1 files changed, 117 insertions, 0 deletions
diff --git a/mit-pthreads/gen/popen.c b/mit-pthreads/gen/popen.c
new file mode 100644
index 00000000000..c15fbdce1fe
--- /dev/null
+++ b/mit-pthreads/gen/popen.c
@@ -0,0 +1,117 @@
+#include <pthread.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <unistd.h>
+#include <string.h>
+#include <errno.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+static pid_t *pids = NULL;
+static int pids_size = 0;
+static int pids_top = 0;
+static pthread_mutex_t pids_lock = PTHREAD_MUTEX_INITIALIZER;
+
+FILE *popen(const char *cmd, const char *mode)
+{
+    int fds[2], parent_fd, child_fd, child_target, new_size, i;
+    pid_t pid, *new_pids;
+
+    /* Verify the mode. */
+    if ((*mode != 'r' && *mode != 'w') || mode[1] != 0)
+	    return NULL;
+
+    /* Generate fds, and choose the parent and child fds. */
+    if (pipe(fds) < 0)
+	    return NULL;
+    parent_fd = (*mode == 'r') ? fds[0] : fds[1];
+    child_fd = (*mode == 'r') ? fds[1] : fds[0];
+
+    /* Ensure that there is space in the pid table. */
+    pthread_mutex_lock(&pids_lock);
+    if (pids_size <= parent_fd) {
+	    new_size = parent_fd + 1;
+	    if ((new_pids = malloc(new_size * sizeof(pid_t))) == NULL) {
+    		pthread_mutex_unlock(&pids_lock);
+	        close(parent_fd);
+	        close(child_fd);
+	        return NULL;
+	    }
+		if (pids) {
+			memcpy(new_pids, pids, pids_size * sizeof(pid_t));
+	        free(pids);
+		}
+		while (pids_size < new_size)
+	    	new_pids[pids_size++] = -1;
+		pids = new_pids;
+    }
+    pthread_mutex_unlock(&pids_lock);
+
+    /* Fork off a child process. */
+	switch (pid = fork()) {
+	case -1: /* Failed to fork. */
+		close(parent_fd);
+		close(child_fd);
+		return NULL;
+		break;
+	case 0: /* Child */
+		/*
+		 * Set the child fd to stdout or stdin as appropriate,
+	 	 * and close the parent fd. 
+		 */
+		child_target = (*mode == 'r') ? STDOUT_FILENO : STDIN_FILENO;
+		if (child_fd != child_target) {
+	    	dup2(child_fd, child_target);
+	    	close(child_fd);
+		}
+		close(parent_fd);
+
+		/* Close all parent fds from previous popens(). */
+		for (i = 0; i < pids_top; i++) {
+		    if (pids[i] != -1)
+			close(i);
+		}
+
+		execl("/bin/sh", "sh", "-c", cmd, NULL);
+		exit(1);
+	default:
+		break;
+	}
+
+    /* Record the parent fd in the pids table. */
+    pthread_mutex_lock(&pids_lock);
+    pids[parent_fd] = pid;
+    if (pids_top < parent_fd + 1)
+	    pids_top = parent_fd + 1;
+    pthread_mutex_unlock(&pids_lock);
+
+    /* Close the child fd and return a stdio buffer for the parent fd. */
+    close(child_fd);
+    return fdopen(parent_fd, mode);
+}
+
+int pclose(fp)
+    FILE *fp;
+{
+    pid_t pid, result;
+    int fd, pstat;
+
+    fd = fileno(fp);
+    pthread_mutex_lock(&pids_lock);
+    /* Make sure this is a popened file. */
+    if ((pids_top <= fd) || ((pid = pids[fd]) == -1)) {
+    	pthread_mutex_unlock(&pids_lock);
+		return -1;
+	}
+    pids[fd] = -1;
+    while (pids_top > 0 && pids[pids_top - 1] == -1)
+	    pids_top--;
+    pthread_mutex_unlock(&pids_lock);
+
+    fclose(fp);
+
+    /* Wait for the subprocess to quit. */
+	return (((result = waitpid(pid, &pstat, 0)) == -1) ? -1 : pstat);
+}
+