Reorganisation of the source tree

[ghc-hetmet.git] / rts / gmp / mpz / kronsz.c

diff --git a/rts/gmp/mpz/kronsz.c b/rts/gmp/mpz/kronsz.c
new file mode 100644 (file)
index 0000000..c8c6752
--- /dev/null
+++ b/rts/gmp/mpz/kronsz.c
@@ -0,0 +1,126 @@
+/* mpz_si_kronecker -- Kronecker/Jacobi symbol. */
+
+/*
+Copyright (C) 1999, 2000 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"
+
+
+int
+#if __STDC__
+mpz_si_kronecker (long a, mpz_srcptr b)
+#else
+mpz_si_kronecker (a, b)
+     long       a;
+     mpz_srcptr b;
+#endif
+{
+  int        b_abs_size;
+  mp_srcptr  b_ptr;
+  mp_limb_t  b_low;
+  int        twos;
+  int        result_bit1;
+
+  b_abs_size = ABSIZ (b);
+  if (b_abs_size == 0)
+    return JACOBI_S0 (a);  /* (a/0) */
+
+  b_ptr = PTR(b);
+  b_low = b_ptr[0];
+
+  /* (0/b) = 1 if b=+/-1, 0 otherwise */
+  if (a == 0)
+    return (b_abs_size == 1) & (b_low == 1);
+
+  /* account for the effect of the sign of b, so can then ignore it */
+  result_bit1 = JACOBI_BSGN_SZ_BIT1 (a, b);
+
+  if ((b_low & 1) == 0)
+    {
+      /* b even */
+
+      if ((a & 1) == 0)
+        return 0;  /* (a/b)=0 if both a,b even */
+
+      /* Require MP_BITS_PER_LIMB even, so that (a/2)^MP_BITS_PER_LIMB = 1,
+         and so that therefore there's no need to account for how many zero
+         limbs are stripped.  */
+      ASSERT ((BITS_PER_MP_LIMB & 1) == 0);
+
+      MPN_STRIP_LOW_ZEROS_NOT_ZERO (b_ptr, b_abs_size);
+      b_low = b_ptr[0];
+
+      if ((b_low & 1) == 0)
+        {
+          /* odd a, even b */
+
+          mp_limb_t  b_shl_bit1;
+
+          count_trailing_zeros (twos, b_low);
+
+          /* b_shl_bit1 is b>>twos, but with only bit 1 guaranteed */
+          if (twos == BITS_PER_MP_LIMB-1)
+            b_shl_bit1 = (b_abs_size == 1) ? 0 : (b_ptr[1] << 1);
+          else
+            b_shl_bit1 = (b_low >> twos);
+
+          result_bit1 ^= JACOBI_ASGN_SU_BIT1 (a, b_shl_bit1);
+          a = ABS(a);
+
+          if (a == 1)
+            return JACOBI_BIT1_TO_PN (result_bit1);  /* (1/b)=1 */
+
+          /* twos (a/2), reciprocity to (b/a), and (b/a) = (b mod a / b) */
+          return mpn_jacobi_base (mpn_mod_1_rshift (b_ptr, b_abs_size,
+                                                    twos, a),
+                                  a,
+                                  result_bit1
+                                  ^ JACOBI_TWOS_U_BIT1 (twos, a)
+                                  ^ JACOBI_RECIP_UU_BIT1 (a, b_shl_bit1));
+        }
+    }
+
+  /* b odd */
+
+  result_bit1 ^= JACOBI_ASGN_SU_BIT1 (a, b_low);
+  a = ABS(a);
+
+  /* (a/1) = 1 for any a */
+  if (b_abs_size == 1 && b_low == 1)
+    return JACOBI_BIT1_TO_PN (result_bit1);
+
+  /* Note a is cast to unsigned because 0x80..00 doesn't fit in a signed. */
+  if ((a & 1) == 0)
+    {
+      count_trailing_zeros (twos, a);
+      a = ((unsigned long) a) >> twos;
+      result_bit1 ^= JACOBI_TWOS_U_BIT1 (twos, b_low);
+    }
+
+  if (a == 1)
+    return JACOBI_BIT1_TO_PN (result_bit1);  /* (1/b)=1 */
+
+  /* reciprocity to (b/a), and (b/a) == (b mod a / a) */
+  return mpn_jacobi_base (mpn_mod_1 (b_ptr, b_abs_size, a), a,
+                          result_bit1 ^ JACOBI_RECIP_UU_BIT1 (a, b_low));
+}