MediaInfo源代码分析 3：Open()函数

我们来看一下MediaInfo中的Open()函数的内部调用过程

首先open函数封装了MediaInfo_Internal类中的open()函数

//打开文件

size_t MediaInfo::Open(const String &File_Name_)

{

	//封装了一层

    return Internal->Open(File_Name_);

}

查看一下MediaInfo_Internal类中的open()函数的源代码：

//打开文件

size_t MediaInfo_Internal::Open(const String &File_Name_)

{

    Close();



    CS.Enter();

    MEDIAINFO_DEBUG_CONFIG_TEXT(Debug+=__T("Open, File=");Debug+=Ztring(File_Name_).c_str();)

    //清空文件列表

		Config.File_Names.clear();

    if (Config.File_FileNameFormat_Get()==__T("CSV"))

    {

        Config.File_Names.Separator_Set(0, __T(","));

        Config.File_Names.Write(File_Name_);

    }

	//添加文件名到文件名列表

    else if (!File_Name_.empty())

        Config.File_Names.push_back(File_Name_);

    if (Config.File_Names.empty())

    {

        CS.Leave();

        return 0;

    }

    Config.File_Names_Pos=1;

    CS.Leave();



    //Parsing

	//解析

    if (BlockMethod==1)

    {

        if (!IsInThread) //If already created, the routine will read the new files

        {

            Run();

            IsInThread=true;

        }

        return 0;

    }

    else

    {

        Entry(); //Normal parsing

        return Count_Get(Stream_General);

    }

}

在打开之前首先调用Close()进行清理，将文件路径添加到一个列表（实际上是一个Vector）中，调用Entry()进行解析。

查看一下Entry()函数的源代码：

//解析函数

void MediaInfo_Internal::Entry()

{

    CS.Enter();

    MEDIAINFO_DEBUG_CONFIG_TEXT(Debug+=__T("Entry");)

    Config.State_Set(0);

    CS.Leave();

	//解析文件名（是否包含MMS？）

	//需要libmms

    if ((Config.File_Names[0].size()>=6

        && Config.File_Names[0][0]==__T('m')

        && Config.File_Names[0][1]==__T('m')

        && Config.File_Names[0][2]==__T('s')

        && Config.File_Names[0][3]==__T(':')

        && Config.File_Names[0][4]==__T('/')

        && Config.File_Names[0][5]==__T('/'))

        || (Config.File_Names[0].size()>=7

        && Config.File_Names[0][0]==__T('m')

        && Config.File_Names[0][1]==__T('m')

        && Config.File_Names[0][2]==__T('s')

        && Config.File_Names[0][3]==__T('h')

        && Config.File_Names[0][4]==__T(':')

        && Config.File_Names[0][5]==__T('/')

        && Config.File_Names[0][6]==__T('/')))

        #if defined(MEDIAINFO_LIBMMS_YES)

            Reader_libmms().Format_Test(this, Config.File_Names[0]);

        #else //MEDIAINFO_LIBMMS_YES

            {

            #if MEDIAINFO_EVENTS

                struct MediaInfo_Event_Log_0 Event;

                Event.EventCode=MediaInfo_EventCode_Create(MediaInfo_Parser_None, MediaInfo_Event_Log, 0);

                Event.Type=0xC0;

                Event.Severity=0xFF;

                Event.MessageCode=0;

                Event.MessageStringU=L"Libmms cupport is disabled due to compilation options";

                Event.MessageStringA="Libmms cupport is disabled due to compilation options";

                MediaInfoLib::Config.Event_Send((const int8u*)&Event, sizeof(MediaInfo_Event_Log_0));

            #endif //MEDIAINFO_EVENTS

            }

        #endif //MEDIAINFO_LIBMMS_YES

	//是否包含网络协议？（标记为://）

	//需要使用libcurl - the multiprotocol file transfer library

    else if (Config.File_Names[0].find(__T("://"))!=string::npos)

        #if defined(MEDIAINFO_LIBCURL_YES)

        {

            CS.Enter();

            if (Reader)

            {

                CS.Leave();

                return; //There is a problem

            }

            Reader=new Reader_libcurl();

            CS.Leave();



            Reader->Format_Test(this, Config.File_Names[0]);



            #if MEDIAINFO_NEXTPACKET

                if (Config.NextPacket_Get())

                    return;

            #endif //MEDIAINFO_NEXTPACKET

        }

        #else //MEDIAINFO_LIBCURL_YES

            {

            #if MEDIAINFO_EVENTS

                struct MediaInfo_Event_Log_0 Event;

                Event.EventCode=MediaInfo_EventCode_Create(MediaInfo_Parser_None, MediaInfo_Event_Log, 0);

                Event.Type=0xC0;

                Event.Severity=0xFF;

                Event.MessageCode=0;

                Event.MessageStringU=L"Libcurl support is disabled due to compilation options";

                Event.MessageStringA="Libcurl support is disabled due to compilation options";

                MediaInfoLib::Config.Event_Send((const int8u*)&Event, sizeof(MediaInfo_Event_Log_0));

            #endif //MEDIAINFO_EVENTS

            }

        #endif //MEDIAINFO_LIBCURL_YES



    #if defined(MEDIAINFO_DIRECTORY_YES)

        else if (Dir::Exists(Config.File_Names[0]))

            Reader_Directory().Format_Test(this, Config.File_Names[0]);

    #endif //MEDIAINFO_DIRECTORY_YES

	//是普通文件，并且文件存在

    #if defined(MEDIAINFO_FILE_YES)

        else if (File::Exists(Config.File_Names[0]))

        {

            #if defined(MEDIAINFO_REFERENCES_YES)

                string Dxw;

                if (Config.File_CheckSideCarFiles_Get() && !Config.File_IsReferenced_Get())

