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/*
*
* test self pipe
$ g++ \
module-test/self_pipe.cc \
-std=c++26 \
-O0 -ggdb3 -fno-omit-frame-pointer -fno-inline -D_GLIBCXX_ASSERTIONS \
-o module-test/self_pipe.out
*/
#include <iostream>
#include <sys/select.h>
#include <unistd.h>
#include <signal.h>
using namespace std;
typedef void handler_t(int);
handler_t *Signal(int signum, handler_t *handler);
void sigusr1_handler(int signum);
int my_read(char *s, int len);
int self_pipe_fd[2] = {-1, -1};
void sigusr1_handler(int signum)
{
char tmp = 'A';
write(self_pipe_fd[1], &tmp, 1);
}
int my_read(char *s, int len)
{
int max_fd;
if (STDIN_FILENO > self_pipe_fd[0]) max_fd = STDIN_FILENO;
else max_fd = self_pipe_fd[0];
fd_set rset;
FD_ZERO(&rset);
FD_SET(STDIN_FILENO, &rset);
FD_SET(self_pipe_fd[0], &rset);
select(max_fd+1, &rset, nullptr, nullptr, nullptr);
if (FD_ISSET(self_pipe_fd[0], &rset))
{
return read(self_pipe_fd[0], s, len);
}
else if (FD_ISSET(STDIN_FILENO, &rset))
{
return read(STDIN_FILENO, s, len);
}
return -1;
}
handler_t *Signal(int signum, handler_t *handler)
{
struct sigaction action, old_action;
action.sa_handler = handler;
sigemptyset(&action.sa_mask); /* block sigs of type being handled */
action.sa_flags = SA_RESTART; /* restart syscalls if possible */
sigaction(signum, &action, &old_action);
return (old_action.sa_handler);
}
int main()
{
Signal(SIGUSR1, sigusr1_handler);
pipe(self_pipe_fd);
cout << "Running PID: " << getpid() << endl;
cout << "Do not enter anything" << endl;
constexpr int tmp_size = 1024;
char tmp[tmp_size];
while (my_read(tmp, tmp_size))
cout << "Hi" << endl;
cout << "Finished" << endl;
return 0;
}
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