til_setup: add til_setup_new() helper

For use when setup functions allocate their private setup to
return in *res_setup.

They specify the size of their private setup, and supply the free
function to use.  This may be libc's free() when it's a simple
setup struct, or a bespoke free function when deep/complex
freeing is required for cleanup.

It's expected that callers will be embedding til_setup_t at the
start of their private setup struct, and returning a pointer to
this in *res_setup which would be the same value as a pointer to
to their private setup struct.

1 files changed, 26 insertions, 0 deletions

diff --git a/src/til_setup.c b/src/til_setup.c
new file mode 100644
index 0000000..c5fd451
--- /dev/null
+++ b/src/til_setup.c
@@ -0,0 +1,26 @@
+#include <assert.h>
+#include <errno.h>
+#include <stdlib.h>
+
+#include "til_setup.h"
+
+
+/* Allocate and initialize a new til_setup_t of size bytes.
+ * free_func is assigned to til_setup_t.free, and will be used for freeing the
+ * instance returned when destroyed.
+ */
+void * til_setup_new(size_t size, void (*free_func)(til_setup_t *setup))
+{
+	til_setup_t	*setup;
+
+	assert(size >= sizeof(til_setup_t));
+	assert(free_func);
+
+	setup = calloc(1, size);
+	if (!setup)
+		return NULL;
+
+	setup->free = free_func;
+
+	return setup;
+}