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length.rs
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length.rs
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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.
//! Defines kernel for length of composite arrays
use crate::{
array::*,
datatypes::DataType,
error::{ArrowError, Result},
types::NativeType,
};
fn unary_offsets_string<O, F>(array: &Utf8Array<O>, op: F) -> PrimitiveArray<O>
where
O: Offset + NativeType,
F: Fn(O) -> O,
{
let values = array
.offsets()
.windows(2)
.map(|offset| op(offset[1] - offset[0]))
.collect::<Vec<_>>();
let data_type = if O::IS_LARGE {
DataType::Int64
} else {
DataType::Int32
};
PrimitiveArray::<O>::new(data_type, values.into(), array.validity().cloned())
}
/// Returns an array of integers with the number of bytes on each string of the array.
pub fn length(array: &dyn Array) -> Result<Box<dyn Array>> {
match array.data_type() {
DataType::Utf8 => {
let array = array.as_any().downcast_ref::<Utf8Array<i32>>().unwrap();
Ok(Box::new(unary_offsets_string::<i32, _>(array, |x| x)))
}
DataType::LargeUtf8 => {
let array = array.as_any().downcast_ref::<Utf8Array<i64>>().unwrap();
Ok(Box::new(unary_offsets_string::<i64, _>(array, |x| x)))
}
_ => Err(ArrowError::InvalidArgumentError(format!(
"length not supported for {:?}",
array.data_type()
))),
}
}
/// Checks if an array of type `datatype` can perform length operation
///
/// # Examples
/// ```
/// use arrow2::compute::length::can_length;
/// use arrow2::datatypes::{DataType};
///
/// let data_type = DataType::Utf8;
/// assert_eq!(can_length(&data_type), true);
///
/// let data_type = DataType::Int8;
/// assert_eq!(can_length(&data_type), false);
/// ```
pub fn can_length(data_type: &DataType) -> bool {
matches!(data_type, DataType::Utf8 | DataType::LargeUtf8)
}