change socket notifier design

instead of keeping the structures in an opaque array (which was a shadow
of the struct pollfd array if poll() was supported), make them directly
addressable.

this has the advantage that notifier-altering operations (mostly
en-/disabling) don't need to look up the structure by file handle each
time.
on the downside, data locality in the main loop is worse.
neither of these have any real effect on performance.

note that the structures are not allocated separately, but embedded into
the the parent structure (like sockets already were).

src/common.h

@@ -127,6 +127,18 @@ uchar arc4_getbyte( void );
 
 int bucketsForSize( int size );
 
+typedef struct notifier {
+	struct notifier *next;
+	void (*cb)( int what, void *aux );
+	void *aux;
+#ifdef HAVE_SYS_POLL_H
+	int index;
+#else
+	int fd, events;
+#endif
+	int faked;
+} notifier_t;
+
 #ifdef HAVE_SYS_POLL_H
 # include <sys/poll.h>
 #else
@@ -135,10 +147,11 @@ int bucketsForSize( int size );
 # define POLLERR 8
 #endif
 
-void add_fd( int fd, void (*cb)( int events, void *aux ), void *aux );
+void init_notifier( notifier_t *sn, int fd, void (*cb)( int, void * ), void *aux );
-void conf_fd( int fd, int and_events, int or_events );
+void conf_notifier( notifier_t *sn, int and_events, int or_events );
-void fake_fd( int fd, int events );
+static INLINE void fake_notifier( notifier_t *sn, int events ) { sn->faked |= events; }
-void del_fd( int fd );
+void wipe_notifier( notifier_t *sn );
+
 void main_loop( void );
 
 #endif

src/socket.c

@@ -67,7 +67,7 @@ ssl_return( const char *func, conn_t *conn, int ret )
 	case SSL_ERROR_NONE:
 		return ret;
 	case SSL_ERROR_WANT_WRITE:
-		conf_fd( conn->fd, POLLIN, POLLOUT );
+		conf_notifier( &conn->notify, POLLIN, POLLOUT );
 		/* fallthrough */
 	case SSL_ERROR_WANT_READ:
 		return 0;
@@ -290,13 +290,13 @@ socket_open_internal( conn_t *sock, int fd )
 {
 	sock->fd = fd;
 	fcntl( fd, F_SETFL, O_NONBLOCK );
-	add_fd( fd, socket_fd_cb, sock );
+	init_notifier( &sock->notify, fd, socket_fd_cb, sock );
 }
 
 static void
 socket_close_internal( conn_t *sock )
 {
-	del_fd( sock->fd );
+	wipe_notifier( &sock->notify );
 	close( sock->fd );
 	sock->fd = -1;
 }
@@ -434,7 +434,7 @@ socket_connect_one( conn_t *sock )
 			socket_connect_failed( sock );
 			return;
 		}
-		conf_fd( s, 0, POLLOUT );
+		conf_notifier( &sock->notify, 0, POLLOUT );
 		sock->state = SCK_CONNECTING;
 		info( "\v\n" );
 		return;
@@ -464,7 +464,7 @@ socket_connected( conn_t *conn )
 #ifdef HAVE_IPV6
 	freeaddrinfo( conn->addrs );
 #endif
-	conf_fd( conn->fd, 0, POLLIN );
+	conf_notifier( &conn->notify, 0, POLLIN );
 	conn->state = SCK_READY;
 	conn->callbacks.connect( 1, conn->callback_aux );
 }
@@ -517,7 +517,7 @@ socket_fill( conn_t *sock )
 		if ((n = ssl_return( "read from", sock, SSL_read( sock->ssl, buf, len ) )) <= 0)
 			return;
 		if (n == len && SSL_pending( sock->ssl ))
-			fake_fd( sock->fd, POLLIN );
+			fake_notifier( &sock->notify, POLLIN );
 	} else
 #endif
 	{
@@ -592,10 +592,10 @@ do_write( conn_t *sock, char *buf, int len )
 			socket_fail( sock );
 		} else {
 			n = 0;
-			conf_fd( sock->fd, POLLIN, POLLOUT );
+			conf_notifier( &sock->notify, POLLIN, POLLOUT );
 		}
 	} else if (n != len) {
-		conf_fd( sock->fd, POLLIN, POLLOUT );
+		conf_notifier( &sock->notify, POLLIN, POLLOUT );
 	}
 	return n;
 }
@@ -632,7 +632,7 @@ do_queued_write( conn_t *conn )
 	}
 #ifdef HAVE_LIBSSL
 	if (conn->ssl && SSL_pending( conn->ssl ))
-		fake_fd( conn->fd, POLLIN );
+		fake_notifier( &conn->notify, POLLIN );
 #endif
 	return conn->write_callback( conn->callback_aux );
 }
@@ -700,7 +700,7 @@ socket_fd_cb( int events, void *aux )
 	}
 
