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4 office 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  
63 int 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  
95 int 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 }