1 files changed, 66 insertions, 0 deletions
diff --git a/mpz/divis_ui.c b/mpz/divis_ui.c
new file mode 100644
index 000000000..9390669cc
--- /dev/null
+++ b/mpz/divis_ui.c
@@ -0,0 +1,66 @@
+/* mpz_divisible_ui_p -- mpz by ulong divisibility test */
+
+/*
+Copyright 2000, 2001 Free Software Foundation, Inc.
+
+This file is part of the GNU MP Library.
+
+The GNU MP Library is free software; you can redistribute it and/or modify
+it under the terms of the GNU Lesser General Public License as published by
+the Free Software Foundation; either version 2.1 of the License, or (at your
+option) any later version.
+
+The GNU MP Library is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
+License for more details.
+
+You should have received a copy of the GNU Lesser General Public License
+along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
+the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+MA 02111-1307, USA.
+*/
+
+#include "gmp.h"
+#include "gmp-impl.h"
+#include "longlong.h"
+
+
+/* A bit mask of all the least significant zero bits of n. */
+#define LOW_ZEROS_MASK(n)  (((n) & -(n)) - 1)
+
+
+int
+mpz_divisible_ui_p (mpz_srcptr a, unsigned long d)
+{
+  mp_size_t  asize;
+  mp_ptr     ap;
+  unsigned   twos;
+
+  if (d == 0)
+    DIVIDE_BY_ZERO;
+
+  asize = SIZ(a);
+  if (asize == 0)  /* 0 divisible by any d */
+    return 1;
+
+  ap = PTR(a);
+  asize = ABS(asize);  /* ignore sign of a */
+
+  if (BELOW_THRESHOLD (asize, MODEXACT_1_ODD_THRESHOLD))
+    return mpn_mod_1 (ap, asize, (mp_limb_t) d) == 0;
+
+  if (! (d & 1))
+    {
+      /* Strip low zero bits to get odd d required by modexact.  If d==e*2^n
+         and a is divisible by 2^n and by e, then it's divisible by d. */
+
+      if ((ap[0] & LOW_ZEROS_MASK (d)) != 0)
+        return 0;
+
+      count_trailing_zeros (twos, (mp_limb_t) d);
+      d >>= twos;
+    }
+
+  return mpn_modexact_1_odd (ap, asize, (mp_limb_t) d) == 0;
+}