add test for custom tags

Author: phip1611

multiboot2/src/lib.rs

@@ -550,6 +550,70 @@ mod tests {
         assert!(bi.command_line_tag().is_none());
     }
 
+    #[test]
+    fn custom_tag() {
+        const CUSTOM_TAG_ID: u32 = 0x1337;
+
+        #[repr(C, align(8))]
+        struct Bytes([u8; 32]);
+        let bytes: Bytes = Bytes([
+            32,
+            0,
+            0,
+            0, // total_size
+            0,
+            0,
+            0,
+            0, // reserved
+            // my custom tag
+            CUSTOM_TAG_ID.to_ne_bytes()[0],
+            CUSTOM_TAG_ID.to_ne_bytes()[1],
+            CUSTOM_TAG_ID.to_ne_bytes()[2],
+            CUSTOM_TAG_ID.to_ne_bytes()[3],
+            13,
+            0,
+            0,
+            0, // tag size
+            110,
+            97,
+            109,
+            101, // ASCII string 'name'
+            0,
+            0,
+            0,
+            0, // null byte + padding
+            0,
+            0,
+            0,
+            0, // end tag type
+            8,
+            0,
+            0,
+            0, // end tag size
+        ]);
+        let addr = bytes.0.as_ptr() as usize;
+        let bi = unsafe { load(addr) };
+        let bi = bi.unwrap();
+        assert_eq!(addr, bi.start_address());
+        assert_eq!(addr + bytes.0.len(), bi.end_address());
+        assert_eq!(bytes.0.len(), bi.total_size());
+
+        #[repr(C, align(8))]
+        struct CustomTag {
+            tag: SpecifiedOrCustomTagTypeSerialized,
+            size: u32,
+            name: u8,
+        }
+
+        let tag = bi
+            .get_tag(SpecifiedOrCustomTagTypeSerialized::from(CUSTOM_TAG_ID).into())
+            .unwrap()
+            .cast_tag::<CustomTag>();
+        let name = &tag.name as *const u8 as *const c_char;
+        let str = unsafe { CStr::from_ptr(name).to_str().unwrap() };
+        assert_eq!(str, "name");
+    }
+
     #[test]
     /// Compile time test for `BootLoaderNameTag`.
     fn name_tag_size() {