Method into_builder

arrow-array/src/array/byte_array.rs:373–452

Returns `GenericByteBuilder` of this byte array for mutating its values if the underlying offset and data buffers are not shared by others.

(self)

    /// Returns `GenericByteBuilder` of this byte array for mutating its values if the underlying
    /// offset and data buffers are not shared by others.
    pub fn into_builder(self) -> Result<GenericByteBuilder<T>, Self> {
        let len = self.len();
        let value_len = T::Offset::as_usize(self.value_offsets()[len] - self.value_offsets()[0]);

        let data = self.into_data();
        let null_bit_buffer = data.nulls().map(|b| b.inner().sliced());

        let element_len = std::mem::size_of::<T::Offset>();
        let offset_buffer = data.buffers()[0]
            .slice_with_length(data.offset() * element_len, (len + 1) * element_len);

        let element_len = std::mem::size_of::<u8>();
        let value_buffer = data.buffers()[1]
            .slice_with_length(data.offset() * element_len, value_len * element_len);

        drop(data);

        let try_mutable_null_buffer = match null_bit_buffer {
            None => Ok(None),
            Some(null_buffer) => {
                // Null buffer exists, tries to make it mutable
                null_buffer.into_mutable().map(Some)
            }
        };

        let try_mutable_buffers = match try_mutable_null_buffer {
            Ok(mutable_null_buffer) => {
                // Got mutable null buffer, tries to get mutable value buffer
                let try_mutable_offset_buffer = offset_buffer.into_mutable();
                let try_mutable_value_buffer = value_buffer.into_mutable();

                // try_mutable_offset_buffer.map(...).map_err(...) doesn't work as the compiler complains
                // mutable_null_buffer is moved into map closure.
                match (try_mutable_offset_buffer, try_mutable_value_buffer) {
                    (Ok(mutable_offset_buffer), Ok(mutable_value_buffer)) => unsafe {
                        Ok(GenericByteBuilder::<T>::new_from_buffer(
                            mutable_offset_buffer,
                            mutable_value_buffer,
                            mutable_null_buffer,
                        ))
                    },
                    (Ok(mutable_offset_buffer), Err(value_buffer)) => Err((
                        mutable_offset_buffer.into(),
                        value_buffer,
                        mutable_null_buffer.map(|b| b.into()),
                    )),
                    (Err(offset_buffer), Ok(mutable_value_buffer)) => Err((
                        offset_buffer,
                        mutable_value_buffer.into(),
                        mutable_null_buffer.map(|b| b.into()),
                    )),
                    (Err(offset_buffer), Err(value_buffer)) => Err((
                        offset_buffer,
                        value_buffer,
                        mutable_null_buffer.map(|b| b.into()),
                    )),
                }
            }