[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.

1 files changed, 12 insertions, 15 deletions

diff --git a/tamer/src/ld/poc.rs b/tamer/src/ld/poc.rs
index 5720f79..689aa9d 100644
--- a/tamer/src/ld/poc.rs
+++ b/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 {