1 files changed, 37 insertions, 0 deletions
diff --git a/src/libnm-std-aux/nm-std-utils.h b/src/libnm-std-aux/nm-std-utils.h
new file mode 100644
index 00000000..76d49d2f
--- /dev/null
+++ b/src/libnm-std-aux/nm-std-utils.h
@@ -0,0 +1,37 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#ifndef __NM_STD_UTILS_H__
+#define __NM_STD_UTILS_H__
+
+#include <stdbool.h>
+
+#include "nm-std-aux.h"
+
+/*****************************************************************************/
+
+/* nm_utils_get_next_realloc_size() is used to grow buffers exponentially, when
+ * the final size is unknown. As such, it has borders for which it allocates
+ * certain buffer sizes.
+ *
+ * The use of these defines is to get favorable allocation sequences.
+ * For example, nm_str_buf_init() asks for an initial allocation size. Note that
+ * it reserves the exactly requested amount, under the assumption that the
+ * user may know how many bytes will be required. However, often the caller
+ * doesn't know in advance, and NMStrBuf grows exponentially by calling
+ * nm_utils_get_next_realloc_size().
+ * Imagine you call nm_str_buf_init() with an initial buffer size 100, and you
+ * add one character at a time. Then the first reallocation will increase the
+ * buffer size only from 100 to 104.
+ * If you however start with an initial buffer size of 104, then the next reallocation
+ * via nm_utils_get_next_realloc_size() gives you 232, and so on. By using
+ * these sizes, it results in one less allocation, if you anyway don't know the
+ * exact size in advance. */
+#define NM_UTILS_GET_NEXT_REALLOC_SIZE_32   ((size_t) 32)
+#define NM_UTILS_GET_NEXT_REALLOC_SIZE_40   ((size_t) 40)
+#define NM_UTILS_GET_NEXT_REALLOC_SIZE_104  ((size_t) 104)
+#define NM_UTILS_GET_NEXT_REALLOC_SIZE_232  ((size_t) 232)
+#define NM_UTILS_GET_NEXT_REALLOC_SIZE_1000 ((size_t) 1000)
+
+size_t nm_utils_get_next_realloc_size(bool true_realloc, size_t requested);
+
+#endif /* __NM_STD_UTILS_H__ */