[pbs-devel] [PATCH proxmox-backup v2 2/5] tools/compression: add DeflateEncoder and helpers

[Dominik Csapak]

implements a deflate encoder that can compress anything that implements
AsyncRead + Unpin into a file with the helper 'compress'

if the inner type is a Stream, it implements Stream itself, this way
some streaming data can be streamed compressed

Signed-off-by: Dominik Csapak <d.csapak at proxmox.com>
---
 Cargo.toml               |   1 +
 src/tools/compression.rs | 191 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 192 insertions(+)

diff --git a/Cargo.toml b/Cargo.toml
index 69b07d41..2f59b310 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -29,6 +29,7 @@ bitflags = "1.2.1"
 bytes = "1.0"
 crc32fast = "1"
 endian_trait = { version = "0.6", features = ["arrays"] }
+flate2 = "1.0"
 anyhow = "1.0"
 futures = "0.3"
 h2 = { version = "0.3", features = [ "stream" ] }
diff --git a/src/tools/compression.rs b/src/tools/compression.rs
index fe15e8fc..cc6ea732 100644
--- a/src/tools/compression.rs
+++ b/src/tools/compression.rs
@@ -1,5 +1,17 @@
+use std::io;
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
 use anyhow::{bail, Error};
+use bytes::Bytes;
+use flate2::{Compress, Compression, FlushCompress};
+use futures::ready;
+use futures::stream::Stream;
 use hyper::header;
+use tokio::io::{AsyncRead, AsyncReadExt, AsyncWrite, AsyncWriteExt};
+
+use proxmox::io_format_err;
+use proxmox::tools::byte_buffer::ByteBuffer;
 
 /// Possible Compression Methods, order determines preference (later is preferred)
 #[derive(Eq, Ord, PartialEq, PartialOrd, Debug)]
@@ -35,3 +47,182 @@ impl std::str::FromStr for CompressionMethod {
         }
     }
 }
+
+pub enum Level {
+    Fastest,
+    Best,
+    Default,
+    Precise(u32),
+}
+
+#[derive(Eq, PartialEq)]
+enum EncoderState {
+    Reading,
+    Writing,
+    Flushing,
+    Finished,
+}
+
+pub struct DeflateEncoder<T> {
+    inner: T,
+    compressor: Compress,
+    buffer: ByteBuffer,
+    input_buffer: Bytes,
+    state: EncoderState,
+}
+
+impl<T> DeflateEncoder<T> {
+    pub fn new(inner: T) -> Self {
+        Self::with_quality(inner, Level::Default)
+    }
+
+    pub fn with_quality(inner: T, level: Level) -> Self {
+        let level = match level {
+            Level::Fastest => Compression::fast(),
+            Level::Best => Compression::best(),
+            Level::Default => Compression::new(3),
+            Level::Precise(val) => Compression::new(val),
+        };
+
+        Self {
+            inner,
+            compressor: Compress::new(level, false),
+            buffer: ByteBuffer::with_capacity(8192),
+            input_buffer: Bytes::new(),
+            state: EncoderState::Reading,
+        }
+    }
+
+    pub fn total_in(&self) -> u64 {
+        self.compressor.total_in()
+    }
+
+    pub fn total_out(&self) -> u64 {
+        self.compressor.total_out()
+    }
+
+    pub fn into_inner(self) -> T {
+        self.inner
+    }
+
+    fn encode(
+        &mut self,
+        inbuf: &[u8],
+        flush: FlushCompress,
+    ) -> Result<(usize, flate2::Status), io::Error> {
+        let old_in = self.compressor.total_in();
+        let old_out = self.compressor.total_out();
+        let res = self
+            .compressor
+            .compress(&inbuf[..], self.buffer.get_free_mut_slice(), flush)?;
+        let new_in = (self.compressor.total_in() - old_in) as usize;
+        let new_out = (self.compressor.total_out() - old_out) as usize;
+        self.buffer.add_size(new_out);
+
+        Ok((new_in, res))
+    }
+}
+
+impl DeflateEncoder<Vec<u8>> {
+    // assume small files
+    pub async fn compress_vec<R>(&mut self, reader: &mut R, size_hint: usize) -> Result<(), Error>
+    where
+        R: AsyncRead + Unpin,
+    {
+        let mut buffer = Vec::with_capacity(size_hint);
+        reader.read_to_end(&mut buffer).await?;
+        self.inner.reserve(size_hint); // should be enough since we want smalller files
+        self.compressor.compress_vec(&buffer[..], &mut self.inner, FlushCompress::Finish)?;
+        Ok(())
+    }
+}
+
+impl<T: AsyncWrite + Unpin> DeflateEncoder<T> {
+    pub async fn compress<R>(&mut self, reader: &mut R) -> Result<(), Error>
+    where
+        R: AsyncRead + Unpin,
+    {
+        let mut buffer = ByteBuffer::with_capacity(8192);
+        let mut eof = false;
+        loop {
+            if !eof && !buffer.is_full() {
+                let read = buffer.read_from_async(reader).await?;
+                if read == 0 {
+                    eof = true;
+                }
+            }
+            let (read, _res) = self.encode(&buffer[..], FlushCompress::None)?;
+            buffer.consume(read);
+
+            self.inner.write_all(&self.buffer[..]).await?;
+            self.buffer.clear();
+
+            if buffer.is_empty() && eof {
+                break;
+            }
+        }
+
+        loop {
+            let (_read, res) = self.encode(&[][..], FlushCompress::Finish)?;
+            self.inner.write_all(&self.buffer[..]).await?;
+            self.buffer.clear();
+            if res == flate2::Status::StreamEnd {
+                break;
+            }
+        }
+
+        Ok(())
+    }
+}
+
+impl<T, O> Stream for DeflateEncoder<T>
+where
+    T: Stream<Item = Result<O, io::Error>> + Unpin,
+    O: Into<Bytes>
+{
+    type Item = Result<Bytes, io::Error>;
+
+    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        let this = self.get_mut();
+
+        loop {
+            match this.state {
+                EncoderState::Reading => {
+                    if let Some(res) = ready!(Pin::new(&mut this.inner).poll_next(cx)) {
+                        let buf = res?;
+                        this.input_buffer = buf.into();
+                        this.state = EncoderState::Writing;
+                    } else {
+                        this.state = EncoderState::Flushing;
+                    }
+                }
+                EncoderState::Writing => {
+                    if this.input_buffer.is_empty() {
+                        return Poll::Ready(Some(Err(io_format_err!("empty input during write"))));
+                    }
+                    let mut buf = this.input_buffer.split_off(0);
+                    let (read, res) = this.encode(&buf[..], FlushCompress::None)?;
+                    this.input_buffer = buf.split_off(read);
+                    if this.input_buffer.is_empty() {
+                        this.state = EncoderState::Reading;
+                    }
+                    if this.buffer.is_full() || res == flate2::Status::BufError {
+                        let bytes = this.buffer.remove_data(this.buffer.len()).to_vec();
+                        return Poll::Ready(Some(Ok(bytes.into())));
+                    }
+                }
+                EncoderState::Flushing => {
+                    let (_read, res) = this.encode(&[][..], FlushCompress::Finish)?;
+                    if !this.buffer.is_empty() {
+                        let bytes = this.buffer.remove_data(this.buffer.len()).to_vec();
+                        return Poll::Ready(Some(Ok(bytes.into())));
+                    }
+                    if res == flate2::Status::StreamEnd {
+                        this.state = EncoderState::Finished;
+                    }
+                }
+                EncoderState::Finished => return Poll::Ready(None),
+            }
+        }
+    }
+}
-- 
2.20.1