-
Notifications
You must be signed in to change notification settings - Fork 13
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
Consolidate common RLE decoding logic into new GenericRle trait
- Loading branch information
Showing
5 changed files
with
151 additions
and
114 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,99 @@ | ||
| // 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::error::{OutOfSpecSnafu, Result}; | ||
|
|
||
| use super::PrimitiveValueDecoder; | ||
|
|
||
| mod sealed { | ||
| use std::io::Read; | ||
|
|
||
| use crate::encoding::{ | ||
| byte::ByteRleDecoder, | ||
| integer::{rle_v1::RleV1Decoder, rle_v2::RleV2Decoder, EncodingSign, NInt}, | ||
| }; | ||
|
|
||
| pub trait Rle {} | ||
|
|
||
| impl<R: Read> Rle for ByteRleDecoder<R> {} | ||
| impl<N: NInt, R: Read, S: EncodingSign> Rle for RleV1Decoder<N, R, S> {} | ||
| impl<N: NInt, R: Read, S: EncodingSign> Rle for RleV2Decoder<N, R, S> {} | ||
| } | ||
|
|
||
| /// Generic decoding behaviour for run length encoded values, such as integers (v1 and v2) | ||
| /// and bytes. | ||
| /// | ||
| /// Assumes an internal buffer which acts like a (single headed) queue where values are first | ||
| /// decoded into, before being copied out into the output buffer (usually an Arrow array). | ||
| pub trait GenericRle<V: Copy> { | ||
| /// Consume N elements from internal buffer to signify the values having been copied out. | ||
| fn advance(&mut self, n: usize); | ||
|
|
||
| /// All values available in internal buffer, respecting the current advancement level. | ||
| fn available(&self) -> &[V]; | ||
|
|
||
| /// This should clear the internal buffer and populate it with the next round of decoded | ||
| /// values. | ||
| // TODO: Have a version that copies directly into the output buffer (e.g. Arrow array). | ||
| // Currently we always decode to the internal buffer first, even if we can copy | ||
| // directly to the output and skip the middle man. Ideally the internal buffer | ||
| // should only be used for leftovers between calls to PrimitiveValueDecoder::decode. | ||
| fn decode_batch(&mut self) -> Result<()>; | ||
| } | ||
|
|
||
| impl<V: Copy, G: GenericRle<V> + sealed::Rle> PrimitiveValueDecoder<V> for G { | ||
| fn decode(&mut self, out: &mut [V]) -> Result<()> { | ||
| let available = self.available(); | ||
| // If we have enough leftover to copy, can skip decoding more. | ||
| if available.len() >= out.len() { | ||
| out.copy_from_slice(&available[..out.len()]); | ||
| self.advance(out.len()); | ||
| return Ok(()); | ||
| } | ||
|
|
||
| // Otherwise progressively decode and copy over chunks. | ||
| let len_to_copy = out.len(); | ||
| let mut copied = 0; | ||
| while copied < len_to_copy { | ||
| if self.available().is_empty() { | ||
| self.decode_batch()?; | ||
| } | ||
|
|
||
| let copying = self.available().len(); | ||
| // At most, we fill to exact length of output buffer (don't overflow). | ||
| let copying = copying.min(len_to_copy - copied); | ||
|
|
||
| let out = &mut out[copied..]; | ||
| out[..copying].copy_from_slice(&self.available()[..copying]); | ||
|
|
||
| copied += copying; | ||
| self.advance(copying); | ||
| } | ||
|
|
||
| // We always expect to be able to fill the output buffer; it is up to the | ||
| // caller to control that size. | ||
| if copied != out.len() { | ||
| // TODO: more descriptive error | ||
| OutOfSpecSnafu { | ||
| msg: "Array length less than expected", | ||
| } | ||
| .fail() | ||
| } else { | ||
| Ok(()) | ||
| } | ||
| } | ||
| } |