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)