fix: as_las_string_lossy ignores anything after the first null charac…

…ter (#100)

I just came across a las file with the following Extra-Attributes VLR: 

```
Vlr {
    user_id: "LASF_Spec\0\0\0\0\0\u{18}\0",
    record_id: 4,
    ...
}
```

The user_id is not properly filled with null characters (see the
`\u{18}` hidden in there...). In this case, `as_las_string_lossy`
currently returns the full string including all null characters. This
results in the extra-bytes VLR not being detected correctly in my own
code. Most other tools like LasTools or CloudCompare seem to have no
problem with this and just ignore anything after the first null
character. I changed `as_las_string_lossy` to work this way, too. Now
`as_las_string_lossy` correctly parses above user id as "LASF_Spec".

Co-authored-by: Tobias Dorra <[email protected]>

src/utils.rs

@@ -41,7 +41,10 @@ impl AsLasStr for &'_ [u8] {
     fn as_las_string_lossy(&self) -> String {
         match self.as_las_str() {
             Ok(s) => s.to_string(),
-            Err(_) => String::from_utf8_lossy(self).to_string(),
+            Err(_) => {
+                let len = self.iter().position(|c| *c == 0).unwrap_or(self.len());
+                String::from_utf8_lossy(&self[..len]).to_string()
+            }
         }
     }
 }
@@ -101,4 +104,10 @@ mod tests {
         let mut bytes = [0; 5];
         assert!(bytes.as_mut().from_las_str("Beer!!").is_err());
     }
+
+    #[test]
+    fn lossy_from_not_null_filled() {
+        let bytes = [65, 66, 67, 0, 68];
+        assert_eq!("ABC", bytes.as_ref().as_las_string_lossy());
+    }
 }

src/vlr.rs

@@ -191,29 +191,23 @@ mod tests {
     #[test]
     fn allow_non_ascii_user_id() {
         let raw_vlr = raw::Vlr {
-            user_id: [0, 42, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
+            user_id: [194, 174, 0, 0, 0, 0, 0, 0, 42, 0, 0, 0, 0, 0, 0, 0],
             ..Default::default()
         };
         let vlr = Vlr::new(raw_vlr);
-        assert_eq!(
-            "\u{0}*\u{0}\u{0}\u{0}\u{0}\u{0}\u{0}\u{0}\u{0}\u{0}\u{0}\u{0}\u{0}\u{0}\u{0}",
-            vlr.user_id
-        );
+        assert_eq!("®", vlr.user_id);
     }
 
     #[test]
     fn allow_non_ascii_description() {
         let raw_vlr = raw::Vlr {
             description: [
-                0, 42, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 42, 0, 0, 0, 0, 0, 0, 0, 0, 0,
-                0, 0, 0, 0, 0,
+                194, 174, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 42, 0, 0, 0, 0, 0, 0, 0, 0,
+                0, 0, 0, 0, 0, 0,
             ],
             ..Default::default()
         };
         let vlr = Vlr::new(raw_vlr);
-        assert_eq!(
-            "\u{0}*\u{0}\u{0}\u{0}\u{0}\u{0}\u{0}\u{0}\u{0}\u{0}\u{0}\u{0}\u{0}\u{0}\u{0}\u{0}*\u{0}\u{0}\u{0}\u{0}\u{0}\u{0}\u{0}\u{0}\u{0}\u{0}\u{0}\u{0}\u{0}\u{0}",
-            vlr.description
-        );
+        assert_eq!("®", vlr.description);
     }
 }