macOS poll work-around

Since polling of character devices is not supported on macOS, add the following
work-around:

- While stdin has not reached EOF, put the tty in non-blocking mode in order to
  simulate polling by peeking for new data.

- Once stdin has reached EOF, just do a blocking read of the tty.

Author: mptre

Makefile.am

@@ -4,7 +4,11 @@ AM_CFLAGS=-Wall -Wextra
 AM_CPPFLAGS=-D_GNU_SOURCE
 
 bin_PROGRAMS=pick
-pick_SOURCES=pick.c compat-reallocarray.c compat-strtonum.c compat.h
+pick_SOURCES=compat-reallocarray.c \
+             compat-strtonum.c \
+             compat-xpoll.c \
+             compat.h \
+             pick.c
 pick_CPPFLAGS=$(AM_CPPFLAGS) $(NCURSES_CFLAGS)
 pick_LDADD=$(NCURSES_LIBS)
 

compat-xpoll.c

@@ -0,0 +1,121 @@
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <stdlib.h>
+#include <poll.h>
+
+#include "compat.h"
+
+#ifdef HAVE_BROKEN_POLL
+
+#include <assert.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+static int	tty_peekc(int);
+
+int
+xpoll(struct pollfd *fds, nfds_t nfds, int timeout)
+{
+	static int	state;
+	int		flags, inready, ttyready;
+	int		nready = 0;
+
+	/* XXX filter_choices() poll disabled */
+	if (nfds == 1 && timeout == 0)
+		return 0;
+
+	if (state == 0) {
+		assert(nfds == 2);
+
+		flags = fcntl(fds[0].fd, F_GETFL, 0);
+		if (flags == -1)
+			return -1;
+		flags |= O_NONBLOCK;
+		if (fcntl(fds[0].fd, F_SETFL, flags) == -1)
+			return -1;
+		state++;
+	}
+
+	if (state == 1) {
+		if (timeout < 0)
+			timeout = 100;
+		while (nready == 0) {
+			if (nfds == 1) {
+				state++;
+				break;
+			}
+
+			inready = poll(&fds[1], 1, timeout);
+			if (inready == -1)
+				return -1;
+			nready += inready;
+
+			ttyready = tty_peekc(fds[0].fd);
+			if (ttyready == -1) {
+				return -1;
+			} else if (ttyready > 0) {
+				fds[0].revents = POLLIN;
+				nready++;
+			} else {
+				fds[0].revents = 0;
+			}
+		}
+	}
+
+	if (state == 2) {
+		flags = fcntl(fds[0].fd, F_GETFL, 0);
+		if (flags == -1)
+			return -1;
+		flags &= ~O_NONBLOCK;
+		if (fcntl(fds[0].fd, F_SETFL, flags) == -1)
+			return -1;
+		state++;
+	}
+
+	if (state == 3) {
+		ttyready = tty_peekc(fds[0].fd);
+		if (ttyready == -1) {
+			return -1;
+		} else if (ttyready > 0) {
+			fds[0].revents = POLLIN;
+			nready++;
+		} else {
+			fds[0].revents = 0;
+		}
+	}
+
+	return nready;
+}
+
+static int
+tty_peekc(int fd)
+{
+	extern int	tty_getc_peek;
+	ssize_t		n;
+	unsigned char	c;
+
+	n = read(fd, &c, sizeof(c));
+	if (n == -1) {
+		if (errno == EAGAIN)
+			return 0;
+		return -1;
+	}
+	if (n > 0) {
+		assert(tty_getc_peek == -1);
+		tty_getc_peek = c;
+	}
+	return n;
+}
+
+#else
+
+int
+xpoll(struct pollfd *fds, nfds_t nfds, int timeout)
+{
+	return poll(fds, nfds, timeout);
+}
+
+#endif /* HAVE_BROKEN_POLL */

compat.h

@@ -32,3 +32,5 @@ long long	strtonum(const char *, long long, long long, const char **);
 #endif /* !HAVE_STRTONUM */
 
 #endif /* COMPAT_H */
+
+int xpoll(struct pollfd *fds, nfds_t nfds, int timeout);

config.h.in

@@ -1,5 +1,8 @@
 /* config.h.in.  Generated from configure.ac by autoheader.  */
 
+/* Define if poll does not support character devices */
+#undef HAVE_BROKEN_POLL
+
 /* Define if ncursesw is available */
 #undef HAVE_NCURSESW_H
 

configure.ac

@@ -2,6 +2,7 @@ AC_PREREQ([2.61])
 AC_INIT([pick], [2.0.2], [[email protected]])
 AM_INIT_AUTOMAKE([subdir-objects])
 AC_CONFIG_HEADERS([config.h])
+AC_CANONICAL_HOST
 AC_PROG_CC
 AM_PROG_CC_C_O
 AC_CHECK_FUNCS([pledge reallocarray strtonum])
@@ -16,7 +17,6 @@ AC_SEARCH_LIBS([setupterm], [curses], [], [
   )
 ])
 AC_DEFUN([AC_MALLOC_OPTIONS], [
-  AC_CANONICAL_HOST
   AC_MSG_CHECKING([for $host_os malloc hardening options])
   case "$host_os" in
   openbsd*) malloc_options="RS";;
@@ -30,5 +30,20 @@ AC_DEFUN([AC_MALLOC_OPTIONS], [
   AC_SUBST([MALLOC_OPTIONS], [$malloc_options])
 ])
 AC_MALLOC_OPTIONS
+AC_DEFUN([AC_BROKEN_POLL], [
+  AC_MSG_CHECKING([for broken poll implementation])
+  case "$host_os" in
+  darwin*) broken=1;;
+  *)       broken=0;;
+  esac
+  if test "$broken" -eq 1; then
+    AC_MSG_RESULT([yes])
+    AC_DEFINE([HAVE_BROKEN_POLL], [1], [
+      Define if poll does not support character devices])
+  else
+    AC_MSG_RESULT([no])
+  fi
+])
+AC_BROKEN_POLL
 AC_CONFIG_FILES([Makefile])
 AC_OUTPUT

pick.c

@@ -3,6 +3,7 @@
 #endif
 
 #include <sys/ioctl.h>
+#include <sys/types.h>
 
 #include <ctype.h>
 #include <err.h>
@@ -70,13 +71,15 @@ struct choice {
 	double		 score;
 };
 
