394 lines
6.0 KiB
C++
394 lines
6.0 KiB
C++
// Bignum multiplication and division
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#include "stdafx.h"
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#include "defs.h"
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extern int ge(unsigned int *, unsigned int *, int);
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static void mulf(unsigned int *, unsigned int *, int, unsigned int);
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static void addf(unsigned int *, unsigned int *, int);
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static void subf(unsigned int *, unsigned int *, int);
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unsigned int *
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mmul(unsigned int *a, unsigned int *b)
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{
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int alen, blen, i, n;
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unsigned int *t, *x;
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if (MZERO(a) || MZERO(b))
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return mint(0);
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if (MLENGTH(a) == 1 && a[0] == 1) {
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t = mcopy(b);
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MSIGN(t) *= MSIGN(a);
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return t;
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}
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if (MLENGTH(b) == 1 && b[0] == 1) {
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t = mcopy(a);
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MSIGN(t) *= MSIGN(b);
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return t;
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}
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alen = MLENGTH(a);
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blen = MLENGTH(b);
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n = alen + blen;
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x = mnew(n);
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t = mnew(alen + 1);
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for (i = 0; i < n; i++)
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x[i] = 0;
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/* sum of partial products */
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for (i = 0; i < blen; i++) {
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mulf(t, a, alen, b[i]);
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addf(x + i, t, alen + 1);
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}
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mfree(t);
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/* length of product */
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for (i = n - 1; i > 0; i--)
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if (x[i])
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break;
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MLENGTH(x) = i + 1;
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MSIGN(x) = MSIGN(a) * MSIGN(b);
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return x;
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}
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unsigned int *
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mdiv(unsigned int *a, unsigned int *b)
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{
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int alen, blen, i, n;
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unsigned int c, *t, *x, *y;
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unsigned long long jj, kk;
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if (MZERO(b))
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stop("divide by zero");
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if (MZERO(a))
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return mint(0);
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alen = MLENGTH(a);
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blen = MLENGTH(b);
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n = alen - blen;
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if (n < 0)
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return mint(0);
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x = mnew(alen + 1);
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for (i = 0; i < alen; i++)
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x[i] = a[i];
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x[i] = 0;
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y = mnew(n + 1);
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t = mnew(blen + 1);
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/* Add 1 here to round up in case the remaining words are non-zero. */
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kk = (unsigned long long) b[blen - 1] + 1;
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for (i = 0; i <= n; i++) {
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y[n - i] = 0;
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for (;;) {
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/* estimate the partial quotient */
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if (little_endian()) {
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((unsigned int *) &jj)[0] = x[alen - i - 1];
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((unsigned int *) &jj)[1] = x[alen - i - 0];
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} else {
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((unsigned int *) &jj)[1] = x[alen - i - 1];
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((unsigned int *) &jj)[0] = x[alen - i - 0];
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}
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c = (unsigned int) (jj / kk);
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if (c == 0) {
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if (ge(x + n - i, b, blen)) { /* see note 1 */
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y[n - i]++;
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subf(x + n - i, b, blen);
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}
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break;
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}
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y[n - i] += c;
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mulf(t, b, blen, c);
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subf(x + n - i, t, blen + 1);
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}
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}
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mfree(t);
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mfree(x);
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/* length of quotient */
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for (i = n; i > 0; i--)
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if (y[i])
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break;
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if (i == 0 && y[0] == 0) {
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mfree(y);
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y = mint(0);
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} else {
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MLENGTH(y) = i + 1;
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MSIGN(y) = MSIGN(a) * MSIGN(b);
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}
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return y;
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}
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// a = a + b
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static void
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addf(unsigned int *a, unsigned int *b, int len)
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{
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int i;
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long long t = 0; /* can be signed or unsigned */
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for (i = 0; i < len; i++) {
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t += (long long) a[i] + b[i];
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a[i] = (unsigned int) t;
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t >>= 32;
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}
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}
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// a = a - b
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static void
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subf(unsigned int *a, unsigned int *b, int len)
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{
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int i;
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long long t = 0; /* must be signed */
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for (i = 0; i < len; i++) {
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t += (long long) a[i] - b[i];
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a[i] = (unsigned int) t;
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t >>= 32;
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}
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}
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// a = b * c
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// 0xffffffff + 0xffffffff * 0xffffffff == 0xffffffff00000000
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static void
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mulf(unsigned int *a, unsigned int *b, int len, unsigned int c)
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{
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int i;
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unsigned long long t = 0; /* must be unsigned */
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for (i = 0; i < len; i++) {
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t += (unsigned long long) b[i] * c;
