add a factory method for creating hdfs env

include/rocksdb/env.h

@@ -947,6 +947,10 @@ class WritableFileWrapper : public WritableFile {
 // *base_env must remain live while the result is in use.
 Env* NewMemEnv(Env* base_env);
 
+// Returns a new environment that is used for HDFS environment.
+// This is a factory method for HdfsEnv declared in hdfs/env_hdfs.h
+Status NewHdfsEnv(Env** hdfs_env, const std::string& fsname);
+
 }  // namespace rocksdb
 
 #endif  // STORAGE_ROCKSDB_INCLUDE_ENV_H_

util/env_hdfs.cc

@@ -594,6 +594,11 @@ Status HdfsEnv::NewLogger(const std::string& fname,
   return Status::OK();
 }
 
+	// The factory method for creating an HDFS Env
+Status NewHdfsEnv(Env** hdfs_env, const std::string& fsname) {
+	*hdfs_env = new HdfsEnv(fsname);
+	return Status::OK();
+}
 }  // namespace rocksdb
 
 #endif // ROCKSDB_HDFS_FILE_C
@@ -607,6 +612,11 @@ namespace rocksdb {
                                    const EnvOptions& options) {
    return Status::NotSupported("Not compiled with hdfs support");
  }
+
+ Status NewHdfsEnv(Env** hdfs_env, const std::string& fsname) {
+	 return Status::NotSupported("Not compiled with hdfs support");
+ }
+
 }
 
 #endif