vortex-zigzag 0.72.0

Vortex zig zag array
Documentation 
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// SPDX-License-Identifier: Apache-2.0
// SPDX-FileCopyrightText: Copyright the Vortex contributors

use vortex_array::ArrayView;
use vortex_array::IntoArray;
use vortex_array::arrays::Primitive;
use vortex_array::arrays::PrimitiveArray;
use vortex_array::dtype::NativePType;
use vortex_array::dtype::PType;
use vortex_array::validity::Validity;
use vortex_buffer::BufferMut;
use vortex_error::VortexExpect;
use vortex_error::VortexResult;
use vortex_error::vortex_bail;
use vortex_error::vortex_panic;
use zigzag::ZigZag as ExternalZigZag;

use crate::ZigZag;
use crate::ZigZagArray;
pub fn zigzag_encode(parray: ArrayView<'_, Primitive>) -> VortexResult<ZigZagArray> {
    let parray = parray.into_owned();
    let validity = parray.validity()?;
    let encoded = match parray.ptype() {
        PType::I8 => zigzag_encode_primitive::<i8>(parray.into_buffer_mut(), validity),
        PType::I16 => zigzag_encode_primitive::<i16>(parray.into_buffer_mut(), validity),
        PType::I32 => zigzag_encode_primitive::<i32>(parray.into_buffer_mut(), validity),
        PType::I64 => zigzag_encode_primitive::<i64>(parray.into_buffer_mut(), validity),
        _ => vortex_bail!(
            "ZigZag can only encode signed integers, got {}",
            parray.ptype()
        ),
    };
    ZigZag::try_new(encoded.into_array())
}

fn zigzag_encode_primitive<T: ExternalZigZag + NativePType>(
    values: BufferMut<T>,
    validity: Validity,
) -> PrimitiveArray
where
    <T as ExternalZigZag>::UInt: NativePType,
{
    PrimitiveArray::new(
        values.map_each_in_place(|v| T::encode(v)).freeze(),
        validity,
    )
}

pub fn zigzag_decode(parray: PrimitiveArray) -> PrimitiveArray {
    let validity = parray
        .validity()
        .vortex_expect("zigzag validity should be derivable");
    match parray.ptype() {
        PType::U8 => zigzag_decode_primitive::<i8>(parray.into_buffer_mut(), validity),
        PType::U16 => zigzag_decode_primitive::<i16>(parray.into_buffer_mut(), validity),
        PType::U32 => zigzag_decode_primitive::<i32>(parray.into_buffer_mut(), validity),
        PType::U64 => zigzag_decode_primitive::<i64>(parray.into_buffer_mut(), validity),
        _ => vortex_panic!(
            "ZigZag can only decode unsigned integers, got {}",
            parray.ptype()
        ),
    }
}

fn zigzag_decode_primitive<T: ExternalZigZag + NativePType>(
    values: BufferMut<T::UInt>,
    validity: Validity,
) -> PrimitiveArray
where
    <T as ExternalZigZag>::UInt: NativePType,
{
    PrimitiveArray::new(
        values.map_each_in_place(|v| T::decode(v)).freeze(),
        validity,
    )
}

#[cfg(test)]
mod test {
    use rstest::rstest;
    use vortex_array::IntoArray;
    use vortex_array::LEGACY_SESSION;
    use vortex_array::VortexSessionExecute;
    use vortex_array::assert_arrays_eq;

    use super::*;
    use crate::ZigZag;

    #[rstest]
    #[case::i8(PrimitiveArray::from_iter(-100_i8..100))]
    #[case::i16(PrimitiveArray::from_iter(-100_i16..100))]
    #[case::i32(PrimitiveArray::from_iter(-100_i32..100))]
    #[case::i64(PrimitiveArray::from_iter(-100_i64..100))]
    fn test_compress(#[case] input: PrimitiveArray) {
        let mut ctx = LEGACY_SESSION.create_execution_ctx();
        let compressed = zigzag_encode(input.as_view()).unwrap().into_array();
        assert!(compressed.is::<ZigZag>());
        let decompressed = compressed.execute::<PrimitiveArray>(&mut ctx).unwrap();
        assert_arrays_eq!(decompressed, input);
    }
}