getopt.rs(3): safe api around optind reading and setting

src/getopt.rs

@@ -34,10 +34,16 @@ extern "C" {
 
 pub struct Opt {
 	pub arg: Option<String>,
-	pub ind: *mut i32,
+	ind: *mut i32,
 	pub opt: String,
 }
 
+impl Opt {
+	pub fn index(&self) -> usize { unsafe { *self.ind as usize } }
+
+	pub fn set_index(&self, ind: i32) { unsafe { *self.ind = ind; } }
+}
+
 pub enum OptError {
 	MissingArg(String),
 	UnknownOpt(String),
@@ -121,9 +127,8 @@ impl GetOpt for Vec<String> {
 						 * characters, it is unspecified how getopt()
 						 * determines which options have already been processed.
 						 *
-						 * This API is unsafe and can be utilized by
-						 * dereferencing the ind field before reading to and
-						 * writing from the optind memory. */
+						 * This API is can be utilized with the index() and
+						 * set_index() methods implemented for Opt. */
 						ind: std::ptr::addr_of_mut!(optind),
 						opt: opt.to_string(), /* option itself */
 					}))