Method remainder_bits

arrow-buffer/src/util/bit_chunk_iterator.rs:267–291

(&self)

    /// Returns the bitmask of remaining bits
    #[inline]
    pub fn remainder_bits(&self) -> u64 {
        let bit_len = self.remainder_len;
        if bit_len == 0 {
            0
        } else {
            let bit_offset = self.bit_offset;
            // number of bytes to read
            // might be one more than sizeof(u64) if the offset is in the middle of a byte
            let byte_len = ceil(bit_len + bit_offset, 8);
            // pointer to remainder bytes after all complete chunks
            let base = unsafe {
                self.buffer
                    .as_ptr()
                    .add(self.chunk_len * std::mem::size_of::<u64>())
            };

            let mut bits = unsafe { std::ptr::read(base) } as u64 >> bit_offset;
            for i in 1..byte_len {
                let byte = unsafe { std::ptr::read(base.add(i)) };
                bits |= (byte as u64) << (i * 8 - bit_offset);
            }

            bits & ((1 << bit_len) - 1)
        }
    }

    /// Return the number of `u64` that are needed to represent all bits
    /// (including remainder).