Avoid some strlen work, primarily via strnlen

* admin/merge-gnulib (GNULIB_MODULES): Add strnlen.
* lib-src/etags.c (find_entries):
* src/emacs.c (main):
* src/nsmenu.m (parseKeyEquiv:):
* src/nsterm.m (ns_xlfd_to_fontname):
* src/term.c (vfatal):
Prefer !*X to !strlen (X).
* lib-src/etags.c (pfnote, add_regex):
* lib-src/pop.c (pop_open):
* lib-src/update-game-score.c (main):
* lwlib/lwlib.c (lw_separator_p):
* src/doprnt.c (doprnt):
* src/emacs.c (main):
* src/inotify.c (inotifyevent_to_event):
* src/keyboard.c (menu_separator_name_p, parse_tool_bar_item):
* src/sysdep.c (get_current_dir_name_or_unreachable):
* src/xdisp.c (store_mode_line_string):
Use strnlen to avoid unnecessary work with strlen.
* lib-src/etags.c (Prolog_functions, prolog_pr)
(Erlang_functions, erlang_func):
Prefer ptrdiff_t to size_t when either will do.
(prolog_pr, erlang_func): New arg LASTLEN, to avoid
unnecessary strlen call. All callers changed.
* lib/gnulib.mk.in, m4/gnulib-comp.m4: Regenerate.
* lib/strnlen.c, m4/strnlen.m4: New files, copied from Gnulib.
* lwlib/lwlib.c (lw_separator_p):
* src/json.c (json_has_prefix):
Use strncmp to avoid unecessary work with strlen + memcmp.
* src/process.c (set_socket_option): Use SBYTES instead of strlen.

1 files changed, 30 insertions, 0 deletions

diff --git a/lib/strnlen.c b/lib/strnlen.c
new file mode 100644
index 00000000000..9fb663509a0
--- /dev/null
+++ b/lib/strnlen.c
@@ -0,0 +1,30 @@
+/* Find the length of STRING, but scan at most MAXLEN characters.
+   Copyright (C) 2005-2007, 2009-2019 Free Software Foundation, Inc.
+   Written by Simon Josefsson.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3, or (at your option)
+   any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, see <https://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+#include <string.h>
+
+/* Find the length of STRING, but scan at most MAXLEN characters.
+   If no '\0' terminator is found in that many characters, return MAXLEN.  */
+
+size_t
+strnlen (const char *string, size_t maxlen)
+{
+  const char *end = memchr (string, '\0', maxlen);
+  return end ? (size_t) (end - string) : maxlen;
+}