pnet_macros: fix num_bytes calculation

pnet_macros/src/util.rs

@@ -382,12 +382,10 @@ pub fn operations(offset: usize, size: usize) -> Option<Vec<GetOperation>> {
         return None;
     }
 
-    let num_full_bytes = size / 8;
-    let num_bytes = if offset > 0 || size % 8 != 0 {
-        num_full_bytes + 1
-    } else {
-        num_full_bytes
-    };
+
+    let start = offset / 8;
+    let end = (offset+size-1) / 8;
+    let num_bytes = (end - start) + 1;
 
     let mut current_offset = offset;
     let mut num_bits_remaining = size;
@@ -627,6 +625,22 @@ fn operations_test() {
             }
         ]
     );
+
+    assert_eq!(
+        operations(6, 6).unwrap(),
+        vec![
+            Op {
+                mask: 3,
+                shiftl: 4,
+                shiftr: 0,
+            },
+            Op {
+                mask: 240,
+                shiftl: 0,
+                shiftr: 4,
+            }
+        ]
+    );
 }
 
 /// Mask `bits` bits of a byte. eg. mask_high_bits(2) == 0b00000011

pnet_macros/tests/run-pass/weird_field_pos.rs

@@ -0,0 +1,40 @@
+// Copyright (c) 2022 Yureka <yuka@yuka.dev>
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+extern crate pnet_macros;
+extern crate pnet_macros_support;
+use pnet_macros::packet;
+use pnet_macros_support::types::*;
+
+#[packet]
+pub struct Test {
+    banana: u2,
+    apple: u4,
+    potato: u6,
+    the_rest: u20be,
+    #[payload]
+    payload: Vec<u8>,
+}
+
+fn main() {
+    let test = Test {
+        banana: 0b10,
+        apple: 0b1010,
+        potato: 0b101010,
+        the_rest: 0b10101010101010101010,
+        payload: vec![],
+    };
+
+    let mut buf = vec![0; TestPacket::packet_size(&test)];
+    let mut packet = MutableTestPacket::new(&mut buf).unwrap();
+    packet.populate(&test);
+    assert_eq!(packet.get_banana(), test.banana);
+    assert_eq!(packet.get_apple(), test.apple);
+    assert_eq!(packet.get_potato(), test.potato);
+    assert_eq!(packet.get_the_rest(), test.the_rest);
+}