lib/mpi: Extend the MPI library

[linux-2.6-block.git] / lib / mpi / mpi-add.c

diff --git a/lib/mpi/mpi-add.c b/lib/mpi/mpi-add.c
new file mode 100644 (file)
index 0000000..2cdae54
--- /dev/null
+++ b/lib/mpi/mpi-add.c
@@ -0,0 +1,155 @@
+/* mpi-add.c  -  MPI functions
+ * Copyright (C) 1994, 1996, 1998, 2001, 2002,
+ *               2003 Free Software Foundation, Inc.
+ *
+ * This file is part of Libgcrypt.
+ *
+ * Note: This code is heavily based on the GNU MP Library.
+ *      Actually it's the same code with only minor changes in the
+ *      way the data is stored; this is to support the abstraction
+ *      of an optional secure memory allocation which may be used
+ *      to avoid revealing of sensitive data due to paging etc.
+ */
+
+#include "mpi-internal.h"
+
+/****************
+ * Add the unsigned integer V to the mpi-integer U and store the
+ * result in W. U and V may be the same.
+ */
+void mpi_add_ui(MPI w, MPI u, unsigned long v)
+{
+       mpi_ptr_t wp, up;
+       mpi_size_t usize, wsize;
+       int usign, wsign;
+
+       usize = u->nlimbs;
+       usign = u->sign;
+       wsign = 0;
+
+       /* If not space for W (and possible carry), increase space.  */
+       wsize = usize + 1;
+       if (w->alloced < wsize)
+               mpi_resize(w, wsize);
+
+       /* These must be after realloc (U may be the same as W).  */
+       up = u->d;
+       wp = w->d;
+
+       if (!usize) {  /* simple */
+               wp[0] = v;
+               wsize = v ? 1:0;
+       } else if (!usign) {  /* mpi is not negative */
+               mpi_limb_t cy;
+               cy = mpihelp_add_1(wp, up, usize, v);
+               wp[usize] = cy;
+               wsize = usize + cy;
+       } else {
+               /* The signs are different.  Need exact comparison to determine
+                * which operand to subtract from which.
+                */
+               if (usize == 1 && up[0] < v) {
+                       wp[0] = v - up[0];
+                       wsize = 1;
+               } else {
+                       mpihelp_sub_1(wp, up, usize, v);
+                       /* Size can decrease with at most one limb. */
+                       wsize = usize - (wp[usize-1] == 0);
+                       wsign = 1;
+               }
+       }
+
+       w->nlimbs = wsize;
+       w->sign   = wsign;
+}
+
+
+void mpi_add(MPI w, MPI u, MPI v)
+{
+       mpi_ptr_t wp, up, vp;
+       mpi_size_t usize, vsize, wsize;
+       int usign, vsign, wsign;
+
+       if (u->nlimbs < v->nlimbs) { /* Swap U and V. */
+               usize = v->nlimbs;
+               usign = v->sign;
+               vsize = u->nlimbs;
+               vsign = u->sign;
+               wsize = usize + 1;
+               RESIZE_IF_NEEDED(w, wsize);
+               /* These must be after realloc (u or v may be the same as w).  */
+               up = v->d;
+               vp = u->d;
+       } else {
+               usize = u->nlimbs;
+               usign = u->sign;
+               vsize = v->nlimbs;
+               vsign = v->sign;
+               wsize = usize + 1;
+               RESIZE_IF_NEEDED(w, wsize);
+               /* These must be after realloc (u or v may be the same as w).  */
+               up = u->d;
+               vp = v->d;
+       }
+       wp = w->d;
+       wsign = 0;
+
+       if (!vsize) {  /* simple */
+               MPN_COPY(wp, up, usize);
+               wsize = usize;
+               wsign = usign;
+       } else if (usign != vsign) { /* different sign */
+               /* This test is right since USIZE >= VSIZE */
+               if (usize != vsize) {
+                       mpihelp_sub(wp, up, usize, vp, vsize);
+                       wsize = usize;
+                       MPN_NORMALIZE(wp, wsize);
+                       wsign = usign;
+               } else if (mpihelp_cmp(up, vp, usize) < 0) {
+                       mpihelp_sub_n(wp, vp, up, usize);
+                       wsize = usize;
+                       MPN_NORMALIZE(wp, wsize);
+                       if (!usign)
+                               wsign = 1;
+               } else {
+                       mpihelp_sub_n(wp, up, vp, usize);
+                       wsize = usize;
+                       MPN_NORMALIZE(wp, wsize);
+                       if (usign)
+                               wsign = 1;
+               }
+       } else { /* U and V have same sign. Add them. */
+               mpi_limb_t cy = mpihelp_add(wp, up, usize, vp, vsize);
+               wp[usize] = cy;
+               wsize = usize + cy;
+               if (usign)
+                       wsign = 1;
+       }
+
+       w->nlimbs = wsize;
+       w->sign = wsign;
+}
+EXPORT_SYMBOL_GPL(mpi_add);
+
+void mpi_sub(MPI w, MPI u, MPI v)
+{
+       MPI vv = mpi_copy(v);
+       vv->sign = !vv->sign;
+       mpi_add(w, u, vv);
+       mpi_free(vv);
+}
+
+
+void mpi_addm(MPI w, MPI u, MPI v, MPI m)
+{
+       mpi_add(w, u, v);
+       mpi_mod(w, w, m);
+}
+EXPORT_SYMBOL_GPL(mpi_addm);
+
+void mpi_subm(MPI w, MPI u, MPI v, MPI m)
+{
+       mpi_sub(w, u, v);
+       mpi_mod(w, w, m);
+}
+EXPORT_SYMBOL_GPL(mpi_subm);