addition: set and get, not tested

include/arraylist.h

@@ -18,7 +18,6 @@ typedef enum {
     ARRLIST_BAD_ALLOC,
     ARRLIST_EMPTY,
     ARRLIST_NULL_ARG,
-    ARRLIST_INVALID_CAPACITY,
     ARRLIST_INVALID_ELEM_SIZE,
 } ArrayListErr;
 

src/arraylist.c

@@ -286,4 +286,36 @@ ArrayListErr arraylist_remove_at(ArrayList *arr, size_t index, void *out) {
     return ARRLIST_OK;
 }
 
+ArrayListErr arraylist_get(const ArrayList *arr, size_t index, void *out) {
+    if (arr == NULL || out == NULL) {
+        return ARRLIST_NULL_ARG;
+    }
 
+    if (index >= arr->capacity) {
+        return ARRLIST_OUT_OF_BOUNDS;
+    }
+
+    memcpy(
+        out,
+        arr->buffer + (index * arr->elem_size),
+        arr->elem_size);
+
+    return ARRLIST_OK;
+}
+
+ArrayListErr arraylist_set(ArrayList *arr, size_t index, void *data) {
+    if (arr == NULL || data == NULL) {
+        return ARRLIST_NULL_ARG;
+    }
+
+    if (index >= arr->capacity) {
+        return ARRLIST_OUT_OF_BOUNDS;
+    }
+
+    memcpy(
+        arr->buffer + (index * arr->elem_size),
+        data,
+        arr->elem_size);
+
+    return ARRLIST_OK;
+}