felipecrv commented on code in PR #35814: URL: https://github.com/apache/arrow/pull/35814#discussion_r1212057047
########## cpp/src/arrow/util/hashing.h: ########## @@ -63,6 +63,27 @@ typedef uint64_t hash_t; template <uint64_t AlgNum> inline hash_t ComputeStringHash(const void* data, int64_t length); +/// \brief A hash function for bitmaps that can handle offsets and lengths in +/// terms of number of bits. The hash only depends on the bits actually hashed. +/// +/// The key (a bitmap) is read as a sequence of 64-bit words before the trailing +/// bytes. So if the input is 64-bit aligned, all memory accesses are aligned. +/// +/// It's the caller's responsibility to ensure that bits_offset + num_bits are +/// readable from the bitmap. +/// +/// \pre bits_offset >= 0 +/// \pre num_bits >= 0 +/// \pre (bits_offset + num_bits + 7) / 8 <= length +/// +/// \param bitmap The pointer to the bitmap. +/// \param length The length of the bitmap in bytes. +/// \param seed The seed for the hash function (useful when chaining hash functions). +/// \param bits_offset The offset in bits relative to the start of the bitmap. +/// \param num_bits The number of bits after the offset to be hashed. +ARROW_EXPORT hash_t ComputeBitmapHash(const uint8_t* bitmap, int64_t length, hash_t seed, Review Comment: OK. I'm removing the `length` parameter now. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: github-unsubscr...@arrow.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
