Tentative macOS poll work-around

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-fdwait.c \
+             compat-reallocarray.c \
+             compat-strtonum.c \
+             compat.h \
+             pick.c
 pick_CPPFLAGS=$(AM_CPPFLAGS) $(NCURSES_CFLAGS)
 pick_LDADD=$(NCURSES_LIBS)
 

compat-fdwait.c

@@ -0,0 +1,154 @@
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <sys/types.h>
+
+#include "compat.h"
+
+#ifdef HAVE_BROKEN_POLL
+
+#include <assert.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <poll.h>
+#include <unistd.h>
+
+extern int tty_getc_peek;
+
+static int ttygetchar(int);
+
+int
+fdwait(int ttyfd, int infd, int timeout)
+{
+	static int	state;
+	struct pollfd	pfd;
+	int		flags, nready;
+	int		res = 0;
+
+	/* XXX filter_choices() poll disabled */
+	if (infd == -1 && timeout == 0)
+		return 0;
+
+	if (state == 0) {
+		flags = fcntl(ttyfd, F_GETFL, 0);
+		if (flags == -1)
+			return -1;
+		flags |= O_NONBLOCK;
+		if (fcntl(ttyfd, F_SETFL, flags) == -1)
+			return -1;
+		state++;
+	}
+
+	if (state == 1) {
+		if (timeout < 0)
+			timeout = 100;
+		pfd.fd = infd;
+		pfd.events = POLLIN;
+		while (res == 0) {
+			if (infd == -1) {
+				state++;
+				break;
+			}
+
+			nready = poll(&pfd, 1, timeout);
+			if (nready == -1)
+				return -1;
+			if (nready > 0) {
+				if (pfd.revents & (POLLERR | POLLNVAL)) {
+					errno = EBADF;
+					return -1;
+				} else if (pfd.revents & (POLLIN | POLLHUP)) {
+					res |= FD_STDIN_READY;
+				}
+			}
+
+			nready = ttygetchar(ttyfd);
+			if (nready == -1) {
+				if (errno == EAGAIN)
+					continue;
+				return -1;
+			} else if (nready > 0) {
+				res |= FD_TTY_READY;
+			}
+		}
+	}
+
+	if (state == 2) {
+		flags = fcntl(ttyfd, F_GETFL, 0);
+		if (flags == -1)
+			return -1;
+		flags &= ~O_NONBLOCK;
+		if (fcntl(ttyfd, F_SETFL, flags) == -1)
+			return -1;
+		state++;
+	}
+
+	if (state == 3) {
+		nready = ttygetchar(ttyfd);
+		if (nready == -1)
+			return -1;
+		else if (nready > 0)
+			res |= FD_TTY_READY;
+	}
+
+	return res;
+}
+
+static int
+ttygetchar(int fd)
+{
+	ssize_t		n;
+	unsigned char	c;
+
+	n = read(fd, &c, sizeof(c));
+	if (n > 0) {
+		assert(tty_getc_peek == -1);
+		tty_getc_peek = c;
+	}
+	return n;
+}
+
+#else
+
+#include <errno.h>
+#include <poll.h>
+
+int
+fdwait(int ttyfd, int infd, int timeout)
+{
+	struct pollfd	fds[2];
+	int		i, nready;
+	int		nfds = 0;
+	int		res = 0;
+
+	if (ttyfd != -1) {
+		fds[nfds].fd = ttyfd;
+		fds[nfds].events = POLLIN;
+		nfds++;
+	}
+	if (infd != -1) {
+		fds[nfds].fd = infd;
+		fds[nfds].events = POLLIN;
+		nfds++;
+	}
+	nready = poll(fds, nfds, timeout);
+	if (nready <= 0)
+		return nready;
+	for (i = 0; i < nfds; i++) {
+		if (fds[i].revents & (POLLERR | POLLNVAL)) {
+			errno = EBADF;
+			return -1;
+		} else if ((fds[i].revents & (POLLIN | POLLHUP)) == 0) {
+			continue;
+		}
+
+		if (fds[i].fd == ttyfd)
+			res |= FD_TTY_READY;
+		else if (fds[i].fd == infd)
+			res |= FD_STDIN_READY;
+	}
+	return res;
+}
+
+#endif /* HAVE_BROKEN_POLL */

compat.h

@@ -32,3 +32,8 @@ long long	strtonum(const char *, long long, long long, const char **);
 #endif /* !HAVE_STRTONUM */
 
