Add mode::Parser and constructors

src/mode/mod.rs

@@ -1,5 +1,11 @@
 //! Functions for parsing and managing permissions
 
+pub fn get_umask() -> u32 {
+    let mask = unsafe { libc::umask(0) };
+    let umask = unsafe {libc::umask(mask) };
+    umask
+}
+
 #[derive(Debug, PartialEq)]
 pub enum Bits {
     Suid = 0o4000,
@@ -33,6 +39,29 @@ pub enum Who {
 
 pub struct Parser {
     mode: u32,
-    op: Op,
-    who: Who,
+    op: Option<Op>,
+    who: Option<Who>,
+}
+
+impl Default for Parser {
+    fn default() -> Self {
+        let umask = get_umask();
+        let mut mode = 0o0777;
+        mode &= umask;
+        Self {
+            mode,
+            op: None,
+            who: None,
+        }
+    }
+}
+
+impl Parser {
+    fn new(mode: u32) -> Self {
+        Self {
+            mode,
+            op: None,
+            who: None,
+        }
+    }
 }