--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/rust/hg-core/src/vfs.rs Mon Sep 06 11:39:59 2021 +0200
@@ -0,0 +1,73 @@
+use crate::errors::{HgError, IoErrorContext, IoResultExt};
+use memmap::{Mmap, MmapOptions};
+use std::io::ErrorKind;
+use std::path::{Path, PathBuf};
+
+/// Filesystem access abstraction for the contents of a given "base" diretory
+#[derive(Clone, Copy)]
+pub struct Vfs<'a> {
+ pub(crate) base: &'a Path,
+}
+
+impl Vfs<'_> {
+ pub fn join(&self, relative_path: impl AsRef<Path>) -> PathBuf {
+ self.base.join(relative_path)
+ }
+
+ pub fn read(
+ &self,
+ relative_path: impl AsRef<Path>,
+ ) -> Result<Vec<u8>, HgError> {
+ let path = self.join(relative_path);
+ std::fs::read(&path).when_reading_file(&path)
+ }
+
+ pub fn mmap_open(
+ &self,
+ relative_path: impl AsRef<Path>,
+ ) -> Result<Mmap, HgError> {
+ let path = self.base.join(relative_path);
+ let file = std::fs::File::open(&path).when_reading_file(&path)?;
+ // TODO: what are the safety requirements here?
+ let mmap = unsafe { MmapOptions::new().map(&file) }
+ .when_reading_file(&path)?;
+ Ok(mmap)
+ }
+
+ pub fn rename(
+ &self,
+ relative_from: impl AsRef<Path>,
+ relative_to: impl AsRef<Path>,
+ ) -> Result<(), HgError> {
+ let from = self.join(relative_from);
+ let to = self.join(relative_to);
+ std::fs::rename(&from, &to)
+ .with_context(|| IoErrorContext::RenamingFile { from, to })
+ }
+}
+
+fn fs_metadata(
+ path: impl AsRef<Path>,
+) -> Result<Option<std::fs::Metadata>, HgError> {
+ let path = path.as_ref();
+ match std::fs::metadata(path) {
+ Ok(meta) => Ok(Some(meta)),
+ Err(error) => match error.kind() {
+ // TODO: when we require a Rust version where `NotADirectory` is
+ // stable, invert this logic and return None for it and `NotFound`
+ // and propagate any other error.
+ ErrorKind::PermissionDenied => Err(error).with_context(|| {
+ IoErrorContext::ReadingMetadata(path.to_owned())
+ }),
+ _ => Ok(None),
+ },
+ }
+}
+
+pub(crate) fn is_dir(path: impl AsRef<Path>) -> Result<bool, HgError> {
+ Ok(fs_metadata(path)?.map_or(false, |meta| meta.is_dir()))
+}
+
+pub(crate) fn is_file(path: impl AsRef<Path>) -> Result<bool, HgError> {
+ Ok(fs_metadata(path)?.map_or(false, |meta| meta.is_file()))
+}