fix: panic on readbuf too small for block

libraries/droplet/Cargo.lock

@@ -249,7 +249,7 @@ dependencies = [
 
 [[package]]
 name = "droplet-rs"
-version = "0.16.2"
+version = "0.16.3"
 dependencies = [
  "anyhow",
  "async-trait",

libraries/droplet/Cargo.toml

@@ -2,7 +2,7 @@
 edition = "2021"
 authors = ["Drop-OSS"]
 name = "droplet-rs"
-version = "0.16.2"
+version = "0.16.3"
 license = "AGPL-3.0-only"
 description = "Droplet is a `napi.rs` Rust/Node.js package full of high-performance and low-level utils for Drop"
 

libraries/droplet/src/manifest.rs

@@ -156,7 +156,7 @@ pub async fn generate_manifest_rusty<T: Fn(String), V: Fn(f32)>(
         let manifest = manifest.clone();
         let reader_semaphore = reader_semaphore.clone();
         futures.spawn(async move {
-            let mut read_buf = vec![0; 1024 * 1024 * 64];
+            let mut read_buf = vec![0u8; 1024 * 1024 * 8];
 
             let uuid = uuid::Uuid::new_v4().to_string();
             let mut hasher = Sha256::new();
@@ -189,9 +189,10 @@ pub async fn generate_manifest_rusty<T: Fn(String), V: Fn(f32)>(
                     }
                     total += amount;
                     hasher.update(&read_buf[0..amount]);
-                    if total as u64 > length {
-                        panic!("read too much: target {}, got {}", length, total);
-                    }
+                }
+
+                if total as u64 > length {
+                    panic!("read too much: target {}, got {}", length, total);
                 }
 
                 chunk_length += length;

libraries/droplet/src/versions/archive_backend.rs

@@ -28,27 +28,53 @@ impl ZipVersionBackend {
     }
 }
 
-struct ArchiveReader {
+struct ArchiveReader<'a> {
     archive: FileReader,
+    prev_block: Option<&'a [u8]>,
 }
 
-impl AsyncRead for ArchiveReader {
+impl<'a> AsyncRead for ArchiveReader<'a> {
     fn poll_read(
-        self: std::pin::Pin<&mut Self>,
+        mut self: std::pin::Pin<&mut Self>,
         _cx: &mut std::task::Context<'_>,
         buf: &mut tokio::io::ReadBuf<'_>,
     ) -> std::task::Poll<std::io::Result<()>> {
+        if let Some(block) = &mut self.prev_block {
+            let to_read = buf.remaining().min(block.len());
+            let result = block.split_off(..to_read);
+            let result = result.unwrap(); // SAFETY: above .min statement
+            buf.put_slice(result);
+
+            // If the block is empty, we can read more
+            if block.is_empty() {
+                self.prev_block = None;
+            } else {
+                return Poll::Ready(Ok(()));
+            }
+        }
         let block = match self.archive.read_block() {
             Ok(v) => v,
             Err(err) => return Poll::Ready(Err(std::io::Error::other(err.to_string()))),
         };
 
-        let block = match block {
+        let mut block = match block {
             Some(v) => v,
             None => return Poll::Ready(Ok(())),
         };
 
-        buf.put_slice(block);
+        let write_amount = buf.remaining().min(block.len());
+        let to_write = block.split_off(..write_amount);
+        let to_write = to_write.unwrap(); // SAFETY: above .min statement
+        buf.put_slice(to_write);
+
+        if !block.is_empty() {
+            #[cfg(debug_assertions)]
+            if self.prev_block.is_some() {
+                panic!("replacing prev_block while it contains data")
+            }
+            self.prev_block.replace(&block[buf.remaining()..]);
+        }
+
         Poll::Ready(Ok(()))
     }
 }
@@ -95,7 +121,10 @@ impl VersionBackend for ZipVersionBackend {
             }
         }
 
-        Ok(Box::new(ArchiveReader { archive }))
+        Ok(Box::new(ArchiveReader {
+            archive,
+            prev_block: None,
+        }))
     }
 
     async fn peek_file(&self, sub_path: String) -> anyhow::Result<VersionFile> {