Answer to Question #9441 in C++ for john

Question

what does Modify_it()do?

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <sys/time.h>

typedef int int32;
typedef char int8;

void change_it(int8 *output, int8 *input_1, const int8 *input_2, int32 length)
{
int32 i = 0;

for(i=0; i<length; i++)
{
output[i] = (int8)(input_1[i] ^ input_2[i]);
}

return;
}

void itoa( int32 num, int8 *alpha, int32 radix )
{
if( radix == 10 )
{
sprintf(alpha, "%i", num);
}
else if( radix == 16 )
{
sprintf(alpha, "%X", num);
}
}

int8 *modify_it(int32 modifier, const int8 *input_1, int32 length)
{
int8 leading[3];
int32 i_leading;
int8 * temp_string = NULL;
int8 * ret;
int32 i = 0;

itoa(modifier/2, leading, 10);
i_leading = atoi(leading);
temp_string = (int8 *) malloc(8);
ret = (int8 *) malloc(length);
memset(temp_string, 0, 8);
temp_string[0] = 0;

if( (modifier+1)%2 == 0 ) {
temp_string[0] = (int8)((i_leading<<4) + 8);
}
else {
temp_string[0] = (int8)(i_leading<<4);
}

for(i=0; i<(length>>3); i++)
{
change_it(ret+i*8, temp_string, input_1+i*8, 8);
}
free(temp_string);
return ret;
}

int main(int argc, char **argv) {
int8 data[32];

memset(data, 0x0A, sizeof(data));
int8 *resp = modify_it(0xFF, data, sizeof(data));

free(resp);

return 0;
}

Answer 1

It modifyes the data, so if for example you want tocalculate a CRC and write it to the last word, you could modify the postlink
function