1 files changed, 45 insertions, 0 deletions
diff --git a/internal.h b/internal.h
index c27ebb7da4..a3b4045cde 100644
--- a/internal.h
+++ b/internal.h
@@ -305,6 +305,51 @@ struct method_table_wrapper {
     size_t serial;
 };
 
+#define RBIGNUM_EMBED_LEN_NUMBITS 3
+#ifndef RBIGNUM_EMBED_LEN_MAX
+# if (SIZEOF_VALUE*3/SIZEOF_ACTUAL_BDIGIT) < (1 << RBIGNUM_EMBED_LEN_NUMBITS)-1
+#   define RBIGNUM_EMBED_LEN_MAX (SIZEOF_VALUE*3/SIZEOF_ACTUAL_BDIGIT)
+# else
+#   define RBIGNUM_EMBED_LEN_MAX ((1 << RBIGNUM_EMBED_LEN_NUMBITS)-1)
+# endif
+#endif
+
+struct RBignum {
+    struct RBasic basic;
+    union {
+        struct {
+            long len;
+            BDIGIT *digits;
+        } heap;
+        BDIGIT ary[RBIGNUM_EMBED_LEN_MAX];
+    } as;
+};
+#define RBIGNUM_SIGN_BIT FL_USER1
+/* sign: positive:1, negative:0 */
+#define RBIGNUM_SIGN(b) ((RBASIC(b)->flags & RBIGNUM_SIGN_BIT) != 0)
+#define RBIGNUM_SET_SIGN(b,sign) \
+  ((sign) ? (RBASIC(b)->flags |= RBIGNUM_SIGN_BIT) \
+          : (RBASIC(b)->flags &= ~RBIGNUM_SIGN_BIT))
+#define RBIGNUM_POSITIVE_P(b) RBIGNUM_SIGN(b)
+#define RBIGNUM_NEGATIVE_P(b) (!RBIGNUM_SIGN(b))
+
+#define RBIGNUM_EMBED_FLAG FL_USER2
+#define RBIGNUM_EMBED_LEN_MASK (FL_USER5|FL_USER4|FL_USER3)
+#define RBIGNUM_EMBED_LEN_SHIFT (FL_USHIFT+RBIGNUM_EMBED_LEN_NUMBITS)
+#define RBIGNUM_LEN(b) \
+    ((RBASIC(b)->flags & RBIGNUM_EMBED_FLAG) ? \
+     (long)((RBASIC(b)->flags >> RBIGNUM_EMBED_LEN_SHIFT) & \
+            (RBIGNUM_EMBED_LEN_MASK >> RBIGNUM_EMBED_LEN_SHIFT)) : \
+     RBIGNUM(b)->as.heap.len)
+/* LSB:RBIGNUM_DIGITS(b)[0], MSB:RBIGNUM_DIGITS(b)[RBIGNUM_LEN(b)-1] */
+#define RBIGNUM_DIGITS(b) \
+    ((RBASIC(b)->flags & RBIGNUM_EMBED_FLAG) ? \
+     RBIGNUM(b)->as.ary : \
+     RBIGNUM(b)->as.heap.digits)
+#define RBIGNUM_LENINT(b) rb_long2int(RBIGNUM_LEN(b))
+
+#define RBIGNUM(obj) (R_CAST(RBignum)(obj))
+
 /* class.c */
 void rb_class_subclass_add(VALUE super, VALUE klass);
 void rb_class_remove_from_super_subclasses(VALUE);