Method from_iter

arrow-buffer/src/buffer/mutable.rs:1143–1193

(iter: I)

/// Creating a `MutableBuffer` instance by setting bits according to the boolean values
impl std::iter::FromIterator<bool> for MutableBuffer {
    fn from_iter<I>(iter: I) -> Self
    where
        I: IntoIterator<Item = bool>,
    {
        let mut iterator = iter.into_iter();
        let mut result = {
            let byte_capacity: usize = iterator.size_hint().0.saturating_add(7) / 8;
            MutableBuffer::new(byte_capacity)
        };

        loop {
            let mut exhausted = false;
            let mut byte_accum: u8 = 0;
            let mut mask: u8 = 1;

            //collect (up to) 8 bits into a byte
            while mask != 0 {
                if let Some(value) = iterator.next() {
                    byte_accum |= match value {
                        true => mask,
                        false => 0,
                    };
                    mask <<= 1;
                } else {
                    exhausted = true;
                    break;
                }
            }

            // break if the iterator was exhausted before it provided a bool for this byte
            if exhausted && mask == 1 {
                break;
            }

            //ensure we have capacity to write the byte
            if result.len() == result.capacity() {
                //no capacity for new byte, allocate 1 byte more (plus however many more the iterator advertises)
                let additional_byte_capacity = 1usize.saturating_add(
                    iterator.size_hint().0.saturating_add(7) / 8, //convert bit count to byte count, rounding up
                );
                result.reserve(additional_byte_capacity)
            }

            // Soundness: capacity was allocated above
            unsafe { result.push_unchecked(byte_accum) };
            if exhausted {
                break;
            }
        }
        result
    }
}

impl<T: ArrowNativeType> std::iter::FromIterator<T> for MutableBuffer {