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a[i] = (unsigned int) t;
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t >>= 32;
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}
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a[i] = (unsigned int) t;
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}
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unsigned int *
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mmod(unsigned int *a, unsigned int *b)
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{
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int alen, blen, i, n;
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unsigned int c, *t, *x, *y;
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unsigned long long jj, kk;
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if (MZERO(b))
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stop("divide by zero");
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if (MZERO(a))
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return mint(0);
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alen = MLENGTH(a);
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blen = MLENGTH(b);
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n = alen - blen;
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if (n < 0)
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return mcopy(a);
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x = mnew(alen + 1);
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for (i = 0; i < alen; i++)
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x[i] = a[i];
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x[i] = 0;
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y = mnew(n + 1);
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t = mnew(blen + 1);
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kk = (unsigned long long) b[blen - 1] + 1;
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for (i = 0; i <= n; i++) {
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y[n - i] = 0;
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for (;;) {
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/* estimate the partial quotient */
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if (little_endian()) {
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((unsigned int *) &jj)[0] = x[alen - i - 1];
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((unsigned int *) &jj)[1] = x[alen - i - 0];
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} else {
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((unsigned int *) &jj)[1] = x[alen - i - 1];
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((unsigned int *) &jj)[0] = x[alen - i - 0];
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}
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c = (int) (jj / kk);
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if (c == 0) {
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if (ge(x + n - i, b, blen)) { /* see note 1 */
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y[n - i]++;
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subf(x + n - i, b, blen);
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}
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break;
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}
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y[n - i] += c;
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mulf(t, b, blen, c);
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subf(x + n - i, t, blen + 1);
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}
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}
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mfree(t);
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mfree(y);
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/* length of remainder */
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for (i = blen - 1; i > 0; i--)
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if (x[i])
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break;
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if (i == 0 && x[0] == 0) {
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mfree(x);
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x = mint(0);
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} else {
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MLENGTH(x) = i + 1;
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MSIGN(x) = MSIGN(a);
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}
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return x;
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}
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// return both quotient and remainder of a/b
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void
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mdivrem(unsigned int **q, unsigned int **r, unsigned int *a, unsigned int *b)
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{
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int alen, blen, i, n;
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unsigned int c, *t, *x, *y;
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unsigned long long jj, kk;
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if (MZERO(b))
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stop("divide by zero");
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if (MZERO(a)) {
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*q = mint(0);
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*r = mint(0);
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return;
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}
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alen = MLENGTH(a);
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blen = MLENGTH(b);
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n = alen - blen;
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if (n < 0) {
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*q = mint(0);
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*r = mcopy(a);
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return;
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}
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x = mnew(alen + 1);
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for (i = 0; i < alen; i++)
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x[i] = a[i];
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x[i] = 0;
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y = mnew(n + 1);
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t = mnew(blen + 1);
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kk = (unsigned long long) b[blen - 1] + 1;
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for (i = 0; i <= n; i++) {
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y[n - i] = 0;
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for (;;) {
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/* estimate the partial quotient */
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if (little_endian()) {
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((unsigned int *) &jj)[0] = x[alen - i - 1];
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((unsigned int *) &jj)[1] = x[alen - i - 0];
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} else {
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((unsigned int *) &jj)[1] = x[alen - i - 1];
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((unsigned int *) &jj)[0] = x[alen - i - 0];
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}
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c = (int) (jj / kk);
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if (c == 0) {
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if (ge(x + n - i, b, blen)) { /* see note 1 */
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y[n - i]++;
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subf(x + n - i, b, blen);
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}
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break;
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}
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y[n - i] += c;
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mulf(t, b, blen, c);
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subf(x + n - i, t, blen + 1);
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}
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}
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mfree(t);
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/* length of quotient */
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for (i = n; i > 0; i--)
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if (y[i])
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break;
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if (i == 0 && y[0] == 0) {
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mfree(y);
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y = mint(0);
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} else {
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MLENGTH(y) = i + 1;
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MSIGN(y) = MSIGN(a) * MSIGN(b);
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}
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/* length of remainder */
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for (i = blen - 1; i > 0; i--)
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if (x[i])
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break;
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if (i == 0 && x[0] == 0) {
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mfree(x);
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x = mint(0);
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} else {
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MLENGTH(x) = i + 1;
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MSIGN(x) = MSIGN(a);
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}
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*q = y;
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*r = x;
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} |