From 8daf31879d3fa24f74a06b14e8685129dd024914 Mon Sep 17 00:00:00 2001
From: yiyi <1692157237@qq.com>
Date: Tue, 25 Mar 2025 09:40:28 +0800
Subject: [PATCH 1/2] Add rt_strnstr function and its configuration options to
 support finding substrings within a specified maximum length

---
 include/klibc/kstring.h |  1 +
 src/klibc/Kconfig       |  6 +++++
 src/klibc/kstring.c     | 56 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 63 insertions(+)

diff --git a/include/klibc/kstring.h b/include/klibc/kstring.h
index fc6c3bfa7dd..9ccd7363724 100644
--- a/include/klibc/kstring.h
+++ b/include/klibc/kstring.h
@@ -25,6 +25,7 @@ rt_int32_t rt_memcmp(const void *cs, const void *ct, rt_size_t count);
 char *rt_strdup(const char *s);
 rt_size_t rt_strnlen(const char *s, rt_ubase_t maxlen);
 char *rt_strstr(const char *str1, const char *str2);
+char *rt_strnstr(const char *s1, const char *s2, rt_size_t maxlen);
 rt_int32_t rt_strcasecmp(const char *a, const char *b);
 char *rt_strcpy(char *dst, const char *src);
 char *rt_strncpy(char *dest, const char *src, rt_size_t n);
diff --git a/src/klibc/Kconfig b/src/klibc/Kconfig
index bc90e90e8fa..bca097b38c0 100644
--- a/src/klibc/Kconfig
+++ b/src/klibc/Kconfig
@@ -178,6 +178,12 @@ menu "klibc options"
         endif
     endmenu # rt_strstr options
 
+    menu "rt_strnstr options"
+        config RT_KLIBC_USING_USER_STRNSTR
+            bool "Enable rt_strnstr to use user-defined version"
+            default n
+    endmenu # rt_strnstr options
+
     menu "rt_strcasecmp options"
         config RT_KLIBC_USING_USER_STRCASECMP
             bool "Enable rt_strcasecmp to use user-defined version"
diff --git a/src/klibc/kstring.c b/src/klibc/kstring.c
index d2988d629cb..be75d595a70 100644
--- a/src/klibc/kstring.c
+++ b/src/klibc/kstring.c
@@ -313,6 +313,62 @@ char *rt_strstr(const char *s1, const char *s2)
 #endif /* RT_KLIBC_USING_USER_STRSTR */
 RTM_EXPORT(rt_strstr);
 
+/**
+ * @brief  This function will return the first occurrence of a string, without the
+ * terminator '\0'.
+ *
+ * @param  s1 is the source string.
+ *
+ * @param  s2 is the find string.
+ *
+ * @param  maxlen is the max size.
+ *
+ * @return The first occurrence of a s2 in s1, or RT_NULL if no found.
+ */
+#ifndef RT_KLIBC_USING_USER_STRNSTR
+char *rt_strnstr(const char *s1, const char *s2, rt_size_t maxlen)
+{
+    rt_size_t l1 = 0, l2 = 0;
+    int max_pos = 0;
+    
+    l2 = rt_strlen(s2);
+    if (!l2) 
+    {
+        return (char *)s1;
+    }
+
+    l1 = rt_strlen(s1);
+    if (!l1)
+    {
+        return RT_NULL;
+    }
+    
+    max_pos = maxlen < l1 ? maxlen : l1;
+    if (max_pos < l2)
+    {
+        return RT_NULL;
+    }
+
+    max_pos = max_pos - l2;
+    while (max_pos >= 0)
+    {
+        if (*s1 == *s2) 
+        {
+            if (!rt_strncmp(s1, s2, l2)) 
+            {
+                return (char *)s1;
+            }
+        }
+
+        s1++;
+        max_pos--;
+    }
+
+    return RT_NULL;
+}
+#endif /* RT_KLIBC_USING_USER_STRNSTR */
+RTM_EXPORT(rt_strnstr);
+
 /**
  * @brief  This function will compare two strings while ignoring differences in case
  *

From 2059adfb16e045ca64e0b4e65fb42250060bb518 Mon Sep 17 00:00:00 2001
From: yiyi <1692157237@qq.com>
Date: Tue, 25 Mar 2025 10:34:50 +0800
Subject: [PATCH 2/2] Optimize code format in rt_strnstr function

---
 src/klibc/kstring.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/klibc/kstring.c b/src/klibc/kstring.c
index be75d595a70..e93783ff2f1 100644
--- a/src/klibc/kstring.c
+++ b/src/klibc/kstring.c
@@ -330,9 +330,9 @@ char *rt_strnstr(const char *s1, const char *s2, rt_size_t maxlen)
 {
     rt_size_t l1 = 0, l2 = 0;
     int max_pos = 0;
-    
+
     l2 = rt_strlen(s2);
-    if (!l2) 
+    if (!l2)
     {
         return (char *)s1;
     }
@@ -342,7 +342,7 @@ char *rt_strnstr(const char *s1, const char *s2, rt_size_t maxlen)
     {
         return RT_NULL;
     }
-    
+
     max_pos = maxlen < l1 ? maxlen : l1;
     if (max_pos < l2)
     {
@@ -352,9 +352,9 @@ char *rt_strnstr(const char *s1, const char *s2, rt_size_t maxlen)
     max_pos = max_pos - l2;
     while (max_pos >= 0)
     {
-        if (*s1 == *s2) 
+        if (*s1 == *s2)
         {
-            if (!rt_strncmp(s1, s2, l2)) 
+            if (!rt_strncmp(s1, s2, l2))
             {
                 return (char *)s1;
             }