uefi: Exclude null byte from CStr8 Display impl

This makes it match the CStr16 Display impl. Added tests for both.

Author: nicholasbishop

uefi/CHANGELOG.md

@@ -10,6 +10,7 @@
 - `SimpleNetwork::transmit` now passes the correct buffer size argument.
   Previously it incorrectly added the header size to the buffer length, which
   could cause the firmware to read past the end of the buffer.
+- The `Display` impl for `CStr8` now excludes the trailing null character.
 
 
 # uefi - 0.34.1 (2025-02-07)

uefi/src/data_types/strs.rs

@@ -196,7 +196,7 @@ impl fmt::Debug for CStr8 {
 
 impl fmt::Display for CStr8 {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        for c in self.0.iter() {
+        for c in &self.0[..&self.0.len() - 1] {
             <Char8 as fmt::Display>::fmt(c, f)?;
         }
         Ok(())
@@ -763,6 +763,7 @@ where
 mod tests {
     use super::*;
     use crate::{cstr16, cstr8};
+    use alloc::format;
     use alloc::string::String;
 
     // Tests if our CStr8 type can be constructed from a valid core::ffi::CStr
@@ -783,6 +784,18 @@ mod tests {
         assert_eq!(<CStr8 as Borrow<[u8]>>::borrow(string), &[b'a', 0]);
     }
 
+    #[test]
+    fn test_cstr8_display() {
+        let s = cstr8!("abc");
+        assert_eq!(format!("{s}"), "abc");
+    }
+
+    #[test]
+    fn test_cstr16_display() {
+        let s = cstr16!("abc");
+        assert_eq!(format!("{s}"), "abc");
+    }
+
     #[test]
     fn test_cstr16_num_bytes() {
         let s = CStr16::from_u16_with_nul(&[65, 66, 67, 0]).unwrap();