get env from DB (#252)

Signed-off-by: zhangjinpeng1987 <zhangjinpeng@pingcap.com>

src/rocksdb.rs

@@ -31,6 +31,7 @@ use std::io;
 use std::ops::Deref;
 use std::path::{Path, PathBuf};
 use std::str::from_utf8;
+use std::sync::Arc;
 use std::{fs, ptr, slice};
 use table_properties::TablePropertiesCollection;
 
@@ -602,6 +603,10 @@ impl DB {
         Ok(cfs)
     }
 
+    pub fn env(&self) -> Option<Arc<Env>> {
+        self.opts.env()
+    }
+
     pub fn pause_bg_work(&self) {
         unsafe {
             crocksdb_ffi::crocksdb_pause_bg_work(self.inner);
@@ -2262,7 +2267,6 @@ mod test {
     use std::path::Path;
     use std::str;
     use std::string::String;
-    use std::sync::*;
     use std::thread;
     use tempdir::TempDir;
 

src/rocksdb_options.rs

@@ -589,6 +589,10 @@ impl DBOptions {
         DBOptions::default()
     }
 
+    pub fn env(&self) -> Option<Arc<Env>> {
+        self.env.clone()
+    }
+
     pub unsafe fn from_raw(inner: *mut Options) -> DBOptions {
         DBOptions {
             inner: inner,