Use Env::GetChildren() instead of readdir (#6139)

Summary:
For more portability, switch from readdir to Env::GetChildren() in ldb's
manifest_dump subcommand.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6139

Test Plan:
```
$make check
```
Manually check ldb command.

Differential Revision: D18898197

Pulled By: riversand963

fbshipit-source-id: 92afca379e9fbe78ab70b2eb40d127daad8df5e2

tools/ldb_cmd.cc

@@ -1016,8 +1016,8 @@ void DumpManifestFile(Options options, std::string file, bool verbose, bool hex,
                       /*block_cache_tracer=*/nullptr);
   Status s = versions.DumpManifest(options, file, verbose, hex, json);
   if (!s.ok()) {
-    printf("Error in processing file %s %s\n", file.c_str(),
+    fprintf(stderr, "Error in processing file %s %s\n", file.c_str(),
-           s.ToString().c_str());
+            s.ToString().c_str());
   }
 }
 
@@ -1066,45 +1066,72 @@ void ManifestDumpCommand::DoCommand() {
   if (!path_.empty()) {
     manifestfile = path_;
   } else {
-    bool found = false;
     // We need to find the manifest file by searching the directory
     // containing the db for files of the form MANIFEST_[0-9]+
 
-    auto CloseDir = [](DIR* p) { closedir(p); };
+    std::vector<std::string> files;
-    std::unique_ptr<DIR, decltype(CloseDir)> d(opendir(db_path_.c_str()),
+    Status s = options_.env->GetChildren(db_path_, &files);
-                                               CloseDir);
+    if (!s.ok()) {
-
+      std::string err_msg = s.ToString();
-    if (d == nullptr) {
+      err_msg.append(": Failed to list the content of ");
-      exec_state_ =
+      err_msg.append(db_path_);
-          LDBCommandExecuteResult::Failed(db_path_ + " is not a directory");
+      exec_state_ = LDBCommandExecuteResult::Failed(err_msg);
       return;
     }
-    struct dirent* entry;
+    const std::string kManifestNamePrefix = "MANIFEST-";
-    while ((entry = readdir(d.get())) != nullptr) {
+    std::string matched_file;
-      unsigned int match;
+#ifdef OS_WIN
-      uint64_t num;
+    const char kPathDelim = '\\';
-      if (sscanf(entry->d_name, "MANIFEST-%" PRIu64 "%n", &num, &match) &&
+#else
-          match == strlen(entry->d_name)) {
+    const char kPathDelim = '/';
-        if (!found) {
+#endif
-          manifestfile = db_path_ + "/" + std::string(entry->d_name);
+    for (const auto& file_path : files) {
-          found = true;
+      // Some Env::GetChildren() return absolute paths. Some directories' path
-        } else {
+      // end with path delim, e.g. '/' or '\\'.
+      size_t pos = file_path.find_last_of(kPathDelim);
+      if (pos == file_path.size() - 1) {
+        continue;
+      }
+      std::string fname;
+      if (pos != std::string::npos) {
+        // Absolute path.
+        fname.assign(file_path, pos + 1, file_path.size() - pos - 1);
+      } else {
+        fname = file_path;
+      }
+      uint64_t file_num = 0;
+      FileType file_type = kLogFile;  // Just for initialization
+      if (ParseFileName(fname, &file_num, &file_type) &&
+          file_type == kDescriptorFile) {
+        if (!matched_file.empty()) {
           exec_state_ = LDBCommandExecuteResult::Failed(
               "Multiple MANIFEST files found; use --path to select one");
           return;
+        } else {
+          matched_file.swap(fname);
         }
       }
     }
+    if (matched_file.empty()) {
+      std::string err_msg("No MANIFEST found in ");
+      err_msg.append(db_path_);
+      exec_state_ = LDBCommandExecuteResult::Failed(err_msg);
+      return;
+    }
+    if (db_path_[db_path_.length() - 1] != '/') {
+      db_path_.append("/");
+    }
+    manifestfile = db_path_ + matched_file;
   }
 
   if (verbose_) {
-    printf("Processing Manifest file %s\n", manifestfile.c_str());
+    fprintf(stdout, "Processing Manifest file %s\n", manifestfile.c_str());
   }
 
