Fix padding fields default value being ignored when using Msb (#57)

* Add tests
* Calculate offset for all fields during member construction

Author: gregorygaines

src/lib.rs

@@ -341,6 +341,13 @@ impl Member {
 
         let ignore = ignore || access == Access::None;
 
+        // compute the offset
+        let offset = if order == Order::Lsb {
+            offset
+        } else {
+            base_bits - offset - bits
+        };
+
         if bits > 0 && !ignore {
             // overflow check
             if offset + bits > base_bits {
@@ -358,13 +365,6 @@ impl Member {
                 Access::None => (quote!(), quote!()),
             };
 
-            // compute the offset
-            let offset = if order == Order::Lsb {
-                offset
-            } else {
-                base_bits - offset - bits
-            };
-
             // auto-conversion from zero
             if default.is_empty() {
                 if !from.is_empty() {
@@ -427,7 +427,8 @@ impl Member {
         let repr_into = &self.repr_into;
         let repr_from = &self.repr_from;
         let bits = self.bits as u32;
-        quote!{
+
+        quote! {
             let mask = #base_ty::MAX >> (#base_ty::BITS - #bits);
             this.0 = #repr_from(#repr_into(this.0) | (((#default as #base_ty) & mask) << #offset));
         }

tests/test.rs

@@ -565,3 +565,31 @@ fn default_without_setter() {
         reserved: bool
     }
 }
+
+#[test]
+fn default_msb_padding_default_value() {
+    #[bitfield(u8, order = Msb)]
+    struct MyMsbByte {
+        #[bits(4, default = 0b1111)]
+        __padding: usize,
+        #[bits(4, default = 0b1010)]
+        kind: usize,
+    }
+    let my_byte_msb = MyMsbByte::new();
+    let val: u8 = my_byte_msb.into();
+    assert_eq!(val, 0b1111_1010);
+}
+
+#[test]
+fn default_lsb_padding_default_value() {
+    #[bitfield(u8, order = Lsb)]
+    struct MyMsbByte {
+        #[bits(4, default = 0b1111)]
+        __padding: usize,
+        #[bits(4, default = 0b1010)]
+        kind: usize,
+    }
+    let my_byte_msb = MyMsbByte::new();
+    let val: u8 = my_byte_msb.into();
+    assert_eq!(val, 0b1010_1111);
+}