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Diffstat (limited to 'third_party/heimdal/lib/hcrypto/libtommath/bn_mp_div.c')
-rw-r--r--third_party/heimdal/lib/hcrypto/libtommath/bn_mp_div.c250
1 files changed, 250 insertions, 0 deletions
diff --git a/third_party/heimdal/lib/hcrypto/libtommath/bn_mp_div.c b/third_party/heimdal/lib/hcrypto/libtommath/bn_mp_div.c
new file mode 100644
index 0000000..71de55b
--- /dev/null
+++ b/third_party/heimdal/lib/hcrypto/libtommath/bn_mp_div.c
@@ -0,0 +1,250 @@
+#include "tommath_private.h"
+#ifdef BN_MP_DIV_C
+/* LibTomMath, multiple-precision integer library -- Tom St Denis */
+/* SPDX-License-Identifier: Unlicense */
+
+#ifdef BN_MP_DIV_SMALL
+
+/* slower bit-bang division... also smaller */
+mp_err mp_div(const mp_int *a, const mp_int *b, mp_int *c, mp_int *d)
+{
+ mp_int ta, tb, tq, q;
+ int n, n2;
+ mp_err err;
+
+ /* is divisor zero ? */
+ if (MP_IS_ZERO(b)) {
+ return MP_VAL;
+ }
+
+ /* if a < b then q=0, r = a */
+ if (mp_cmp_mag(a, b) == MP_LT) {
+ if (d != NULL) {
+ err = mp_copy(a, d);
+ } else {
+ err = MP_OKAY;
+ }
+ if (c != NULL) {
+ mp_zero(c);
+ }
+ return err;
+ }
+
+ /* init our temps */
+ if ((err = mp_init_multi(&ta, &tb, &tq, &q, NULL)) != MP_OKAY) {
+ return err;
+ }
+
+
+ mp_set(&tq, 1uL);
+ n = mp_count_bits(a) - mp_count_bits(b);
+ if ((err = mp_abs(a, &ta)) != MP_OKAY) goto LBL_ERR;
+ if ((err = mp_abs(b, &tb)) != MP_OKAY) goto LBL_ERR;
+ if ((err = mp_mul_2d(&tb, n, &tb)) != MP_OKAY) goto LBL_ERR;
+ if ((err = mp_mul_2d(&tq, n, &tq)) != MP_OKAY) goto LBL_ERR;
+
+ while (n-- >= 0) {
+ if (mp_cmp(&tb, &ta) != MP_GT) {
+ if ((err = mp_sub(&ta, &tb, &ta)) != MP_OKAY) goto LBL_ERR;
+ if ((err = mp_add(&q, &tq, &q)) != MP_OKAY) goto LBL_ERR;
+ }
+ if ((err = mp_div_2d(&tb, 1, &tb, NULL)) != MP_OKAY) goto LBL_ERR;
+ if ((err = mp_div_2d(&tq, 1, &tq, NULL)) != MP_OKAY) goto LBL_ERR;
+ }
+
+ /* now q == quotient and ta == remainder */
+ n = a->sign;
+ n2 = (a->sign == b->sign) ? MP_ZPOS : MP_NEG;
+ if (c != NULL) {
+ mp_exch(c, &q);
+ c->sign = MP_IS_ZERO(c) ? MP_ZPOS : n2;
+ }
+ if (d != NULL) {
+ mp_exch(d, &ta);
+ d->sign = MP_IS_ZERO(d) ? MP_ZPOS : n;
+ }
+LBL_ERR:
+ mp_clear_multi(&ta, &tb, &tq, &q, NULL);
+ return err;
+}
+
+#else
+
+/* integer signed division.
+ * c*b + d == a [e.g. a/b, c=quotient, d=remainder]
+ * HAC pp.598 Algorithm 14.20
+ *
+ * Note that the description in HAC is horribly
+ * incomplete. For example, it doesn't consider
+ * the case where digits are removed from 'x' in
+ * the inner loop. It also doesn't consider the
+ * case that y has fewer than three digits, etc..
+ *
+ * The overall algorithm is as described as
+ * 14.20 from HAC but fixed to treat these cases.
