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0bcb8184 MW |
1 | /* |
2 | * qfarith.h: utilities for quick field arithmetic | |
3 | */ | |
4 | /* | |
5 | * This file is Free Software. It has been modified to as part of its | |
6 | * incorporation into secnet. | |
7 | * | |
8 | * Copyright 2017 Mark Wooding | |
9 | * | |
10 | * You may redistribute this file and/or modify it under the terms of | |
11 | * the permissive licence shown below. | |
12 | * | |
13 | * You may redistribute secnet as a whole and/or modify it under the | |
14 | * terms of the GNU General Public License as published by the Free | |
15 | * Software Foundation; either version 3, or (at your option) any | |
16 | * later version. | |
17 | * | |
18 | * This program is distributed in the hope that it will be useful, | |
19 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
20 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
21 | * GNU General Public License for more details. | |
22 | * | |
23 | * You should have received a copy of the GNU General Public License | |
24 | * along with this program; if not, see | |
25 | * https://www.gnu.org/licenses/gpl.html. | |
26 | */ | |
27 | /* | |
28 | * Imported from Catacomb, and modified for Secnet (2017-04-30): | |
29 | * | |
30 | * * Use `fake-mLib-bits.h' in place of the real <mLib/bits.h>. | |
31 | * | |
32 | * * Use C99 signed integer types instead of our own local probing. | |
33 | * | |
34 | * * Remove the support for non-two's-complement targets. | |
35 | * | |
36 | * The file's original comment headers are preserved below. | |
37 | */ | |
b7a5ecfc MW |
38 | /* -*-c-*- |
39 | * | |
40 | * Utilities for quick field arithmetic | |
41 | * | |
42 | * (c) 2017 Straylight/Edgeware | |
43 | */ | |
44 | ||
45 | /*----- Licensing notice --------------------------------------------------* | |
46 | * | |
47 | * This file is part of Catacomb. | |
48 | * | |
49 | * Catacomb is free software; you can redistribute it and/or modify | |
50 | * it under the terms of the GNU Library General Public License as | |
51 | * published by the Free Software Foundation; either version 2 of the | |
52 | * License, or (at your option) any later version. | |
53 | * | |
54 | * Catacomb is distributed in the hope that it will be useful, | |
55 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
56 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
57 | * GNU Library General Public License for more details. | |
58 | * | |
59 | * You should have received a copy of the GNU Library General Public | |
60 | * License along with Catacomb; if not, write to the Free | |
61 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, | |
62 | * MA 02111-1307, USA. | |
63 | */ | |
64 | ||
65 | #ifndef CATACOMB_QFARITH_H | |
66 | #define CATACOMB_QFARITH_H | |
67 | ||
68 | #ifdef __cplusplus | |
69 | extern "C" { | |
70 | #endif | |
71 | ||
72 | /*----- Header files ------------------------------------------------------*/ | |
73 | ||
74 | #include <limits.h> | |
0bcb8184 | 75 | #include <stdint.h> |
b7a5ecfc | 76 | |
0bcb8184 | 77 | #include "fake-mLib-bits.h" |
b7a5ecfc MW |
78 | |
79 | /*----- Signed integer types ----------------------------------------------*/ | |
80 | ||
0bcb8184 MW |
81 | typedef int_fast32_t int32; |
82 | typedef int_fast64_t int64; | |
83 | #define HAVE_INT64 1 | |
b7a5ecfc MW |
84 | |
85 | /*----- General bit-hacking utilities -------------------------------------*/ | |
86 | ||
87 | /* Individual bits, and masks for low bits. */ | |
88 | #define BIT(n) (1ul << (n)) | |
89 | #define MASK(n) (BIT(n) - 1) | |
90 | ||
91 | /* Arithmetic right shift. If X is a value of type TY, and N is a | |
92 | * nonnegative integer, then return the value of X shifted right by N bits; | |
93 | * alternatively, this is floor(X/2^N). | |
94 | * | |
95 | * GCC manages to compile this into a simple shift operation if one is | |
96 | * available, but it's correct for all C targets. | |
97 | */ | |
98 | #define ASR(ty, x, n) (((x) - (ty)((u##ty)(x)&MASK(n)))/(ty)BIT(n)) | |
99 | ||
100 | /*----- Constant-time utilities -------------------------------------------*/ | |
101 | ||
102 | /* The following have better implementations on a two's complement target. */ | |
103 | #ifdef NEG_TWOC | |
104 | ||
105 | /* If we have two's complement arithmetic then masks are signed; this | |
