Merge pull request #4355 from wasmerio/fix-static-file

Fix the `virtual_fs::StaticFile` implementation

Cargo.toml

@@ -87,6 +87,7 @@ enumset = "1.1.0"
 memoffset = "0.9.0"
 wasmer-toml = "0.9.2"
 webc = { version = "5.8.0", default-features = false, features = ["package"] }
+shared-buffer = "0.1.4"
 
 [build-dependencies]
 test-generator = { path = "tests/lib/test-generator" }

lib/api/Cargo.toml

@@ -34,7 +34,7 @@ bytes = "1"
 wat = { version = "=1.0.71", optional = true }
 tracing = { version = "0.1", optional = true }
 rustc-demangle = "0.1"
-shared-buffer = "0.1"
+shared-buffer = { workspace = true }
 
 # Dependencies and Development Dependencies for `sys`.
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]

lib/compiler/Cargo.toml

@@ -35,7 +35,7 @@ enum-iterator = "0.7.0"
 bytes = "1.0"
 self_cell = "1.0"
 rkyv = { version = "0.7.40", features = ["indexmap", "validation", "strict"] }
-shared-buffer = "0.1"
+shared-buffer = { workspace = true }
 
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]
 wasmer-vm = { path = "../vm", version = "=4.2.4" }

lib/virtual-fs/Cargo.toml

@@ -10,24 +10,25 @@ repository.workspace = true
 rust-version.workspace = true
 
 [dependencies]
-libc = { version = "^0.2", default-features = false, optional = true }
-thiserror = "1"
-futures = { version = "0.3" }
-tracing = { version = "0.1" }
-typetag = { version = "0.1", optional = true }
-webc = { version = "5.0", optional = true }
-slab = { version = "0.4" }
-derivative = "2.2.0"
 anyhow = { version = "1.0.66", optional = true }
 async-trait = { version = "^0.1" }
-lazy_static = "1.4"
-fs_extra = { version = "1.2.0", optional = true }
-filetime = { version = "0.2.18", optional = true }
 bytes = "1"
-tokio = { version = "1", features = ["io-util", "sync", "macros"], default_features = false }
-pin-project-lite = "0.2.9"
+derivative = "2.2.0"
+filetime = { version = "0.2.18", optional = true }
+fs_extra = { version = "1.2.0", optional = true }
+futures = { version = "0.3" }
 indexmap = "1.9.2"
+lazy_static = "1.4"
+libc = { version = "^0.2", default-features = false, optional = true }
+pin-project-lite = "0.2.9"
 replace_with = "0.1.7"
+shared-buffer = { workspace = true }
+slab = { version = "0.4" }
+thiserror = "1"
+tokio = { version = "1", features = ["io-util", "sync", "macros"], default_features = false }
+tracing = { version = "0.1" }
+typetag = { version = "0.1", optional = true }
+webc = { version = "5.0", optional = true }
 
 [target.'cfg(not(all(target_arch = "wasm32", target_os = "unknown")))'.dependencies]
 getrandom = { version = "0.2" }

lib/virtual-fs/src/static_file.rs

@@ -1,27 +1,28 @@
+use std::{
+    convert::TryInto,
+    io::{self, Cursor},
+    pin::Pin,
+    task::{Context, Poll},
+};
+
 use futures::future::BoxFuture;
+use shared_buffer::OwnedBuffer;
 use tokio::io::{AsyncRead, AsyncSeek, AsyncWrite};
 
-use std::borrow::Cow;
-use std::convert::TryInto;
-use std::io::{self, SeekFrom};
-use std::pin::Pin;
-use std::task::{Context, Poll};
-
 use crate::{FsError, VirtualFile};
 
-#[derive(Debug)]
-pub struct StaticFile {
-    bytes: Cow<'static, [u8]>,
-    cursor: u64,
-    len: u64,
-}
+/// An immutable file backed by an [`OwnedBuffer`].
+#[derive(Debug, Clone, PartialEq)]
+pub struct StaticFile(Cursor<OwnedBuffer>);
+
 impl StaticFile {
-    pub fn new(bytes: Cow<'static, [u8]>) -> Self {
-        Self {
-            len: bytes.len() as u64,
-            bytes,
-            cursor: 0,
-        }
+    pub fn new(bytes: impl Into<OwnedBuffer>) -> Self {
+        StaticFile(Cursor::new(bytes.into()))
+    }
+
+    /// Access the underlying buffer.
+    pub fn contents(&self) -> &OwnedBuffer {
+        self.0.get_ref()
     }
 }
 
