From 311c9baf659b4ca084f407a6335e7439e45859db Mon Sep 17 00:00:00 2001
From: Benjamin Sago <ogham@bsago.me>
Date: Sun, 11 Apr 2021 23:34:29 +0100
Subject: [PATCH] Explain device IDs with a comment

---
 src/fs/file.rs | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/src/fs/file.rs b/src/fs/file.rs
index 0df998c..b57777d 100644
--- a/src/fs/file.rs
+++ b/src/fs/file.rs
@@ -319,10 +319,15 @@ impl<'dir> File<'dir> {
             f::Size::None
         }
         else if self.is_char_device() || self.is_block_device() {
-            let dev = self.metadata.rdev();
+            let device_ids = self.metadata.rdev().to_be_bytes();
+
+            // In C-land, getting the major and minor device IDs is done with
+            // preprocessor macros called `major` and `minor` that depend on
+            // the size of `dev_t`, but we just take the second-to-last and
+            // last bytes.
             f::Size::DeviceIDs(f::DeviceIDs {
-                major: (dev / 256) as u8,
-                minor: (dev % 256) as u8,
+                major: device_ids[6],
+                minor: device_ids[7],
             })
         }
         else {