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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::{null_sentinel, Rows};
use arrow_array::builder::BufferBuilder;
use arrow_array::{ArrowPrimitiveType, BooleanArray, FixedSizeBinaryArray};
use arrow_buffer::{bit_util, i256, ArrowNativeType, Buffer, MutableBuffer};
use arrow_data::{ArrayData, ArrayDataBuilder};
use arrow_schema::{DataType, SortOptions};
use half::f16;
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: ArrowPrimitiveType,
T::Native: FixedLengthEncoding,
{
T::Native::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;
}
}
pub fn encode_fixed_size_binary(
out: &mut Rows,
array: &FixedSizeBinaryArray,
opts: SortOptions,
) {
let len = array.value_length() as usize;
for (offset, maybe_val) in out.offsets.iter_mut().skip(1).zip(array.iter()) {
let end_offset = *offset + len + 1;
if let Some(val) = maybe_val {
let to_write = &mut out.buffer[*offset..end_offset];
to_write[0] = 1;
to_write[1..].copy_from_slice(&val[..len]);
if opts.descending {
// Flip bits to reverse order
to_write[1..1 + len].iter_mut().for_each(|v| *v = !*v)
}
} else {
out.buffer[*offset] = null_sentinel(opts);
}
*offset = end_offset;
}
}
/// Splits `len` bytes from `src`
#[inline]
fn split_off<'a>(src: &mut &'a [u8], len: usize) -> &'a [u8] {
let v = &src[..len];
*src = &src[len..];
v
}
/// Decodes a `BooleanArray` from rows
pub fn decode_bool(rows: &mut [&[u8]], options: SortOptions) -> BooleanArray {
let true_val = match options.descending {
true => !1,
false => 1,
};
let len = rows.len();
let mut null_count = 0;
let mut nulls = MutableBuffer::new(bit_util::ceil(len, 64) * 8);
let mut values = MutableBuffer::new(bit_util::ceil(len, 64) * 8);
let chunks = len / 64;
let remainder = len % 64;
for chunk in 0..chunks {
let mut null_packed = 0;
let mut values_packed = 0;
for bit_idx in 0..64 {
let i = split_off(&mut rows[bit_idx + chunk * 64], 2);
let (null, value) = (i[0] == 1, i[1] == true_val);
null_count += !null as usize;
null_packed |= (null as u64) << bit_idx;
values_packed |= (value as u64) << bit_idx;
}
nulls.push(null_packed);
values.push(values_packed);
}
if remainder != 0 {
let mut null_packed = 0;
let mut values_packed = 0;
for bit_idx in 0..remainder {
let i = split_off(&mut rows[bit_idx + chunks * 64], 2);
let (null, value) = (i[0] == 1, i[1] == true_val);
null_count += !null as usize;
null_packed |= (null as u64) << bit_idx;
values_packed |= (value as u64) << bit_idx;
}
nulls.push(null_packed);
values.push(values_packed);
}
let builder = ArrayDataBuilder::new(DataType::Boolean)
.len(rows.len())
.null_count(null_count)
.add_buffer(values.into())
.null_bit_buffer(Some(nulls.into()));
// SAFETY:
// Buffers are the correct length
unsafe { BooleanArray::from(builder.build_unchecked()) }
}
/// Decodes a single byte from each row, interpreting `0x01` as a valid value
/// and all other values as a null
///
/// Returns the null count and null buffer
pub fn decode_nulls(rows: &[&[u8]]) -> (usize, Buffer) {
let mut null_count = 0;
let buffer = MutableBuffer::collect_bool(rows.len(), |idx| {
let valid = rows[idx][0] == 1;
null_count += !valid as usize;
valid
})
.into();
(null_count, buffer)
}
/// Decodes a `ArrayData` from rows based on the provided `FixedLengthEncoding` `T`
///
/// # Safety
///
/// `data_type` must be appropriate native type for `T`
unsafe fn decode_fixed<T: FixedLengthEncoding + ArrowNativeType>(
rows: &mut [&[u8]],
data_type: DataType,
options: SortOptions,
) -> ArrayData {
let len = rows.len();
let mut values = BufferBuilder::<T>::new(len);
let (null_count, nulls) = decode_nulls(rows);
for row in rows {
let i = split_off(row, T::ENCODED_LEN);
let value = T::Encoded::from_slice(&i[1..], options.descending);
values.append(T::decode(value));
}
let builder = ArrayDataBuilder::new(data_type)
.len(len)
.null_count(null_count)
.add_buffer(values.finish())
.null_bit_buffer(Some(nulls));
// SAFETY: Buffers correct length
builder.build_unchecked()
}
/// Decodes a `PrimitiveArray` from rows
pub fn decode_primitive<T: ArrowPrimitiveType>(
rows: &mut [&[u8]],
data_type: DataType,
options: SortOptions,
) -> PrimitiveArray<T>
where
T::Native: FixedLengthEncoding,
{
assert_eq!(
std::mem::discriminant(&T::DATA_TYPE),
std::mem::discriminant(&data_type),
);
// SAFETY:
// Validated data type above
unsafe { decode_fixed::<T::Native>(rows, data_type, options).into() }
}
/// Decodes a `FixedLengthBinary` from rows
pub fn decode_fixed_size_binary(
rows: &mut [&[u8]],
size: i32,
options: SortOptions,
) -> FixedSizeBinaryArray {
let len = rows.len();
let mut values = MutableBuffer::new(size as usize * rows.len());
let (null_count, nulls) = decode_nulls(rows);
let encoded_len = size as usize + 1;
for row in rows {
let i = split_off(row, encoded_len);
values.extend_from_slice(&i[1..]);
}
if options.descending {
for v in values.as_slice_mut() {
*v = !*v;
}
}
let builder = ArrayDataBuilder::new(DataType::FixedSizeBinary(size))
.len(len)
.null_count(null_count)
.add_buffer(values.into())
.null_bit_buffer(Some(nulls));
// SAFETY: Buffers correct length
unsafe { builder.build_unchecked().into() }
}