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 */
110
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