[DEV-7084] TAMER: fs: Basic filesystem abstraction

This also includes an implementation to visit paths only once.  Note that it
does not yet canonicalize the path before visiting, so relative paths to the
same file can slip through, and relative paths to _different_ files could be
erroneously considered to have been visited.

This will be fixed in an upcoming commit.

tamer/src/fs.rs

@@ -0,0 +1,177 @@
+// Light filesystem abstractions
+//
+//  Copyright (C) 2014-2020 Ryan Specialty Group, LLC.
+//
+//  This file is part of TAME.
+//
+//  This program is free software: you can redistribute it and/or modify
+//  it under the terms of the GNU General Public License as published by
+//  the Free Software Foundation, either version 3 of the License, or
+//  (at your option) any later version.
+//
+//  This program is distributed in the hope that it will be useful,
+//  but WITHOUT ANY WARRANTY; without even the implied warranty of
+//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//  GNU General Public License for more details.
+//
+//  You should have received a copy of the GNU General Public License
+//  along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Lightweight filesystem abstraction.
+//!
+//! This abstraction is intended to provide generics missing from Rust core,
+//!   but makes no attempt to be comprehensive---it
+//!     includes only what is needed for TAMER.
+//!
+//!   - [`File`] provides a trait for operating on files; and
+//!   - [`Filesystem`] provides a generic way to access files by path.
+//!
+//! This implements traits directly atop of Rust's core structs where
+//!   possible.
+//!
+//!
+//! Visiting Files Once
+//! ===================
+//! [`VisitOnceFilesystem`] produces [`VisitOnceFile::FirstVisit`] the first
+//!   time it encounters a given path,
+//!     and [`VisitOnceFile::Visited`] every time thereafter.
+
+use std::collections::hash_map::RandomState;
+use std::collections::HashSet;
+use std::ffi::OsString;
+use std::fs;
+use std::hash::BuildHasher;
+use std::io::Result;
+use std::path::Path;
+
+/// A file.
+pub trait File
+where
+    Self: Sized,
+{
+    fn open<P: AsRef<Path>>(path: P) -> Result<Self>;
+}
+
+impl File for fs::File {
+    fn open<P: AsRef<Path>>(path: P) -> Result<Self> {
+        Self::open(path)
+    }
+}
+
+/// A filesystem.
+///
+/// Opening a file (using [`open`](Filesystem::open)) proxies to `F::open`.
+/// The type of files opened by this abstraction can therefore be controlled
+///   via generics.
+pub trait Filesystem<F: File>
+where
+    Self: Sized,
+{
+    fn open<P: AsRef<Path>>(&mut self, path: P) -> Result<F> {
+        F::open(path)
+    }
+}
+
+/// A potentially visited [`File`].
+///
+/// See [`VisitOnceFilesystem`] for more information.
+#[derive(Debug, PartialEq)]
+pub enum VisitOnceFile<F: File> {
+    /// First time visiting file at requested path.
+    FirstVisit(F),
+
+    /// Requested path has already been visited.
+    Visited,
+}
+
+impl<F: File> File for VisitOnceFile<F> {
+    fn open<P: AsRef<Path>>(path: P) -> Result<Self> {
+        F::open(path).map(|file| Self::FirstVisit(file))
+    }
+}
+
+/// Opens each path only once.
+///
+/// When a [`File`] is first opened,
+///   it will be wrapped in [`VisitOnceFile::FirstVisit`]
+/// Subsequent calls to `open` will yield
+///   [`VisitOnceFile::Visited`] without attempting to open the file.
+///
+/// A file will not be marked as visited if it fails to be opened.
+pub struct VisitOnceFilesystem<S = RandomState>
+where
+    S: BuildHasher,
+{
+    visited: HashSet<OsString, S>,
+}
+
+impl<S> VisitOnceFilesystem<S>
+where
+    S: BuildHasher + Default,
+{
+    /// New filesystem with no recorded paths.
+    pub fn new() -> Self {
+        Self {
+            visited: Default::default(),
+        }
+    }
+
+    /// Number of visited paths.
+    pub fn visit_len(&self) -> usize {
+        self.visited.len()
+    }
+}
+
+impl<S, F> Filesystem<VisitOnceFile<F>> for VisitOnceFilesystem<S>
+where
+    S: BuildHasher,
+    F: File,
+{
+    /// Open a file, marking `path` as visited.
+    ///
+    /// The next time the same path is requested,
+    ///   [`VisitOnceFile::Visited`] will be returned.
+    ///
+    /// `path` will not be marked as visited if opening fails.
+    fn open<P: AsRef<Path>>(&mut self, path: P) -> Result<VisitOnceFile<F>> {
+        let ostr = path.as_ref().as_os_str();
+
+        if self.visited.contains(ostr) {
+            return Ok(VisitOnceFile::Visited);
+        }
+
+        VisitOnceFile::open(ostr).and_then(|file| {
+            self.visited.insert(ostr.to_os_string());
+            Ok(file)
+        })
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use std::path::PathBuf;
+
+    #[derive(Debug, PartialEq)]
+    struct DummyFile(PathBuf);
+
+    impl File for DummyFile {
+        fn open<P: AsRef<Path>>(path: P) -> Result<Self> {
+            Ok(Self(path.as_ref().to_path_buf()))
+        }
+    }
+
+    #[test]
+    fn vist_once() {
+        let mut fs = VisitOnceFilesystem::<RandomState>::new();
+        let path: PathBuf = "foo/bar".into();
+        let result = fs.open(path.clone()).unwrap();
+
+        // First time, return file.
+        assert_eq!(VisitOnceFile::FirstVisit(DummyFile(path.clone())), result);
+
+        // Second time, already visited.
+        let result_2: VisitOnceFile<DummyFile> = fs.open(path).unwrap();
+        assert_eq!(VisitOnceFile::Visited, result_2);
+    }
+}

