lib/mpi/mpi-inline.h

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2 /* mpi-inline.h  -  Internal to the Multi Precision Integers
   3  *      Copyright (C) 1994, 1996, 1998, 1999 Free Software Foundation, Inc.
   4  *
   5  * This file is part of GnuPG.
   6  *
   7  * Note: This code is heavily based on the GNU MP Library.
   8  *       Actually it's the same code with only minor changes in the
   9  *       way the data is stored; this is to support the abstraction
  10  *       of an optional secure memory allocation which may be used
  11  *       to avoid revealing of sensitive data due to paging etc.
  12  *       The GNU MP Library itself is published under the LGPL;
  13  *       however I decided to publish this code under the plain GPL.
  14  */
  15
  16 #ifndef G10_MPI_INLINE_H
  17 #define G10_MPI_INLINE_H
  18
  19 #ifndef G10_MPI_INLINE_DECL
  20 #define G10_MPI_INLINE_DECL  static inline
  21 #endif
  22
  23 G10_MPI_INLINE_DECL mpi_limb_t
  24 mpihelp_add_1(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
  25               mpi_size_t s1_size, mpi_limb_t s2_limb)
  26 {
  27         mpi_limb_t x;
  28
  29         x = *s1_ptr++;
  30         s2_limb += x;
  31         *res_ptr++ = s2_limb;
  32         if (s2_limb < x) {      /* sum is less than the left operand: handle carry */
  33                 while (--s1_size) {
  34                         x = *s1_ptr++ + 1;      /* add carry */
  35                         *res_ptr++ = x; /* and store */
  36                         if (x)  /* not 0 (no overflow): we can stop */
  37                                 goto leave;
  38                 }
  39                 return 1;       /* return carry (size of s1 to small) */
  40         }
  41
  42 leave:
  43         if (res_ptr != s1_ptr) {        /* not the same variable */
  44                 mpi_size_t i;   /* copy the rest */
  45                 for (i = 0; i < s1_size - 1; i++)
  46                         res_ptr[i] = s1_ptr[i];
  47         }
  48         return 0;               /* no carry */
  49 }
  50
  51 G10_MPI_INLINE_DECL mpi_limb_t
  52 mpihelp_add(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr, mpi_size_t s1_size,
  53             mpi_ptr_t s2_ptr, mpi_size_t s2_size)
  54 {
  55         mpi_limb_t cy = 0;
  56
  57         if (s2_size)
  58                 cy = mpihelp_add_n(res_ptr, s1_ptr, s2_ptr, s2_size);
  59
  60         if (s1_size - s2_size)
  61                 cy = mpihelp_add_1(res_ptr + s2_size, s1_ptr + s2_size,
  62                                    s1_size - s2_size, cy);
  63         return cy;
  64 }
  65
  66 G10_MPI_INLINE_DECL mpi_limb_t
  67 mpihelp_sub_1(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr,
  68               mpi_size_t s1_size, mpi_limb_t s2_limb)
  69 {
  70         mpi_limb_t x;
  71
  72         x = *s1_ptr++;
  73         s2_limb = x - s2_limb;
  74         *res_ptr++ = s2_limb;
  75         if (s2_limb > x) {
  76                 while (--s1_size) {
  77                         x = *s1_ptr++;
  78                         *res_ptr++ = x - 1;
  79                         if (x)
  80                                 goto leave;
  81                 }
  82                 return 1;
  83         }
  84
  85 leave:
  86         if (res_ptr != s1_ptr) {
  87                 mpi_size_t i;
  88                 for (i = 0; i < s1_size - 1; i++)
  89                         res_ptr[i] = s1_ptr[i];
  90         }
  91         return 0;
  92 }
  93
  94 G10_MPI_INLINE_DECL mpi_limb_t
  95 mpihelp_sub(mpi_ptr_t res_ptr, mpi_ptr_t s1_ptr, mpi_size_t s1_size,
  96             mpi_ptr_t s2_ptr, mpi_size_t s2_size)
  97 {
  98         mpi_limb_t cy = 0;
  99
 100         if (s2_size)
 101                 cy = mpihelp_sub_n(res_ptr, s1_ptr, s2_ptr, s2_size);
 102
 103         if (s1_size - s2_size)
 104                 cy = mpihelp_sub_1(res_ptr + s2_size, s1_ptr + s2_size,
 105                                    s1_size - s2_size, cy);
 106         return cy;
 107 }
 108
 109 #endif /*G10_MPI_INLINE_H */