string-desc: New module.

* lib/string-desc.h: New file.
* lib/string-desc.c: New file.
* lib/string-desc-contains.c: New file.
* modules/string-desc: New file.

1 files changed, 44 insertions, 0 deletions

diff --git a/lib/string-desc-contains.c b/lib/string-desc-contains.c
new file mode 100644
index 0000000000..c02617629e
--- /dev/null
+++ b/lib/string-desc-contains.c
@@ -0,0 +1,44 @@
+/* String descriptors.
+   Copyright (C) 2023 Free Software Foundation, Inc.
+
+   This file is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Lesser General Public License as
+   published by the Free Software Foundation, either version 3 of the
+   License, or (at your option) any later version.
+
+   This file 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 Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+/* Written by Bruno Haible <bruno@clisp.org>, 2023.  */
+
+#ifdef HAVE_CONFIG_H
+# include "config.h"
+#endif
+
+/* Specification.  */
+#include "string-desc.h"
+
+#include <string.h>
+
+
+/* This function is in a separate compilation unit, because not all users
+   of the 'string-desc' module need this function and it depends on 'memmem'
+   which — depending on platforms — costs up to 2 KB of binary code.  */
+
+ptrdiff_t
+string_desc_contains (string_desc_t haystack, string_desc_t needle)
+{
+  if (needle._nbytes == 0)
+    return 0;
+  void *found =
+    memmem (haystack._data, haystack._nbytes, needle._data, needle._nbytes);
+  if (found != NULL)
+    return (char *) found - haystack._data;
+  else
+    return -1;
+}