uefi: Revise comments to be more descriptive and use macros for CStr16

Co-authored-by: Philipp Schuster <phip1611@gmail.com>

Author: RenTrieu

uefi-test-runner/src/proto/shell.rs

@@ -25,9 +25,9 @@ pub fn test_env(shell: &ScopedProtocol<Shell>) {
     /* Test setting and getting a specific environment variable */
     let cur_env_vec = shell.get_envs();
     let mut test_env_buf = [0u16; 32];
-    let test_var = CStr16::from_str_with_buf("test_var", &mut test_env_buf).unwrap();
+    let test_var = cstr16!("test_var");
     let mut test_val_buf = [0u16; 32];
-    let test_val = CStr16::from_str_with_buf("test_val", &mut test_val_buf).unwrap();
+    let test_val = cstr16!("test_val");
     assert!(shell.get_env(test_var).is_none());
     let status = shell.set_env(test_var, test_val, false);
     assert_eq!(status, Status::SUCCESS);
@@ -56,7 +56,7 @@ pub fn test_env(shell: &ScopedProtocol<Shell>) {
     assert_eq!(cur_env_vec.count(), default_len + 1);
 
     /* Test deleting environment variable */
-    let test_val = CStr16::from_str_with_buf("", &mut test_val_buf).unwrap();
+    let test_val = cstr16!("");
     let status = shell.set_env(test_var, test_val, false);
     assert_eq!(status, Status::SUCCESS);
     assert!(shell.get_env(test_var).is_none());
@@ -73,13 +73,13 @@ pub fn test_env(shell: &ScopedProtocol<Shell>) {
     assert_eq!(cur_env_vec.count(), default_len);
 }
 
-/// Test ``get_cur_dir()`` and ``set_cur_dir()``
+/// Test `get_cur_dir()` and `set_cur_dir()`
 pub fn test_cur_dir(shell: &ScopedProtocol<Shell>) {
     let mut test_buf = [0u16; 128];
 
     /* Test setting and getting current file system and current directory */
     let mut fs_buf = [0u16; 16];
-    let fs_var = CStr16::from_str_with_buf("fs0:", &mut fs_buf).unwrap();
+    let fs_var = cstr16!("fs0:")
     let mut dir_buf = [0u16; 32];
     let dir_var = CStr16::from_str_with_buf("/", &mut dir_buf).unwrap();
     let status = shell.set_cur_dir(Some(fs_var), Some(dir_var));

uefi/src/proto/shell/mod.rs

@@ -18,7 +18,7 @@ use crate::{CStr16, Char16};
 #[unsafe_protocol(ShellProtocol::GUID)]
 pub struct Shell(ShellProtocol);
 
-/// Contains environment variables
+/// Iterator over the names of environmental variables obtained from the Shell protocol.
 #[derive(Debug)]
 pub struct Vars<'a> {
     /// Char16 containing names of environment variables
@@ -29,6 +29,8 @@ pub struct Vars<'a> {
 
 impl<'a> Iterator for Vars<'a> {
     type Item = &'a CStr16;
+    // We iterate a list of NUL terminated CStr16s.
+    // The list is terminated with a double NUL.
     fn next(&mut self) -> Option<Self::Item> {
         let cur_start = self.inner;
         let mut cur_len = 0;