[PATCH linux-phy 1/4] string.h: Add str_has_proper_prefix()

[Marek Behún]

Add str_has_proper_prefix(), similar to str_has_prefix(), but requires
that the prefix is proper: the string itself must be longer than the
prefix.

Signed-off-by: Marek Behún <kabel at kernel.org>
---
Andy, Kees, could you ack this if it is ok?
---
 include/linux/string.h | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/include/linux/string.h b/include/linux/string.h
index 61ec7e4f6311..375f51b9182c 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -316,4 +316,22 @@ static __always_inline size_t str_has_prefix(const char *str, const char *prefix
 	return strncmp(str, prefix, len) == 0 ? len : 0;
 }
 
+/**
+ * str_has_proper_prefix - Test if a string has a proper prefix
+ * @str: The string to test
+ * @prefix: The string to see if @str starts with
+ *
+ * This is like str_has_prefix(), but fails if the strings are equal.
+ *
+ * Returns:
+ * * strlen(@prefix) if @str starts with @prefix and they aren't equal
+ * * 0 otherwise
+ */
+static __always_inline size_t str_has_proper_prefix(const char *str,
+						    const char *prefix)
+{
+	size_t len = strlen(prefix);
+	return strncmp(str, prefix, len) == 0 && len != strlen(str) ? len : 0;
+}
+
 #endif /* _LINUX_STRING_H_ */
-- 
2.35.1