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, j; 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 i = a->top; 109 ap = a->d; 110 j = i - (ap[i - 1] == 1); 111 if (a != r) { 112 if (bn_wexpand(r, j) == NULL) 113 return (0); 114 r->neg = a->neg; 115 } 116 rp = r->d; 117 t = ap[--i]; 118 c = (t & 1) ? BN_TBIT : 0; 119 if (t >>= 1) 120 rp[i] = t; 121 while (i > 0) { 122 t = ap[--i]; 123 rp[i] = ((t >> 1) & BN_MASK2) | c; 124 c = (t & 1) ? BN_TBIT : 0; 125 } 126 r->top = j; 127 bn_check_top(r); 128 return (1); 129} 130 131int BN_lshift(BIGNUM *r, const BIGNUM *a, int n) 132{ 133 int i, nw, lb, rb; 134 BN_ULONG *t, *f; 135 BN_ULONG l; 136 137 bn_check_top(r); 138 bn_check_top(a); 139 140 if (n < 0) { 141 BNerr(BN_F_BN_LSHIFT, BN_R_INVALID_SHIFT); 142 return 0; 143 } 144 145 r->neg = a->neg; 146 nw = n / BN_BITS2; 147 if (bn_wexpand(r, a->top + nw + 1) == NULL) 148 return (0); 149 lb = n % BN_BITS2; 150 rb = BN_BITS2 - lb; 151 f = a->d; 152 t = r->d; 153 t[a->top + nw] = 0; 154 if (lb == 0) 155 for (i = a->top - 1; i >= 0; i--) 156 t[nw + i] = f[i]; 157 else 158 for (i = a->top - 1; i >= 0; i--) { 159 l = f[i]; 160 t[nw + i + 1] |= (l >> rb) & BN_MASK2; 161 t[nw + i] = (l << lb) & BN_MASK2; 162 } 163 memset(t, 0, nw * sizeof(t[0])); 164 /* 165 * for (i=0; i<nw; i++) t[i]=0; 166 */ 167 r->top = a->top + nw + 1; 168 bn_correct_top(r); 169 bn_check_top(r); 170 return (1); 171} 172 173int BN_rshift(BIGNUM *r, const BIGNUM *a, int n) 174{ 175 int i, j, nw, lb, rb; 176 BN_ULONG *t, *f; 177 BN_ULONG l, tmp; 178 179 bn_check_top(r); 180 bn_check_top(a); 181 182 if (n < 0) { 183 BNerr(BN_F_BN_RSHIFT, BN_R_INVALID_SHIFT); 184 return 0; 185 } 186 187 nw = n / BN_BITS2; 188 rb = n % BN_BITS2; 189 lb = BN_BITS2 - rb; 190 if (nw >= a->top || a->top == 0) { 191 BN_zero(r); 192 return (1); 193 } 194 i = (BN_num_bits(a) - n + (BN_BITS2 - 1)) / BN_BITS2; 195 if (r != a) { 196 r->neg = a->neg; 197 if (bn_wexpand(r, i) == NULL) 198 return (0); 199 } else { 200 if (n == 0) 201 return 1; /* or the copying loop will go berserk */ 202 } 203 204 f = &(a->d[nw]); 205 t = r->d; 206 j = a->top - nw; 207 r->top = i; 208 209 if (rb == 0) { 210 for (i = j; i != 0; i--) 211 *(t++) = *(f++); 212 } else { 213 l = *(f++); 214 for (i = j - 1; i != 0; i--) { 215 tmp = (l >> rb) & BN_MASK2; 216 l = *(f++); 217 *(t++) = (tmp | (l << lb)) & BN_MASK2; 218 } 219 if ((l = (l >> rb) & BN_MASK2)) 220 *(t) = l; 221 } 222 bn_check_top(r); 223 return (1); 224} 225