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git.ipfire.org Git - thirdparty/openssl.git/blob - crypto/bn/bn_word.c
2 * Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.
4 * Licensed under the OpenSSL license (the "License"). You may not use
5 * this file except in compliance with the License. You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
10 #include "internal/cryptlib.h"
13 BN_ULONG
BN_mod_word(const BIGNUM
*a
, BN_ULONG w
)
27 * If |w| is too long and we don't have BN_ULLONG then we need to fall
28 * back to using BN_div_word
30 if (w
> ((BN_ULONG
)1 << BN_BITS4
)) {
31 BIGNUM
*tmp
= BN_dup(a
);
35 ret
= BN_div_word(tmp
, w
);
44 for (i
= a
->top
- 1; i
>= 0; i
--) {
47 * We can assume here that | w <= ((BN_ULONG)1 << BN_BITS4) | and so
48 * | ret < ((BN_ULONG)1 << BN_BITS4) | and therefore the shifts here are
49 * safe and will not overflow
51 ret
= ((ret
<< BN_BITS4
) | ((a
->d
[i
] >> BN_BITS4
) & BN_MASK2l
)) % w
;
52 ret
= ((ret
<< BN_BITS4
) | (a
->d
[i
] & BN_MASK2l
)) % w
;
54 ret
= (BN_ULLONG
) (((ret
<< (BN_ULLONG
) BN_BITS2
) | a
->d
[i
]) %
61 BN_ULONG
BN_div_word(BIGNUM
*a
, BN_ULONG w
)
70 /* actually this an error (division by zero) */
75 /* normalize input (so bn_div_words doesn't complain) */
76 j
= BN_BITS2
- BN_num_bits_word(w
);
78 if (!BN_lshift(a
, a
, j
))
81 for (i
= a
->top
- 1; i
>= 0; i
--) {
85 d
= bn_div_words(ret
, l
, w
);
86 ret
= (l
- ((d
* w
) & BN_MASK2
)) & BN_MASK2
;
89 if ((a
->top
> 0) && (a
->d
[a
->top
- 1] == 0))
93 a
->neg
= 0; /* don't allow negative zero */
98 int BN_add_word(BIGNUM
*a
, BN_ULONG w
)
106 /* degenerate case: w is zero */
109 /* degenerate case: a is zero */
111 return BN_set_word(a
, w
);
112 /* handle 'a' when negative */
115 i
= BN_sub_word(a
, w
);
120 for (i
= 0; w
!= 0 && i
< a
->top
; i
++) {
121 a
->d
[i
] = l
= (a
->d
[i
] + w
) & BN_MASK2
;
124 if (w
&& i
== a
->top
) {
125 if (bn_wexpand(a
, a
->top
+ 1) == NULL
)
134 int BN_sub_word(BIGNUM
*a
, BN_ULONG w
)
141 /* degenerate case: w is zero */
144 /* degenerate case: a is zero */
146 i
= BN_set_word(a
, w
);
148 BN_set_negative(a
, 1);
151 /* handle 'a' when negative */
154 i
= BN_add_word(a
, w
);
159 if ((a
->top
== 1) && (a
->d
[0] < w
)) {
160 a
->d
[0] = w
- a
->d
[0];
170 a
->d
[i
] = (a
->d
[i
] - w
) & BN_MASK2
;
175 if ((a
->d
[i
] == 0) && (i
== (a
->top
- 1)))
181 int BN_mul_word(BIGNUM
*a
, BN_ULONG w
)
191 ll
= bn_mul_words(a
->d
, a
->d
, a
->top
, w
);
193 if (bn_wexpand(a
, a
->top
+ 1) == NULL
)