lib/mpi/mpi-inline.h

   1 /* mpi-inline.h  -  Internal to the Multi Precision Integers
   2  *      Copyright (C) 1994, 1996, 1998, 1999 Free Software Foundation, Inc.
   3  *
   4  * This file is part of GnuPG.
   5  *
   6  * GnuPG is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * GnuPG is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
  19  *
  20  * Note: This code is heavily based on the GNU MP Library.
  21  *       Actually it's the same code with only minor changes in the
  22  *       way the data is stored; this is to support the abstraction
  23  *       of an optional secure memory allocation which may be used
  24  *       to avoid revealing of sensitive data due to paging etc.
  25  *       The GNU MP Library itself is published under the LGPL;
  26  *       however I decided to publish this code under the plain GPL.
  27  */
  28
  29 #ifndef G10_MPI_INLINE_H
  30 #define G10_MPI_INLINE_H
  31
  32 #ifndef G10_MPI_INLINE_DECL
  33 #define G10_MPI_INLINE_DECL  static inline
  34 #endif
  35
  36 G10_MPI_INLINE_DECL mpi_limb_t
  37 mpihelp_add_1(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
  38               mpi_size_t s1_size, mpi_limb_t s2_limb)
  39 {
  40         mpi_limb_t x;
  41
  42         x = *s1_ptr++;
  43         s2_limb += x;
  44         *res_ptr++ = s2_limb;
  45         if (s2_limb < x) {      /* sum is less than the left operand: handle carry */
  46                 while (--s1_size) {
  47                         x = *s1_ptr++ + 1;      /* add carry */
  48                         *res_ptr++ = x; /* and store */
  49                         if (x)  /* not 0 (no overflow): we can stop */
  50                                 goto leave;
  51                 }
  52                 return 1;       /* return carry (size of s1 to small) */
  53         }
  54
  55 leave:
  56         if (res_ptr != s1_ptr) {        /* not the same variable */
  57                 mpi_size_t i;   /* copy the rest */
  58                 for (i = 0; i < s1_size - 1; i++)
  59                         res_ptr[i] = s1_ptr[i];
  60         }
  61         return 0;               /* no carry */
  62 }
  63
  64 G10_MPI_INLINE_DECL mpi_limb_t
  65 mpihelp_add(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr, mpi_size_t s1_size,
  66             mpi_ptr_t s2_ptr, mpi_size_t s2_size)
  67 {
  68         mpi_limb_t cy = 0;
  69
  70         if (s2_size)
  71                 cy = mpihelp_add_n(res_ptr, s1_ptr, s2_ptr, s2_size);
  72
  73         if (s1_size - s2_size)
  74                 cy = mpihelp_add_1(res_ptr + s2_size, s1_ptr + s2_size,
  75                                    s1_size - s2_size, cy);
  76         return cy;
  77 }
  78
  79 G10_MPI_INLINE_DECL mpi_limb_t
  80 mpihelp_sub_1(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
  81               mpi_size_t s1_size, mpi_limb_t s2_limb)
  82 {
  83         mpi_limb_t x;
  84
  85         x = *s1_ptr++;
  86         s2_limb = x - s2_limb;
  87         *res_ptr++ = s2_limb;
  88         if (s2_limb > x) {
  89                 while (--s1_size) {
  90                         x = *s1_ptr++;
  91                         *res_ptr++ = x - 1;
  92                         if (x)
  93                                 goto leave;
  94                 }
  95                 return 1;
  96         }
  97
  98 leave:
  99         if (res_ptr != s1_ptr) {
 100                 mpi_size_t i;
 101                 for (i = 0; i < s1_size - 1; i++)
 102                         res_ptr[i] = s1_ptr[i];
 103         }
 104         return 0;
 105 }
 106
 107 G10_MPI_INLINE_DECL mpi_limb_t
 108 mpihelp_sub(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr, mpi_size_t s1_size,
 109             mpi_ptr_t s2_ptr, mpi_size_t s2_size)
 110 {
 111         mpi_limb_t cy = 0;
 112
 113         if (s2_size)
 114                 cy = mpihelp_sub_n(res_ptr, s1_ptr, s2_ptr, s2_size);
 115
 116         if (s1_size - s2_size)
 117                 cy = mpihelp_sub_1(res_ptr + s2_size, s1_ptr + s2_size,
 118                                    s1_size - s2_size, cy);
 119         return cy;
 120 }
 121
 122 #endif /*G10_MPI_INLINE_H */