addition: resize and reserve, not tested

include/arraylist.h

@@ -19,6 +19,7 @@ typedef enum {
     ARRLIST_EMPTY,
     ARRLIST_NULL_ARG,
     ARRLIST_INVALID_ELEM_SIZE,
+    ARRLIST_INVALID_CAPACITY,
 } ArrayListErr;
 
 ArrayList *arraylist_init(size_t capacity, size_t elem_size);

src/arraylist.c

@@ -319,3 +319,44 @@ ArrayListErr arraylist_set(ArrayList *arr, size_t index, void *data) {
 
     return ARRLIST_OK;
 }
+
+ArrayListErr arraylist_resize(ArrayList *arr, size_t new_capacity) {
+    if (arr == NULL) {
+        return ARRLIST_NULL_ARG;
+    }
+
+    if (new_capacity < 1) {
+        return ARRLIST_INVALID_CAPACITY;
+    }
+
+    uint8_t *tmp = realloc(arr->buffer, new_capacity * arr->elem_size);
+    if (tmp == NULL) {
+        return ARRLIST_BAD_ALLOC;
+    }
+
+    arr->buffer = tmp;
+    arr->capacity = new_capacity;
+    return ARRLIST_OK;
+}
+
+ArrayListErr arraylist_reserve(ArrayList *arr, size_t size_to_reserve) {
+    if (arr == NULL) {
+        return ARRLIST_NULL_ARG;
+    }
+
+    if (size_to_reserve < 1) {
+        return ARRLIST_INVALID_CAPACITY;
+    }
+
+    uint8_t *tmp = realloc(
+        arr->buffer,
+        (arr->capacity + size_to_reserve) * arr->elem_size);
+
+    if (tmp == NULL) {
+        return ARRLIST_BAD_ALLOC;
+    }
+
+    arr->buffer = tmp;
+    arr->capacity += size_to_reserve;
+    return ARRLIST_OK;
+}