[PATCH 1/3] libgen: implement posix_basename

[Sascha Hauer]

There are two different versions of basename(): The GNU version and the
POSIX version. The GNU version never modifies its argument and returns
the empty string when path has a trailing slash, and in particular also
when it is "/". The POSIX version modifies its argument and thus works
properly with strings which have a trailing "/".

Signed-off-by: Sascha Hauer <s.hauer at pengutronix.de>
---
 include/libgen.h |  1 +
 lib/libgen.c     | 23 +++++++++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/include/libgen.h b/include/libgen.h
index cd27fd11e3..71f06eb6f6 100644
--- a/include/libgen.h
+++ b/include/libgen.h
@@ -2,6 +2,7 @@
 #define __LIBGEN_H
 
 char *basename (char *path);
+char *posix_basename(char *path);
 char *dirname (char *path);
 
 #endif /* __LIBGEN_H */
diff --git a/lib/libgen.c b/lib/libgen.c
index 1e43cf3f29..08ef3528af 100644
--- a/lib/libgen.c
+++ b/lib/libgen.c
@@ -37,6 +37,29 @@ char *basename (char *path)
 }
 EXPORT_SYMBOL(basename);
 
+/*
+ * There are two different versions of basename(): The GNU version implemented
+ * above and the POSIX version. The GNU version never modifies its argument and
+ * returns the empty string when path has a trailing slash, and in particular
+ * also when it is "/".
+ */
+char *posix_basename(char *path)
+{
+	char *fname;
+
+	fname = path + strlen(path) - 1;
+
+	while (*fname == '/') {
+		if (fname == path)
+			return path;
+		*fname = '\0';
+		fname--;
+	}
+
+	return basename(path);
+}
+EXPORT_SYMBOL(posix_basename);
+
 char *dirname (char *path)
 {
 	char *fname;
-- 
2.11.0