r5197: moved events code to lib/events/ (suggestion from metze)

(This used to be commit 7f54c8a339f36aa43c9340be70ab7f0067593ef2)

1 files changed, 520 insertions, 0 deletions

diff --git a/source4/lib/events/events.c b/source4/lib/events/events.c
new file mode 100644
index 0000000000..a852df68eb
--- /dev/null
+++ b/source4/lib/events/events.c
@@ -0,0 +1,520 @@
+/* 
+   Unix SMB/CIFS implementation.
+   main select loop and event handling
+   Copyright (C) Andrew Tridgell 2003
+   
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 2 of the License, or
+   (at your option) any later version.
+   
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+   
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+/*
+  PLEASE READ THIS BEFORE MODIFYING!
+
+  This module is a general abstraction for the main select loop and
+  event handling. Do not ever put any localised hacks in here, instead
+  register one of the possible event types and implement that event
+  somewhere else.
+
+  There are 2 types of event handling that are handled in this module:
+
+  1) a file descriptor becoming readable or writeable. This is mostly
+     used for network sockets, but can be used for any type of file
+     descriptor. You may only register one handler for each file
+     descriptor/io combination or you will get unpredictable results
+     (this means that you can have a handler for read events, and a
+     separate handler for write events, but not two handlers that are
+     both handling read events)
+
+  2) a timed event. You can register an event that happens at a
+     specific time.  You can register as many of these as you
+     like. They are single shot - add a new timed event in the event
+     handler to get another event.
+
+  To setup a set of events you first need to create a event_context
+  structure using the function event_context_init(); This returns a
+  'struct event_context' that you use in all subsequent calls.
+
+  After that you can add/remove events that you are interested in
+  using event_add_*() and talloc_free()
+
+  Finally, you call event_loop_wait() to block waiting for one of the
+  events to occor. In normal operation event_loop_wait() will loop
+  forever.
+
+*/
+
+#include "includes.h"
+#include "system/time.h"
+#include "system/select.h"
+#include "dlinklist.h"
+#include "lib/events/events.h"
+
+/* use epoll if it is available */
+#if defined(HAVE_EPOLL_CREATE) && defined(HAVE_SYS_EPOLL_H)
+#define WITH_EPOLL 1
+#endif
+
+#if WITH_EPOLL
+#include <sys/epoll.h>
+#endif
+
+struct event_context {	
+	/* list of filedescriptor events */
+	struct fd_event {
+		struct event_context *event_ctx;
+		struct fd_event *next, *prev;
+		int fd;
+		uint16_t flags; /* see EVENT_FD_* flags */
+		event_fd_handler_t handler;
+		void *private;
+	} *fd_events;
+
+	/* list of timed events */
+	struct timed_event {
+		struct event_context *event_ctx;
+		struct timed_event *next, *prev;
+		struct timeval next_event;
+		event_timed_handler_t handler;
+		void *private;
+	} *timed_events;
+
+	/* the maximum file descriptor number in fd_events */
+	int maxfd;
+
+	/* information for exiting from the event loop */
+	int exit_code;
+
+	/* this is changed by the destructors for the fd event
+	   type. It is used to detect event destruction by event
+	   handlers, which means the code that is calling the event
+	   handler needs to assume that the linked list is no longer
+	   valid
+	*/
+	uint32_t destruction_count;
+
+#if WITH_EPOLL
+	/* when using epoll this is the handle from epoll_create */
+	int epoll_fd;
+#endif
+};
+
+
+/*
+  create a event_context structure. This must be the first events
+  call, and all subsequent calls pass this event_context as the first
+  element. Event handlers also receive this as their first argument.
