port env background threads setters (#672)

* port background threads setters
Signed-off-by: tabokie <xy.tao@outlook.com>

* format and fix build
Signed-off-by: tabokie <xy.tao@outlook.com>

* fix build
Signed-off-by: tabokie <xy.tao@outlook.com>

* fix test
Signed-off-by: tabokie <xy.tao@outlook.com>

* fix test
Signed-off-by: tabokie <xy.tao@outlook.com>

* fix test
Signed-off-by: tabokie <xy.tao@outlook.com>

* switch to i32
Signed-off-by: tabokie <xy.tao@outlook.com>

* format
Signed-off-by: tabokie <xy.tao@outlook.com>

librocksdb_sys/src/lib.rs

@@ -1626,6 +1626,8 @@ extern "C" {
     pub fn crocksdb_env_file_exists(env: *mut DBEnv, path: *const c_char, err: *mut *mut c_char);
     pub fn crocksdb_env_delete_file(env: *mut DBEnv, path: *const c_char, err: *mut *mut c_char);
     pub fn crocksdb_env_destroy(env: *mut DBEnv);
+    pub fn crocksdb_env_set_background_threads(env: *mut DBEnv, n: c_int);
+    pub fn crocksdb_env_set_high_priority_background_threads(env: *mut DBEnv, n: c_int);
 
     // EnvOptions
     pub fn crocksdb_envoptions_create() -> *mut EnvOptions;

src/rocksdb.rs

@@ -2700,6 +2700,18 @@ impl Env {
             Ok(())
         }
     }
+
+    pub fn set_background_threads(&self, n: i32) {
+        unsafe {
+            crocksdb_ffi::crocksdb_env_set_background_threads(self.inner, n);
+        }
+    }
+
+    pub fn set_high_priority_background_threads(&self, n: i32) {
+        unsafe {
+            crocksdb_ffi::crocksdb_env_set_high_priority_background_threads(self.inner, n);
+        }
+    }
 }
 
 impl Drop for Env {
@@ -3728,4 +3740,14 @@ mod test {
         db.ingest_external_file_cf(db.cf_handle("default").unwrap(), &ingest_opt, &[p1, p2])
             .unwrap();
     }
+
+    #[test]
+    fn test_env_operations() {
+        let env = Env::new_mem();
+        assert!(env.file_exists("a").unwrap_err().contains("NotFound"));
+        env.set_background_threads(4);
+        env.set_background_threads(0);
+        env.set_high_priority_background_threads(4);
+        env.set_high_priority_background_threads(0);
+    }
 }