+int tty_getc_peek = -1;
+
 static int			 choice_cmp(const void *, const void *);
 static const char		*choice_description(const struct choice *);
 static const char		*choice_string(const struct choice *);
 static void			 delete_between(char *, size_t, size_t, size_t);
 static char			*eager_strpbrk(const char *, const char *);
 static int			 filter_choices(size_t);
-static size_t			 get_choices(int, size_t);
+static size_t			 get_choices(int, ssize_t);
 static enum key			 get_key(const char **);
 static void			 handle_sigwinch(int);
 static int			 isu8cont(unsigned char);
@@ -224,7 +227,7 @@ usage(int status)
 }
 
 size_t
-get_choices(int fd, size_t insert)
+get_choices(int fd, ssize_t insert)
 {
 	static const char	*ifs;
 	static char		*buf;
@@ -291,7 +294,7 @@ get_choices(int fd, size_t insert)
 	}
 	offset = start - buf;
 	dchoices = choices.length - nchoices;
-	if (dchoices == 0 || nchoices == 0)
+	if (dchoices == 0 || nchoices == 0 || insert == -1)
 		return n;
 
 	/* Move new choices after the given insert index. */
@@ -325,11 +328,12 @@ selected_choice(void)
 {
 	struct pollfd	 fds[2];
 	const char	*buf;
+	ssize_t		 insert;
 	size_t		 cursor_position, i, j, length, nfds, xscroll;
 	size_t		 choices_count = 0;
 	size_t		 selection = 0;
 	size_t		 yscroll = 0;
-	int		 dokey, doread, timo;
+	int		 dokey, doread, nready, timo;
 	int		 choices_reset = 1;
 	int		 dochoices = 0;
 	int		 dofilter = 1;
@@ -346,7 +350,8 @@ selected_choice(void)
 	for (;;) {
 		dokey = doread = 0;
 		toggle_sigwinch(1);
-		if (poll(fds, nfds, timo) == -1 && errno != EINTR)
+		nready = xpoll(fds, nfds, timo);
+		if (nready == -1 && errno != EINTR)
 			err(1, "poll");
 		toggle_sigwinch(0);
 		if (gotsigwinch) {
@@ -355,33 +360,33 @@ selected_choice(void)
 		}
 		timo = -1;
 		for (i = 0; i < nfds; i++) {
-			if (fds[i].revents & (POLLERR | POLLNVAL))
-				errx(1, "%d: bad file descriptor", fds[i].fd);
+			if (fds[i].revents & (POLLERR | POLLNVAL)) {
+				errno = EBADF;
+				err(1, "poll");
+			}
 			if ((fds[i].revents & (POLLIN | POLLHUP)) == 0)
 				continue;
 
-			if (fds[i].fd == fds[0].fd)
-				dokey = 1;
-			else if (fds[i].fd == fds[1].fd)
+			if (fds[i].fd == STDIN_FILENO)
 				doread = 1;
+			else if (fds[i].fd == fileno(tty_in))
+				dokey = 1;
 		}
 
 		length = choices.length;
 		if (doread) {
-			if (get_choices(STDIN_FILENO, query_length > 0 ?
-				    choices_count : 0)) {
+			insert = query_length > 0 ? (ssize_t)choices_count : -1;
+			if (get_choices(fds[1].fd, insert)) {
 				if (query_length > 0) {
 					dofilter = 1;
 					choices_reset = 0;
 					choices_count += choices.length -
 					    length;
 				}
 			} else {
-				nfds = 1; /* EOF */
+				nfds--; /* EOF */
 			}
 		}
-		if (!dokey && query_length == 0 && length >= choices_lines)
-			continue; /* prevent redundant rendering */
 		if (!dokey)
 			goto render;
 
@@ -589,8 +594,8 @@ selected_choice(void)
 int
 filter_choices(size_t nchoices)
 {
-	struct choice	*c;
 	struct pollfd	 pfd;
+	struct choice	*c;
 	size_t		 i, match_length;
 	int		 nready;
 
@@ -610,7 +615,7 @@ filter_choices(size_t nchoices)
 		if (i > 0 && i % 50 == 0) {
 			pfd.fd = fileno(tty_in);
 			pfd.events = POLLIN;
-			if ((nready = poll(&pfd, 1, 0)) == -1)
+			if ((nready = xpoll(&pfd, 1, 0)) == -1)
 				err(1, "poll");
 			if (nready == 1 && pfd.revents & (POLLIN | POLLHUP))
 				return 0;
@@ -1116,6 +1121,12 @@ tty_getc(void)
 	ssize_t		n;
 	unsigned char	c;
 
+	if (tty_getc_peek != -1) {
+		c = tty_getc_peek;
+		tty_getc_peek = -1;
+		return c;
+	}
+
 	n = read(fileno(tty_in), &c, sizeof(c));
 	if (n == -1)
 		err(1, "read");

tests/pick-test.c

@@ -6,6 +6,7 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <limits.h>
+#include <poll.h>
 #include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>