1 files changed, 15 insertions, 0 deletions
diff --git a/mem.h b/mem.h
index d13e02f..e7edb82 100644
--- a/mem.h
+++ b/mem.h
@@ -13,6 +13,21 @@ void *M(State *S, void *ptr, size_t old, size_t new);
 #define RENEW_ARR(S,p,ty,old,new) (ty*)M(S, (p), (old)*sizeof(ty), (new)*sizeof(ty))
 #define NEW_OBJ(S,ty, oty) (ty*)alloc_obj(S, sizeof(ty), oty)
 
+// needs len,cap,d fields
+#define ENSURE_CAP(S, darr, type, needed) \
+	if (darr.cap < needed) { \
+		size_t __newsz = next_pwrof2(needed); \
+	    if (__newsz < 8) __newsz = 8;
+		darr.d = RENEW_ARR(S, darr.d, type, darr.cap, __newsz); \
+	    darr.cap = __newsz; \
+	}
+
+inline size_t next_pwrof2(size_t x) {
+	size_t p = 1;
+	while (p < x) p <<= 1;
+	return p;
+}
+
 #define FREE(S,p,ty) M(S, p, sizeof(ty), 0)
 #define FREE_ARR(S,p,ty,old) M(S, p, (old)*sizeof(ty), 0)