1 files changed, 78 insertions, 0 deletions
diff --git a/src/librustdoc/docfs.rs b/src/librustdoc/docfs.rs
new file mode 100644
index 000000000..be066bdaf
--- /dev/null
+++ b/src/librustdoc/docfs.rs
@@ -0,0 +1,78 @@
+//! Rustdoc's FileSystem abstraction module.
+//!
+//! On Windows this indirects IO into threads to work around performance issues
+//! with Defender (and other similar virus scanners that do blocking operations).
+//! On other platforms this is a thin shim to fs.
+//!
+//! Only calls needed to permit this workaround have been abstracted: thus
+//! fs::read is still done directly via the fs module; if in future rustdoc
+//! needs to read-after-write from a file, then it would be added to this
+//! abstraction.
+
+use std::fs;
+use std::io;
+use std::path::{Path, PathBuf};
+use std::string::ToString;
+use std::sync::mpsc::Sender;
+
+pub(crate) trait PathError {
+    fn new<S, P: AsRef<Path>>(e: S, path: P) -> Self
+    where
+        S: ToString + Sized;
+}
+
+pub(crate) struct DocFS {
+    sync_only: bool,
+    errors: Option<Sender<String>>,
+}
+
+impl DocFS {
+    pub(crate) fn new(errors: Sender<String>) -> DocFS {
+        DocFS { sync_only: false, errors: Some(errors) }
+    }
+
+    pub(crate) fn set_sync_only(&mut self, sync_only: bool) {
+        self.sync_only = sync_only;
+    }
+
+    pub(crate) fn close(&mut self) {
+        self.errors = None;
+    }
+
+    pub(crate) fn create_dir_all<P: AsRef<Path>>(&self, path: P) -> io::Result<()> {
+        // For now, dir creation isn't a huge time consideration, do it
+        // synchronously, which avoids needing ordering between write() actions
+        // and directory creation.
+        fs::create_dir_all(path)
+    }
+
+    pub(crate) fn write<E>(
+        &self,
+        path: PathBuf,
+        contents: impl 'static + Send + AsRef<[u8]>,
+    ) -> Result<(), E>
+    where
+        E: PathError,
+    {
+        #[cfg(windows)]
+        if !self.sync_only {
+            // A possible future enhancement after more detailed profiling would
+            // be to create the file sync so errors are reported eagerly.
+            let sender = self.errors.clone().expect("can't write after closing");
+            rayon::spawn(move || {
+                fs::write(&path, contents).unwrap_or_else(|e| {
+                    sender.send(format!("\"{}\": {}", path.display(), e)).unwrap_or_else(|_| {
+                        panic!("failed to send error on \"{}\"", path.display())
+                    })
+                });
+            });
+        } else {
+            fs::write(&path, contents).map_err(|e| E::new(e, path))?;
+        }
+
+        #[cfg(not(windows))]
+        fs::write(&path, contents).map_err(|e| E::new(e, path))?;
+
+        Ok(())
+    }
+}