[RFC][PATCH 2/7] implement memmem()

[Al Viro]

From: Al Viro <viro@xxxxxxxxxxxxxxxxxx>

Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
 include/linux/string.h |  1 +
 lib/string.c           | 34 ++++++++++++++++++++++------------
 2 files changed, 23 insertions(+), 12 deletions(-)

diff --git a/include/linux/string.h b/include/linux/string.h
index 2e22a2e..87f9fba 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -75,6 +75,7 @@ extern char * strstr(const char *, const char *);
 #endif
 #ifndef __HAVE_ARCH_STRNSTR
 extern char * strnstr(const char *, const char *, size_t);
+extern void * memmem(const void *, size_t, const void *, size_t);
 #endif
 #ifndef __HAVE_ARCH_STRLEN
 extern __kernel_size_t strlen(const char *);
diff --git a/lib/string.c b/lib/string.c
index 1006330..2035dbe 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -740,27 +740,37 @@ EXPORT_SYMBOL(strstr);
 #endif
 
 #ifndef __HAVE_ARCH_STRNSTR
+
 /**
- * strnstr - Find the first substring in a length-limited string
+ * memmem - Find the first length-limited substring in a length-limited string
  * @s1: The string to be searched
+ * @len1: the maximum number of characters to search
  * @s2: The string to search for
- * @len: the maximum number of characters to search
+ * @len2: the length of the string being searched
  */
-char *strnstr(const char *s1, const char *s2, size_t len)
+void *memmem(const void *s1, size_t len1, const void *s2, size_t len2)
 {
-	size_t l2;
-
-	l2 = strlen(s2);
-	if (!l2)
-		return (char *)s1;
-	while (len >= l2) {
-		len--;
-		if (!memcmp(s1, s2, l2))
-			return (char *)s1;
+	if (!len2)
+		return (void *)s1;
+	while (len1 >= len2) {
+		len1--;
+		if (!memcmp(s1, s2, len2))
+			return (void *)s1;
 		s1++;
 	}
 	return NULL;
 }
+EXPORT_SYMBOL(memmem);
+/**
+ * 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)
+{
+	return memmem(s1, len, s2, strlen(s2));
+}
 EXPORT_SYMBOL(strnstr);
 #endif
 
-- 
2.1.4

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