Root/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 extern inline
34#endif
35
36G10_MPI_INLINE_DECL mpi_limb_t
37mpihelp_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
55leave:
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
64G10_MPI_INLINE_DECL mpi_limb_t
65mpihelp_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
79G10_MPI_INLINE_DECL mpi_limb_t
80mpihelp_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
98leave:
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
107G10_MPI_INLINE_DECL mpi_limb_t
108mpihelp_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 */
123

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