Update Tor to use Libevent 2.0 APIs when available.

This patch adds a new compat_libevent.[ch] set of files, and moves our
Libevent compatibility and utilitity functions there.  We build them
into a separate .a so that nothing else in src/commmon depends on
Libevent (partially fixing bug 507).

Also, do not use our own built-in evdns copy when we have Libevent
2.0, whose evdns is finally good enough (thus fixing Bug 920).

5 files changed, 195 insertions, 65 deletions

diff --git a/src/common/Makefile.am b/src/common/Makefile.am
index ad54e1aaaa..78f73db25f 100644
--- a/src/common/Makefile.am
+++ b/src/common/Makefile.am
@@ -1,5 +1,5 @@
 
-noinst_LIBRARIES = libor.a libor-crypto.a
+noinst_LIBRARIES = libor.a libor-crypto.a libor-event.a
 
 EXTRA_DIST = common_sha1.i
 
@@ -14,8 +14,9 @@ endif
 libor_a_SOURCES = address.c log.c util.c compat.c container.c mempool.c \
 	memarea.c util_codedigest.c $(libor_extra_source)
 libor_crypto_a_SOURCES = crypto.c aes.c tortls.c torgzip.c
+libor_event_a_SOURCES = compat_libevent.c
 
-noinst_HEADERS = address.h log.h crypto.h test.h util.h compat.h aes.h torint.h tortls.h strlcpy.c strlcat.c torgzip.h container.h ht.h mempool.h memarea.h ciphers.inc
+noinst_HEADERS = address.h log.h crypto.h test.h util.h compat.h aes.h torint.h tortls.h strlcpy.c strlcat.c torgzip.h container.h ht.h mempool.h memarea.h ciphers.inc compat_libevent.h
 
