[refactor] Organize STRING

kernel/memory/heap.cpp

@@ -1,6 +1,7 @@
 #include <memory/heap.h>
 #include <memory/pmm.h>
 #include <serial.h>
+#include <string_utils.h>
 
 struct heap_block {
     UINTN  size;   // includes header; bit 0 = 1 used, 0 free
@@ -184,10 +185,7 @@ void* kcalloc(UINTN num, UINTN size) {
     UINTN total = num * size;
     void* ptr = kmalloc(total);
     if (ptr) {
-        UINT8* p = (UINT8*)ptr;
-        for (UINTN i = 0; i < total; i++) {
-            p[i] = 0;
-        }
+        mem_set(ptr, 0, total);
     }
     return ptr;
 }
@@ -216,11 +214,7 @@ void* krealloc(void* ptr, UINTN new_size) {
 
     void* new_ptr = kmalloc(new_size);
     if (new_ptr) {
-        UINT8* src = (UINT8*)ptr;
-        UINT8* dst = (UINT8*)new_ptr;
-        for (UINTN i = 0; i < old_size; i++) {
-            dst[i] = src[i];
-        }
+        mem_copy(new_ptr, ptr, old_size);
         kfree(ptr);
     }
     return new_ptr;