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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301,
  19  * USA.
  20  *
  21  * Note: This code is heavily based on the GNU MP Library.
  22  *       Actually it's the same code with only minor changes in the
  23  *       way the data is stored; this is to support the abstraction
  24  *       of an optional secure memory allocation which may be used
  25  *       to avoid revealing of sensitive data due to paging etc.
  26  *       The GNU MP Library itself is published under the LGPL;
  27  *       however I decided to publish this code under the plain GPL.
  28  */
  29
  30 #ifndef G10_MPI_INLINE_H
  31 #define G10_MPI_INLINE_H
  32
  33 #ifndef G10_MPI_INLINE_DECL
  34 #define G10_MPI_INLINE_DECL  extern __inline__
  35 #endif
  36
  37 G10_MPI_INLINE_DECL  mpi_limb_t
  38 mpihelp_add_1( mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
  39                mpi_size_t s1_size, mpi_limb_t s2_limb)
  40 {
  41     mpi_limb_t x;
  42
  43     x = *s1_ptr++;
  44     s2_limb += x;
  45     *res_ptr++ = s2_limb;
  46     if( s2_limb < x ) { /* sum is less than the left operand: handle carry */
  47         while( --s1_size ) {
  48             x = *s1_ptr++ + 1;  /* add carry */
  49             *res_ptr++ = x;     /* and store */
  50             if( x )             /* not 0 (no overflow): we can stop */
  51                 goto leave;
  52         }
  53         return 1; /* return carry (size of s1 to small) */
  54     }
  55
  56   leave:
  57     if( res_ptr != s1_ptr ) { /* not the same variable */
  58         mpi_size_t i;          /* copy the rest */
  59         for( i=0; i < s1_size-1; i++ )
  60             res_ptr[i] = s1_ptr[i];
  61     }
  62     return 0; /* no carry */
  63 }
  64
  65
  66
  67 G10_MPI_INLINE_DECL mpi_limb_t
  68 mpihelp_add(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr, mpi_size_t s1_size,
  69                                mpi_ptr_t s2_ptr, mpi_size_t s2_size)
  70 {
  71     mpi_limb_t cy = 0;
  72
  73     if( s2_size )
  74         cy = mpihelp_add_n( res_ptr, s1_ptr, s2_ptr, s2_size );
  75
  76     if( s1_size - s2_size )
  77         cy = mpihelp_add_1( res_ptr + s2_size, s1_ptr + s2_size,
  78                             s1_size - s2_size, cy);
  79     return cy;
  80 }
  81
  82
  83 G10_MPI_INLINE_DECL mpi_limb_t
  84 mpihelp_sub_1(mpi_ptr_t res_ptr,  mpi_ptr_t s1_ptr,
  85               mpi_size_t s1_size, mpi_limb_t s2_limb )
  86 {
  87     mpi_limb_t x;
  88
  89     x = *s1_ptr++;
  90     s2_limb = x - s2_limb;
  91     *res_ptr++ = s2_limb;
  92     if( s2_limb > x ) {
  93         while( --s1_size ) {
  94             x = *s1_ptr++;
  95             *res_ptr++ = x - 1;
  96             if( x )
  97                 goto leave;
  98         }
  99         return 1;
 100     }
 101
 102   leave:
 103     if( res_ptr != s1_ptr ) {
 104         mpi_size_t i;
 105         for( i=0; i < s1_size-1; i++ )
 106             res_ptr[i] = s1_ptr[i];
 107     }
 108     return 0;
 109 }
 110
 111
 112
 113 G10_MPI_INLINE_DECL   mpi_limb_t
 114 mpihelp_sub( mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr, mpi_size_t s1_size,
 115                                 mpi_ptr_t s2_ptr, mpi_size_t s2_size)
 116 {
 117     mpi_limb_t cy = 0;
 118
 119     if( s2_size )
 120         cy = mpihelp_sub_n(res_ptr, s1_ptr, s2_ptr, s2_size);
 121
 122     if( s1_size - s2_size )
 123         cy = mpihelp_sub_1(res_ptr + s2_size, s1_ptr + s2_size,
 124                                       s1_size - s2_size, cy);
 125     return cy;
 126 }
 127
 128 #endif /*G10_MPI_INLINE_H*/