@@ -30,49 +31,44 @@ impl VirtualFile for StaticFile {
     fn last_accessed(&self) -> u64 {
         0
     }
+
     fn last_modified(&self) -> u64 {
         0
     }
+
     fn created_time(&self) -> u64 {
         0
     }
+
     fn size(&self) -> u64 {
-        self.len
+        self.0.get_ref().len().try_into().unwrap()
     }
-    fn set_len(&mut self, _new_size: u64) -> crate::Result<()> {
-        Ok(())
+
+    fn set_len(&mut self, _new_size: u64) -> Result<(), FsError> {
+        Err(FsError::PermissionDenied)
     }
+
     fn unlink(&mut self) -> BoxFuture<'static, Result<(), FsError>> {
-        Box::pin(async { Ok(()) })
+        Box::pin(async { Err(FsError::PermissionDenied) })
     }
+
     fn poll_read_ready(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<io::Result<usize>> {
-        let remaining = self.len - self.cursor;
-        Poll::Ready(Ok(remaining as usize))
+        let remaining = self.0.position() - self.size();
+        Poll::Ready(Ok(remaining.try_into().unwrap()))
     }
+
     fn poll_write_ready(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<io::Result<usize>> {
-        Poll::Ready(Ok(0))
+        Poll::Ready(Err(std::io::ErrorKind::PermissionDenied.into()))
     }
 }
 
 impl AsyncRead for StaticFile {
     fn poll_read(
-        self: Pin<&mut Self>,
-        _cx: &mut Context<'_>,
+        mut self: Pin<&mut Self>,
+        cx: &mut Context<'_>,
         buf: &mut tokio::io::ReadBuf<'_>,
     ) -> Poll<io::Result<()>> {
-        let bytes = self.bytes.as_ref();
-
-        let cursor: usize = self.cursor.try_into().unwrap_or(u32::MAX as usize);
-        let _start = cursor.min(bytes.len());
-        let bytes = &bytes[cursor..];
-
-        if bytes.len() > buf.remaining() {
-            let remaining = buf.remaining();
-            buf.put_slice(&bytes[..remaining]);
-        } else {
-            buf.put_slice(bytes);
-        }
-        Poll::Ready(Ok(()))
+        Pin::new(&mut self.0).poll_read(cx, buf)
     }
 }
 
@@ -82,9 +78,9 @@ impl AsyncWrite for StaticFile {
     fn poll_write(
         self: Pin<&mut Self>,
         _cx: &mut Context<'_>,
-        buf: &[u8],
+        _buf: &[u8],
     ) -> Poll<io::Result<usize>> {
-        Poll::Ready(Ok(buf.len()))
+        Poll::Ready(Err(std::io::ErrorKind::PermissionDenied.into()))
     }
     fn poll_flush(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<io::Result<()>> {
         Poll::Ready(Ok(()))
@@ -96,28 +92,43 @@ impl AsyncWrite for StaticFile {
 
 impl AsyncSeek for StaticFile {
     fn start_seek(mut self: Pin<&mut Self>, pos: io::SeekFrom) -> io::Result<()> {
-        let self_size = self.size();
-        match pos {
-            SeekFrom::Start(s) => {
-                self.cursor = s.min(self_size);
-            }
-            SeekFrom::End(e) => {
-                let self_size_i64 = self_size.try_into().unwrap_or(i64::MAX);
-                self.cursor = ((self_size_i64).saturating_add(e))
-                    .min(self_size_i64)
-                    .try_into()
-                    .unwrap_or(i64::MAX as u64);
-            }
-            SeekFrom::Current(c) => {
-                self.cursor = (self
-                    .cursor
-                    .saturating_add(c.try_into().unwrap_or(i64::MAX as u64)))
-                .min(self_size);
-            }
-        }
-        Ok(())
-    }
-    fn poll_complete(self: Pin<&mut Self>, _cx: &mut Context<'_>) -> Poll<io::Result<u64>> {
-        Poll::Ready(Ok(self.cursor))
+        Pin::new(&mut self.0).start_seek(pos)
+    }
+
+    fn poll_complete(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<io::Result<u64>> {
+        Pin::new(&mut self.0).poll_complete(cx)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use tokio::io::AsyncReadExt;
+
+    use super::*;
+
+    #[tokio::test]
+    async fn read_a_static_file_to_end() {
+        let mut file = StaticFile::new(OwnedBuffer::from_static(b"Hello, World!"));
+        let mut buffer = [0; 5];
+
+        let bytes_read = file.read(&mut buffer).await.unwrap();
+        assert_eq!(bytes_read, 5);
+        assert_eq!(&buffer[..bytes_read], b"Hello");
+        assert_eq!(file.0.position(), 5);
+
+        let bytes_read = file.read(&mut buffer).await.unwrap();
+        assert_eq!(bytes_read, 5);
+        assert_eq!(&buffer[..bytes_read], b", Wor");
+        assert_eq!(file.0.position(), 10);
+
+        let bytes_read = file.read(&mut buffer).await.unwrap();
+        assert_eq!(bytes_read, 3);
+        assert_eq!(&buffer[..bytes_read], b"ld!");
+        assert_eq!(file.0.position(), 13);
+
+        let bytes_read = file.read(&mut buffer).await.unwrap();
+        assert_eq!(bytes_read, 0);
+        assert_eq!(&buffer[..bytes_read], b"");
+        assert_eq!(file.0.position(), 13);
     }
 }

lib/wasix/src/state/env.rs

@@ -937,7 +937,7 @@ impl WasiEnv {
                     }
                     WasiFsRoot::Backing(fs) => {
                         let mut f = fs.new_open_options().create(true).write(true).open(path)?;
-                        f.copy_reference(Box::new(StaticFile::new(atom.into())));
+                        f.copy_reference(Box::new(StaticFile::new(atom)));
                     }
                 }