编译frostwire项目jlibtorrent_jni.cpp
欧阳成弘
在上一篇文章中已经编译好了boost库，libtorrent库，openssl，接下来编译libtorrent_jni.cpp;
这个文件是供jni调用底层libtorrent库的接口，为了方便在java程序中使用这些接口，需将libtorrent_jni.cpp编译成dll动态库；
在项目frostwire-jlibtorrent-master中已经给出了编译的脚本build_windows.bat;
<span style="font-size:18px;">@echo off
rem This script is mean to be executed from the root folder of this project as: `build\build_windows.bat`
rem =====================================================================================================================================================
rem DOWNLOAD BOOST BINARIES THAT MATCH YOUR VISUAL STUDIO VERSION
rem =====================================================================================================================================================
rem WARNING: Stay away from boost 1.56, 1.57, networking functions will cause a periodic freezing with libtorrent.
rem You will need Visual Studio 2013.
rem Use the "VS2013 x86 Native Tools Command Prompt"
rem 1. Download boost_1_58 source code
rem 2. Extract it in "c:\boost_1_58_0"
rem 2. invoke bootstrap.bat to have bjam working, you will need it to build libtorrent
rem To build (1.58)
rem %BOOST_ROOT%\b2 cxxflags="/O2 /DBOOST_ASIO_DISABLE_CONNECTEX=1" variant=release link=static runtime-link=static --stagedir=windows stage --without-context --without-coroutine --without-python --without-mpi --without-wave --without-test --without-graph --without-graph_parallel --without-iostreams --without-math
rem =====================================================================================================================================================
rem BUILDING LIBTORRENT
rem =====================================================================================================================================================
rem Download a libtorrent subversion "braches/RC_1_0/" snapshot from http://sourceforge.net/p/libtorrent/code/HEAD/tree/trunk/
rem set BOOST_ROOT=C:\boost_1_58_0
rem %BOOST_ROOT%\bjam toolset=msvc cxxflags="/O2 /DBOOST_ASIO_DISABLE_CONNECTEX=1" variant=release link=static runtime-link=static deprecated-functions=off logging=none encryption=openssl boost=source
rem =====================================================================================================================================================
rem BUILD OPTIONS AND VARIABLES (adjust paths depending on your build environment)
rem =====================================================================================================================================================
echo on
set CXXFLAGS=/MT /O2 /fp:fast /nologo /DWIN32 /EHsc /c /DBOOST_ASIO_DISABLE_CONNECTEX=1 /DNDEBUG=1 /DBOOST_ASIO_SEPARATE_COMPILATION=1 /DTORRENT_DISABLE_GEO_IP=1 /DTORRENT_NO_DEPRECATE=1 /DTORRENT_USE_OPENSSL=1
set BOOST_ROOT=C:\boost_1_55_0
set LIBTORRENT_ROOT=C:\libtorrent-RC_1_0
set JAVA_HOME=C:\Program Files (x86)\Java\jdk1.8.0_25
set VS_VERSION=12
set VS_ROOT=C:\Program Files (x86)\Microsoft Visual Studio %VS_VERSION%.0
set VS_INCLUDE=/I"%VS_ROOT%\VC\include"
set BOOST_INCLUDE=/I"%BOOST_ROOT%"
set JAVA_INCLUDES=/I"%JAVA_HOME%\include" /I"%JAVA_HOME%\include\win32"
set LIBTORRENT_INCLUDE=/I"%LIBTORRENT_ROOT%\include"
set INCLUDE_PATHS=%VS_INCLUDE% %BOOST_INCLUDE% %LIBTORRENT_INCLUDE% %JAVA_INCLUDES%
set BOOST_LIBPATH=%BOOST_ROOT%\lib32-msvc-12.0
set LIBTORRENT_LIBPATH=%LIBTORRENT_ROOT%\bin\msvc-%VS_VERSION%.0\release\boost-source\deprecated-functions-off\encryption-openssl\link-static\runtime-link-static\threading-multi
set VS_LIBPATH=%VS_ROOT%\VC\lib
@echo off
rem =====================================================================================================================================================
rem LINK OPTIONS AND VARIABLES
rem =====================================================================================================================================================
rem (If you have cygwin/bin on your PATH, you must remove it from the PATH,
rem otherwise link.exe will be GNU's link and it's not compatible with the options passed below.
echo on
set LIBS=user32.lib gdi32.lib advapi32.lib libtorrent.lib libeay32MT.lib ssleay32MT.lib
set LOPT=/RELEASE /NOLOGO /MACHINE:X86 /ENTRY:_DllMainCRTStartup@12 /DLL
set LIB_PATHS=/LIBPATH:%BOOST_LIBPATH% /LIBPATH:%LIBTORRENT_LIBPATH% /LIBPATH:"%VS_LIBPATH%"
cl %CXXFLAGS% %INCLUDE_PATHS% swig\libtorrent_jni.cpp
link %LOPT% %LIB_PATHS% /OUT:jlibtorrent.dll %LIBS% libtorrent_jni.obj
copy jlibtorrent.dll binaries\windows\x86\</span>将其地址改成相应的自己安装的地址；执行此脚本，即可得到jlibtorrent.dll.、
注：编译过程中极有可能处于LNK error 2019，此类错误一般是库文件的依赖找不到产生的，我遇到的错误是：
<span style="font-size:18px;"> 正在创建库 jlibtorrent.lib 和对象 jlibtorrent.exp
libtorrent.lib(asio_ssl.obj) : error LNK2019: 无法解析的外部符号 "long __cdecl S
SL_CTX_clear_options(struct ssl_ctx_st *,long)" (?SSL_CTX_clear_options@@YAJPAUs
sl_ctx_st@@J@Z)，该符号在函数 "public: class boost::system::error_code __thiscal
l boost::asio::ssl::context::clear_options(long,class boost::system::error_code
&)" (?clear_options@context@ssl@asio@boost@@QAE?AVerror_code@system@4@JAAV564@@Z
) 中被引用</span>根据错误中提示的clear_options函数定位到引起错误的boost库文件context.ipp(在boost库中/boost/asio/ssl/impl文件夹中），我修改错误的方法是注释掉此函数的实现，以及context.hpp中的声明；重新编译boost库，在依据这个boost库编译libtorrent库，再将这两个库用于jlibtorrent.dll的编译。错误消失，成功得到jlibtorrent.dll;
用这个jlibtorrent.dll库替代frostwire-desktop-master中的jlibtorrent.dll;并把此动态库拷贝到win32目录下，eclipse中运行frostwire，成功！
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