106 | * avoids a switch to unsigned representation, with the consequent problem | |
107 | * of overflow when we convert back. | |
108 | */ | |
109 | typedef int32 mask32; | |
110 | ||
111 | /* Convert an unsigned mask M into a `mask32'. This is a hairy-looking | |
112 | * no-op on many targets, but, given that we have two's complement | |
113 | * integers, it is free of arithmetic overflow. | |
114 | */ | |
115 | # define FIX_MASK32(m) \ | |
116 | ((mask32)((m)&0x7fffffffu) + (-(mask32)0x7fffffff - 1)*(((m) >> 31)&1u)) | |
117 | ||
118 | /* If Z is zero and M has its low 32 bits set, then copy (at least) the low | |
119 | * 32 bits of X to Z; if M is zero, do nothing. Otherwise, scramble Z | |
120 | * unhelpfully. | |
121 | */ | |
122 | # define CONDPICK(z, x, m) do { (z) |= (x)&(m); } while (0) | |
123 | ||
124 | /* If M has its low 32 bits set, then return (at least) the low 32 bits of | |
125 | * X in Z; if M is zero, then return (at least) the low 32 bits of Y in Z. | |
126 | * Otherwise, return an unhelful result. | |
127 | */ | |
128 | # define PICK2(x, y, m) (((x)&(m)) | ((y)&~(m))) | |
129 | ||
130 | /* If M has its low 32 bits set then swap (at least) the low 32 bits of X | |
131 | * and Y; if M is zero, then do nothing. Otherwise, scramble X and Y | |
132 | * unhelpfully. | |
133 | */ | |
134 | # define CONDSWAP(x, y, m) \ | |
135 | do { mask32 t_ = ((x) ^ (y))&(m); (x) ^= t_; (y) ^= t_; } while (0) | |
136 | #else | |
0bcb8184 | 137 | # error "Targets without two's complement arithmetic aren't supported" |
b7a5ecfc MW |
138 | #endif |
139 | ||
140 | /* Return zero if bit 31 of X is clear, or a mask with (at least) the low 32 | |
141 | * bits set if bit 31 of X is set. | |
142 | */ | |
143 | #define SIGN(x) (-(mask32)(((uint32)(x) >> 31)&1)) | |
144 | ||
145 | /* Return zero if X is zero, or a mask with (at least) the low 32 bits set if | |
146 | * X is nonzero. | |
147 | */ | |
148 | #define NONZEROP(x) SIGN((U32(x) >> 1) - U32(x)) | |
149 | ||
150 | /*----- Debugging utilities -----------------------------------------------*/ | |
151 | ||
152 | /* Define a debugging function DUMPFN, which will dump an integer represented | |
153 | * modulo M. The integer is represented as a vector of NPIECE pieces of type | |
154 | * PIECETY. The pieces are assembled at possibly irregular offsets: piece i | |
155 | * logically has width PIECEWD(i), but may overhang the next piece. The | |
156 | * pieces may be signed. GETMOD is an expression which calculates and | |
157 | * returns the value of M, as an `mp *'. | |
158 | * | |
159 | * The generated function writes the value of such an integer X to the stream | |
160 | * FP, labelled with the string WHAT. | |
161 | * | |
162 | * The definition assumes that <stdio.h>, <catacomb/mp.h>, and | |
163 | * <catacomb/mptext.h> have been included. | |
164 | */ | |
165 | #define DEF_FDUMP(dumpfn, piecety, piecewd, npiece, noctet, getmod) \ | |
166 | static void dumpfn(FILE *fp, const char *what, const piecety *x) \ | |
167 | { \ | |
168 | mpw w; \ | |
169 | mp m, *y = MP_ZERO, *t = MP_NEW, *p; \ | |
170 | octet b[noctet]; \ | |
171 | unsigned i, o; \ | |
172 | \ | |
173 | p = getmod; \ | |
174 | mp_build(&m, &w, &w + 1); \ | |
175 | for (i = o = 0; i < npiece; i++) { \ | |
176 | if (x[i] >= 0) { w = x[i]; m.f &= ~MP_NEG; } \ | |
177 | else { w = -x[i]; m.f |= MP_NEG; } \ | |
178 | t = mp_lsl(t, &m, o); \ | |
179 | y = mp_add(y, y, t); \ | |
180 | o += piecewd(i); \ | |
181 | } \ | |
182 | \ | |
183 | fprintf(fp, "%s = <", what); \ | |
184 | for (i = 0; i < npiece; i++) { \ | |
185 | if (i) fputs(", ", fp); \ | |
186 | fprintf(fp, "%ld", (long)x[i]); \ | |
187 | } \ | |
188 | fputs(">\n\t= ", fp); \ | |
189 | mp_writefile(y, fp, 10); \ | |
190 | fputs("\n\t== ", fp); \ | |
191 | mp_div(0, &y, y, p); \ | |
192 | mp_writefile(y, fp, 10); \ | |
193 | fputs("\n\t= 0x", fp); \ | |
194 | mp_writefile(y, fp, 16); \ | |
195 | fputs(" (mod 2^255 - 19)\n\t= [", fp); \ | |
196 | mp_storel(y, b, sizeof(b)); \ | |
197 | for (i = 0; i < 32; i++) { \ | |
198 | if (i && !(i%4)) fputc(':', fp); \ | |
199 | fprintf(fp, "%02x", b[i]); \ | |
200 | } \ | |
201 | fputs("]\n", fp); \ | |
202 | mp_drop(y); mp_drop(p); mp_drop(t); \ | |
203 | } | |
204 | ||
205 | /*----- That's all, folks -------------------------------------------------*/ | |
206 | ||
207 | #ifdef __cplusplus | |
208 | } | |
209 | #endif | |
210 | ||
211 | #endif |