add strstr

kernel/include/std/string.h

@@ -11,6 +11,8 @@ char* strncpy(char* dest, const char* src, size_t n);
 int strncmp(const char* s1, const char* s2, size_t n);
 char* strncat(char* dest, const char* src, size_t n);
 
+char* strstr(char* haystack, char* needle);
+
 void* memcpy(void* dest, const void* src, size_t n);
 void* memset(void* dest, int c, size_t n);
 int memcmp(const void* a, const void* b, size_t n);

kernel/src/std/string.cpp

@@ -66,6 +66,26 @@ char* strcat(char* dest, const char* src)
     return dest;
 }
 
+char* strstr(char* haystack, char* needle)
+{
+    size_t needle_size = strlen(needle);
+    size_t haystack_size = strlen(haystack);
+    while (*haystack)
+    {
+        if (*haystack == *needle)
+        {
+            if (needle_size <= haystack_size)
+            {
+                if (!strncmp(haystack, needle, needle_size)) return haystack;
+            }
+            else { return NULL; }
+        }
+        haystack++;
+        haystack_size--;
+    }
+    return NULL;
+}
+
 void* memcpy(void* dest, const void* src, size_t n)
 {
     for (size_t i = 0; i < n; ++i) { *((char*)dest + i) = *((char*)src + i); }