feat(str): add lv_strdup (#4498)

Signed-off-by: Xu Xingliang <xuxingliang@xiaomi.com>

src/stdlib/builtin/lv_string_builtin.c

@@ -11,6 +11,7 @@
 #include "../../misc/lv_log.h"
 #include "../../misc/lv_math.h"
 #include "../../stdlib/lv_string.h"
+#include "../../stdlib/lv_mem.h"
 
 /*********************
  *      DEFINES
@@ -170,6 +171,16 @@ char * lv_strcpy(char * dst, const char * src)
     return tmp;
 }
 
+char * lv_strdup(const char * src)
+{
+    size_t len = lv_strlen(src) + 1;
+    char * dst = lv_malloc(len);
+    if(dst == NULL) return NULL;
+
+    lv_memcpy(dst, src, len); /*do memcpy is faster than strncpy when length is known*/
+    return dst;
+}
+
 /**********************
  *   STATIC FUNCTIONS
  **********************/

src/stdlib/clib/lv_string_clib.c

@@ -64,6 +64,11 @@ char * lv_strcpy(char * dst, const char * src)
     return strcpy(dst, src);
 }
 
+char * lv_strdup(const char * src)
+{
+    return strdup(src);
+}
+
 /**********************
  *   STATIC FUNCTIONS
  **********************/

src/stdlib/lv_string.h

@@ -83,6 +83,12 @@ char * lv_strncpy(char * dst, const char * src, size_t dest_size);
  */
 char * lv_strcpy(char * dst, const char * src);
 
+/**
+ * @brief Duplicate a string by allocating a new one and copying the content.
+ * @param src Pointer to the source of data to be copied.
+ * @return A pointer to the new allocated string. NULL if failed.
+ */
+char * lv_strdup(const char * src);
 
 /**********************
  *      MACROS