From fbdbeb284237f6df4b3251401787c13aa000822b Mon Sep 17 00:00:00 2001
From: Szymon Walter <walter.szymon.98@gmail.com>
Date: Tue, 20 Mar 2018 12:38:22 +0100
Subject: [PATCH] fix `Address::sub`

---
 src/block.rs | 2 +-
 src/fs.rs    | 5 +++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/block.rs b/src/block.rs
index 83af087..ad60f7a 100644
--- a/src/block.rs
+++ b/src/block.rs
@@ -177,7 +177,7 @@ impl<S: Size> Sub for Address<S> {
     type Output = Address<S>;
     fn sub(self, rhs: Address<S>) -> Address<S> {
         Address::new(
-            self.block + rhs.block,
+            self.block - rhs.block,
             self.offset as isize - rhs.offset as isize,
         )
     }
diff --git a/src/fs.rs b/src/fs.rs
index 1c90de1..e100351 100644
--- a/src/fs.rs
+++ b/src/fs.rs
@@ -229,6 +229,11 @@ mod tests {
     #[test]
     fn file_len() {
         let file = RefCell::new(File::open("ext2.img").unwrap());
+        assert_eq!(
+            Address::<Size512>::from(2048_usize)
+                - Address::<Size512>::from(1024_usize),
+            Address::<Size512>::new(2, 0)
+        );
         assert_eq!(
             unsafe {
                 file.slice_unchecked(