mpi: Add _gcry_mpih_cmp_ui.

* mpi/mpih-const-time.c (_gcry_mpih_cmp_ui): New.

Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>

2 files changed, 15 insertions, 0 deletions

diff --git a/mpi/mpi-internal.h b/mpi/mpi-internal.h
index 4111d905..8ccdeada 100644
--- a/mpi/mpi-internal.h
+++ b/mpi/mpi-internal.h
@@ -274,6 +274,7 @@ void _gcry_mpih_abs_cond (mpi_ptr_t wp, mpi_ptr_t up,
                           mpi_size_t usize, unsigned long op_enable);
 mpi_ptr_t _gcry_mpih_mod (mpi_ptr_t vp, mpi_size_t vsize,
                           mpi_ptr_t up, mpi_size_t usize);
+int _gcry_mpih_cmp_ui (mpi_ptr_t up, mpi_size_t usize, unsigned long v);
 
 
 /* Define stuff for longlong.h.  */
diff --git a/mpi/mpih-const-time.c b/mpi/mpih-const-time.c
index d91bf1a9..5ebb8d11 100644
--- a/mpi/mpih-const-time.c
+++ b/mpi/mpih-const-time.c
@@ -180,3 +180,17 @@ _gcry_mpih_mod (mpi_ptr_t vp, mpi_size_t vsize,
 
   return rp;
 }
+
+int
+_gcry_mpih_cmp_ui (mpi_ptr_t up, mpi_size_t usize, unsigned long v)
+{
+  int is_all_zero = 1;
+  mpi_size_t i;
+
+  for (i = 1; i < usize; i++)
+    is_all_zero &= (up[i] == 0);
+
+  if (is_all_zero)
+    return up[0] - v;
+  return 1;
+}