linux-kernel - [PATCH 1/6] lib/string: add strnchrnul()

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Message-Id: <20190428032936.1317-2-ynorov@marvell.com>
Date:   Sat, 27 Apr 2019 20:29:31 -0700
From:   Yury Norov <yury.norov@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Amritha Nambiar <amritha.nambiar@...el.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Matthew Wilcox <willy@...radead.org>,
        "Tobin C . Harding" <tobin@...nel.org>,
        Will Deacon <will.deacon@....com>,
        Miklos Szeredi <mszeredi@...hat.com>,
        Vineet Gupta <vineet.gupta1@...opsys.com>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Arnaldo Carvalho de Melo <acme@...hat.com>
Cc:     Yury Norov <ynorov@...vell.com>, linux-kernel@...r.kernel.org,
        Yury Norov <yury.norov@...il.com>,
        Jens Axboe <axboe@...nel.dk>,
        Steffen Klassert <steffen.klassert@...unet.com>
Subject: [PATCH 1/6] lib/string: add strnchrnul()

New function works like strchrnul() with a length limited strings.

Signed-off-by: Yury Norov <ynorov@...vell.com>
---
 include/linux/string.h |  3 +++
 lib/string.c           | 20 ++++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/include/linux/string.h b/include/linux/string.h
index 4deb11f7976b..69e8df51b630 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -62,6 +62,9 @@ extern char * strchr(const char *,int);
 #ifndef __HAVE_ARCH_STRCHRNUL
 extern char * strchrnul(const char *,int);
 #endif
+#ifndef __HAVE_ARCH_STRNCHRNUL
+extern char * strnchrnul(const char *, int, int);
+#endif
 #ifndef __HAVE_ARCH_STRNCHR
 extern char * strnchr(const char *, size_t, int);
 #endif
diff --git a/lib/string.c b/lib/string.c
index 6016eb3ac73d..dd99e6ac517a 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -429,6 +429,26 @@ char *strchrnul(const char *s, int c)
 EXPORT_SYMBOL(strchrnul);
 #endif
 
+#ifndef __HAVE_ARCH_STRNCHRNUL
+/**
+ * strnchrnul - Find and return a character in a length limited string,
+ * or end of string
+ * @s: The string to be searched
+ * @count: The number of characters to be searched
+ * @c: The character to search for
+ *
+ * Returns pointer to first occurrence of 'c' in s. If c is not found,
+ * then return a pointer to the null byte at the end of s.
+ */
+char *strnchrnul(const char *s, int count, int c)
+{
+	while (count-- && *s && *s != (char)c)
+		s++;
+	return (char *)s;
+}
+EXPORT_SYMBOL(strnchrnul);
+#endif
+
 #ifndef __HAVE_ARCH_STRRCHR
 /**
  * strrchr - Find the last occurrence of a character in a string
-- 
2.17.1