0. 前言
我使用的版本是libevent-2.0.21-stable。高级的应用还是得看官网文档http://www.wangafu.net/~nickm/libevent-2.0/doxygen/html/
1. 功能总结
libevent的核心作用是实现消息循环、消息队列管理与回调，可用来监听文件（socket也算文件）属性变化、超时、锁状态变化，其中超时可以用作Timer。额外的功能是作为HTTP的server或client。
2. 编译
2.1 Linux版编译
在目录下
./configure && make
即可在./.lib/下得到5个.a静态库。 不确定是否在此之前我已安装好各种依赖库所以没遇到任何障碍。
liuhx@uc ~/Downloads/libevent-2.0.21-stable/.libs $ ll *.a -rw-r--r-- 1 liuhx liuhx 2309114 Feb 17 13:38 libevent.a -rw-r--r-- 1 liuhx liuhx 1431730 Feb 17 13:38 libevent_core.a -rw-r--r-- 1 liuhx liuhx 877456 Feb 17 13:38 libevent_extra.a -rw-r--r-- 1 liuhx liuhx 195868 Feb 17 13:38 libevent_openssl.a -rw-r--r-- 1 liuhx liuhx 21998 Feb 17 13:38 libevent_pthreads.a查看Makefile文件的内容，可得知4个静态库对应的源文件：
CORE_SRC = event.c evthread.c buffer.c \ bufferevent.c bufferevent_sock.c bufferevent_filter.c \ bufferevent_pair.c listener.c bufferevent_ratelim.c \ evmap.c log.c evutil.c evutil_rand.c strlcpy.c $(SYS_SRC) EXTRA_SRC = event_tagging.c http.c evdns.c evrpc.c libevent_pthreads_la_SOURCES = evthread_pthread.c libevent_openssl_la_SOURCES = bufferevent_openssl.c即libevent_core.a里是核心功能，其中$(SYS_SRC)在各个平台会不同，linux下是select.c、poll.c、epoll.c、signal.c等，windows下是win32select.c evthread_win32.c等，不一一列举了。libevent_extra.a里包含http、dns等功能。另外两个libevent_*.a就见名知意了。而libevent.a是libevent_core.a和libevent_extra.a的集合。
2.2 Windows版编译
可以用VS的Command Prompt（开始菜单->Visual Studio 2013->Visual Studio Tools->VS2013 x64 Native Tools Command Prompt，VS和CPU版本应对应到你所用的）在libevent目录下
nmake Makefile.nmake
就能得到
2015/02/26 10:40 336,040 libevent_extras.lib 2015/02/26 10:40 789,110 libevent.lib 2015/02/26 10:40 453,366 libevent_core.lib3个静态库文件。
不过一般会习惯做成VS工程。所以新建一个VS静态库工程，对着Makefile.nmake的内容添加源文件、引用目录、预编译命令就行了。vcproj的部分内容如下：
<ClCompile Include="..\..\..\third_party\libevent-2.0.21-stable\buffer.c" /> <ClCompile Include="..\..\..\third_party\libevent-2.0.21-stable\bufferevent.c" /> <ClCompile Include="..\..\..\third_party\libevent-2.0.21-stable\bufferevent_async.c" /> <ClCompile Include="..\..\..\third_party\libevent-2.0.21-stable\bufferevent_filter.c" /> <ClCompile Include="..\..\..\third_party\libevent-2.0.21-stable\bufferevent_pair.c" /> <ClCompile Include="..\..\..\third_party\libevent-2.0.21-stable\bufferevent_ratelim.c" /> <ClCompile Include="..\..\..\third_party\libevent-2.0.21-stable\bufferevent_sock.c" /> <ClCompile Include="..\..\..\third_party\libevent-2.0.21-stable\buffer_iocp.c" /> <ClCompile Include="..\..\..\third_party\libevent-2.0.21-stable\evdns.c" /> <ClCompile Include="..\..\..\third_party\libevent-2.0.21-stable\event.c" /> <ClCompile Include="..\..\..\third_party\libevent-2.0.21-stable\event_iocp.c" /> <ClCompile Include="..