tustvold commented on code in PR #2593: URL: https://github.com/apache/arrow-rs/pull/2593#discussion_r966427967
########## arrow/src/row/fixed.rs: ########## @@ -0,0 +1,146 @@ +// 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; + +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; $n] { + let mut b = self.to_be_bytes(); + // Toggle top bit + b[0] ^= 0x80; + b + } + } + }; +} + +encode_signed!(1, i8); +encode_signed!(2, i16); +encode_signed!(4, i32); +encode_signed!(8, i64); +encode_signed!(16, i128); + +macro_rules! encode_unsigned { + ($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(); + val.reverse(); + val[0] ^= 0x80; + val + } +} + +impl FixedLengthEncoding<32> for Decimal256 { + fn encode(self) -> [u8; 32] { + let mut val = *self.raw_value(); + val.reverse(); + val[0] ^= 0x80; + val + } +} + +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 { + encoded.iter_mut().for_each(|v| *v = !*v) + } + to_write[1..].copy_from_slice(&encoded) Review Comment: Shouldn't be, they are fixed length slices so it should optimise away -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
