lib: Introduce strnstr()

It differs strstr() in that it limits the length to be searched in the first string. Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> LKML-Reference: <4B4E8743.6030805@cn.fujitsu.com> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

lib: Introduce strnstr()
It differs strstr() in that it limits the length to be searched in the first string. Signed-off-by: Li Zefan <lizf@cn.fujitsu.com> LKML-Reference: <4B4E8743.6030805@cn.fujitsu.com> Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Li Zefan · Steven Rostedt
1 parent a3291c14ec
Showing 2 changed files with 30 additions and 2 deletions Side-by-side Diff
include/linux/string.h
lib/string.c
@@ -72,7 +72,10 @@
 }
  
 #ifndef __HAVE_ARCH_STRSTR
-extern char * strstr(const char *,const char *);
+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 *);
@@ -667,7 +667,7 @@
  */
 char *strstr(const char *s1, const char *s2)
 {
-	int l1, l2;
+	size_t l1, l2;
  
 	l2 = strlen(s2);
 	if (!l2)
@@ -682,6 +682,31 @@
 	return NULL;
 }
 EXPORT_SYMBOL(strstr);
+#endif
+
+#ifndef __HAVE_ARCH_STRNSTR
+/**
+ * strnstr - Find the first substring in a length-limited string
+ * @s1: The string to be searched
+ * @s2: The string to search for
+ * @len: the maximum number of characters to search
+ */
+char *strnstr(const char *s1, const char *s2, size_t len)
+{
+	size_t l1 = len, l2;
+
+	l2 = strlen(s2);
+	if (!l2)
+		return (char *)s1;
+	while (l1 >= l2) {
+		l1--;
+		if (!memcmp(s1, s2, l2))
+			return (char *)s1;
+		s1++;
+	}
+	return NULL;
+}
+EXPORT_SYMBOL(strnstr);
 #endif
  
 #ifndef __HAVE_ARCH_MEMCHR
...	...	@@ -72,7 +72,10 @@
72	72	}
73	73
74	74	#ifndef __HAVE_ARCH_STRSTR
75		-extern char * strstr(const char ,const char );
	75	+extern char * strstr(const char , const char );
	76	+#endif
	77	+#ifndef __HAVE_ARCH_STRNSTR
	78	+extern char * strnstr(const char , const char , size_t);
76	79	#endif
77	80	#ifndef __HAVE_ARCH_STRLEN
78	81	extern __kernel_size_t strlen(const char *);
...	...	@@ -667,7 +667,7 @@
667	667	*/
668	668	char strstr(const char s1, const char *s2)
669	669	{
670		- int l1, l2;
	670	+ size_t l1, l2;
671	671
672	672	l2 = strlen(s2);
673	673	if (!l2)
...	...	@@ -682,6 +682,31 @@
682	682	return NULL;
683	683	}
684	684	EXPORT_SYMBOL(strstr);
	685	+#endif
	686	+
	687	+#ifndef __HAVE_ARCH_STRNSTR
	688	+/**
	689	+ * strnstr - Find the first substring in a length-limited string
	690	+ * @s1: The string to be searched
	691	+ * @s2: The string to search for
	692	+ * @len: the maximum number of characters to search
	693	+ */
	694	+char strnstr(const char s1, const char *s2, size_t len)
	695	+{
	696	+ size_t l1 = len, l2;
	697	+
	698	+ l2 = strlen(s2);
	699	+ if (!l2)
	700	+ return (char *)s1;
	701	+ while (l1 >= l2) {
	702	+ l1--;
	703	+ if (!memcmp(s1, s2, l2))
	704	+ return (char *)s1;
	705	+ s1++;
	706	+ }
	707	+ return NULL;
	708	+}
	709	+EXPORT_SYMBOL(strnstr);
685	710	#endif
686	711
687	712	#ifndef __HAVE_ARCH_MEMCHR