[RFC PATCH 01/11] lib: string: Add strlower()

[Simon Glass <sjg@chromium.org>]

Add a helper that lower-cases an ASCII string in place. It returns
the input pointer so calls can be chained:

    do_thing(strlower(name));

A new test in test/lib/string.c covers the basic cases.

Signed-off-by: Simon Glass <sjg@chromium.org>
---

 include/linux/string.h | 12 ++++++++++++
 lib/string.c           | 10 ++++++++++
 test/lib/string.c      | 27 +++++++++++++++++++++++++++
 3 files changed, 49 insertions(+)

diff --git a/include/linux/string.h b/include/linux/string.h
index a8a6cf4af50..15efe0ff5dd 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -49,6 +49,18 @@ int strcasecmp(const char *s1, const char *s2);
 #ifndef __HAVE_ARCH_STRNCASECMP
 extern int strncasecmp(const char *s1, const char *s2, __kernel_size_t len);
 #endif
+
+/**
+ * strlower() - Lower-case an ASCII string in place
+ * @s: The string to convert
+ *
+ * Walks @s and replaces each character with its lower-case equivalent.
+ * Returns @s so the call can be chained, e.g. ``foo(strlower(buf))``.
+ *
+ * Return: @s.
+ */
+char *strlower(char *s);
+
 #ifndef __HAVE_ARCH_STRCHR
 extern char * strchr(const char *,int);
 #endif
diff --git a/lib/string.c b/lib/string.c
index 302efe048b0..8464366dac9 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -65,6 +65,16 @@ int strcasecmp(const char *s1, const char *s2)
 	return strncasecmp(s1, s2, -1U);
 }
 
+char *strlower(char *s)
+{
+	char *p;
+
+	for (p = s; *p; p++)
+		*p = tolower(*p);
+
+	return s;
+}
+
 char * ___strtok;
 
 #ifndef __HAVE_ARCH_STRCPY
diff --git a/test/lib/string.c b/test/lib/string.c
index f56c2e4c946..598be1101a1 100644
--- a/test/lib/string.c
+++ b/test/lib/string.c
@@ -298,3 +298,30 @@ static int lib_strim(struct unit_test_state *uts)
 	return 0;
 }
 LIB_TEST(lib_strim, 0);
+
+static int lib_strlower(struct unit_test_state *uts)
+{
+	char buf[32];
+	char *p;
+
+	/* Mixed case is fully lowered, returns @s */
+	strcpy(buf, "SHA256");
+	p = strlower(buf);
+	ut_asserteq_ptr(p, buf);
+	ut_asserteq_str("sha256", buf);
+
+	/* Already lower-case is unchanged */
+	strcpy(buf, "abc");
+	ut_asserteq_str("abc", strlower(buf));
+
+	/* Non-letters and digits pass through */
+	strcpy(buf, "Hello, World! 1234");
+	ut_asserteq_str("hello, world! 1234", strlower(buf));
+
+	/* Empty string */
+	strcpy(buf, "");
+	ut_asserteq_str("", strlower(buf));
+
+	return 0;
+}
+LIB_TEST(lib_strlower, 0);
-- 
2.43.0