tamer/src/ld/poc.rs

@@ -20,6 +20,7 @@
 //! **This is a poorly-written proof of concept; do not use!**  It has been
 //! banished to its own file to try to make that more clear.
 
+use crate::fs::{Filesystem, VisitOnceFile, VisitOnceFilesystem};
 use crate::global;
 use crate::ir::asg::{
     Asg, AsgError, DefaultAsg, IdentKind, IdentObject, IdentObjectData,
@@ -28,7 +29,7 @@ use crate::ir::asg::{
 use crate::obj::xmle::writer::XmleWriter;
 use crate::obj::xmlo::reader::{XmloError, XmloEvent, XmloReader};
 use crate::sym::{DefaultInterner, Interner, Symbol};
-use fxhash::{FxHashMap, FxHashSet};
+use fxhash::{FxBuildHasher, FxHashMap, FxHashSet};
 use std::convert::TryInto;
 use std::error::Error;
 use std::fs;
@@ -41,7 +42,7 @@ type LoadResult<'i> =
     Result<Option<(Option<&'i Symbol<'i>>, Option<String>)>, Box<dyn Error>>;
 
 pub fn main(package_path: &str, output: &str) -> Result<(), Box<dyn Error>> {
-    let mut pkgs_seen: FxHashSet<String> = Default::default();
+    let mut fs = VisitOnceFilesystem::new();
     let mut fragments: FxHashMap<&str, String> = Default::default();
     let mut depgraph = LinkerAsg::with_capacity(65536, 65536);
     let mut roots = Vec::new();
@@ -51,7 +52,7 @@ pub fn main(package_path: &str, output: &str) -> Result<(), Box<dyn Error>> {
 
     let (name, relroot) = load_xmlo(
         &abs_path.to_str().unwrap().to_string(),
-        &mut pkgs_seen,
+        &mut fs,
         &mut fragments,
         &mut depgraph,
         &interner,
@@ -119,26 +120,22 @@ pub fn main(package_path: &str, output: &str) -> Result<(), Box<dyn Error>> {
 
 fn load_xmlo<'a, 'i, I: Interner<'i>>(
     path_str: &'a str,
-    pkgs_seen: &mut FxHashSet<String>,
+    fs: &mut VisitOnceFilesystem<FxBuildHasher>,
     fragments: &mut FxHashMap<&'i str, String>,
     depgraph: &mut LinkerAsg<'i>,
     interner: &'i I,
     roots: &mut Vec<LinkerObjectRef>,
 ) -> LoadResult<'i> {
     let path = fs::canonicalize(path_str)?;
-    let path_str = path.to_str().unwrap();
-
-    let first = pkgs_seen.len() == 0;
-
-    if !pkgs_seen.insert(path_str.to_string()) {
-        return Ok(None);
-    }
-
-    //println!("processing {}", path_str);
+    let first = fs.visit_len() == 0;
 
     let mut found: FxHashSet<&str> = Default::default();
 
-    let file = fs::File::open(&path)?;
+    let file: fs::File = match fs.open(&path)? {
+        VisitOnceFile::FirstVisit(file) => file,
+        VisitOnceFile::Visited => return Ok(None),
+    };
+
     let reader = BufReader::new(file);
     let mut xmlo: XmloReader<'_, _, _> = (reader, interner).into();
     let mut elig = None;
@@ -253,7 +250,7 @@ fn load_xmlo<'a, 'i, I: Interner<'i>>(
         let path_abs = path_buf.canonicalize()?;
         let path = path_abs.to_str().unwrap();
 
-        load_xmlo(path, pkgs_seen, fragments, depgraph, interner, roots)?;
+        load_xmlo(path, fs, fragments, depgraph, interner, roots)?;
     }
 
     if first {

tamer/src/lib.rs

@@ -24,6 +24,7 @@ pub mod global;
 #[macro_use]
 pub mod sym;
 
+pub mod fs;
 pub mod ir;
 pub mod ld;
 pub mod obj;