027_Paridad.c

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#include <stdio.h>
#include <stdlib.h>
#include <time.h>
 
#define BIT(n)          (1<<(n))
#define BIT_TOGGLE(x,n) ((x) ^= BIT(n))
#define NC              100
 
int main(int argc, char *argv[])
{
    char msg[NC+1], p, v;
    int i, nc, _nc, _nb;
    srand(time(NULL));
    i=0;
    do{
        msg[i++] = getc(stdin);
    }while(msg[i-1]!=10&&i<NC);
    nc = i-1;
    msg[nc] = '\0';
    for(i=0, p=0; i<nc; i++)
        p^=msg[i];
    for(i=0, v=p; i<nc; i++)
        v^=msg[i];
    printf("MSG: %s(%d)-%c-%d\n", msg, nc, p, (int )v);
    _nc = rand()%nc;
    _nb = rand()%(8*sizeof(char));
    BIT_TOGGLE(msg[_nc], _nb);
    for(i=0, v=p; i<nc; i++)
        v^=msg[i];
    printf("MSG: %s(%d)-%c-%u\n", msg, nc, p, (unsigned int)v);
    return 0;
}