[v8,1/4] rust: move BStr,CStr Display impls behind method

Commit Message

Tamir Duberstein Feb. 3, 2025, 11:50 a.m. UTC

There are two reasons for doing this:
- Moving the Display impl behind a display method matches the style used
  in the standard library for printing non-Unicode data.
- The standard library's core::ffi::CStr doesn't implement Display;
  moving Display to a helper struct is a necessary step toward using it.

Signed-off-by: Tamir Duberstein <[e-mail]>
---
 rust/kernel/kunit.rs |   9 ++--
 rust/kernel/str.rs   | 121 +++++++++++++++++++++++++++++++++++----------------
 2 files changed, 90 insertions(+), 40 deletions(-)

Patch

diff --git a/rust/kernel/kunit.rs b/rust/kernel/kunit.rs
index 824da0e9738a..630b947c708c 100644
--- a/rust/kernel/kunit.rs
+++ b/rust/kernel/kunit.rs
@@ -56,6 +56,7 @@  macro_rules! kunit_assert {
                 break 'out;
             }
 
+            static NAME: &'static $crate::str::CStr = $crate::c_str!($name);
             static FILE: &'static $crate::str::CStr = $crate::c_str!($file);
             static LINE: i32 = core::line!() as i32 - $diff;
             static CONDITION: &'static $crate::str::CStr = $crate::c_str!(stringify!($condition));
@@ -71,11 +72,13 @@  macro_rules! kunit_assert {
                 //
                 // This mimics KUnit's failed assertion format.
                 $crate::kunit::err(format_args!(
-                    "    # {}: ASSERTION FAILED at {FILE}:{LINE}\n",
-                    $name
+                    "    # {NAME}: ASSERTION FAILED at {FILE}:{LINE}\n",
+                    NAME = NAME.display(),
+                    FILE = FILE.display(),
                 ));
                 $crate::kunit::err(format_args!(
-                    "    Expected {CONDITION} to be true, but is false\n"
+                    "    Expected {CONDITION} to be true, but is false\n",
+                    CONDITION = CONDITION.display(),
                 ));
                 $crate::kunit::err(format_args!(
                     "    Failure not reported to KUnit since this is a non-KUnit task\n"
diff --git a/rust/kernel/str.rs b/rust/kernel/str.rs
index 28e2201604d6..c273f1367607 100644
--- a/rust/kernel/str.rs
+++ b/rust/kernel/str.rs
@@ -31,29 +31,77 @@  pub const fn from_bytes(bytes: &[u8]) -> &Self {
         // SAFETY: `BStr` is transparent to `[u8]`.
         unsafe { &*(bytes as *const [u8] as *const BStr) }
     }
-}
 
-impl fmt::Display for BStr {
-    /// Formats printable ASCII characters, escaping the rest.
+    /// Returns an object that implements [`Display`] for safely printing a [`BStr`] that may
+    /// contain non-Unicode data. If you would like an implementation which escapes the [`BStr`]
+    /// please use [`Debug`] instead.
+    ///
+    /// [`Display`]: fmt::Display
+    /// [`Debug`]: fmt::Debug
+    ///
+    /// # Examples
     ///
     /// ```
-    /// # use kernel::{fmt, b_str, str::{BStr, CString}};
+    /// # use kernel::{fmt, b_str, str::CString};
     /// let ascii = b_str!("Hello, BStr!");
-    /// let s = CString::try_from_fmt(fmt!("{}", ascii))?;
+    /// let s = CString::try_from_fmt(fmt!("{}", ascii.display()))?;
     /// assert_eq!(s.as_bytes(), "Hello, BStr!".as_bytes());
     ///
     /// let non_ascii = b_str!("