 common_sha1.i: $(libor_SOURCES) $(libor_crypto_a_SOURCES) $(noinst_HEADERS)
 	if test "@SHA1SUM@" != none; then \
diff --git a/src/common/compat_libevent.c b/src/common/compat_libevent.c
new file mode 100644
index 0000000000..d2ef112079
--- /dev/null
+++ b/src/common/compat_libevent.c
@@ -0,0 +1,153 @@
+/* Copyright (c) 2009, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file compat_libevent.c
+ * \brief Wrappers to handle porting between different versions of libevent.
+ *
+ * In an ideal world, we'd just use Libevent 2.0 from now on.  But as of June
+ * 2009, Libevent 2.0 is still in alpha, and we will have old versions of
+ * Libevent for the forseeable future.
+ **/
+
+#include "orconfig.h"
+#include "compat_libevent.h"
+
+#include "compat.h"
+#include "util.h"
+#include "log.h"
+
+#ifdef HAVE_EVENT2_EVENT_H
+#include <event2/event.h>
+#else
+#include <event.h>
+#endif
+
+#ifdef HAVE_EVENT_SET_LOG_CALLBACK
+/** A string which, if it appears in a libevent log, should be ignored. */
+static const char *suppress_msg = NULL;
+/** Callback function passed to event_set_log() so we can intercept
+ * log messages from libevent. */
+static void
+libevent_logging_callback(int severity, const char *msg)
+{
+  char buf[1024];
+  size_t n;
+  if (suppress_msg && strstr(msg, suppress_msg))
+    return;
+  n = strlcpy(buf, msg, sizeof(buf));
+  if (n && n < sizeof(buf) && buf[n-1] == '\n') {
+    buf[n-1] = '\0';
+  }
+  switch (severity) {
+    case _EVENT_LOG_DEBUG:
+      log(LOG_DEBUG, LD_NET, "Message from libevent: %s", buf);
+      break;
+    case _EVENT_LOG_MSG:
+      log(LOG_INFO, LD_NET, "Message from libevent: %s", buf);
+      break;
+    case _EVENT_LOG_WARN:
+      log(LOG_WARN, LD_GENERAL, "Warning from libevent: %s", buf);
+      break;
+    case _EVENT_LOG_ERR:
+      log(LOG_ERR, LD_GENERAL, "Error from libevent: %s", buf);
+      break;
+    default:
+      log(LOG_WARN, LD_GENERAL, "Message [%d] from libevent: %s",
+          severity, buf);
+      break;
+  }
+}
+/** Set hook to intercept log messages from libevent. */
+void
+configure_libevent_logging(void)
+{
+  event_set_log_callback(libevent_logging_callback);
+}
+/** Ignore any libevent log message that contains <b>msg</b>. */
+void
+suppress_libevent_log_msg(const char *msg)
+{
+  suppress_msg = msg;
+}
+#else
+void
+configure_libevent_logging(void)
+{
+}
+void
+suppress_libevent_log_msg(const char *msg)
+{
+  (void)msg;
+}
+#endif
+
+#ifndef HAVE_EVENT2_EVENT_H
+/** Work-alike replacement for event_new() on pre-Libevent-2.0 systems. */
+struct event *
+tor_event_new(struct event_base *base, int sock, short what,
+              void (*cb)(int, short, void *), void *arg)
+{
+  struct event *e = tor_malloc_zero(sizeof(struct event));
+  event_set(e, sock, what, cb, arg);
+  event_base_set(base, e);
+  return e;
+}
+/** Work-alike replacement for evtimer_new() on pre-Libevent-2.0 systems. */
+struct event *
+tor_evtimer_new(struct event_base *base,
+                void (*cb)(int, short, void *), void *arg)
+{
+  return tor_event_new(base, -1, 0, cb, arg);
+}
+/** Work-alike replacement for evsignal_new() on pre-Libevent-2.0 systems. */
+struct event *
+tor_evsignal_new(struct event_base * base, int sig,
+                 void (*cb)(int, short, void *), void *arg)
+{
+  return tor_event_new(base, sig, EV_SIGNAL, cb, arg);
+}
+/** Work-alike replacement for event_free() on pre-Libevent-2.0 systems. */
+void
+tor_event_free(struct event *ev)
+{
+  event_del(ev);
+  tor_free(ev);
+}
+#endif
+
+/** Global event base for use by the main thread. */
+struct event_base *the_event_base = NULL;
+
+/** Initialize the Libevent library and set up the event base. */
+void
+tor_libevent_initialize(void)
+{
+  tor_assert(the_event_base == NULL);
+#ifdef HAVE_EVENT2_EVENT_H
+  the_event_base = event_base_new();
+#else
+  the_event_base = event_init();
+#endif
+}
+
+/** Return the current Libevent event base that we're set up to use. */
+struct event_base *
+tor_libevent_get_base(void)
+{
+  return the_event_base;
+}
+
+/** Return the name of the Libevent backend we're using. */
+const char *
+tor_libevent_get_method(void)
+{
+#ifdef HAVE_EVENT2_EVENT_H
+  return event_base_get_method(the_event_base);
+#elif defined(HAVE_EVENT_GET_METHOD)
+  return event_get_method();
+#else
+  return "<unknown>";
+#endif
+}
+
diff --git a/src/common/compat_libevent.h b/src/common/compat_libevent.h
new file mode 100644
index 0000000000..a95285f460
--- /dev/null
+++ b/src/common/compat_libevent.h
@@ -0,0 +1,39 @@
+/* Copyright (c) 2009, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+#ifndef _TOR_COMPAT_LIBEVENT_H
+#define _TOR_COMPAT_LIBEVENT_H
+
+#include "orconfig.h"
+
+#ifdef HAVE_EVENT2_EVENT_H
+#include <event2/event.h>
+#else
+#include <event.h>
+#define evutil_socket_t int
+#endif
+
+void configure_libevent_logging(void);
+void suppress_libevent_log_msg(const char *msg);
+
+#ifdef HAVE_EVENT2_EVENT_H
+#define tor_event_new     event_new
+#define tor_evtimer_new   evtimer_new
+#define tor_evsignal_new  evsignal_new
+#define tor_event_free    event_free
+#else
+struct event *tor_event_new(struct event_base * base, evutil_socket_t sock,
+           short what, void (*cb)(evutil_socket_t, short, void *), void *arg);
+struct event *tor_evtimer_new(struct event_base * base,
+            void (*cb)(evutil_socket_t, short, void *), void *arg);
+struct event *tor_evsignal_new(struct event_base * base, int sig,
+            void (*cb)(evutil_socket_t, short, void *), void *arg);
+void tor_event_free(struct event *ev);
+#endif
+
+void tor_libevent_initialize(void);
+struct event_base *tor_libevent_get_base(void);
+const char *tor_libevent_get_method(void);
+
+#endif
+
diff --git a/src/common/log.c b/src/common/log.c
index a7b0c12c4a..b12462a42f 100644
--- a/src/common/log.c
+++ b/src/common/log.c
@@ -36,8 +36,6 @@
 #include "log.h"
 #include "container.h"
 
