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