From b29b875d8476d2e1603e7703ef5309cbd7cae79f Mon Sep 17 00:00:00 2001
From: Nick Mathewson <nickm@torproject.org>
Date: Fri, 10 Apr 2009 20:43:08 +0000
Subject: [PATCH] Facility to make evbuffers get their callbacks deferred.

svn:r1154
---
 buffer.c                | 41 +++++++++++++++++++++++++++++++++++++++--
 evbuffer-internal.h     |  6 ++++++
 include/event2/buffer.h | 10 ++++++++++
 3 files changed, 55 insertions(+), 2 deletions(-)

diff --git a/buffer.c b/buffer.c
index 2b42c384..37c43ec2 100644
--- a/buffer.c
+++ b/buffer.c
@@ -134,6 +134,7 @@ static int use_mmap = 1;
 #define CHAIN_PINNED(ch)  (((ch)->flags & EVBUFFER_MEM_PINNED_ANY) != 0)
 
 static void evbuffer_chain_align(struct evbuffer_chain *chain);
+static void evbuffer_deferred_callback(struct deferred_cb *cb, void *arg);
 
 static struct evbuffer_chain *
 evbuffer_chain_new(size_t size)
@@ -260,6 +261,18 @@ evbuffer_new(void)
 	return (buffer);
 }
 
+int
+evbuffer_defer_callbacks(struct evbuffer *buffer, struct event_base *base)
+{
+	EVBUFFER_LOCK(buffer, EVTHREAD_WRITE);
+	buffer->ev_base = base;
+	buffer->deferred_cbs = 1;
+	event_deferred_cb_init(&buffer->deferred,
+	    evbuffer_deferred_callback, buffer);
+	EVBUFFER_UNLOCK(buffer, EVTHREAD_WRITE);
+	return 0;
+}
+
 int
 evbuffer_enable_locking(struct evbuffer *buf, void *lock)
 {
@@ -284,8 +297,8 @@ evbuffer_enable_locking(struct evbuffer *buf, void *lock)
 #endif
 }
 
-static inline void
-evbuffer_invoke_callbacks(struct evbuffer *buffer)
+static void
+evbuffer_run_callbacks(struct evbuffer *buffer)
 {
 	struct evbuffer_cb_entry *cbent, *next;
         struct evbuffer_cb_info info;
@@ -328,6 +341,28 @@ evbuffer_invoke_callbacks(struct evbuffer *buffer)
 	}
 }
 
+static inline void
+evbuffer_invoke_callbacks(struct evbuffer *buffer)
+{
+	if (buffer->deferred_cbs) {
+		event_deferred_cb_schedule(buffer->ev_base, &buffer->deferred);
+	} else {
+		evbuffer_run_callbacks(buffer);
+	}
+}
+
+static void
+evbuffer_deferred_callback(struct deferred_cb *cb, void *arg)
+{
+	struct evbuffer *buffer = arg;
+	static int which = 0;
+	printf("FOO #%d\n", which++);
+
+	EVBUFFER_LOCK(buffer, EVTHREAD_WRITE);
+	evbuffer_run_callbacks(buffer);
+	EVBUFFER_UNLOCK(buffer, EVTHREAD_WRITE);
+}
+
 static void
 evbuffer_remove_all_callbacks(struct evbuffer *buffer)
 {
@@ -351,6 +386,8 @@ evbuffer_free(struct evbuffer *buffer)
 		evbuffer_chain_free(chain);
 	}
 	evbuffer_remove_all_callbacks(buffer);
+	if (buffer->deferred_cbs)
+		event_deferred_cb_cancel(buffer->ev_base, &buffer->deferred);
         if (buffer->own_lock)
                 EVTHREAD_FREE_LOCK(buffer->lock);
 	mm_free(buffer);
diff --git a/evbuffer-internal.h b/evbuffer-internal.h
index 521fae07..7ec714ab 100644
--- a/evbuffer-internal.h
+++ b/evbuffer-internal.h
@@ -33,6 +33,7 @@ extern "C" {
 
 #include "event-config.h"
 #include "evutil.h"
+#include "defer-internal.h"
 
 #include <sys/queue.h>
 /* minimum allocation for a chain. */
@@ -78,9 +79,14 @@ struct evbuffer {
 	unsigned own_lock : 1;
 	unsigned freeze_start : 1;
 	unsigned freeze_end : 1;
+	unsigned deferred_cbs : 1;
+
+	struct event_base *ev_base;
 
         int lock_count;
 
+	struct deferred_cb deferred;
+
 	TAILQ_HEAD(evbuffer_cb_queue, evbuffer_cb_entry) callbacks;
 };
 
diff --git a/include/event2/buffer.h b/include/event2/buffer.h
index 786fd2df..a4b9a4cf 100644
--- a/include/event2/buffer.h
+++ b/include/event2/buffer.h
@@ -587,6 +587,16 @@ int evbuffer_freeze(struct evbuffer *buf, int at_front);
  */
 int evbuffer_unfreeze(struct evbuffer *buf, int at_front);
 
+struct event_base;
+/**
+   Force all the callbacks on an evbuffer to be run, not immediately after
+   the evbuffer is altered, but instead from inside the event loop.
+
+   This can be used to serialize all the callbacks to a single thread
+   of execution.
+ */
+int evbuffer_defer_callbacks(struct evbuffer *buffer, struct event_base *base);
+
 #ifdef __cplusplus
 }
 #endif
-- 
2.40.0