\..\..\third_party\libevent-2.0.21-stable\event_tagging.c" /> <ClCompile Include="..\..\..\third_party\libevent-2.0.21-stable\evmap.c" /> <ClCompile Include="..\..\..\third_party\libevent-2.0.21-stable\evrpc.c" /> <ClCompile Include="..\..\..\third_party\libevent-2.0.21-stable\evthread.c" /> <ClCompile Include="..\..\..\third_party\libevent-2.0.21-stable\evthread_win32.c" /> <ClCompile Include="..\..\..\third_party\libevent-2.0.21-stable\evutil.c" /> <ClCompile Include="..\..\..\third_party\libevent-2.0.21-stable\evutil_rand.c" /> <ClCompile Include="..\..\..\third_party\libevent-2.0.21-stable\http.c" /> <ClCompile Include="..\..\..\third_party\libevent-2.0.21-stable\listener.c" /> <ClCompile Include="..\..\..\third_party\libevent-2.0.21-stable\log.c" /> <ClCompile Include="..\..\..\third_party\libevent-2.0.21-stable\signal.c" /> <ClCompile Include="..\..\..\third_party\libevent-2.0.21-stable\strlcpy.c" /> <ClCompile Include="..\..\..\third_party\libevent-2.0.21-stable\win32select.c" />
windows平台在链接时需要加入ws2_32.lib和wsock32.lib
2.3 Android版编译
若是能看懂linux和windows的Makefile，那是很容易写好Android.mk的。但在此之前需要生成好android版的config.h和event-config.h。目录下运行（ndk版本随意，请替换成对应的路径）：
SYSROOT=~/Applications/android-ndk-r8e/platforms/android-8/arch-arm ./configure --host=arm-linux-androideabi CC=~/Applications/android-ndk-r8e/toolchains/arm-linux-androideabi-4.4.3/prebuilt/linux-x86_64/bin/arm-linux-androideabi-gcc CFLAGS=--sysroot=$SYSROOT
这样就会生成好config.h了。然后再
make
过程中会调用sed修改好event-config.h。顺利的话会生成四个.a
liuhx@uc ~/Downloads/libevent-2.0.21-stable/.libs $ ll *.a -rw-r--r-- 1 liuhx liuhx 455082 Feb 26 14:59 libevent.a -rw-r--r-- 1 liuhx liuhx 267398 Feb 26 14:59 libevent_core.a -rw-r--r-- 1 liuhx liuhx 187756 Feb 26 14:59 libevent_extra.a -rw-r--r-- 1 liuhx liuhx 4014 Feb 26 14:59 libevent_pthreads.a因为没有编译OpenSSL，所以不会有libevent_openssl.a。
前面的过程会弄好config.h和event-config.h，其中event-config.h是对应android版本的配置，是必须的，不然编不过，所以无法一上来就用Android.mk。过了make这一步才行，也就是要保留修改过的event-config.h来使用下面的Android.mk
LOCAL_PATH := $(call my-dir)/..
include $(CLEAR_VARS)
LOCAL_MODULE := libevent
LOCAL_SRC_FILES := \
event.c \
evutil.c \
epoll.c \
log.c \
poll.c \
select.c \
signal.c \
http.c \
buffer.c \
evthread.c \
evmap.c \
bufferevent.c \
listener.c \
evutil_rand.c \
bufferevent_sock.c \
bufferevent_filter.c \
bufferevent_pair.c \
strlcpy.c \
event_tagging.c \
evrpc.c \
bufferevent_ratelim.c \
evdns.c \
evthread_pthread.c
LOCAL_C_INCLUDES := \
$(LOCAL_PATH) \
$(LOCAL_PATH)/include \
$(LOCAL_PATH)/compat
LOCAL_CFLAGS := -DHAVE_CONFIG_H
include $(BUILD_SHARED_LIBRARY)
注意最后一行在集成到app时应该把BUILD_SHARED_LIBRARY应该替换成BUILD_STATIC_LIBRARY，这里仅为了编译。