 	if (events & POLLOUT)
-		conf_fd( conn->fd, POLLIN, 0 );
+		conf_notifier( &conn->notify, POLLIN, 0 );
 
 #ifdef HAVE_LIBSSL
 	if (conn->state == SCK_STARTTLS) {

src/socket.h

@@ -86,6 +86,8 @@ typedef struct {
 	} callbacks;
 	void *callback_aux;
 
+	notifier_t notify;
+
 	/* writing */
 	buff_chunk_t *write_buf, **write_buf_append; /* buffer head & tail */
 	int write_offset; /* offset into buffer head */

src/util.c

@@ -584,84 +584,73 @@ bucketsForSize( int size )
 	}
 }
 
+static notifier_t *notifiers;
+static int changed;  /* Iterator may be invalid now. */
 #ifdef HAVE_SYS_POLL_H
 static struct pollfd *pollfds;
+static int npolls, rpolls;
 #else
 # ifdef HAVE_SYS_SELECT_H
 #  include <sys/select.h>
 # endif
-# define pollfds fdparms
 #endif
-static struct {
-	void (*cb)( int what, void *aux );
-	void *aux;
-#ifndef HAVE_SYS_POLL_H
-	int fd, events;
-#endif
-	int faked;
-} *fdparms;
-static int npolls, rpolls, changed;
-
-static int
-find_fd( int fd )
-{
-	int n;
-
-	for (n = 0; n < npolls; n++)
-		if (pollfds[n].fd == fd)
-			return n;
-	return -1;
-}
 
 void
-add_fd( int fd, void (*cb)( int events, void *aux ), void *aux )
+init_notifier( notifier_t *sn, int fd, void (*cb)( int, void * ), void *aux )
 {
-	int n;
+#ifdef HAVE_SYS_POLL_H
-
+	int idx = npolls++;
-	assert( find_fd( fd ) < 0 );
-	n = npolls++;
 	if (rpolls < npolls) {
 		rpolls = npolls;
-#ifdef HAVE_SYS_POLL_H
+		pollfds = nfrealloc( pollfds, npolls * sizeof(*pollfds) );
-		pollfds = nfrealloc(pollfds, npolls * sizeof(*pollfds));
-#endif
-		fdparms = nfrealloc(fdparms, npolls * sizeof(*fdparms));
 	}
-	pollfds[n].fd = fd;
+	pollfds[idx].fd = fd;
-	pollfds[n].events = 0; /* POLLERR & POLLHUP implicit */
+	pollfds[idx].events = 0; /* POLLERR & POLLHUP implicit */
-	fdparms[n].faked = 0;
+	sn->index = idx;
-	fdparms[n].cb = cb;
+#else
-	fdparms[n].aux = aux;
+	sn->fd = fd;
-	changed = 1;
+	sn->events = 0;
-}
-
-void
-conf_fd( int fd, int and_events, int or_events )
-{
-	int n = find_fd( fd );
-	assert( n >= 0 );
-	pollfds[n].events = (pollfds[n].events & and_events) | or_events;
-}
-
-void
-fake_fd( int fd, int events )
-{
-	int n = find_fd( fd );
-	assert( n >= 0 );
-	fdparms[n].faked |= events;
-}
-
-void
-del_fd( int fd )
-{
-	int n = find_fd( fd );
-	assert( n >= 0 );
-	npolls--;
-#ifdef HAVE_SYS_POLL_H
-	memmove(pollfds + n, pollfds + n + 1, (npolls - n) * sizeof(*pollfds));
 #endif
-	memmove(fdparms + n, fdparms + n + 1, (npolls - n) * sizeof(*fdparms));
+	sn->cb = cb;
+	sn->aux = aux;
+	sn->faked = 0;
+	sn->next = notifiers;
+	notifiers = sn;
+}
+
+void
+conf_notifier( notifier_t *sn, int and_events, int or_events )
+{
+#ifdef HAVE_SYS_POLL_H
+	int idx = sn->index;
+	pollfds[idx].events = (pollfds[idx].events & and_events) | or_events;
+#else
+	sn->events = (sn->events & and_events) | or_events;
+#endif
+}
+
+void
+wipe_notifier( notifier_t *sn )
+{
+	notifier_t **snp;
+#ifdef HAVE_SYS_POLL_H
+	int idx;
+#endif
+
+	for (snp = &notifiers; *snp != sn; snp = &(*snp)->next)
+		assert( *snp );
+	*snp = sn->next;
+	sn->next = 0;
 	changed = 1;
+
+#ifdef HAVE_SYS_POLL_H
+	idx = sn->index;
+	memmove( pollfds + idx, pollfds + idx + 1, (--npolls - idx) * sizeof(*pollfds) );
+	for (sn = notifiers; sn; sn = sn->next) {
+		if (sn->index > idx)
+			sn->index--;
+	}
+#endif
 }
 
