Initial

1 files changed, 197 insertions, 0 deletions

diff --git a/piper.c b/piper.c
new file mode 100644
index 0000000..af35e6e
--- /dev/null
+++ b/piper.c
@@ -0,0 +1,197 @@
+#include <errno.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#define NUM_PROCS 2
+
+struct proc {
+	pid_t pid;
+	char *cmd;
+	char **argv;
+	int  _stdin;
+	int  _stdout;
+	int  _stderr;
+} procs[NUM_PROCS];
+
+int fds[2];
+
+volatile sig_atomic_t terminate = 0;
+volatile sig_atomic_t sendsignal = 0;
+
+void
+gen_argv(struct proc *proc)
+{
+	int i;
+	char *saveptr, *tmp;
+	char **argv = malloc(sizeof(char*) * 1024);
+	char **head = argv;
+	char *cmd2 = strdup(proc->cmd);
+	// XXX: Check malloc/strdup return
+	// XXX: Check for overflow in tmp
+	
+	for (i = 0; i < 1024; i++)
+		argv[i] = NULL;
+
+	tmp = strtok_r(cmd2, " \t", &saveptr);
+	while (tmp != NULL) {
+		*(head++) = strdup(tmp);
+		tmp = strtok_r(NULL, " \t", &saveptr);
+	}
+	*head = NULL;
+
+	free(cmd2);
+
+	proc->argv = argv;
+}
+
+int
+run_cmd(struct proc *proc)
+{
+	pid_t cpid;
+
+	cpid = fork();
+	if (cpid == 0) {
+		if (proc->_stdin != -1) {
+			close(0);
+			dup2(proc->_stdin, 0);
+		}
+		if (proc->_stdout != -1) {
+			close(1);
+			dup2(proc->_stdout, 1);
+		}
+		if (proc->_stderr != -1) {
+			close(2);
+			dup2(proc->_stderr, 2);
+		}
+		close(fds[0]);
+		close(fds[1]);
+
+		execvp(proc->argv[0], proc->argv);
+		perror("execvp");
+	} else if (cpid == -1) {
+		// error D:
+		return -1;
+	} else {
+		proc->pid = cpid;
+	}
+
+	return 0;
+}
+
+int
+have_child()
+{
+	int i;
+	for (i = 0; i < NUM_PROCS; i++) {
+		if (procs[i].pid != -1)
+			return 1;
+	}
+
+	return 0;
+}
+
+struct proc *
+proc_by_pid(pid_t pid)
+{
+	int i;
+	for (i = 0; i < NUM_PROCS; i++) {
+		if (procs[i].pid == pid)
+			return &procs[i];
+	}
+
+	return NULL;
+}
+
+void
+signal_procs()
+{
+	int i;
+	for (i = 0; i < NUM_PROCS; i++) {
+		if (procs[i].pid != -1)
+			kill(procs[i].pid, sendsignal); //XXX: Check return?
+	}
+
+	sendsignal = 0;
+}
+
+void
+handle_nonfatal(int sig, siginfo_t *siginfo, void *ucontext)
+{
+	sendsignal = sig;
+}
+
+void
+handle_fatal(int sig, siginfo_t *siginfo, void *ucontext)
+{
+	terminate = 1;
+	sendsignal = sig;
+}
+
+int
+main(int argc, char **argv)
+{
+	if (argc < 2) {
+		fprintf(stderr, "Usage: piper <cmd1> <cmd2>\n");
+		return 1;
+	}
+
+	struct sigaction act;
+	memset(&act, 0, sizeof(act));
+
+	act.sa_sigaction = &handle_fatal;
+	act.sa_flags = SA_SIGINFO;
+
+	sigaction(SIGINT,  &act, NULL);
+	sigaction(SIGHUP,  &act, NULL);
+	sigaction(SIGTERM, &act, NULL);
+
+	act.sa_sigaction = &handle_nonfatal;
+	sigaction(SIGUSR1, &act, NULL);
+	sigaction(SIGUSR2, &act, NULL);
+
+	procs[0].cmd = strdup(argv[1]);
+	procs[1].cmd = strdup(argv[2]);
+
+	int i;
+	for (i = 0; i < NUM_PROCS; i++) {
+		procs[i].pid = -1;
+		procs[i]._stdin = -1;
+		procs[i]._stdout = -1;
+		procs[i]._stderr = -1;
+		gen_argv(&procs[i]);
+	}
+
+	pipe(fds); // XXX: Check return code
+
+	procs[0]._stdout = fds[1];
+	procs[0]._stderr = fds[1];
+	procs[1]._stdin  = fds[0];
+
+	run_cmd(&procs[0]);
+	run_cmd(&procs[1]); // XXX: Check return codes
+	
+	while (have_child()) {
+		int status;
+		pid_t pid;
+
+		if (sendsignal != 0)
+			signal_procs();
+
+		pid = wait(&status);
+		if (pid == -1 && errno == EINTR)
+			continue;
+
+		struct proc *p = proc_by_pid(pid); // XXX: Check return code
+		p->pid = -1;
+
+		if (!terminate)
+			run_cmd(p); // XXX: Check return code
+	}
+
+	return 0;
+}