vfs: Add stub MemoryBackend

vfs/src/lib.rs

@@ -1,3 +1,4 @@
+mod memory_backend;
 mod noop_backend;
 mod std_backend;
 
@@ -5,6 +6,7 @@ use std::io;
 use std::path::{Path, PathBuf};
 use std::sync::{Arc, Mutex};
 
+pub use memory_backend::MemoryBackend;
 pub use noop_backend::NoopBackend;
 pub use std_backend::StdBackend;
 
@@ -13,6 +15,7 @@ mod sealed {
 
     pub trait Sealed {}
 
+    impl Sealed for MemoryBackend {}
     impl Sealed for NoopBackend {}
     impl Sealed for StdBackend {}
 }

vfs/src/memory_backend.rs

@@ -0,0 +1,76 @@
+use std::io;
+use std::path::Path;
+
+use crate::{Metadata, ReadDir, VfsBackend, VfsEvent};
+
+/// `VfsBackend` that reads from an in-memory filesystem.
+#[non_exhaustive]
+pub struct MemoryBackend;
+
+impl MemoryBackend {
+    pub fn new() -> Self {
+        Self
+    }
+}
+
+impl VfsBackend for MemoryBackend {
+    fn read(&mut self, _path: &Path) -> io::Result<Vec<u8>> {
+        Err(io::Error::new(
+            io::ErrorKind::Other,
+            "MemoryBackend doesn't do anything",
+        ))
+    }
+
+    fn write(&mut self, _path: &Path, _data: &[u8]) -> io::Result<()> {
+        Err(io::Error::new(
+            io::ErrorKind::Other,
+            "MemoryBackend doesn't do anything",
+        ))
+    }
+
+    fn read_dir(&mut self, _path: &Path) -> io::Result<ReadDir> {
+        Err(io::Error::new(
+            io::ErrorKind::Other,
+            "MemoryBackend doesn't do anything",
+        ))
+    }
+
+    fn remove_file(&mut self, _path: &Path) -> io::Result<()> {
+        Err(io::Error::new(
+            io::ErrorKind::Other,
+            "MemoryBackend doesn't do anything",
+        ))
+    }
+
+    fn remove_dir_all(&mut self, _path: &Path) -> io::Result<()> {
+        Err(io::Error::new(
+            io::ErrorKind::Other,
+            "MemoryBackend doesn't do anything",
+        ))
+    }
+
+    fn metadata(&mut self, _path: &Path) -> io::Result<Metadata> {
+        Err(io::Error::new(
+            io::ErrorKind::Other,
+            "MemoryBackend doesn't do anything",
+        ))
+    }
+
+    fn event_receiver(&self) -> crossbeam_channel::Receiver<VfsEvent> {
+        crossbeam_channel::never()
+    }
+
+    fn watch(&mut self, _path: &Path) -> io::Result<()> {
+        Err(io::Error::new(
+            io::ErrorKind::Other,
+            "MemoryBackend doesn't do anything",
+        ))
+    }
+
+    fn unwatch(&mut self, _path: &Path) -> io::Result<()> {
+        Err(io::Error::new(
+            io::ErrorKind::Other,
+            "MemoryBackend doesn't do anything",
+        ))
+    }
+}