0. 前言

1. 功能總結

libevent的核心作用是實現訊息迴圈、訊息佇列管理與回撥，可用來監聽檔案（socket也算檔案）屬性變化、超時、鎖狀態變化，其中超時可以用作Timer。
額外的功能是作為HTTP的server或client。

2. 編譯

2.1 Linux版編譯

在目錄下
./configure && make
即可在./.lib/下得到5個.a靜態庫。 不確定是否在此之前我已安裝好各種依賴庫所以沒遇到任何障礙。

[email protected] ~/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
 

檢視Makefile檔案的內容，可得知4個靜態庫對應的原始檔：

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裡是核心功能，其中$(SYS_SRC)在各個平臺會不同，linux下是select.c、poll.c、epoll.c、signal.c等，windows下是win32select.c evthread_win32.c等，不一一列舉了。libevent_extra.a裡包含http、dns等功能。另外兩個libevent_*.a就見名知意了。而libevent.a是libevent_core.a和libevent_extra.a的集合。

2.2 Windows版編譯

可以用VS的Command Prompt（開始選單->Visual Studio 2013->Visual Studio Tools->VS2013 x64 Native Tools Command Prompt，VS和CPU版本應對應到你所用的）在libevent目錄下
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.lib

3個靜態庫檔案。

不過一般會習慣做成VS工程。所以新建一個VS靜態庫工程，對著Makefile.nmake的內容新增原始檔、引用目錄、預編譯命令就行了。vcproj的部分內容如下：

<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平臺在連結時需要加入ws2_32.lib和wsock32.lib

2.3 Android版編譯

若是能看懂linux和windows的Makefile，那是很容易寫好Android.mk的。但在此之前需要生成好android版的config.h和event-config.h。

目錄下執行（ndk版本隨意，請替換成對應的路徑）：

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

這樣就會生成好config.h了。然後再
make
過程中會呼叫sed修改好event-config.h。順利的話會生成四個.a

[email protected] ~/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

因為沒有編譯OpenSSL，所以不會有libevent_openssl.a。

前面的過程會弄好config.h和event-config.h，其中event-config.h是對應android版本的配置，是必須的，不然編不過，所以無法一上來就用Android.mk。過了make這一步才行，也就是要保留修改過的event-config.h來使用下面的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)

注意最後一行在整合到app時應該把BUILD_SHARED_LIBRARY應該替換成BUILD_STATIC_LIBRARY，這裡僅為了編譯。