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// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements. See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership. The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied. See the License for the
// specific language governing permissions and limitations
// under the License.
use crate::builder::ArrayBuilder;
use crate::{ArrayRef, NullArray};
use arrow_data::ArrayData;
use arrow_schema::DataType;
use std::any::Any;
use std::sync::Arc;
/// Builder for [`NullArray`]
///
/// # Example
///
/// Create a `NullArray` from a `NullBuilder`
///
/// ```
///
/// # use arrow_array::{Array, NullArray, builder::NullBuilder};
///
/// let mut b = NullBuilder::new();
/// b.append_empty_value();
/// b.append_null();
/// b.append_nulls(3);
/// b.append_empty_values(3);
/// let arr = b.finish();
///
/// assert_eq!(8, arr.len());
/// assert_eq!(0, arr.null_count());
/// ```
#[derive(Debug)]
pub struct NullBuilder {
len: usize,
}
impl Default for NullBuilder {
fn default() -> Self {
Self::new()
}
}
impl NullBuilder {
/// Creates a new null builder
pub fn new() -> Self {
Self { len: 0 }
}
/// Creates a new null builder with space for `capacity` elements without re-allocating
pub fn with_capacity(capacity: usize) -> Self {
Self { len: capacity }
}
/// Returns the capacity of this builder measured in slots of type `T`
pub fn capacity(&self) -> usize {
self.len
}
/// Appends a null slot into the builder
#[inline]
pub fn append_null(&mut self) {
self.len += 1;
}
/// Appends `n` `null`s into the builder.
#[inline]
pub fn append_nulls(&mut self, n: usize) {
self.len += n;
}
/// Appends a null slot into the builder
#[inline]
pub fn append_empty_value(&mut self) {
self.append_null();
}
/// Appends `n` `null`s into the builder.
#[inline]
pub fn append_empty_values(&mut self, n: usize) {
self.append_nulls(n);
}
/// Builds the [NullArray] and reset this builder.
pub fn finish(&mut self) -> NullArray {
let len = self.len();
let builder = ArrayData::new_null(&DataType::Null, len).into_builder();
let array_data = unsafe { builder.build_unchecked() };
NullArray::from(array_data)
}
/// Builds the [NullArray] without resetting the builder.
pub fn finish_cloned(&self) -> NullArray {
let len = self.len();
let builder = ArrayData::new_null(&DataType::Null, len).into_builder();
let array_data = unsafe { builder.build_unchecked() };
NullArray::from(array_data)
}
}
impl ArrayBuilder for NullBuilder {
/// Returns the builder as a non-mutable `Any` reference.
fn as_any(&self) -> &dyn Any {
self
}
/// Returns the builder as a mutable `Any` reference.
fn as_any_mut(&mut self) -> &mut dyn Any {
self
}
/// Returns the boxed builder as a box of `Any`.
fn into_box_any(self: Box<Self>) -> Box<dyn Any> {
self
}
/// Returns the number of array slots in the builder
fn len(&self) -> usize {
self.len
}
/// Builds the array and reset this builder.
fn finish(&mut self) -> ArrayRef {
Arc::new(self.finish())
}
/// Builds the array without resetting the builder.
fn finish_cloned(&self) -> ArrayRef {
Arc::new(self.finish_cloned())
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::Array;
#[test]
fn test_null_array_builder() {
let mut builder = NullArray::builder(10);
builder.append_null();
builder.append_nulls(4);
builder.append_empty_value();
builder.append_empty_values(4);
let arr = builder.finish();
assert_eq!(20, arr.len());
assert_eq!(0, arr.offset());
assert_eq!(0, arr.null_count());
assert!(arr.is_nullable());
}
#[test]
fn test_null_array_builder_finish_cloned() {
let mut builder = NullArray::builder(16);
builder.append_null();
builder.append_empty_value();
builder.append_empty_values(3);
let mut array = builder.finish_cloned();
assert_eq!(21, array.len());
builder.append_empty_values(5);
array = builder.finish();
assert_eq!(26, array.len());
}
}