytes to decode.
+ /// value_bit_width is the size in bits of each encoded value.
+ BitPackedDecoder(const uint8_t* data, rle_size_t data_size,
+ rle_size_t value_bit_width) noexcept {
+ Reset(data, data_size, value_bit_width);
+ }
+
+ void Reset(const uint8_t* data, rle_size_t data_size,
+ rle_size_t value_bit_width) noexcept {
+ value_bit_width_ = value_bit_width;
+ const auto value_count = (static_cast<int64_t>(data_size) * 8) /
value_bit_width;
+ ARROW_DCHECK_LE(value_count, std::numeric_limits<rle_size_t>::max());
Review Comment:
Done.
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