Backup, new approach to ast

memory.c

@@ -40,6 +40,23 @@ arena_push_size(Arena *a, SizeU size){
   return result;
 }
 
+function void
+arena_pop_pos(Arena *arena, SizeU pos){
+  pos = clamp_top_sizeu(pos, arena->len);
+  arena->len = pos;
+}
+
+function Arena_Checkpoint
+arena_checkpoint(Arena *arena){
+  Arena_Checkpoint result = {arena, arena->len};
+  return result;
+}
+
+function void
+arena_restore(Arena_Checkpoint checkpoint){
+  arena_pop_pos(checkpoint.arena, checkpoint.pos);
+}
+
 function String
 arena_push_string_copy(Arena *arena, String string){
   U8 *copy = arena_push_array(arena, U8, string.len+1);
@@ -47,3 +64,28 @@ arena_push_string_copy(Arena *arena, String string){
   copy[string.len] = 0;
   return (String){copy, string.len};
 }
+
+function String
+string_fmtv(Arena *arena, const char *str, va_list args1) {
+  va_list args2;
+  va_copy(args2, args1);
+  U64 len = vsnprintf(0, 0, str, args2);
+  va_end(args2);
+  
+  char *result = (char *)arena_push_size(arena, len + 1);
+  vsnprintf(result, len + 1, str, args1);
+  if (arena->len > 0)
+    arena->len -= 1;
+  
+  return (String){(U8 *)result, len};
+}
+
+function String 
+string_fmt(Arena *arena, const char *str, ...) {
+  va_list args1;
+  va_start(args1, str);
+  String result = string_fmtv(arena, str, args1);
+  va_end(args1);
+  return result;
+}
+