Add dynarray_cut and fix a bug

Author: oleggromov

dynarray.c

@@ -53,7 +53,7 @@ void* dynarray_set(dynarray_t* arr, size_t index, void* value)
 
   void* old_value_ptr = dynarray_get(arr, index);
   arr->_arr[index] = value;
-  arr->len += 1;
+  arr->len = index > arr->len ? index + 1: arr->len + 1; // when array is sparse
   return old_value_ptr;
 }
 
@@ -63,6 +63,25 @@ void* dynarray_get(dynarray_t* arr, size_t index)
   return arr->_arr[index];
 }
 
+// Cuts the value at index from array1
+// Returns a pointer to the deleted item (may be void*)
+void* dynarray_cut(dynarray_t* arr, size_t index)
+{
+  void *old_value_ptr = dynarray_get(arr, index);
+
+  // index = 1, len = 5
+  // {1, 2, 3, 4, 5} => // {1, 3, 4, 5}
+  size_t move_items = arr->len - index; // should be -1 but +1 item is to ensure zeroing
+  memmove(
+    arr->_arr + index * sizeof(void*),
+    arr->_arr + index * sizeof(void*) + 1,
+    move_items * sizeof(void*)
+  );
+  arr->len = arr->len - 1;
+
+  return old_value_ptr;
+}
+
 void dynarray_append(dynarray_t* arr, void* value)
 {
   dynarray_set(arr, arr->len, value);

dynarray.h

@@ -14,6 +14,8 @@ void dynarray_free(dynarray_t** arr);
 
 void* dynarray_set(dynarray_t* arr, size_t index, void* value);
 void* dynarray_get(dynarray_t* arr, size_t index);
+void* dynarray_cut(dynarray_t* arr, size_t index);
+
 void dynarray_append(dynarray_t* arr, void* value);
 void* dynarray_get_top(dynarray_t* arr);
 void* dynarray_remove_top(dynarray_t* arr);

dynarray_test.c

@@ -7,6 +7,18 @@ static void print_stat(dynarray_t* arr)
   printf("len = %zu, capacity = %zu\n", arr->len, arr->_capacity);
 }
 
+static void print_items_int(dynarray_t* arr)
+{
+  for (size_t i = 0; i < arr->len; i++) {
+    int* value = dynarray_get(arr, i);
+    if (value) {
+      printf("[%d] = %d\n", (int) i, *value);
+    } else {
+      printf("[%d] = NULL\n", (int) i);
+    }
+  }
+}
+
 int main()
 {
   dynarray_t* array = dynarray_create();
@@ -39,5 +51,32 @@ int main()
   }
   print_stat(array);
 
+  printf("\n\ndynarray 2\n");
+  dynarray_t* arr2 = dynarray_create();
+  for (int j = 0; j < 10; j += 2) {
+    dynarray_set(arr2, j, &j);
+  }
+  print_stat(arr2);
+  print_items_int(arr2);
+  printf("[9] = %d\n", dynarray_get(arr2, 9));
+  printf("[10] = %d\n", dynarray_get(arr2, 10));
+
+  int* item = dynarray_cut(arr2, 0);
+  printf("cut item = %d\n", *item);
+  print_stat(arr2);
+  print_items_int(arr2);
+  printf("[8] = %d\n", dynarray_get(arr2, 8));
+  printf("[9] = %d\n", dynarray_get(arr2, 9));
+  printf("[10] = %d\n", dynarray_get(arr2, 10));
+
+  printf("\n\ndynarray 3\n");
+  dynarray_t* arr3 = dynarray_create();
+  for (int j = 0; j < 10; j++) {
+    dynarray_set(arr3, j, &j);
+  }
+  print_stat(arr3);
+  print_items_int(arr3);
+
   printf("&array[67] = %p\n", dynarray_get(array, 128));
+
 }