1 files changed, 23 insertions, 5 deletions
diff --git a/ruby.h b/ruby.h
index 6a2d2db4c0..b9943fdd80 100644
--- a/ruby.h
+++ b/ruby.h
@@ -390,15 +390,33 @@ struct RString {
      RSTRING(str)->as.ary : \
      RSTRING(str)->as.heap.ptr)
 
+#define RARRAY_EMBED_LEN_MAX 3
 struct RArray {
     struct RBasic basic;
-    long len;
     union {
-	long capa;
-	VALUE shared;
-    } aux;
-    VALUE *ptr;
+	struct {
+	    long len;
+	    union {
+		long capa;
+		VALUE shared;
+	    } aux;
+	    VALUE *ptr;
+	} heap;
+	VALUE ary[RARRAY_EMBED_LEN_MAX];
+    } as;
 };
+#define RARRAY_NOEMBED FL_USER3
+#define RARRAY_EMBED_LEN_MASK (FL_USER4|FL_USER5)
+#define RARRAY_EMBED_LEN_SHIFT (FL_USHIFT+4)
+#define RARRAY_LEN(a) \
+    (!(RBASIC(a)->flags & RARRAY_NOEMBED) ? \
+     (long)((RBASIC(a)->flags >> RARRAY_EMBED_LEN_SHIFT) & \
+            (RARRAY_EMBED_LEN_MASK >> RARRAY_EMBED_LEN_SHIFT)) : \
+     RARRAY(a)->as.heap.len)
+#define RARRAY_PTR(a) \
+    (!(RBASIC(a)->flags & RARRAY_NOEMBED) ? \
+     RARRAY(a)->as.ary : \
+     RARRAY(a)->as.heap.ptr)
 
 struct RRegexp {
     struct RBasic basic;