[pbs-devel] [PATCH proxmox v3 3/5] compression: deflate: add a decoder

[Maximiliano Sandoval]

Signed-off-by: Maximiliano Sandoval <m.sandoval at proxmox.com>
---
 .../src/deflate/decompression.rs              | 141 ++++++++++++++++++
 proxmox-compression/src/deflate/mod.rs        |   2 +
 proxmox-compression/src/lib.rs                |   2 +-
 3 files changed, 144 insertions(+), 1 deletion(-)
 create mode 100644 proxmox-compression/src/deflate/decompression.rs

diff --git a/proxmox-compression/src/deflate/decompression.rs b/proxmox-compression/src/deflate/decompression.rs
new file mode 100644
index 00000000..45ed8579
--- /dev/null
+++ b/proxmox-compression/src/deflate/decompression.rs
@@ -0,0 +1,141 @@
+use std::io;
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+use anyhow::Error;
+use bytes::Bytes;
+use flate2::{Decompress, FlushDecompress};
+use futures::ready;
+use futures::stream::Stream;
+
+use proxmox_io::ByteBuffer;
+
+#[derive(Eq, PartialEq)]
+enum DecoderState {
+    Reading,
+    Writing,
+    Flushing,
+    Finished,
+}
+
+pub struct DeflateDecoder<T> {
+    inner: T,
+    decompressor: Decompress,
+    buffer: ByteBuffer,
+    input_buffer: Bytes,
+    state: DecoderState,
+}
+
+pub struct DeflateDecoderBuilder<T> {
+    inner: T,
+    is_zlib: bool,
+    buffer_size: usize,
+}
+
+impl<T> DeflateDecoderBuilder<T> {
+    pub fn zlib(mut self, is_zlib: bool) -> Self {
+        self.is_zlib = is_zlib;
+        self
+    }
+
+    pub fn buffer_size(mut self, buffer_size: usize) -> Self {
+        self.buffer_size = buffer_size;
+        self
+    }
+
+    pub fn build(self) -> DeflateDecoder<T> {
+        DeflateDecoder {
+            inner: self.inner,
+            decompressor: Decompress::new(self.is_zlib),
+            buffer: ByteBuffer::with_capacity(self.buffer_size),
+            input_buffer: Bytes::new(),
+            state: DecoderState::Reading,
+        }
+    }
+}
+
+impl<T> DeflateDecoder<T> {
+    pub fn new(inner: T) -> Self {
+        Self::builder(inner).build()
+    }
+
+    pub fn builder(inner: T) -> DeflateDecoderBuilder<T> {
+        DeflateDecoderBuilder {
+            inner,
+            is_zlib: false,
+            buffer_size: super::BUFFER_SIZE,
+        }
+    }
+
+    fn decode(
+        &mut self,
+        inbuf: &[u8],
+        flush: FlushDecompress,
+    ) -> Result<(usize, flate2::Status), io::Error> {
+        let old_in = self.decompressor.total_in();
+        let old_out = self.decompressor.total_out();
+        let res = self
+            .decompressor
+            .decompress(inbuf, self.buffer.get_free_mut_slice(), flush)?;
+        let new_in = (self.decompressor.total_in() - old_in) as usize;
+        let new_out = (self.decompressor.total_out() - old_out) as usize;
+        self.buffer.add_size(new_out);
+
+        Ok((new_in, res))
+    }
+}
+
+impl<T, O, E> Stream for DeflateDecoder<T>
+where
+    T: Stream<Item = Result<O, E>> + Unpin,
+    O: Into<Bytes>,
+    E: Into<Error>,
+{
+    type Item = Result<Bytes, anyhow::Error>;
+
+    fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        let this = self.get_mut();
+
+        loop {
+            match this.state {
+                DecoderState::Reading => {
+                    if let Some(res) = ready!(Pin::new(&mut this.inner).poll_next(cx)) {
+                        let buf = res.map_err(Into::into)?;
+                        this.input_buffer = buf.into();
+                        this.state = DecoderState::Writing;
+                    } else {
+                        this.state = DecoderState::Flushing;
+                    }
+                }
+                DecoderState::Writing => {
+                    if this.input_buffer.is_empty() {
+                        return Poll::Ready(Some(Err(anyhow::format_err!(
+                            "empty input during write"
+                        ))));
+                    }
+                    let mut buf = this.input_buffer.split_off(0);
+                    let (read, res) = this.decode(&buf[..], FlushDecompress::None)?;
+                    this.input_buffer = buf.split_off(read);
+                    if this.input_buffer.is_empty() {
+                        this.state = DecoderState::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())));
+                    }
+                }
+                DecoderState::Flushing => {
+                    let (_read, res) = this.decode(&[][..], FlushDecompress::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 = DecoderState::Finished;
+                    }
+                }
+                DecoderState::Finished => return Poll::Ready(None),
+            }
+        }
+    }
+}
diff --git a/proxmox-compression/src/deflate/mod.rs b/proxmox-compression/src/deflate/mod.rs
index 514ccbdc..6867176c 100644
--- a/proxmox-compression/src/deflate/mod.rs
+++ b/proxmox-compression/src/deflate/mod.rs
@@ -1,5 +1,7 @@
 mod compression;
+mod decompression;
 
 pub use compression::{DeflateEncoder, Level};
+pub use decompression::DeflateDecoder;
 
 const BUFFER_SIZE: usize = 8192;
diff --git a/proxmox-compression/src/lib.rs b/proxmox-compression/src/lib.rs
index 239de623..f33212e5 100644
--- a/proxmox-compression/src/lib.rs
+++ b/proxmox-compression/src/lib.rs
@@ -1,4 +1,4 @@
-pub use deflate::{DeflateEncoder, Level};
+pub use deflate::{DeflateDecoder, DeflateEncoder, Level};
 
 pub(crate) mod deflate;
 pub mod tar;
-- 
2.39.2