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 <string.h> 61#include "bn_lcl.h" 62 63int BN_lshift(BIGNUM *r, const BIGNUM *a, int n) 64 { 65 int i,nw,lb,rb; 66 BN_ULONG *t,*f; 67 BN_ULONG l; 68 69 r->neg=a->neg; 70 if (bn_wexpand(r,a->top+(n/BN_BITS2)+1) == NULL) return(0); 71 nw=n/BN_BITS2; 72 lb=n%BN_BITS2; 73 rb=BN_BITS2-lb; 74 f=a->d; 75 t=r->d; 76 t[a->top+nw]=0; 77 if (lb == 0) 78 for (i=a->top-1; i>=0; i--) 79 t[nw+i]=f[i]; 80 else 81 for (i=a->top-1; i>=0; i--) 82 { 83 l=f[i]; 84 t[nw+i+1]|=(l>>rb)&BN_MASK2; 85 t[nw+i]=(l<<lb)&BN_MASK2; 86 } 87 memset(t,0,nw*sizeof(t[0])); 88/* for (i=0; i<nw; i++) 89 t[i]=0;*/ 90 r->top=a->top+nw+1; 91 bn_fix_top(r); 92 return(1); 93 } 94 95int BN_rshift(BIGNUM *r, BIGNUM *a, int n) 96 { 97 int i,j,nw,lb,rb; 98 BN_ULONG *t,*f; 99 BN_ULONG l,tmp; 100 101 nw=n/BN_BITS2; 102 rb=n%BN_BITS2; 103 lb=BN_BITS2-rb; 104 if (nw > a->top || a->top == 0) 105 { 106 BN_zero(r); 107 return(1); 108 } 109 if (r != a) 110 { 111 r->neg=a->neg; 112 if (bn_wexpand(r,a->top-nw+1) == NULL) return(0); 113 } 114 115 f= &(a->d[nw]); 116 t=r->d; 117 j=a->top-nw; 118 r->top=j; 119 120 if (rb == 0) 121 { 122 for (i=j+1; i > 0; i--) 123 *(t++)= *(f++); 124 } 125 else 126 { 127 l= *(f++); 128 for (i=1; i<j; i++) 129 { 130 tmp =(l>>rb)&BN_MASK2; 131 l= *(f++); 132 *(t++) =(tmp|(l<<lb))&BN_MASK2; 133 } 134 *(t++) =(l>>rb)&BN_MASK2; 135 } 136 *t=0; 137 bn_fix_top(r); 138 return(1); 139 } 140