+*/
+struct event_context *event_context_init(TALLOC_CTX *mem_ctx)
+{
+	struct event_context *ev;
+
+	ev = talloc_zero(mem_ctx, struct event_context);
+	if (!ev) return NULL;
+
+#if WITH_EPOLL
+	ev->epoll_fd = epoll_create(64);
+#endif
+
+	return ev;
+}
+
+
+/*
+  recalculate the maxfd
+*/
+static void calc_maxfd(struct event_context *ev)
+{
+	struct fd_event *e;
+	ev->maxfd = 0;
+	for (e=ev->fd_events; e; e=e->next) {
+		if (e->fd > ev->maxfd) {
+			ev->maxfd = e->fd;
+		}
+	}
+}
+
+
+/* to mark the ev->maxfd invalid
+ * this means we need to recalculate it
+ */
+#define EVENT_INVALID_MAXFD (-1)
+
+
+#if WITH_EPOLL
+/*
+  called when a epoll call fails, and we should fallback
+  to using select
+*/
+static void epoll_fallback_to_select(struct event_context *ev, const char *reason)
+{
+	DEBUG(0,("%s - using select() - %s\n", reason, strerror(errno)));
+	close(ev->epoll_fd);
+	ev->epoll_fd = -1;
+}
+#endif
+
+
+#if WITH_EPOLL
+/*
+  map from EVENT_FD_* to EPOLLIN/EPOLLOUT
+*/
+static uint32_t epoll_map_flags(uint16_t flags)
+{
+	uint32_t ret = 0;
+	if (flags & EVENT_FD_READ) ret |= EPOLLIN;
+	if (flags & EVENT_FD_WRITE) ret |= EPOLLOUT;
+	return ret;
+}
+#endif
+
+/*
+  destroy an fd_event
+*/
+static int event_fd_destructor(void *ptr)
+{
+	struct fd_event *fde = talloc_get_type(ptr, struct fd_event);
+	struct event_context *ev = fde->event_ctx;
+
+	if (ev->maxfd == fde->fd) {
+		ev->maxfd = EVENT_INVALID_MAXFD;
+	}
+	DLIST_REMOVE(ev->fd_events, fde);
+	ev->destruction_count++;
+#if WITH_EPOLL
+	if (ev->epoll_fd != -1) {
+		struct epoll_event event;
+		ZERO_STRUCT(event);
+		event.events = epoll_map_flags(fde->flags);
+		event.data.ptr = fde;
+		if (epoll_ctl(ev->epoll_fd, EPOLL_CTL_DEL, fde->fd, &event) != 0) {
+			epoll_fallback_to_select(ev, "EPOLL_CTL_DEL failed");
+		}
+	}
+#endif
+	return 0;
+}
+
+/*
+  add a fd based event
+  return NULL on failure (memory allocation error)
+*/
+struct fd_event *event_add_fd(struct event_context *ev, TALLOC_CTX *mem_ctx,
+			      int fd, uint16_t flags, event_fd_handler_t handler,
+			      void *private)
+{
+	struct fd_event *e = talloc(ev, struct fd_event);
+	if (!e) return NULL;
+
+	e->event_ctx = ev;
+	e->fd        = fd;
+	e->flags     = flags;
+	e->handler   = handler;
+	e->private   = private;
+
+	DLIST_ADD(ev->fd_events, e);
+
+	if (e->fd > ev->maxfd) {
+		ev->maxfd = e->fd;
+	}
+
+	talloc_set_destructor(e, event_fd_destructor);
+	if (mem_ctx) {
+		talloc_steal(mem_ctx, e);
+	}
+
+#if WITH_EPOLL
+	if (ev->epoll_fd != -1) {
+		struct epoll_event event;
+		ZERO_STRUCT(event);
+		event.events = epoll_map_flags(flags);
+		event.data.ptr = e;
+		if (epoll_ctl(ev->epoll_fd, EPOLL_CTL_ADD, e->fd, &event) != 0) {
+			epoll_fallback_to_select(ev, "EPOLL_CTL_ADD failed");
+		}
+	}
+#endif
+
+	return e;
+}
+
+
+/*
+  return the fd event flags
+*/
+uint16_t event_fd_flags(struct fd_event *fde)
+{
+	return fde?fde->flags:0;
+}
+
+/*
+  set the fd event flags
+*/
+void event_fd_setflags(struct fd_event *fde, uint16_t flags)
+{
+#if WITH_EPOLL
