Using back to get the last element (#9415)

Summary: Pull Request resolved: https://github.com/facebook/rocksdb/pull/9415

Reviewed By: ajkr

Differential Revision: D33773673

Pulled By: riversand963

fbshipit-source-id: 52b59ec5a6b01a91d3f990b7f2b0f16320afb49b

tools/ldb_cmd.cc

@@ -1191,7 +1191,7 @@ void ManifestDumpCommand::DoCommand() {
       exec_state_ = LDBCommandExecuteResult::Failed(err_msg);
       return;
     }
-    if (db_path_[db_path_.length() - 1] != '/') {
+    if (db_path_.back() != '/') {
       db_path_.append("/");
     }
     manifestfile = db_path_ + matched_file;

tools/ldb_cmd_test.cc

@@ -187,7 +187,7 @@ class FileChecksumTestHelper {
   Status VerifyChecksumInManifest(
       const std::vector<LiveFileMetaData>& live_files) {
     // Step 1: verify if the dbname_ is correct
-    if (dbname_[dbname_.length() - 1] != '/') {
+    if (dbname_.back() != '/') {
       dbname_.append("/");
     }