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
63 int 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 {
73 r->neg=a->neg;
74 if (bn_wexpand(r,a->top+1) == NULL) return(0);
75 r->top=a->top;
76 }
77 else
78 {
79 if (bn_wexpand(r,a->top+1) == NULL) return(0);
80 }
81 ap=a->d;
82 rp=r->d;
83 c=0;
84 for (i=0; i<a->top; i++)
85 {
86 t= *(ap++);
87 *(rp++)=((t<<1)|c)&BN_MASK2;
88 c=(t & BN_TBIT)?1:0;
89 }
90 if (c)
91 {
92 *rp=1;
93 r->top++;
94 }
95 bn_check_top(r);
96 return(1);
97 }
98
99 int BN_rshift1(BIGNUM *r, const BIGNUM *a)
100 {
101 BN_ULONG *ap,*rp,t,c;
102 int i,j;
103
104 bn_check_top(r);
105 bn_check_top(a);
106
107 if (BN_is_zero(a))
108 {
109 BN_zero(r);
110 return(1);
111 }
112 i = a->top;
113 ap= a->d;
114 j = i-(ap[i-1]==1);
115 if (a != r)
116 {
117 if (bn_wexpand(r,j) == NULL) return(0);
118 r->neg=a->neg;
119 }
120 rp=r->d;
121 t=ap[--i];
122 c=(t&1)?BN_TBIT:0;
123 if (t>>=1) rp[i]=t;
124 while (i>0)
125 {
126 t=ap[--i];
127 rp[i]=((t>>1)&BN_MASK2)|c;
128 c=(t&1)?BN_TBIT:0;
129 }
130 r->top=j;
131 bn_check_top(r);
132 return(1);
133 }
134
135 int BN_lshift(BIGNUM *r, const BIGNUM *a, int n)
136 {
137 int i,nw,lb,rb;
138 BN_ULONG *t,*f;
139 BN_ULONG l;
140
141 bn_check_top(r);
142 bn_check_top(a);
143
144 r->neg=a->neg;
145 nw=n/BN_BITS2;
146 if (bn_wexpand(r,a->top+nw+1) == NULL) return(0);
147 lb=n%BN_BITS2;
148 rb=BN_BITS2-lb;
149 f=a->d;
150 t=r->d;
151 t[a->top+nw]=0;
152 if (lb == 0)
153 for (i=a->top-1; i>=0; i--)
154 t[nw+i]=f[i];
155 else
156 for (i=a->top-1; i>=0; i--)
157 {
158 l=f[i];
159 t[nw+i+1]|=(l>>rb)&BN_MASK2;
160 t[nw+i]=(l<<lb)&BN_MASK2;
161 }
162 memset(t,0,nw*sizeof(t[0]));
163 /* for (i=0; i<nw; i++)
164 t[i]=0;*/
165 r->top=a->top+nw+1;
166 bn_correct_top(r);
167 bn_check_top(r);
168 return(1);
169 }
170
171 int BN_rshift(BIGNUM *r, const BIGNUM *a, int n)
172 {
173 int i,j,nw,lb,rb;
174 BN_ULONG *t,*f;
175 BN_ULONG l,tmp;
176
177 bn_check_top(r);
178 bn_check_top(a);
179
180 nw=n/BN_BITS2;
181 rb=n%BN_BITS2;
182 lb=BN_BITS2-rb;
183 if (nw >= a->top || a->top == 0)
184 {
185 BN_zero(r);
186 return(1);
187 }
188 i = (BN_num_bits(a)-n+(BN_BITS2-1))/BN_BITS2;
189 if (r != a)
190 {
191 r->neg=a->neg;
192 if (bn_wexpand(r,i) == NULL) return(0);
193 }
194 else
195 {
196 if (n == 0)
197 return 1; /* or the copying loop will go berserk */
198 }
199
200 f= &(a->d[nw]);
201 t=r->d;
202 j=a->top-nw;
203 r->top=i;
204
205 if (rb == 0)
206 {
207 for (i=j; i != 0; i--)
208 *(t++)= *(f++);
209 }
210 else
211 {
212 l= *(f++);
213 for (i=j-1; i != 0; i--)
214 {
215 tmp =(l>>rb)&BN_MASK2;
216 l= *(f++);
217 *(t++) =(tmp|(l<<lb))&BN_MASK2;
218 }
219 if ((l = (l>>rb)&BN_MASK2)) *(t) = l;
220 }
221 bn_check_top(r);
222 return(1);
223 }