 #define shifted_bit(in, from, to) \
@@ -672,12 +661,13 @@ del_fd( int fd )
 static void
 event_wait( void )
 {
-	int m, n;
+	notifier_t *sn;
+	int m;
 
 #ifdef HAVE_SYS_POLL_H
 	int timeout = -1;
-	for (n = 0; n < npolls; n++)
+	for (sn = notifiers; sn; sn = sn->next)
-		if (fdparms[n].faked) {
+		if (sn->faked) {
 			timeout = 0;
 			break;
 		}
@@ -685,16 +675,18 @@ event_wait( void )
 		perror( "poll() failed in event loop" );
 		abort();
 	}
-	for (n = 0; n < npolls; n++)
+	for (sn = notifiers; sn; sn = sn->next) {
-		if ((m = pollfds[n].revents | fdparms[n].faked)) {
+		int n = sn->index;
+		if ((m = pollfds[n].revents | sn->faked)) {
 			assert( !(m & POLLNVAL) );
-			fdparms[n].faked = 0;
+			sn->faked = 0;
-			fdparms[n].cb( m | shifted_bit( m, POLLHUP, POLLIN ), fdparms[n].aux );
+			sn->cb( m | shifted_bit( m, POLLHUP, POLLIN ), sn->aux );
 			if (changed) {
 				changed = 0;
 				break;
 			}
 		}
+	}
 #else
 	struct timeval *timeout = 0;
 	static struct timeval null_tv;
@@ -705,13 +697,13 @@ event_wait( void )
 	FD_ZERO( &wfds );
 	FD_ZERO( &efds );
 	m = -1;
-	for (n = 0; n < npolls; n++) {
+	for (sn = notifiers; sn; sn = sn->next) {
-		if (fdparms[n].faked)
+		if (sn->faked)
 			timeout = &null_tv;
-		fd = fdparms[n].fd;
+		fd = sn->fd;
-		if (fdparms[n].events & POLLIN)
+		if (sn->events & POLLIN)
 			FD_SET( fd, &rfds );
-		if (fdparms[n].events & POLLOUT)
+		if (sn->events & POLLOUT)
 			FD_SET( fd, &wfds );
 		FD_SET( fd, &efds );
 		if (fd > m)
@@ -721,9 +713,9 @@ event_wait( void )
 		perror( "select() failed in event loop" );
 		abort();
 	}
-	for (n = 0; n < npolls; n++) {
+	for (sn = notifiers; sn; sn = sn->next) {
-		fd = fdparms[n].fd;
+		fd = sn->fd;
-		m = fdparms[n].faked;
+		m = sn->faked;
 		if (FD_ISSET( fd, &rfds ))
 			m |= POLLIN;
 		if (FD_ISSET( fd, &wfds ))
@@ -731,8 +723,8 @@ event_wait( void )
 		if (FD_ISSET( fd, &efds ))
 			m |= POLLERR;
 		if (m) {
-			fdparms[n].faked = 0;
+			sn->faked = 0;
-			fdparms[n].cb( m, fdparms[n].aux );
+			sn->cb( m, sn->aux );
 			if (changed) {
 				changed = 0;
 				break;
@@ -745,6 +737,6 @@ event_wait( void )
 void
 main_loop( void )
 {
-	while (npolls)
+	while (notifiers)
 		event_wait();
 }