gistfile1.h

VALUE 
io_from_spawning_new_process(VALUE prog, VALUE mode)
{
	// Allocate space for a new IO struct.
	VALUE io = io_alloc(rb_cIO, 0);
    rb_io_t *io_struct = ExtractIOStruct(io);
	io_struct->readStream = NULL;
	io_struct->writeStream = NULL;
	posix_spawn_file_actions_t actions;

	// Streams for reading and writing.
	CFReadStreamRef r;
    CFWriteStreamRef w;

	// Required variables for pipe() and posix_spawn().
	pid_t pid;
	int comms[2] = {};
	
	socketpair(PF_LOCAL, SOCK_STREAM, 0, comms);
	
	posix_spawn_file_actions_init(&actions);
	posix_spawn_file_actions_adddup2(&actions, comms[1], STDOUT_FILENO);
	posix_spawn_file_actions_adddup2(&actions, STDOUT_FILENO, STDERR_FILENO);
	posix_spawn_file_actions_addclose(&actions, comms[0]);
	posix_spawn_file_actions_addclose(&actions, comms[1]);
	
	char *spawnedArgs[] = {(char*)_PATH_BSHELL, "-c", (char*)RSTRING_PTR(prog), NULL};
	int error = posix_spawn(&pid, spawnedArgs[0], &actions, NULL, spawnedArgs, *(_NSGetEnviron()));

	if (error != 0) {
		close(comms[0]);
		close(comms[1]);
		rb_bug("posix_spawn failed.");
	} 
	else {
		if (convert_mode_string_to_fmode(mode) != FMODE_WRITABLE) {
			r = _CFReadStreamCreateFromFileDescriptor(NULL, comms[0]);
			if (r != NULL) {
				CFReadStreamOpen(r); 
				CFMakeCollectable(r);
				GC_WB(&io_struct->readStream, r);
			}
		}
		
		if (convert_mode_string_to_fmode(mode) != FMODE_READABLE) {
			w = _CFWriteStreamCreateFromFileDescriptor(NULL, comms[1]);
			if (w != NULL) {
				CFWriteStreamOpen(w);
				CFMakeCollectable(w);
				GC_WB(&io_struct->writeStream, w);
			}
		}
		io_struct->fd = comms[0];
		io_struct->pid = pid;
		io_struct->ungetc_buf = NULL;
		io_struct->ungetc_buf_len = 0;
		io_struct->ungetc_buf_pos = 0;
		posix_spawn_file_actions_destroy(&actions);
	}

	return io;
}