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⚡ Optimize DeflateEncoder to safely avoid zero-filling output buffers #378

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⚡ Optimize DeflateEncoder to safely avoid zero-filling output buffers #378

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79 changes: 28 additions & 51 deletions src/stream.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,6 @@ use crate::decompress::{DecompressResult, Decompressor, DecompressorState};
use rayon::prelude::*;
use std::cmp::min;
use std::io::{self, Read, Write};
use std::mem::MaybeUninit;

/// A streaming encoder that compresses data using the DEFLATE algorithm.
///
Expand Down Expand Up @@ -63,32 +62,25 @@ impl<W: Write + Send> DeflateEncoder<W> {
let compressor = &mut self.compressors[0];
let output = &mut self.output_buffers[0];
let bound = Compressor::deflate_compress_bound(chunk.len());
if output.len() < bound {
output
.try_reserve(bound - output.len())
.map_err(|e| io::Error::new(io::ErrorKind::Other, e))?;
// SAFETY: We just reserved sufficient capacity. The compressor writes to
// the buffer using `MaybeUninit` pointers, so uninitialized memory is fine.
unsafe {
output.set_len(bound);
}
}
output.clear();
output
.try_reserve(bound)
.map_err(|e| io::Error::new(io::ErrorKind::Other, e))?;

let mode = if final_block {
crate::compress::FlushMode::Finish
} else {
crate::compress::FlushMode::Sync
};
let out_uninit = unsafe {
std::slice::from_raw_parts_mut(
output.as_mut_ptr() as *mut MaybeUninit<u8>,
output.len(),
)
};

let out_uninit = output.spare_capacity_mut();
let (res, size, _) = compressor.compress(chunk, out_uninit, mode);
if res == CompressResult::Success {
unsafe {
output.set_len(size);
}
if let Some(writer) = &mut self.writer {
writer.write_all(&output[..size])?;
writer.write_all(output)?;
}
} else {
return Err(io::Error::new(io::ErrorKind::Other, "Compression failed"));
Expand All @@ -101,30 +93,23 @@ impl<W: Write + Send> DeflateEncoder<W> {
.enumerate()
.map(|(i, ((&chunk, compressor), output))| {
let bound = Compressor::deflate_compress_bound(chunk.len());
if output.len() < bound {
output
.try_reserve(bound - output.len())
.map_err(|e| io::Error::new(io::ErrorKind::Other, e))?;
// SAFETY: We just reserved sufficient capacity. The compressor writes to
// the buffer using `MaybeUninit` pointers, so uninitialized memory is fine.
unsafe {
output.set_len(bound);
}
}
output.clear();
output
.try_reserve(bound)
.map_err(|e| io::Error::new(io::ErrorKind::Other, e))?;

let mode = if final_block && i == num_chunks - 1 {
crate::compress::FlushMode::Finish
} else {
crate::compress::FlushMode::Sync
};
let out_uninit = unsafe {
std::slice::from_raw_parts_mut(
output.as_mut_ptr() as *mut MaybeUninit<u8>,
output.len(),
)
};

let out_uninit = output.spare_capacity_mut();
let (res, size, _) = compressor.compress(chunk, out_uninit, mode);
if res == CompressResult::Success {
unsafe {
output.set_len(size);
}
Ok(size)
} else {
Err(io::Error::new(io::ErrorKind::Other, "Compression failed"))
Expand All @@ -150,32 +135,24 @@ impl<W: Write + Send> DeflateEncoder<W> {
let compressor = &mut self.compressors[0];
let output = &mut self.output_buffers[0];
let bound = Compressor::deflate_compress_bound(self.buffer.len());
if output.len() < bound {
output
.try_reserve(bound - output.len())
.map_err(|e| io::Error::new(io::ErrorKind::Other, e))?;
// SAFETY: We just reserved sufficient capacity. The compressor writes to
// the buffer using `MaybeUninit` pointers, so uninitialized memory is fine.
unsafe {
output.set_len(bound);
}
}
output.clear();
output
.try_reserve(bound)
.map_err(|e| io::Error::new(io::ErrorKind::Other, e))?;

let mode = if final_block {
crate::compress::FlushMode::Finish
} else {
crate::compress::FlushMode::Sync
};
let out_uninit = unsafe {
std::slice::from_raw_parts_mut(
output.as_mut_ptr() as *mut MaybeUninit<u8>,
output.len(),
)
};
let out_uninit = output.spare_capacity_mut();
let (res, size, _) = compressor.compress(&self.buffer, out_uninit, mode);
if res == CompressResult::Success {
unsafe {
output.set_len(size);
}
if let Some(writer) = &mut self.writer {
writer.write_all(&output[..size])?;
writer.write_all(output)?;
}
} else {
return Err(io::Error::new(io::ErrorKind::Other, "Compression failed"));
Expand Down