add version getting example

examples/version.rs

@@ -0,0 +1,19 @@
+fn main() -> Result<(), un_pak::Error> {
+    // drag onto or open any pak with the example
+    let path = std::env::args().nth(1).unwrap_or_default();
+    for ver in un_pak::Version::iter() {
+        match un_pak::Pak::new(
+            std::io::BufReader::new(std::fs::OpenOptions::new().read(true).open(&path)?),
+            ver,
+        ) {
+            Ok(un_pak::Pak { version, .. }) | Err(un_pak::Error::Version { version, .. }) => {
+                println!("{}", version);
+                break;
+            }
+            _ => continue,
+        }
+    }
+    // so you can read the results
+    std::thread::sleep(std::time::Duration::from_secs(10));
+    Ok(())
+}

src/error.rs

@@ -12,8 +12,11 @@ pub enum Error {
     IntoInner(#[from] std::io::IntoInnerError<std::io::BufWriter<Vec<u8>>>),
     #[error("found magic of {0:#x} instead of {:#x}", super::MAGIC)]
     Magic(u32),
-    #[error("used version {0} but pak is version {1}")]
+    #[error("used version {used} but pak is version {version}")]
-    Version(super::Version, super::Version),
+    Version {
+        used: super::Version,
+        version: super::Version,
+    },
     #[error("got {0}, which is not a boolean")]
     Bool(u8),
     #[error("{0}")]

src/footer.rs

@@ -57,7 +57,10 @@ impl Footer {
             return Err(super::Error::Magic(footer.magic));
         }
         if version != footer.version {
-            return Err(super::Error::Version(version, footer.version));
+            return Err(super::Error::Version {
+                used: version,
+                version: footer.version,
+            });
         }
         Ok(footer)
     }