1 files changed, 14 insertions, 0 deletions
diff --git a/nix-rust/src/foreign.rs b/nix-rust/src/foreign.rs
new file mode 100644
index 000000000..7bce7753c
--- /dev/null
+++ b/nix-rust/src/foreign.rs
@@ -0,0 +1,14 @@
+/// A wrapper around Nix's Source class that provides the Read trait.
+#[repr(C)]
+pub struct Source {
+    fun: extern "C" fn(this: *mut libc::c_void, data: &mut [u8]) -> usize,
+    this: *mut libc::c_void,
+}
+
+impl std::io::Read for Source {
+    fn read(&mut self, buf: &mut [u8]) -> std::result::Result<usize, std::io::Error> {
+        let n = (self.fun)(self.this, buf);
+        assert!(n <= buf.len());
+        Ok(n)
+    }
+}