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signal.c
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signal.c
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#include <signal.h>
#include <stdio.h>
#include <sys/wait.h>
#include <errno.h>
#include <unistd.h>
#include <stdlib.h>
#include <assert.h>
#include <math.h>
#define message 1005069
#define n_bits 8
#define base 10
unsigned char *create_storage(int num, int *size_of_num);
void receiver_handler(int);
void sender_handler(int);
// uses to check incoming signal
char send_flag = 0;
// last received bit
int cur_bit = 0;
// means that receiver got bit
int received_flag = 0;
int main()
{
int p_pid = getpid();
// uses to check the incoming signal
char send_flag_old = send_flag;
//define SIGUSR1 to confirm the receiver readiness
signal(SIGUSR1, sender_handler);
int pid = fork();
if (pid == 0)
{
// SIGUSR1 => 0, SIGUSR1 => 1
signal(SIGUSR1, receiver_handler);
signal(SIGUSR2, receiver_handler);
#define receive_byte(var) \
for (int k = 0; k < n_bits; k++) \
{ \
/* tell sender to send new bit*/ \
kill(p_pid, SIGUSR1); \
while (received_flag == 0); \
received_flag = 0; \
\
(var) += pow(2, k) * cur_bit; \
}
int n_bytes = 0;
receive_byte(n_bytes);
//printf("number of digits = %d\n", n_bytes);
int num = 0;
for (int i = 0; i < n_bytes; i++)
{
int cur_byte = 0;
received_flag = 0;
receive_byte(cur_byte);
num += cur_byte * pow(10, n_bytes - i - 1);
}
printf("value = %d\n", num);
}
#undef receive_byte
// receiver part
else
{
#define get_bit(val, pos) ((val) & (1u << (pos)))
#define send_byte(byte) \
for (int k = 0; k < n_bits; k++) \
{ \
/* to confirm the receiver readiness */ \
while (send_flag_old == send_flag); \
send_flag_old = send_flag; \
\
if (get_bit(byte, k)) \
{ \
if (kill(pid, SIGUSR2) < 0) \
perror("kill() fail"); \
} \
else \
{ \
if (kill(pid, SIGUSR1) < 0) \
perror("kill() fail"); \
} \
}
int msg_sz = 0;
unsigned char *msg_byte = create_storage(message, &msg_sz);
// send number of bytes in message
send_byte(msg_sz);
// send message
for (int i = 0; i < msg_sz; i++)
send_byte(msg_byte[i])
free(msg_byte);
}
return 0;
}
#undef send_byte
#undef get_bit
void sender_handler(int sign)
{
send_flag = !send_flag;
}
void receiver_handler(int sign)
{
received_flag = 1;
switch (sign)
{
case SIGUSR1:
{
cur_bit = 0;
break;
}
case SIGUSR2:
{
cur_bit = 1;
break;
}
default:
break;
}
}
unsigned char *create_storage(int num, int *size_of_num)
{
int tmp_num = num;
int digit_counter = 0;
while (tmp_num != 0)
{
tmp_num = tmp_num / base;
digit_counter++;
}
if (size_of_num)
*size_of_num = digit_counter;
//12345 => [1, 2, 3, 4, 5]
unsigned char *digit_arr = (unsigned char *) calloc((size_t) digit_counter + 1, sizeof(char *));
if (digit_arr == 0)
{
fprintf(stderr, "calloc() fail");
exit(EXIT_FAILURE);
}
tmp_num = num;
for (int i = 0; i < digit_counter; i++)
{
digit_arr[digit_counter - i - 1] = tmp_num % base;
tmp_num = tmp_num / base;
}
return digit_arr;
}