test: Added test for init and destroy

Also changed a few things like destroy tanking a double pointer so that
is more secure and making sure before hand that capacity is not that
ridiculous of a size, still, shit can get pass but generally is fine

src/arraylist.c

@@ -26,6 +26,10 @@ ArrayList *arraylist_init(size_t capacity, size_t elem_size) {
         return NULL;
     }
 
+    if (capacity > SIZE_MAX / elem_size) {
+        return NULL;
+    }
+
     ArrayList *arr = malloc(sizeof(ArrayList));
     if (arr == NULL) {
         return NULL;
@@ -42,17 +46,16 @@ ArrayList *arraylist_init(size_t capacity, size_t elem_size) {
     return arr;
 }
 
-ArrayListErr arraylist_destroy(ArrayList *arr) {
-    if (arr == NULL) {
+ArrayListErr arraylist_destroy(ArrayList **arr) {
+    if (arr == NULL || *arr == NULL) {
         return ARRLIST_NULL_ARG;
     }
 
-    arr->capacity = 0;
-    arr->elem_size = 0;
-    arr->len = 0;
-    free(arr->buffer);
-    arr->buffer = NULL;
-    free(arr);
+    // No problem on using free on NULL :)
+    free((*arr)->buffer);
+    free(*arr);
+    *arr = NULL;
+
     return ARRLIST_OK;
 }
 
@@ -94,10 +97,16 @@ static ArrayListErr arraylist_grow(ArrayList *arr) {
     // and only used by funtions that already verified
     // arr is not null, same with shrink.
     size_t new_capacity = arr->capacity * 2;
+
+    if (new_capacity > SIZE_MAX / arr->elem_size) {
+        return  ARRLIST_ALLOC_OVERFLOW;
+    }
+
     void *tmp = realloc(arr->buffer, new_capacity * arr->elem_size);
     if (tmp == NULL) {
         return ARRLIST_BAD_ALLOC;
     }
+
     arr->capacity = new_capacity;
     arr->buffer = tmp;
     return ARRLIST_OK;
@@ -105,10 +114,16 @@ static ArrayListErr arraylist_grow(ArrayList *arr) {
 
 static ArrayListErr arraylist_shrink(ArrayList *arr) {
     size_t new_capacity = arr->capacity / 2;
+
+    if (new_capacity > SIZE_MAX / arr->elem_size) {
+        return  ARRLIST_ALLOC_OVERFLOW;
+    }
+    
     void *tmp = realloc(arr->buffer, new_capacity *arr->elem_size);
     if (tmp == NULL) {
         return ARRLIST_BAD_ALLOC;
     }
+
     arr->capacity = new_capacity;
     arr->buffer = tmp;
     return ARRLIST_OK;
@@ -146,14 +161,17 @@ ArrayListErr arraylist_push_front(ArrayList *arr, void *data) {
     }
 
     // No problem if array is full because  it grows if it's full
-    for (size_t i = arr->len - 1; i >= 0; i--) {
-        memcpy(
-            arr->buffer + ((i + 1) * arr->elem_size),
-            arr->buffer + (i * arr->elem_size),
-            arr->elem_size);
-    }
+    memmove(
+        arr->buffer,
+        arr->buffer + arr->elem_size,
+        (arr->len - 1) * arr->elem_size
+    );
+
+    memcpy(
+        arr->buffer,
+        data,
+        arr->elem_size);
 
-    memcpy(arr->buffer, data, arr->elem_size);
     arr->len++;
 
     return ARRLIST_OK;
@@ -164,7 +182,7 @@ ArrayListErr arraylist_insert(ArrayList *arr, size_t index, void *data) {
         return ARRLIST_NULL_ARG;
     }
 
-    if (index >= arr->len) {
+    if (index > arr->len) {
         return ARRLIST_OUT_OF_BOUNDS;
     }
 
@@ -175,14 +193,15 @@ ArrayListErr arraylist_insert(ArrayList *arr, size_t index, void *data) {
         }
     }
 
-    for (size_t i = arr->len - 1; i >= index; i--) {
-        memcpy(
-            arr->buffer + ((i + 1) * arr->elem_size),
-            arr->buffer + (i * arr->elem_size),
-            arr->elem_size);
-    }
+    memmove(
+        arr->buffer + ((index + 1) * arr->elem_size),
+        arr->buffer + (index * arr->elem_size),
+        (arr->len - index) * arr->elem_size);
+
+    memcpy(arr->buffer + (index * arr->elem_size),
+           data,
+           arr->elem_size);
 
-    memcpy(arr->buffer + (index * arr->elem_size), data, arr->elem_size);
     arr->len++;
 
     return ARRLIST_OK;
@@ -240,12 +259,10 @@ ArrayListErr arraylist_pop_front(ArrayList *arr, void *out) {
         );
     }
 
-    for (size_t i = 0; i < arr->len; i++) {
-        memcpy(
-            arr->buffer + (i * arr->elem_size),
-            arr->buffer + ((i + 1) * arr->elem_size),
-            arr->elem_size);
-    }
+    memmove(
+        arr->buffer + arr->elem_size,
+        arr->buffer,
+        (arr->len - 1) * arr->elem_size);
 
     arr->len--;
 
@@ -329,6 +346,10 @@ ArrayListErr arraylist_resize(ArrayList *arr, size_t new_capacity) {
         return ARRLIST_INVALID_CAPACITY;
     }
 
+    if (new_capacity > SIZE_MAX / arr->elem_size) {
+        return  ARRLIST_ALLOC_OVERFLOW;
+    }
+
     uint8_t *tmp = realloc(arr->buffer, new_capacity * arr->elem_size);
     if (tmp == NULL) {
         return ARRLIST_BAD_ALLOC;
@@ -348,6 +369,10 @@ ArrayListErr arraylist_reserve(ArrayList *arr, size_t size_to_reserve) {
         return ARRLIST_INVALID_CAPACITY;
     }
 
+    if (arr->capacity + size_to_reserve > SIZE_MAX / arr->elem_size) {
+        return  ARRLIST_ALLOC_OVERFLOW;
+    }
+
     uint8_t *tmp = realloc(
         arr->buffer,
         (arr->capacity + size_to_reserve) * arr->elem_size);