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, size: s2_size); |
59 | |
60 | if (s1_size - s2_size) |
61 | cy = mpihelp_add_1(res_ptr: res_ptr + s2_size, s1_ptr: s1_ptr + s2_size, |
62 | s1_size: s1_size - s2_size, s2_limb: 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, size: s2_size); |
102 | |
103 | if (s1_size - s2_size) |
104 | cy = mpihelp_sub_1(res_ptr: res_ptr + s2_size, s1_ptr: s1_ptr + s2_size, |
105 | s1_size: s1_size - s2_size, s2_limb: cy); |
106 | return cy; |
107 | } |
108 | |
109 | #endif /*G10_MPI_INLINE_H */ |
110 | |