 #endif /* COMPAT_H */
+
+#define FD_STDIN_READY	0x1
+#define FD_TTY_READY	0x2
+
+int fdwait(int, int, int);

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

@@ -9,7 +9,6 @@
 #include <errno.h>
 #include <limits.h>
 #include <locale.h>
-#include <poll.h>
 #include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -70,13 +69,15 @@ 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 +225,7 @@ 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 +292,7 @@ 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. */
@@ -323,66 +324,53 @@ eager_strpbrk(const char *string, const char *separators)
 const struct choice *
 selected_choice(void)
 {
-	struct pollfd	 fds[2];
 	const char	*buf;
-	size_t		 cursor_position, i, j, length, nfds, xscroll;
+	ssize_t		 insert;
+	size_t		 cursor_position, i, j, length, xscroll;
 	size_t		 choices_count = 0;
 	size_t		 selection = 0;
 	size_t		 yscroll = 0;
-	int		 dokey, doread, timo;
+	int		 fd, ready, timo;
 	int		 choices_reset = 1;
 	int		 dochoices = 0;
 	int		 dofilter = 1;
 
 	cursor_position = query_length;
 
-	fds[0].fd = fileno(tty_in);
-	fds[0].events = POLLIN;
-	fds[1].fd = STDIN_FILENO;
-	fds[1].events = POLLIN;
-	nfds = 2;
-	/* No timeout on first call to poll in order to render the UI fast. */
+	/* No timeout on first call to fdwait in order to render the UI fast. */
 	timo = 0;
+	fd = STDIN_FILENO;
 	for (;;) {
-		dokey = doread = 0;
 		toggle_sigwinch(1);
-		if (poll(fds, nfds, timo) == -1 && errno != EINTR)
-			err(1, "poll");
+		ready = fdwait(fileno(tty_in), fd, timo);
+		if (ready == -1) {
+			if (errno == EINTR)
+				ready = 0;
+			else
+				err(1, "fdwait");
+		}
 		toggle_sigwinch(0);
 		if (gotsigwinch) {
 			gotsigwinch = 0;
 			goto resize;
 		}
 		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 & (POLLIN | POLLHUP)) == 0)
-				continue;
-
-			if (fds[i].fd == fds[0].fd)
-				dokey = 1;
-			else if (fds[i].fd == fds[1].fd)
-				doread = 1;
-		}
 
 		length = choices.length;
-		if (doread) {
-			if (get_choices(STDIN_FILENO, query_length > 0 ?
-				    choices_count : 0)) {
+		if (ready & FD_STDIN_READY) {
+			insert = query_length > 0 ? (ssize_t)choices_count : -1;
+			if (get_choices(STDIN_FILENO, insert)) {
 				if (query_length > 0) {
 					dofilter = 1;
 					choices_reset = 0;
 					choices_count += choices.length -
 					    length;
 				}
 			} else {
-				nfds = 1; /* EOF */
+				fd = -1; /* EOF */
 			}
 		}
-		if (!dokey && query_length == 0 && length >= choices_lines)
-			continue; /* prevent redundant rendering */
-		if (!dokey)
+		if ((ready & FD_TTY_READY) == 0)
 			goto render;
 
 		switch (get_key(&buf)) {
@@ -590,9 +578,8 @@ int
 filter_choices(size_t nchoices)
 {
 	struct choice	*c;
-	struct pollfd	 pfd;
 	size_t		 i, match_length;
-	int		 nready;
+	int		 ready;
 
 	for (i = 0; i < nchoices; i++) {
 		c = &choices.v[i];
@@ -608,11 +595,8 @@ 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)
-				err(1, "poll");
-			if (nready == 1 && pfd.revents & (POLLIN | POLLHUP))
+			ready = fdwait(fileno(tty_in), -1, 0);
+			if (ready != -1 && (ready & FD_TTY_READY) != 0)
 				return 0;
 		}
 	}
@@ -1116,6 +1100,12 @@ 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");