+	struct event_context *ev;
+	if (fde == NULL) return;
+	ev = fde->event_ctx;
+	if (ev->epoll_fd != -1) {
+		struct epoll_event event;
+		ZERO_STRUCT(event);
+		event.events = epoll_map_flags(flags);
+		event.data.ptr = fde;
+		if (epoll_ctl(ev->epoll_fd, EPOLL_CTL_MOD, fde->fd, &event) != 0) {
+			epoll_fallback_to_select(ev, "EPOLL_CTL_MOD failed");
+		}
+	}
+#endif
+	if (fde) {
+		fde->flags = flags;
+	}
+}
+
+/*
+  destroy a timed event
+*/
+static int event_timed_destructor(void *ptr)
+{
+	struct timed_event *te = talloc_get_type(ptr, struct timed_event);
+	DLIST_REMOVE(te->event_ctx->timed_events, te);
+	return 0;
+}
+
+/*
+  add a timed event
+  return NULL on failure (memory allocation error)
+*/
+struct timed_event *event_add_timed(struct event_context *ev, TALLOC_CTX *mem_ctx,
+				    struct timeval next_event, 
+				    event_timed_handler_t handler, 
+				    void *private) 
+{
+	struct timed_event *te, *e;
+
+	e = talloc(mem_ctx?mem_ctx:ev, struct timed_event);
+	if (e == NULL) return NULL;
+
+	e->event_ctx  = ev;
+	e->next_event = next_event;
+	e->handler    = handler;
+	e->private    = private;
+
+	/* keep the list ordered */
+	if (ev->timed_events == NULL || 
+	    timeval_compare(&e->next_event, &ev->timed_events->next_event) > 0) {
+		DLIST_ADD(ev->timed_events, e);
+	} else {
+		for (te=ev->timed_events;te && te->next;te=te->next) {
+			if (!timeval_is_zero(&te->next_event) &&
+			    timeval_compare(&te->next_event, &e->next_event) < 0) {
+				break;
+			}
+		}
+		DLIST_ADD_AFTER(ev->timed_events, e, te);
+	}
+
+	talloc_set_destructor(e, event_timed_destructor);
+
+	return e;
+}
+
+/*
+  a timer has gone off - call it
+*/
+static void event_loop_timer(struct event_context *ev)
+{
+	struct timeval t = timeval_current();
+	struct timed_event *te = ev->timed_events;
+
+	te->next_event = timeval_zero();
+
+	te->handler(ev, te, t, te->private);
+
+	/* note the care taken to prevent referencing a event
+	   that could have been freed by the handler */
+	if (ev->timed_events && timeval_is_zero(&ev->timed_events->next_event)) {
+		talloc_free(ev->timed_events);
+	}
+}
+
+#if WITH_EPOLL
+/*
+  event loop handling using epoll
+*/
+static int event_loop_epoll(struct event_context *ev, struct timeval *tvalp)
+{
+	int ret, i;
+	const int maxevents = 8;
+	struct epoll_event events[maxevents];
+	uint32_t destruction_count = ev->destruction_count;
+	int timeout = -1;
+
+	if (tvalp) {
+		timeout = (tvalp->tv_usec / 1000) + (tvalp->tv_sec*1000);
+	}
+
+	ret = epoll_wait(ev->epoll_fd, events, maxevents, timeout);
+
+	if (ret == -1 && errno != EINTR) {
+		epoll_fallback_to_select(ev, "epoll_wait() failed");
+		return -1;
+	}
+
+	if (ret == 0 && tvalp) {
+		event_loop_timer(ev);
+		return 0;
+	}
+
+	for (i=0;i<ret;i++) {
+		struct fd_event *fde = talloc_get_type(events[i].data.ptr, 
+						       struct fd_event);
+		uint16_t flags = 0;
+
+		if (fde == NULL) {
+			epoll_fallback_to_select(ev, "epoll_wait() gave bad data");
+			return -1;
+		}
+		if (events[i].events & EPOLLIN) flags |= EVENT_FD_READ;
