rt_struct: Create `rt_struct.{c,h}`, and add `create_rts()`

This is a simple implementation of runtime structs, which was taken
from lavignes' librts, and modified to make it alot easier to work with.

Link to librts:
https://github.com/lavignes/librts

1 files changed, 49 insertions, 0 deletions

diff --git a/rt_struct.c b/rt_struct.c
new file mode 100644
index 0000000..314407c
--- /dev/null
+++ b/rt_struct.c
@@ -0,0 +1,49 @@
+#include <stdlib.h>
+#include <string.h>
+#include "macros.h"
+#include "rt_struct.h"
+
+static int is_root_type(rts_type_tag tag) {
+	return tag != TAG_STRUCT && tag != TAG_UNION;
+}
+
+int create_rts(rts_type *type) {
+	if (type == NULL) {
+		return 1;
+	}
+
+	if (is_root_type(type->tag)) {
+		return 0;
+	}
+
+	if (type->members == NULL || type->members[0] == NULL) {
+		return 1;
+	} else {
+		size_t offset = 0;
+		size_t max_align = 0;
+		size_t remainder = 0;
+		size_t padding = 0;
+		rts_member **members = type->members;
+		for (int i = 0; members[i] != NULL; ++i) {
+			rts_type *member_type = members[i]->type;
+			if (create_rts(member_type)) {
+				return 1;
+			} else {
+				const size_t align = member_type->alignment;
+				max_align = max(max_align, align);
+				if (type->tag == TAG_STRUCT) {
+					remainder = offset % align;
+					padding = (remainder) ? align - remainder : 0;
+					offset += padding;
+					type->offsets[i] = offset;
+					offset += member_type->size;
+				}
+			}
+		}
+		type->alignment = max_align;
+		remainder = offset % max_align;
+		padding = (remainder) ? max_align - remainder : 0;
+		type->size = offset + padding;
+		return 0;
+	}
+}