adding version function to environment

.gitignore

@@ -1,3 +1,4 @@
+.DS_Store
 target/
 **/*.rs.bk
 Cargo.lock

src/backend/impl_lmdb/environment.rs

@@ -218,6 +218,10 @@ impl<'e> BackendEnvironment<'e> for EnvironmentImpl {
             .map_err(ErrorImpl::LmdbError)
     }
 
+    fn version(&self) -> &str {
+        self.lmdbenv.version()
+    }
+
     fn begin_ro_txn(&'e self) -> Result<Self::RoTransaction, Self::Error> {
         self.lmdbenv
             .begin_ro_txn()

src/backend/impl_safe/environment.rs

@@ -323,4 +323,9 @@ impl<'e> BackendEnvironment<'e> for EnvironmentImpl {
         db_filename.push(DEFAULT_DB_FILENAME);
         vec![db_filename]
     }
+
+    fn version(&self) -> &str {
+        let ret: &str = "unknown";
+        ret
+    }
 }

src/backend/traits.rs

@@ -117,6 +117,8 @@ pub trait BackendEnvironment<'e>: Debug {
 
     fn info(&self) -> Result<Self::Info, Self::Error>;
 
+    fn version(&self) -> &str;
+
     fn freelist(&self) -> Result<usize, Self::Error>;
 
     fn load_ratio(&self) -> Result<Option<f32>, Self::Error>;

src/env.rs

@@ -272,6 +272,10 @@ where
         self.env.info().map_err(|e| e.into())
     }
 
+    pub fn version(&self) -> &str {
+        self.env.version()
+    }
+
     /// Retrieve the load ratio (# of used pages / total pages) about this environment.
     ///
     /// With the formular: (last_page_no - freelist_pages) / total_pages.