+		if (events[i].events & EPOLLOUT) flags |= EVENT_FD_WRITE;
+		if (flags) {
+			fde->handler(ev, fde, flags, fde->private);
+			if (destruction_count != ev->destruction_count) {
+				break;
+			}
+		}
+	}
+
+	return 0;
+}		
+#endif
+
+/*
+  event loop handling using select()
+*/
+static int event_loop_select(struct event_context *ev, struct timeval *tvalp)
+{
+	fd_set r_fds, w_fds;
+	int selrtn;
+	uint32_t destruction_count = ev->destruction_count;
+	struct fd_event *fe;
+
+	/* we maybe need to recalculate the maxfd */
+	if (ev->maxfd == EVENT_INVALID_MAXFD) {
+		calc_maxfd(ev);
+	}
+		
+	FD_ZERO(&r_fds);
+	FD_ZERO(&w_fds);
+
+	/* setup any fd events */
+	for (fe=ev->fd_events; fe; ) {
+		struct fd_event *next = fe->next;
+		if (fe->flags & EVENT_FD_READ) {
+			FD_SET(fe->fd, &r_fds);
+		}
+		if (fe->flags & EVENT_FD_WRITE) {
+			FD_SET(fe->fd, &w_fds);
+		}
+		fe = next;
+	}
+
+	selrtn = select(ev->maxfd+1, &r_fds, &w_fds, NULL, tvalp);
+		
+	if (selrtn == -1 && errno == EBADF) {
+		/* the socket is dead! this should never
+		   happen as the socket should have first been
+		   made readable and that should have removed
+		   the event, so this must be a bug. This is a
+		   fatal error. */
+		DEBUG(0,("ERROR: EBADF on event_loop_once\n"));
+		ev->exit_code = EBADF;
+		return -1;
+	}
+
+	if (selrtn == 0 && tvalp) {
+		event_loop_timer(ev);
+		return 0;
+	}
+
+	if (selrtn > 0) {
+		/* at least one file descriptor is ready - check
+		   which ones and call the handler, being careful to allow
+		   the handler to remove itself when called */
+		for (fe=ev->fd_events; fe; fe=fe->next) {
+			uint16_t flags = 0;
+			if (FD_ISSET(fe->fd, &r_fds)) flags |= EVENT_FD_READ;
+			if (FD_ISSET(fe->fd, &w_fds)) flags |= EVENT_FD_WRITE;
+			if (flags) {
+				fe->handler(ev, fe, flags, fe->private);
+				if (destruction_count != ev->destruction_count) {
+					break;
+				}
+			}
+		}
+	}
+
+	return 0;
+}		
+
+/*
+  do a single event loop using the events defined in ev 
+*/
+int event_loop_once(struct event_context *ev)
+{
+	struct timeval tval, *tvalp;
+
+	tvalp = NULL;
+		
+	/* work out the right timeout for all timed events */
+	if (ev->timed_events) {
+		struct timeval t = timeval_current();
+		tval = timeval_diff(&ev->timed_events->next_event, &t);
+		tvalp = &tval;
+		if (timeval_is_zero(tvalp)) {
+			event_loop_timer(ev);
+			return 0;
+		}
+	}
+
+#if WITH_EPOLL
+	if (ev->epoll_fd != -1) {
+		if (event_loop_epoll(ev, tvalp) == 0) {
+			return 0;
+		}
+	}
+#endif
+
+	return event_loop_select(ev, tvalp);
+}
+
+/*
+  go into an event loop using the events defined in ev this function
+  will return with the specified code if one of the handlers calls
+  event_loop_exit()
+
+  also return (with code 0) if all fd events are removed
+*/
+int event_loop_wait(struct event_context *ev)
+{
+	ev->exit_code = 0;
+	ev->maxfd = EVENT_INVALID_MAXFD;
+
+	while (ev->fd_events && ev->exit_code == 0) {
+		if (event_loop_once(ev) != 0) {
+			break;
+		}
+	}
+
+	return ev->exit_code;
+}