use crate::errors::{HgError, IoErrorContext, IoResultExt}; use memmap2::{Mmap, MmapOptions}; use std::io::{ErrorKind, Write}; 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, } struct FileNotFound(std::io::Error, PathBuf); impl Vfs<'_> { pub fn join(&self, relative_path: impl AsRef) -> PathBuf { self.base.join(relative_path) } pub fn symlink_metadata( &self, relative_path: impl AsRef, ) -> Result { let path = self.join(relative_path); std::fs::symlink_metadata(&path).when_reading_file(&path) } pub fn read_link( &self, relative_path: impl AsRef, ) -> Result { let path = self.join(relative_path); std::fs::read_link(&path).when_reading_file(&path) } pub fn read( &self, relative_path: impl AsRef, ) -> Result, HgError> { let path = self.join(relative_path); std::fs::read(&path).when_reading_file(&path) } /// Returns `Ok(None)` if the file does not exist. pub fn try_read( &self, relative_path: impl AsRef, ) -> Result>, HgError> { match self.read(relative_path) { Err(e) => match &e { HgError::IoError { error, .. } => match error.kind() { ErrorKind::NotFound => Ok(None), _ => Err(e), }, _ => Err(e), }, Ok(v) => Ok(Some(v)), } } fn mmap_open_gen( &self, relative_path: impl AsRef, ) -> Result, HgError> { let path = self.join(relative_path); let file = match std::fs::File::open(&path) { Err(err) => { if let ErrorKind::NotFound = err.kind() { return Ok(Err(FileNotFound(err, path))); }; return (Err(err)).when_reading_file(&path); } Ok(file) => file, }; // TODO: what are the safety requirements here? let mmap = unsafe { MmapOptions::new().map(&file) } .when_reading_file(&path)?; Ok(Ok(mmap)) } pub fn mmap_open_opt( &self, relative_path: impl AsRef, ) -> Result, HgError> { self.mmap_open_gen(relative_path).map(|res| res.ok()) } pub fn mmap_open( &self, relative_path: impl AsRef, ) -> Result { match self.mmap_open_gen(relative_path)? { Err(FileNotFound(err, path)) => Err(err).when_reading_file(&path), Ok(res) => Ok(res), } } pub fn rename( &self, relative_from: impl AsRef, relative_to: impl AsRef, ) -> 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 }) } pub fn remove_file( &self, relative_path: impl AsRef, ) -> Result<(), HgError> { let path = self.join(relative_path); std::fs::remove_file(&path) .with_context(|| IoErrorContext::RemovingFile(path)) } #[cfg(unix)] pub fn create_symlink( &self, relative_link_path: impl AsRef, target_path: impl AsRef, ) -> Result<(), HgError> { let link_path = self.join(relative_link_path); std::os::unix::fs::symlink(target_path, &link_path) .when_writing_file(&link_path) } /// Write `contents` into a temporary file, then rename to `relative_path`. /// This makes writing to a file "atomic": a reader opening that path will /// see either the previous contents of the file or the complete new /// content, never a partial write. pub fn atomic_write( &self, relative_path: impl AsRef, contents: &[u8], ) -> Result<(), HgError> { let mut tmp = tempfile::NamedTempFile::new_in(self.base) .when_writing_file(self.base)?; tmp.write_all(contents) .and_then(|()| tmp.flush()) .when_writing_file(tmp.path())?; let path = self.join(relative_path); tmp.persist(&path) .map_err(|e| e.error) .when_writing_file(&path)?; Ok(()) } } fn fs_metadata( path: impl AsRef, ) -> Result, 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) -> Result { Ok(fs_metadata(path)?.map_or(false, |meta| meta.is_dir())) } pub(crate) fn is_file(path: impl AsRef) -> Result { Ok(fs_metadata(path)?.map_or(false, |meta| meta.is_file())) }