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