-#include <event.h>
-
 #define TRUNCATED_STR "[...truncated]"
 #define TRUNCATED_STR_LEN 14
 
@@ -921,65 +919,6 @@ switch_logs_debug(void)
   UNLOCK_LOGS();
 }
 
-#ifdef HAVE_EVENT_SET_LOG_CALLBACK
-/** A string which, if it appears in a libevent log, should be ignored. */
-static const char *suppress_msg = NULL;
-/** Callback function passed to event_set_log() so we can intercept
- * log messages from libevent. */
-static void
-libevent_logging_callback(int severity, const char *msg)
-{
-  char buf[1024];
-  size_t n;
-  if (suppress_msg && strstr(msg, suppress_msg))
-    return;
-  n = strlcpy(buf, msg, sizeof(buf));
-  if (n && n < sizeof(buf) && buf[n-1] == '\n') {
-    buf[n-1] = '\0';
-  }
-  switch (severity) {
-    case _EVENT_LOG_DEBUG:
-      log(LOG_DEBUG, LD_NET, "Message from libevent: %s", buf);
-      break;
-    case _EVENT_LOG_MSG:
-      log(LOG_INFO, LD_NET, "Message from libevent: %s", buf);
-      break;
-    case _EVENT_LOG_WARN:
-      log(LOG_WARN, LD_GENERAL, "Warning from libevent: %s", buf);
-      break;
-    case _EVENT_LOG_ERR:
-      log(LOG_ERR, LD_GENERAL, "Error from libevent: %s", buf);
-      break;
-    default:
-      log(LOG_WARN, LD_GENERAL, "Message [%d] from libevent: %s",
-          severity, buf);
-      break;
-  }
-}
-/** Set hook to intercept log messages from libevent. */
-void
-configure_libevent_logging(void)
-{
-  event_set_log_callback(libevent_logging_callback);
-}
-/** Ignore any libevent log message that contains <b>msg</b>. */
-void
-suppress_libevent_log_msg(const char *msg)
-{
-  suppress_msg = msg;
-}
-#else
-void
-configure_libevent_logging(void)
-{
-}
-void
-suppress_libevent_log_msg(const char *msg)
-{
-  (void)msg;
-}
-#endif
-
 #if 0
 static void
 dump_log_info(logfile_t *lf)
diff --git a/src/common/log.h b/src/common/log.h
index 834b1724b3..6745baabc6 100644
--- a/src/common/log.h
+++ b/src/common/log.h
@@ -134,8 +134,6 @@ void add_temp_log(int min_severity);
 void close_temp_logs(void);
 void rollback_log_changes(void);
 void mark_logs_temp(void);
-void configure_libevent_logging(void);
-void suppress_libevent_log_msg(const char *msg);
 void change_callback_log_severity(int loglevelMin, int loglevelMax,
                                   log_callback cb);
 void log_set_application_name(const char *name);