diff --git a/libc/bionic/grp_pwd_file.h b/libc/bionic/grp_pwd_file.h
new file mode 100644
index 0000000..ae8cd98
--- /dev/null
+++ b/libc/bionic/grp_pwd_file.h
@@ -0,0 +1,97 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#ifndef GRP_PWD_FILE_H
+#define GRP_PWD_FILE_H
+
+#include <grp.h>
+#include <pwd.h>
+
+#include "private/bionic_lock.h"
+#include "private/bionic_macros.h"
+#include "private/grp_pwd.h"
+
+class MmapFile {
+ public:
+  MmapFile(const char* filename);
+  ~MmapFile();
+
+  template <typename Line>
+  bool FindById(uid_t uid, Line* line);
+  template <typename Line>
+  bool FindByName(const char* name, Line* line);
+
+  DISALLOW_COPY_AND_ASSIGN(MmapFile);
+
+ private:
+  enum class FileStatus {
+    Uninitialized,
+    Initialized,
+    Error,
+  };
+
+  bool GetFile(const char** start, const char** end);
+  bool DoMmap();
+
+  template <typename Line, typename Predicate>
+  bool Find(Line* line, Predicate predicate);
+
+  FileStatus status_ = FileStatus::Uninitialized;
+  Lock lock_;
+  const char* filename_ = nullptr;
+  const char* start_ = nullptr;
+  const char* end_ = nullptr;
+};
+
+class PasswdFile {
+ public:
+  PasswdFile(const char* filename);
+
+  bool FindById(uid_t id, passwd_state_t* passwd_state);
+  bool FindByName(const char* name, passwd_state_t* passwd_state);
+
+  DISALLOW_COPY_AND_ASSIGN(PasswdFile);
+
+ private:
+  MmapFile mmap_file_;
+};
+
+class GroupFile {
+ public:
+  GroupFile(const char* filename);
+
+  bool FindById(gid_t id, group_state_t* group_state);
+  bool FindByName(const char* name, group_state_t* group_state);
+
+  DISALLOW_COPY_AND_ASSIGN(GroupFile);
+
+ private:
+  MmapFile mmap_file_;
+};
+
+#endif