[PATCH 1/3] lib: implement strnstr()

[Heinrich Schuchardt]

Implement library function strnstr().
Implement strstr() using strnstr().
Sort the includes.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt at canonical.com>
---
 include/linux/string.h |  3 +++
 lib/string.c           | 49 +++++++++++++++++++++++++++++-------------
 2 files changed, 37 insertions(+), 15 deletions(-)

diff --git a/include/linux/string.h b/include/linux/string.h
index 27b2beb9ddb..8a377a8176a 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -72,6 +72,9 @@ extern char * strrchr(const char *,int);
 #ifndef __HAVE_ARCH_STRSTR
 extern char * strstr(const char *,const char *);
 #endif
+#ifndef __HAVE_ARCH_STRNSTR
+extern char *strnstr(const char *, const char *, size_t);
+#endif
 #ifndef __HAVE_ARCH_STRLEN
 extern __kernel_size_t strlen(const char *);
 #endif
diff --git a/lib/string.c b/lib/string.c
index feae9519f2f..d5a486fb89d 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -16,11 +16,12 @@
  */
 
 #include <config.h>
+#include <malloc.h>
+#include <stdint.h>
 #include <linux/compiler.h>
+#include <linux/ctype.h>
 #include <linux/types.h>
 #include <linux/string.h>
-#include <linux/ctype.h>
-#include <malloc.h>
 
 /**
  * strncasecmp - Case insensitive, length-limited string comparison
@@ -678,30 +679,48 @@ char *memdup(const void *src, size_t len)
 	return p;
 }
 
-#ifndef __HAVE_ARCH_STRSTR
+#ifndef __HAVE_ARCH_STRNSTR
 /**
- * strstr - Find the first substring in a %NUL terminated string
- * @s1: The string to be searched
- * @s2: The string to search for
+ * strnstr() - find the first substring occurrence in a NUL terminated string
+ *
+ * @s1:		string to be searched
+ * @s2:		string to search for
+ * @len:	maximum number of characters in s2 to consider
+ *
+ * Return:	pointer to the first occurrence or NULL
  */
-char * strstr(const char * s1,const char * s2)
+char *strnstr(const char *s1, const char *s2, size_t len)
 {
-	int l1, l2;
+	size_t l1, l2;
 
+	l1 = strnlen(s1, len);
 	l2 = strlen(s2);
-	if (!l2)
-		return (char *) s1;
-	l1 = strlen(s1);
-	while (l1 >= l2) {
-		l1--;
-		if (!memcmp(s1,s2,l2))
+
+	for (; l1 >= l2; --l1, ++s1) {
+		if (!memcmp(s1, s2, l2))
 			return (char *) s1;
-		s1++;
 	}
+
 	return NULL;
 }
 #endif
 
+#ifndef __HAVE_ARCH_STRSTR
+/**
+ * strstr() - find the first substring occurrence in a NUL terminated string
+ *
+ * @s1:		string to be searched
+ * @s2:		string to search for
+ * @len:	maximum number of characters in s2 to consider
+ *
+ * Return:	pointer to the first occurrence or NULL
+ */
+char *strstr(const char *s1, const char *s2)
+{
+	return strnstr(s1, s2, SIZE_MAX);
+}
+#endif
+
 #ifndef __HAVE_ARCH_MEMCHR
 /**
  * memchr - Find a character in an area of memory.
-- 
2.47.1