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/*
Author: Pate Williams (c) 1997
Multiple-precision addition. See "Handbook of
Applied Cryptography" by Alfred J. Menezes et
al 14.2.2 Section pages 594 - 595.
*/
#include
#include
#define BASE 10
typedef long * mp;
void mp_free(mp *mpa)
{
free(*mpa);
*mpa = 0;
}
void mp_set_length(long length, mp *mpa)
{
mp mpx = *mpa;
if (mpx != 0 && length <= mpx[0]) return;
if (mpx != 0) free(mpx);
mpx = calloc(length + 1, sizeof(long));
mpx[0] = length;
*mpa = mpx;
}
void mp_add(mp mpx, mp mpy, mp *mpw)
{
long c = 0, i, s, x_len = mpx[0], y_len = mpy[0];
long mx = max(x_len, y_len);
long mn = min(x_len, y_len);
long w_len = mx + 1;
mp_set_length(w_len, mpw);
for (i = 1; i <= mn; i++) {
s = mpx[i] + mpy[i] + c;
(*mpw)[i] = s % BASE;
c = s < BASE ? 0 : 1;
}
if (x_len > y_len) {
for (i = mn + 1; i <= x_len; i++) {
s = mpx[i] + c;
(*mpw)[i] = s % BASE;
c = s < BASE ? 0 : 1;
}
}
else if (x_len < y_len) {
for (i = mn + 1; i <= y_len; i++) {
s = mpy[i] + c;
(*mpw)[i] = s % BASE;
c = s < BASE ? 0 : 1;
}
}
(*mpw)[w_len] = c;
}
void mp_dump(mp mpa)
{
long i;
for (i = mpa[0]; i >= 1; i--)
printf("%ld", mpa[i]);
printf("\n");
}
void main(void)
{
mp mpw = 0, mpx = 0, mpy = 0;
mp_set_length(2, &mpx);
mp_set_length(3, &mpy);
mpx[1] = 9, mpx[2] = 9;
mpy[1] = 1, mpy[2] = 0, mpy[3] = 1;
mp_add(mpx, mpy, &mpw);
mp_dump(mpx);
mp_dump(mpy);
mp_dump(mpw);
mp_set_length(3, &mpx);
mp_set_length(2, &mpy);
mpx[1] = 1, mpx[2] = 2, mpx[3] = 3;
mpy[1] = 9, mpy[2] = 8;
mp_add(mpx, mpy, &mpw);
mp_dump(mpx);
mp_dump(mpy);
mp_dump(mpw);
mp_set_length(3, &mpx);
mp_set_length(3, &mpy);
mpx[1] = 1, mpx[2] = 2, mpx[3] = 3;
mpy[1] = 4, mpy[2] = 5; mpy[3] = 7;
mp_add(mpx, mpy, &mpw);
mp_dump(mpx);
mp_dump(mpy);
mp_dump(mpw);
mp_free(&mpw);
mp_free(&mpx);
mp_free(&mpy);
}