177 lines
3.8 KiB
C
177 lines
3.8 KiB
C
/*
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* Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.
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*
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* Licensed under the OpenSSL license (the "License"). You may not use
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* this file except in compliance with the License. You can obtain a copy
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* in the file LICENSE in the source distribution or at
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* https://www.openssl.org/source/license.html
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*/
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#include "internal/cryptlib.h"
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#include "bn_lcl.h"
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BN_ULONG BN_mod_word(const BIGNUM *a, BN_ULONG w)
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{
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#ifndef BN_LLONG
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BN_ULONG ret = 0;
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#else
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BN_ULLONG ret = 0;
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#endif
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int i;
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if (w == 0)
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return (BN_ULONG)-1;
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bn_check_top(a);
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w &= BN_MASK2;
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for (i = a->top - 1; i >= 0; i--) {
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#ifndef BN_LLONG
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ret = ((ret << BN_BITS4) | ((a->d[i] >> BN_BITS4) & BN_MASK2l)) % w;
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ret = ((ret << BN_BITS4) | (a->d[i] & BN_MASK2l)) % w;
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#else
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ret = (BN_ULLONG) (((ret << (BN_ULLONG) BN_BITS2) | a->d[i]) %
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(BN_ULLONG) w);
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#endif
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}
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return ((BN_ULONG)ret);
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}
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BN_ULONG BN_div_word(BIGNUM *a, BN_ULONG w)
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{
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BN_ULONG ret = 0;
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int i, j;
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bn_check_top(a);
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w &= BN_MASK2;
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if (!w)
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/* actually this an error (division by zero) */
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return (BN_ULONG)-1;
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if (a->top == 0)
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return 0;
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/* normalize input (so bn_div_words doesn't complain) */
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j = BN_BITS2 - BN_num_bits_word(w);
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w <<= j;
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if (!BN_lshift(a, a, j))
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return (BN_ULONG)-1;
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for (i = a->top - 1; i >= 0; i--) {
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BN_ULONG l, d;
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l = a->d[i];
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d = bn_div_words(ret, l, w);
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ret = (l - ((d * w) & BN_MASK2)) & BN_MASK2;
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a->d[i] = d;
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}
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if ((a->top > 0) && (a->d[a->top - 1] == 0))
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a->top--;
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ret >>= j;
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bn_check_top(a);
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return (ret);
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}
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int BN_add_word(BIGNUM *a, BN_ULONG w)
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{
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BN_ULONG l;
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int i;
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bn_check_top(a);
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w &= BN_MASK2;
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/* degenerate case: w is zero */
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if (!w)
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return 1;
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/* degenerate case: a is zero */
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if (BN_is_zero(a))
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return BN_set_word(a, w);
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/* handle 'a' when negative */
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if (a->neg) {
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a->neg = 0;
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i = BN_sub_word(a, w);
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if (!BN_is_zero(a))
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a->neg = !(a->neg);
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return (i);
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}
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for (i = 0; w != 0 && i < a->top; i++) {
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a->d[i] = l = (a->d[i] + w) & BN_MASK2;
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w = (w > l) ? 1 : 0;
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}
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if (w && i == a->top) {
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if (bn_wexpand(a, a->top + 1) == NULL)
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return 0;
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a->top++;
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a->d[i] = w;
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}
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bn_check_top(a);
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return (1);
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}
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int BN_sub_word(BIGNUM *a, BN_ULONG w)
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{
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int i;
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bn_check_top(a);
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w &= BN_MASK2;
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/* degenerate case: w is zero */
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if (!w)
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return 1;
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/* degenerate case: a is zero */
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if (BN_is_zero(a)) {
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i = BN_set_word(a, w);
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if (i != 0)
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BN_set_negative(a, 1);
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return i;
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}
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/* handle 'a' when negative */
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if (a->neg) {
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a->neg = 0;
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i = BN_add_word(a, w);
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a->neg = 1;
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return (i);
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}
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if ((a->top == 1) && (a->d[0] < w)) {
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a->d[0] = w - a->d[0];
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a->neg = 1;
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return (1);
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}
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i = 0;
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for (;;) {
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if (a->d[i] >= w) {
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a->d[i] -= w;
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break;
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} else {
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a->d[i] = (a->d[i] - w) & BN_MASK2;
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i++;
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w = 1;
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}
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}
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if ((a->d[i] == 0) && (i == (a->top - 1)))
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a->top--;
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bn_check_top(a);
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return (1);
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}
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int BN_mul_word(BIGNUM *a, BN_ULONG w)
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{
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BN_ULONG ll;
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bn_check_top(a);
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w &= BN_MASK2;
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if (a->top) {
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if (w == 0)
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BN_zero(a);
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else {
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ll = bn_mul_words(a->d, a->d, a->top, w);
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if (ll) {
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if (bn_wexpand(a, a->top + 1) == NULL)
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return (0);
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a->d[a->top++] = ll;
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}
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}
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}
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bn_check_top(a);
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return (1);
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}
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