Module loading system

Detects cyclic imports and loads each module only once per compilation.

1 files changed, 16 insertions, 2 deletions

diff --git a/src/loading/mod.rs b/src/loading/mod.rs
index 818e7e3c..b4e5d160 100644
--- a/src/loading/mod.rs
+++ b/src/loading/mod.rs
@@ -6,6 +6,7 @@ mod fs;
 #[cfg(feature = "fs")]
 pub use fs::*;
 
+use std::path::Path;
 use std::rc::Rc;
 
 use crate::font::FaceInfo;
@@ -18,13 +19,22 @@ pub trait Loader {
     /// Descriptions of all font faces this loader serves.
     fn faces(&self) -> &[FaceInfo];
 
+    /// Resolve a hash that is the same for all paths pointing to the same file.
+    ///
+    /// Should return `None` if the file does not exist.
+    fn resolve(&self, path: &Path) -> Option<FileHash>;
+
     /// Load the font face with the given index in [`faces()`](Self::faces).
     fn load_face(&mut self, idx: usize) -> Option<Buffer>;
 
     /// Load a file from a path.
-    fn load_file(&mut self, path: &str) -> Option<Buffer>;
+    fn load_file(&mut self, path: &Path) -> Option<Buffer>;
 }
 
+/// A hash that must be the same for all paths pointing to the same file.
+#[derive(Debug, Copy, Clone, Eq, PartialEq, Hash)]
+pub struct FileHash(pub u64);
+
 /// A loader which serves nothing.
 pub struct BlankLoader;
 
@@ -33,11 +43,15 @@ impl Loader for BlankLoader {
         &[]
     }
 
+    fn resolve(&self, _: &Path) -> Option<FileHash> {
+        None
+    }
+
     fn load_face(&mut self, _: usize) -> Option<Buffer> {
         None
     }
 
-    fn load_file(&mut self, _: &str) -> Option<Buffer> {
+    fn load_file(&mut self, _: &Path) -> Option<Buffer> {
         None
     }
 }