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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,
compute::sort::SortOptions,
types::{f16, i256, NativeType},
};
use super::{null_sentinel, Rows};
pub trait FromSlice {
fn from_slice(slice: &[u8], invert: bool) -> Self;
}
impl<const N: usize> FromSlice for [u8; N] {
#[inline]
fn from_slice(slice: &[u8], invert: bool) -> Self {
let mut t: Self = slice.try_into().unwrap();
if invert {
t.iter_mut().for_each(|o| *o = !*o);
}
t
}
}
/// Encodes a value of a particular fixed width type into bytes according to the rules
/// described on [`super::RowConverter`]
pub trait FixedLengthEncoding: Copy {
const ENCODED_LEN: usize = 1 + std::mem::size_of::<Self::Encoded>();
type Encoded: Sized + Copy + FromSlice + AsRef<[u8]> + AsMut<[u8]>;
fn encode(self) -> Self::Encoded;
fn decode(encoded: Self::Encoded) -> Self;
}
impl FixedLengthEncoding for bool {
type Encoded = [u8; 1];
fn encode(self) -> [u8; 1] {
[self as u8]
}
fn decode(encoded: Self::Encoded) -> Self {
encoded[0] != 0
}
}
macro_rules! encode_signed {
($n:expr, $t:ty) => {
impl FixedLengthEncoding for $t {
type Encoded = [u8; $n];
fn encode(self) -> [u8; $n] {
let mut b = self.to_be_bytes();
// Toggle top "sign" bit to ensure consistent sort order
b[0] ^= 0x80;
b
}
fn decode(mut encoded: Self::Encoded) -> Self {
// Toggle top "sign" bit
encoded[0] ^= 0x80;
Self::from_be_bytes(encoded)
}
}
};
}
encode_signed!(1, i8);
encode_signed!(2, i16);
encode_signed!(4, i32);
encode_signed!(8, i64);
encode_signed!(16, i128);
encode_signed!(32, i256);
macro_rules! encode_unsigned {
($n:expr, $t:ty) => {
impl FixedLengthEncoding for $t {
type Encoded = [u8; $n];
fn encode(self) -> [u8; $n] {
self.to_be_bytes()
}
fn decode(encoded: Self::Encoded) -> Self {
Self::from_be_bytes(encoded)
}
}
};
}
encode_unsigned!(1, u8);
encode_unsigned!(2, u16);
encode_unsigned!(4, u32);
encode_unsigned!(8, u64);
impl FixedLengthEncoding for f16 {
type Encoded = [u8; 2];
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()
}
fn decode(encoded: Self::Encoded) -> Self {
let bits = i16::decode(encoded);
let val = bits ^ (((bits >> 15) as u16) >> 1) as i16;
Self::from_bits(val as u16)
}
}
impl FixedLengthEncoding for f32 {
type Encoded = [u8; 4];
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()
}
fn decode(encoded: Self::Encoded) -> Self {
let bits = i32::decode(encoded);
let val = bits ^ (((bits >> 31) as u32) >> 1) as i32;
Self::from_bits(val as u32)
}
}
impl FixedLengthEncoding for f64 {
type Encoded = [u8; 8];
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()
}
fn decode(encoded: Self::Encoded) -> Self {
let bits = i64::decode(encoded);
let val = bits ^ (((bits >> 63) as u64) >> 1) as i64;
Self::from_bits(val as u64)
}
}
/// Returns the total encoded length (including null byte) for a value of type `T::Native`
pub const fn encoded_len<T>(_col: &PrimitiveArray<T>) -> usize
where
T: NativeType + FixedLengthEncoding,
{
T::ENCODED_LEN
}
/// Fixed width types are encoded as
///
/// - 1 byte `0` if null or `1` if valid
/// - bytes of [`FixedLengthEncoding`]
pub fn encode<T: FixedLengthEncoding, 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 + T::ENCODED_LEN;
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.as_mut().iter_mut().for_each(|v| *v = !*v)
}
to_write[1..].copy_from_slice(encoded.as_ref())
} else {
out.buffer[*offset] = null_sentinel(opts);
}
*offset = end_offset;
}
}