mpi: Add functions to manipulate the sign.

* src/gcrypt.h.in (gcry_mpi_is_neg): New.
(gcry_mpi_neg, gcry_mpi_abs): New.
* mpi/mpiutil.c (_gcry_mpi_is_neg): New.
(_gcry_mpi_neg, _gcry_mpi_abs): New.
* src/visibility.c, src/visibility.h: Add wrappers.
* src/libgcrypt.def, src/libgcrypt.vers: Export them.
* src/mpi.h (mpi_is_neg): New.  Rename old macro to mpi_has_sign.
* mpi/mpi-mod.c (_gcry_mpi_mod_barrett): Use mpi_has_sign.
* mpi/mpi-mpow.c (calc_barrett): Ditto.
* cipher/primegen.c (_gcry_derive_x931_prime): Ditto
* cipher/rsa.c (secret): Ditto.

1 files changed, 39 insertions, 0 deletions

diff --git a/mpi/mpiutil.c b/mpi/mpiutil.c
index a65d2361..433dda6b 100644
--- a/mpi/mpiutil.c
+++ b/mpi/mpiutil.c
@@ -324,6 +324,45 @@ gcry_mpi_copy( gcry_mpi_t a )
 }
 
 
+/* Return true if A is negative.  */
+int
+_gcry_mpi_is_neg (gcry_mpi_t a)
+{
+  if (a->sign && _gcry_mpi_cmp_ui (a, 0))
+    return 1;
+  else
+    return 0;
+}
+
+
+/* W = - U */
+void
+_gcry_mpi_neg (gcry_mpi_t w, gcry_mpi_t u)
+{
+  if (mpi_is_immutable (w))
+    {
+      mpi_immutable_failed ();
+      return;
+    }
+
+  w->sign = !u->sign;
+}
+
+
+/* W = [W] */
+void
+_gcry_mpi_abs (gcry_mpi_t w)
+{
+  if (mpi_is_immutable (w))
+    {
+      mpi_immutable_failed ();
+      return;
+    }
+
+  w->sign = 0;
+}
+
+
 /****************
  * This function allocates an MPI which is optimized to hold
  * a value as large as the one given in the argument and allocates it