arrow 20.0.0

Rust implementation of Apache Arrow
Documentation 
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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::datatypes::DataType;
use half::f16;

/// A type that Rust's custom allocator knows how to allocate and deallocate.
/// This is implemented for all Arrow's physical types whose in-memory representation
/// matches Rust's physical types. Consider this trait sealed.
/// # Safety
/// Do not implement this trait.
pub unsafe trait NativeType:
    Sized + Copy + std::fmt::Debug + std::fmt::Display + PartialEq + Default + Sized + 'static
{
    type Bytes: AsRef<[u8]>;

    /// Whether a DataType is a valid type for this physical representation.
    fn is_valid(data_type: &DataType) -> bool;

    /// How this type represents itself as bytes in little endianess.
    /// This is used for IPC, where data is communicated with a specific endianess.
    fn to_le_bytes(&self) -> Self::Bytes;
}

macro_rules! create_native {
    ($native_ty:ty,$($impl_pattern:pat_param)|+) => {
        unsafe impl NativeType for $native_ty {
            type Bytes = [u8; std::mem::size_of::<Self>()];

            #[inline]
            fn to_le_bytes(&self) -> Self::Bytes {
                Self::to_le_bytes(*self)
            }

            #[inline]
            fn is_valid(data_type: &DataType) -> bool {
                matches!(data_type, $($impl_pattern)|+)
            }
        }
    };
}

create_native!(u8, DataType::UInt8);
create_native!(u16, DataType::UInt16);
create_native!(u32, DataType::UInt32);
create_native!(u64, DataType::UInt64);
create_native!(i8, DataType::Int8);
create_native!(i16, DataType::Int16);
create_native!(
    i32,
    DataType::Int32 | DataType::Date32 | DataType::Time32(_)
);
create_native!(
    i64,
    DataType::Int64 | DataType::Date64 | DataType::Time64(_) | DataType::Timestamp(_, _)
);
create_native!(f16, DataType::Float16);
create_native!(f32, DataType::Float32);
create_native!(f64, DataType::Float64);