Make argh directly parse into Utf8CString

native/src/base/cstr.rs

@@ -7,7 +7,7 @@ use std::fmt::{Debug, Display, Formatter, Write};
 use std::ops::Deref;
 use std::os::unix::ffi::OsStrExt;
 use std::path::{Path, PathBuf};
-use std::str::Utf8Error;
+use std::str::{FromStr, Utf8Error};
 use std::{fmt, mem, slice, str};
 use thiserror::Error;
 
@@ -200,7 +200,18 @@ impl From<String> for Utf8CString {
 
 impl From<&str> for Utf8CString {
     fn from(value: &str) -> Self {
-        value.to_string().into()
+        let mut s = String::with_capacity(value.len() + 1);
+        s.push_str(value);
+        s.nul_terminate();
+        Utf8CString(s)
+    }
+}
+
+impl FromStr for Utf8CString {
+    type Err = String;
+
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        Ok(s.into())
     }
 }
 

native/src/base/misc.rs

@@ -1,4 +1,4 @@
-use crate::{Utf8CStr, cstr, ffi};
+use crate::{Utf8CStr, Utf8CString, cstr, ffi};
 use argh::{EarlyExit, MissingRequirements};
 use libc::c_char;
 use std::{
@@ -105,9 +105,9 @@ impl<T> EarlyExitExt<T> for Result<T, EarlyExit> {
 pub struct PositionalArgParser<'a>(pub slice::Iter<'a, &'a str>);
 
 impl PositionalArgParser<'_> {
-    pub fn required(&mut self, field_name: &'static str) -> Result<String, EarlyExit> {
+    pub fn required(&mut self, field_name: &'static str) -> Result<Utf8CString, EarlyExit> {
         if let Some(next) = self.0.next() {
-            Ok(next.to_string())
+            Ok((*next).into())
         } else {
             let mut missing = MissingRequirements::default();
             missing.missing_positional_arg(field_name);
@@ -116,17 +116,17 @@ impl PositionalArgParser<'_> {
         }
     }
 
-    pub fn optional(&mut self) -> Option<String> {
-        self.0.next().map(ToString::to_string)
+    pub fn optional(&mut self) -> Option<Utf8CString> {
+        self.0.next().map(|s| (*s).into())
     }
 
-    pub fn last_required(&mut self, field_name: &'static str) -> Result<String, EarlyExit> {
+    pub fn last_required(&mut self, field_name: &'static str) -> Result<Utf8CString, EarlyExit> {
         let r = self.required(field_name)?;
         self.ensure_end()?;
         Ok(r)
     }
 
-    pub fn last_optional(&mut self) -> Result<Option<String>, EarlyExit> {
+    pub fn last_optional(&mut self) -> Result<Option<Utf8CString>, EarlyExit> {
         let r = self.optional();
         if r.is_none() {
             return Ok(r);