   DumpManifestFile(options_, manifestfile, verbose_, is_key_hex_, json_);
 
   if (verbose_) {
-    printf("Processing Manifest file %s done\n", manifestfile.c_str());
+    fprintf(stdout, "Processing Manifest file %s done\n", manifestfile.c_str());
   }
 }
 
@@ -1126,19 +1153,19 @@ void ListColumnFamiliesCommand::DoCommand() {
   std::vector<std::string> column_families;
   Status s = DB::ListColumnFamilies(options_, db_path_, &column_families);
   if (!s.ok()) {
-    printf("Error in processing db %s %s\n", db_path_.c_str(),
+    fprintf(stderr, "Error in processing db %s %s\n", db_path_.c_str(),
-           s.ToString().c_str());
+            s.ToString().c_str());
   } else {
-    printf("Column families in %s: \n{", db_path_.c_str());
+    fprintf(stdout, "Column families in %s: \n{", db_path_.c_str());
     bool first = true;
     for (auto cf : column_families) {
       if (!first) {
-        printf(", ");
+        fprintf(stdout, ", ");
       }
       first = false;
-      printf("%s", cf.c_str());
+      fprintf(stdout, "%s", cf.c_str());
     }
-    printf("}\n");
+    fprintf(stdout, "}\n");
   }
 }
 
@@ -2761,7 +2788,7 @@ void CheckPointCommand::DoCommand() {
   Status status = Checkpoint::Create(db_, &checkpoint);
   status = checkpoint->CreateCheckpoint(checkpoint_dir_);
   if (status.ok()) {
-    printf("OK\n");
+    fprintf(stdout, "OK\n");
   } else {
     exec_state_ = LDBCommandExecuteResult::Failed(status.ToString());
   }
@@ -2785,7 +2812,7 @@ void RepairCommand::DoCommand() {
   options.info_log.reset(new StderrLogger(InfoLogLevel::WARN_LEVEL));
   Status status = RepairDB(db_path_, options);
   if (status.ok()) {
-    printf("OK\n");
+    fprintf(stdout, "OK\n");
   } else {
     exec_state_ = LDBCommandExecuteResult::Failed(status.ToString());
   }
@@ -2865,7 +2892,7 @@ void BackupCommand::DoCommand() {
     assert(GetExecuteState().IsFailed());
     return;
   }
-  printf("open db OK\n");
+  fprintf(stdout, "open db OK\n");
   Env* custom_env = nullptr;
   Env::LoadEnv(backup_env_uri_, &custom_env, &backup_env_guard_);
   assert(custom_env != nullptr);
@@ -2876,14 +2903,14 @@ void BackupCommand::DoCommand() {
   backup_options.max_background_operations = num_threads_;
   status = BackupEngine::Open(custom_env, backup_options, &backup_engine);
   if (status.ok()) {
-    printf("open backup engine OK\n");
+    fprintf(stdout, "open backup engine OK\n");
   } else {
     exec_state_ = LDBCommandExecuteResult::Failed(status.ToString());
     return;
   }
   status = backup_engine->CreateNewBackup(db_);
   if (status.ok()) {
-    printf("create new backup OK\n");
+    fprintf(stdout, "create new backup OK\n");
   } else {
     exec_state_ = LDBCommandExecuteResult::Failed(status.ToString());
     return;
@@ -2921,11 +2948,11 @@ void RestoreCommand::DoCommand() {
     }
   }
   if (status.ok()) {
-    printf("open restore engine OK\n");
+    fprintf(stdout, "open restore engine OK\n");
     status = restore_engine->RestoreDBFromLatestBackup(db_path_, db_path_);
   }
   if (status.ok()) {
-    printf("restore from backup OK\n");
+    fprintf(stdout, "restore from backup OK\n");
   } else {
     exec_state_ = LDBCommandExecuteResult::Failed(status.ToString());
   }