bn_shift.c revision 296465
1/* crypto/bn/bn_shift.c */ 2/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com) 3 * All rights reserved. 4 * 5 * This package is an SSL implementation written 6 * by Eric Young (eay@cryptsoft.com). 7 * The implementation was written so as to conform with Netscapes SSL. 8 * 9 * This library is free for commercial and non-commercial use as long as 10 * the following conditions are aheared to. The following conditions 11 * apply to all code found in this distribution, be it the RC4, RSA, 12 * lhash, DES, etc., code; not just the SSL code. The SSL documentation 13 * included with this distribution is covered by the same copyright terms 14 * except that the holder is Tim Hudson (tjh@cryptsoft.com). 15 * 16 * Copyright remains Eric Young's, and as such any Copyright notices in 17 * the code are not to be removed. 18 * If this package is used in a product, Eric Young should be given attribution 19 * as the author of the parts of the library used. 20 * This can be in the form of a textual message at program startup or 21 * in documentation (online or textual) provided with the package. 22 * 23 * Redistribution and use in source and binary forms, with or without 24 * modification, are permitted provided that the following conditions 25 * are met: 26 * 1. Redistributions of source code must retain the copyright 27 * notice, this list of conditions and the following disclaimer. 28 * 2. Redistributions in binary form must reproduce the above copyright 29 * notice, this list of conditions and the following disclaimer in the 30 * documentation and/or other materials provided with the distribution. 31 * 3. All advertising materials mentioning features or use of this software 32 * must display the following acknowledgement: 33 * "This product includes cryptographic software written by 34 * Eric Young (eay@cryptsoft.com)" 35 * The word 'cryptographic' can be left out if the rouines from the library 36 * being used are not cryptographic related :-). 37 * 4. If you include any Windows specific code (or a derivative thereof) from 38 * the apps directory (application code) you must include an acknowledgement: 39 * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)" 40 * 41 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND 42 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 43 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 44 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 45 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 46 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 47 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 48 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 49 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 50 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 51 * SUCH DAMAGE. 52 * 53 * The licence and distribution terms for any publically available version or 54 * derivative of this code cannot be changed. i.e. this code cannot simply be 55 * copied and put under another distribution licence 56 * [including the GNU Public Licence.] 57 */ 58 59#include <stdio.h> 60#include "cryptlib.h" 61#include "bn_lcl.h" 62 63int BN_lshift1(BIGNUM *r, const BIGNUM *a) 64{ 65 register BN_ULONG *ap, *rp, t, c; 66 int i; 67 68 bn_check_top(r); 69 bn_check_top(a); 70 71 if (r != a) { 72 r->neg = a->neg; 73 if (bn_wexpand(r, a->top + 1) == NULL) 74 return (0); 75 r->top = a->top; 76 } else { 77 if (bn_wexpand(r, a->top + 1) == NULL) 78 return (0); 79 } 80 ap = a->d; 81 rp = r->d; 82 c = 0; 83 for (i = 0; i < a->top; i++) { 84 t = *(ap++); 85 *(rp++) = ((t << 1) | c) & BN_MASK2; 86 c = (t & BN_TBIT) ? 1 : 0; 87 } 88 if (c) { 89 *rp = 1; 90 r->top++; 91 } 92 bn_check_top(r); 93 return (1); 94} 95 96int BN_rshift1(BIGNUM *r, const BIGNUM *a) 97{ 98 BN_ULONG *ap, *rp, t, c; 99 int i; 100 101 bn_check_top(r); 102 bn_check_top(a); 103 104 if (BN_is_zero(a)) { 105 BN_zero(r); 106 return (1); 107 } 108 if (a != r) { 109 if (bn_wexpand(r, a->top) == NULL) 110 return (0); 111 r->top = a->top; 112 r->neg = a->neg; 113 } 114 ap = a->d; 115 rp = r->d; 116 c = 0; 117 for (i = a->top - 1; i >= 0; i--) { 118 t = ap[i]; 119 rp[i] = ((t >> 1) & BN_MASK2) | c; 120 c = (t & 1) ? BN_TBIT : 0; 121 } 122 bn_correct_top(r); 123 bn_check_top(r); 124 return (1); 125} 126 127int BN_lshift(BIGNUM *r, const BIGNUM *a, int n) 128{ 129 int i, nw, lb, rb; 130 BN_ULONG *t, *f; 131 BN_ULONG l; 132 133 bn_check_top(r); 134 bn_check_top(a); 135 136 if (n < 0) { 137 BNerr(BN_F_BN_LSHIFT, BN_R_INVALID_SHIFT); 138 return 0; 139 } 140 141 r->neg = a->neg; 142 nw = n / BN_BITS2; 143 if (bn_wexpand(r, a->top + nw + 1) == NULL) 144 return (0); 145 lb = n % BN_BITS2; 146 rb = BN_BITS2 - lb; 147 f = a->d; 148 t = r->d; 149 t[a->top + nw] = 0; 150 if (lb == 0) 151 for (i = a->top - 1; i >= 0; i--) 152 t[nw + i] = f[i]; 153 else 154 for (i = a->top - 1; i >= 0; i--) { 155 l = f[i]; 156 t[nw + i + 1] |= (l >> rb) & BN_MASK2; 157 t[nw + i] = (l << lb) & BN_MASK2; 158 } 159 memset(t, 0, nw * sizeof(t[0])); 160 /* 161 * for (i=0; i<nw; i++) t[i]=0; 162 */ 163 r->top = a->top + nw + 1; 164 bn_correct_top(r); 165 bn_check_top(r); 166 return (1); 167} 168 169int BN_rshift(BIGNUM *r, const BIGNUM *a, int n) 170{ 171 int i, j, nw, lb, rb; 172 BN_ULONG *t, *f; 173 BN_ULONG l, tmp; 174 175 bn_check_top(r); 176 bn_check_top(a); 177 178 if (n < 0) { 179 BNerr(BN_F_BN_RSHIFT, BN_R_INVALID_SHIFT); 180 return 0; 181 } 182 183 nw = n / BN_BITS2; 184 rb = n % BN_BITS2; 185 lb = BN_BITS2 - rb; 186 if (nw >= a->top || a->top == 0) { 187 BN_zero(r); 188 return (1); 189 } 190 if (r != a) { 191 r->neg = a->neg; 192 if (bn_wexpand(r, a->top - nw + 1) == NULL) 193 return (0); 194 } else { 195 if (n == 0) 196 return 1; /* or the copying loop will go berserk */ 197 } 198 199 f = &(a->d[nw]); 200 t = r->d; 201 j = a->top - nw; 202 r->top = j; 203 204 if (rb == 0) { 205 for (i = j; i != 0; i--) 206 *(t++) = *(f++); 207 } else { 208 l = *(f++); 209 for (i = j - 1; i != 0; i--) { 210 tmp = (l >> rb) & BN_MASK2; 211 l = *(f++); 212 *(t++) = (tmp | (l << lb)) & BN_MASK2; 213 } 214 *(t++) = (l >> rb) & BN_MASK2; 215 } 216 bn_correct_top(r); 217 bn_check_top(r); 218 return (1); 219} 220