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fixed.rs
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fixed.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.
use crate::array::PrimitiveArray;
use crate::compute::SortOptions;
use crate::datatypes::ArrowPrimitiveType;
use crate::row::Rows;
use crate::util::decimal::{Decimal128, Decimal256};
use half::f16;
/// Encodes a value of a particular fixed width type into bytes according to the rules
/// described on [`super::RowConverter`]
pub trait FixedLengthEncoding<const N: usize>: Copy {
fn encode(self) -> [u8; N];
}
impl FixedLengthEncoding<1> for bool {
fn encode(self) -> [u8; 1] {
[self as u8]
}
}
macro_rules! encode_signed {
($n:expr, $t:ty) => {
impl FixedLengthEncoding<$n> for $t {
fn encode(self) -> [u8; $n] {
let mut b = self.to_be_bytes();
// Toggle top "sign" bit to ensure consistent sort order
b[0] ^= 0x80;
b
}
}
};
}
encode_signed!(1, i8);
encode_signed!(2, i16);
encode_signed!(4, i32);
encode_signed!(8, i64);
encode_signed!(16, i128);
macro_rules! encode_unsigned {
($n:expr, $t:ty) => {
impl FixedLengthEncoding<$n> for $t {
fn encode(self) -> [u8; $n] {
self.to_be_bytes()
}
}
};
}
encode_unsigned!(1, u8);
encode_unsigned!(2, u16);
encode_unsigned!(4, u32);
encode_unsigned!(8, u64);
impl FixedLengthEncoding<2> for f16 {
fn encode(self) -> [u8; 2] {
// https://github.com/rust-lang/rust/blob/9c20b2a8cc7588decb6de25ac6a7912dcef24d65/library/core/src/num/f32.rs#L1176-L1260
let s = self.to_bits() as i16;
let val = s ^ (((s >> 15) as u16) >> 1) as i16;
val.encode()
}
}
impl FixedLengthEncoding<4> for f32 {
fn encode(self) -> [u8; 4] {
// https://github.com/rust-lang/rust/blob/9c20b2a8cc7588decb6de25ac6a7912dcef24d65/library/core/src/num/f32.rs#L1176-L1260
let s = self.to_bits() as i32;
let val = s ^ (((s >> 31) as u32) >> 1) as i32;
val.encode()
}
}
impl FixedLengthEncoding<8> for f64 {
fn encode(self) -> [u8; 8] {
// https://github.com/rust-lang/rust/blob/9c20b2a8cc7588decb6de25ac6a7912dcef24d65/library/core/src/num/f32.rs#L1176-L1260
let s = self.to_bits() as i64;
let val = s ^ (((s >> 63) as u64) >> 1) as i64;
val.encode()
}
}
impl FixedLengthEncoding<16> for Decimal128 {
fn encode(self) -> [u8; 16] {
let mut val = *self.raw_value();
// Convert to big endian representation
val.reverse();
// Toggle top "sign" bit to ensure consistent sort order
val[0] ^= 0x80;
val
}
}
impl FixedLengthEncoding<32> for Decimal256 {
fn encode(self) -> [u8; 32] {
let mut val = *self.raw_value();
// Convert to big endian representation
val.reverse();
// Toggle top "sign" bit to ensure consistent sort order
val[0] ^= 0x80;
val
}
}
/// Returns the total encoded length (including null byte) for a value of type `T::Native`
pub const fn encoded_len<T: ArrowPrimitiveType>(_col: &PrimitiveArray<T>) -> usize {
std::mem::size_of::<T::Native>() + 1
}
/// Fixed width types are encoded as
///
/// - 1 byte `0` if null or `1` if valid
/// - bytes of [`FixedLengthEncoding`]
pub fn encode<
const N: usize,
T: FixedLengthEncoding<N>,
I: IntoIterator<Item = Option<T>>,
>(
out: &mut Rows,
i: I,
opts: SortOptions,
) {
for (offset, maybe_val) in out.offsets.iter_mut().skip(1).zip(i) {
let end_offset = *offset + N + 1;
if let Some(val) = maybe_val {
let to_write = &mut out.buffer[*offset..end_offset];
to_write[0] = 1;
let mut encoded = val.encode();
if opts.descending {
// Flip bits to reverse order
encoded.iter_mut().for_each(|v| *v = !*v)
}
to_write[1..].copy_from_slice(&encoded)
} else if !opts.nulls_first {
out.buffer[*offset] = 0xFF;
}
*offset = end_offset;
}
}