+*/
+mp_err mp_div(const mp_int *a, const mp_int *b, mp_int *c, mp_int *d)
+{
+ mp_int q, x, y, t1, t2;
+ int n, t, i, norm;
+ mp_sign neg;
+ mp_err err;
+
+ /* is divisor zero ? */
+ if (MP_IS_ZERO(b)) {
+ return MP_VAL;
+ }
+
+ /* if a < b then q=0, r = a */
+ if (mp_cmp_mag(a, b) == MP_LT) {
+ if (d != NULL) {
+ err = mp_copy(a, d);
+ } else {
+ err = MP_OKAY;
+ }
+ if (c != NULL) {
+ mp_zero(c);
+ }
+ return err;
+ }
+
+ if ((err = mp_init_size(&q, a->used + 2)) != MP_OKAY) {
+ return err;
+ }
+ q.used = a->used + 2;
+
+ if ((err = mp_init(&t1)) != MP_OKAY) goto LBL_Q;
+
+ if ((err = mp_init(&t2)) != MP_OKAY) goto LBL_T1;
+
+ if ((err = mp_init_copy(&x, a)) != MP_OKAY) goto LBL_T2;
+
+ if ((err = mp_init_copy(&y, b)) != MP_OKAY) goto LBL_X;
+
+ /* fix the sign */
+ neg = (a->sign == b->sign) ? MP_ZPOS : MP_NEG;
+ x.sign = y.sign = MP_ZPOS;
+
+ /* normalize both x and y, ensure that y >= b/2, [b == 2**MP_DIGIT_BIT] */
+ norm = mp_count_bits(&y) % MP_DIGIT_BIT;
+ if (norm < (MP_DIGIT_BIT - 1)) {
+ norm = (MP_DIGIT_BIT - 1) - norm;
+ if ((err = mp_mul_2d(&x, norm, &x)) != MP_OKAY) goto LBL_Y;
+ if ((err = mp_mul_2d(&y, norm, &y)) != MP_OKAY) goto LBL_Y;
+ } else {
+ norm = 0;
+ }
+
+ /* note hac does 0 based, so if used==5 then its 0,1,2,3,4, e.g. use 4 */
+ n = x.used - 1;
+ t = y.used - 1;
+
+ /* while (x >= y*b**n-t) do { q[n-t] += 1; x -= y*b**{n-t} } */
+ /* y = y*b**{n-t} */
+ if ((err = mp_lshd(&y, n - t)) != MP_OKAY) goto LBL_Y;
+
+ while (mp_cmp(&x, &y) != MP_LT) {
+ ++(q.dp[n - t]);
+ if ((err = mp_sub(&x, &y, &x)) != MP_OKAY) goto LBL_Y;
+ }
+
+ /* reset y by shifting it back down */
+ mp_rshd(&y, n - t);
+
+ /* step 3. for i from n down to (t + 1) */
+ for (i = n; i >= (t + 1); i--) {
+ if (i > x.used) {
+ continue;
+ }
+
+ /* step 3.1 if xi == yt then set q{i-t-1} to b-1,
+ * otherwise set q{i-t-1} to (xi*b + x{i-1})/yt */
+ if (x.dp[i] == y.dp[t]) {
+ q.dp[(i - t) - 1] = ((mp_digit)1 << (mp_digit)MP_DIGIT_BIT) - (mp_digit)1;
+ } else {
+ mp_word tmp;
+ tmp = (mp_word)x.dp[i] << (mp_word)MP_DIGIT_BIT;
+ tmp |= (mp_word)x.dp[i - 1];
+ tmp /= (mp_word)y.dp[t];
+ if (tmp > (mp_word)MP_MASK) {
+ tmp = MP_MASK;
+ }
+ q.dp[(i - t) - 1] = (mp_digit)(tmp & (mp_word)MP_MASK);
+ }
+
+ /* while (q{i-t-1} * (yt * b + y{t-1})) >
+ xi * b**2 + xi-1 * b + xi-2
+
+ do q{i-t-1} -= 1;
+ */
+ q.dp[(i - t) - 1] = (q.dp[(i - t) - 1] + 1uL) & (mp_digit)MP_MASK;
+ do {
+ q.dp[(i - t) - 1] = (q.dp[(i - t) - 1] - 1uL) & (mp_digit)MP_MASK;
+
+ /* find left hand */
+ mp_zero(&t1);
+ t1.dp[0] = ((t - 1) < 0) ? 0u : y.dp[t - 1];
+ t1.dp[1] = y.dp[t];
+ t1.used = 2;
+ if ((err = mp_mul_d(&t1, q.dp[(i - t) - 1], &t1)) != MP_OKAY) goto LBL_Y;
+
+ /* find right hand */
+ t2.dp[0] = ((i - 2) < 0) ? 0u : x.dp[i - 2];
+ t2.dp[1] = x.dp[i - 1]; /* i >= 1 always holds */
+ t2.dp[2] = x.dp[i];
+ t2.used = 3;
+ } while (mp_cmp_mag(&t1, &t2) == MP_GT);
+
+ /* step 3.3 x = x - q{i-t-1} * y * b**{i-t-1} */
+ if ((err = mp_mul_d(&y, q.dp[(i - t) - 1], &t1)) != MP_OKAY) goto LBL_Y;
+
+ if ((err = mp_lshd(&t1, (i - t) - 1)) != MP_OKAY) goto LBL_Y;
+
+ if ((err = mp_sub(&x, &t1, &x)) != MP_OKAY) goto LBL_Y;
+
+ /* if x < 0 then { x = x + y*b**{i-t-1}; q{i-t-1} -= 1; } */
+ if (x.sign == MP_NEG) {
+ if ((err = mp_copy(&y, &t1)) != MP_OKAY) goto LBL_Y;
+ if ((err = mp_lshd(&t1, (i - t) - 1)) != MP_OKAY) goto LBL_Y;
+ if ((err = mp_add(&x, &t1, &x)) != MP_OKAY) goto LBL_Y;
+
+ q.dp[(i - t) - 1] = (q.dp[(i - t) - 1] - 1uL) & MP_MASK;
+ }
+ }
+
+ /* now q is the quotient and x is the remainder
+ * [which we have to normalize]
+ */
+
+ /* get sign before writing to c */
+ x.sign = (x.used == 0) ? MP_ZPOS : a->sign;
+
+ if (c != NULL) {
+ mp_clamp(&q);
+ mp_exch(&q, c);
+ c->sign = neg;
+ }
+
+ if (d != NULL) {
+ if ((err = mp_div_2d(&x, norm, &x, NULL)) != MP_OKAY) goto LBL_Y;
+ mp_exch(&x, d);
+ }
+
+ err = MP_OKAY;
+
+LBL_Y:
+ mp_clear(&y);
+LBL_X:
+ mp_clear(&x);
+LBL_T2:
+ mp_clear(&t2);
+LBL_T1:
+ mp_clear(&t1);
+LBL_Q:
+ mp_clear(&q);
+ return err;
+}
+
+#endif
+
+#endif
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