                {

					//Zenlib中竟然包含专用于文件名操作的类！

                    FileName Test(Config.File_Names[0]);

					//获得小写的文件名后缀

                    Ztring FileExtension=Test.Extension_Get();

                    FileExtension.MakeLowerCase();

					//逐个比较（这些都是文本文件的后缀）

                    if (FileExtension!=__T("dfxp"))

                    {

                        Test.Extension_Set(__T("dfxp"));

                        if (File::Exists(Test))

                            Dxw+=" <clip file=\""+Test.Name_Get().To_UTF8()+".dfxp\" />\r\n";

                    }

                    if (FileExtension!=__T("sami"))

                    {

                        Test.Extension_Set(__T("sami"));

                        if (File::Exists(Test))

                            Dxw+=" <clip file=\""+Test.Name_Get().To_UTF8()+".sami\" />\r\n";

                    }

                    if (FileExtension!=__T("sc2"))

                    {

                        Test.Extension_Set(__T("sc2"));

                        if (File::Exists(Test))

                            Dxw+=" <clip file=\""+Test.Name_Get().To_UTF8()+".sc2\" />\r\n";

                    }

                    if (FileExtension!=__T("scc"))

                    {

                        Test.Extension_Set(__T("scc"));

                        if (File::Exists(Test))

                            Dxw+=" <clip file=\""+Test.Name_Get().To_UTF8()+".scc\" />\r\n";

                    }

                    if (FileExtension!=__T("smi"))

                    {

                        Test.Extension_Set(__T("smi"));

                        if (File::Exists(Test))

                            Dxw+=" <clip file=\""+Test.Name_Get().To_UTF8()+".smi\" />\r\n";

                    }

					//字幕

                    if (FileExtension!=__T("srt"))

                    {

                        Test.Extension_Set(__T("srt"));

                        if (File::Exists(Test))

                            Dxw+=" <clip file=\""+Test.Name_Get().To_UTF8()+".srt\" />\r\n";

                    }

                    if (FileExtension!=__T("stl"))

                    {

                        Test.Extension_Set(__T("stl"));

                        if (File::Exists(Test))

                            Dxw+=" <clip file=\""+Test.Name_Get().To_UTF8()+".stl\" />\r\n";

                    }



                    Ztring Name=Test.Name_Get();

                    Ztring BaseName=Name.SubString(Ztring(), __T("_"));

                    if (!BaseName.empty())

                    {

                        ZtringList List;

                        List+=Dir::GetAllFileNames(Test.Path_Get()+PathSeparator+BaseName+__T("_*_audio.mp4"), Dir::Include_Files);

                        List+=Dir::GetAllFileNames(Test.Path_Get()+PathSeparator+BaseName+__T("_*_sub.dfxp"), Dir::Include_Files);

                        List+=Dir::GetAllFileNames(Test.Path_Get()+PathSeparator+BaseName+__T("_*_sub.sami"), Dir::Include_Files);

                        List+=Dir::GetAllFileNames(Test.Path_Get()+PathSeparator+BaseName+__T("_*_sub.sc2"), Dir::Include_Files);

                        List+=Dir::GetAllFileNames(Test.Path_Get()+PathSeparator+BaseName+__T("_*_sub.scc"), Dir::Include_Files);

                        List+=Dir::GetAllFileNames(Test.Path_Get()+PathSeparator+BaseName+__T("_*_sub.smi"), Dir::Include_Files);

                        List+=Dir::GetAllFileNames(Test.Path_Get()+PathSeparator+BaseName+__T("_*_sub.srt"), Dir::Include_Files);

                        List+=Dir::GetAllFileNames(Test.Path_Get()+PathSeparator+BaseName+__T("_*_sub.stl"), Dir::Include_Files);

                        List+=Dir::GetAllFileNames(Test.Path_Get()+PathSeparator+BaseName+__T("_*_forcesub.dfxp"), Dir::Include_Files);

                        List+=Dir::GetAllFileNames(Test.Path_Get()+PathSeparator+BaseName+__T("_*_forcesub.sami"), Dir::Include_Files);

                        List+=Dir::GetAllFileNames(Test.Path_Get()+PathSeparator+BaseName+__T("_*_forcesub.sc2"), Dir::Include_Files);

                        List+=Dir::GetAllFileNames(Test.Path_Get()+PathSeparator+BaseName+__T("_*_forcesub.scc"), Dir::Include_Files);

                        List+=Dir::GetAllFileNames(Test.Path_Get()+PathSeparator+BaseName+__T("_*_forcesub.smi"), Dir::Include_Files);

                        List+=Dir::GetAllFileNames(Test.Path_Get()+PathSeparator+BaseName+__T("_*_forcesub.srt"), Dir::Include_Files);

                        List+=Dir::GetAllFileNames(Test.Path_Get()+PathSeparator+BaseName+__T("_*_forcesub.stl"), Dir::Include_Files);

                        List+=Dir::GetAllFileNames(Test.Path_Get()+PathSeparator+BaseName+__T("_*_cc.dfxp"), Dir::Include_Files);

                        List+=Dir::GetAllFileNames(Test.Path_Get()+PathSeparator+BaseName+__T("_*_cc.sami"), Dir::Include_Files);

                        List+=Dir::GetAllFileNames(Test.Path_Get()+PathSeparator+BaseName+__T("_*_cc.sc2"), Dir::Include_Files);

                        List+=Dir::GetAllFileNames(Test.Path_Get()+PathSeparator+BaseName+__T("_*_cc.scc"), Dir::Include_Files);

                        List+=Dir::GetAllFileNames(Test.Path_Get()+PathSeparator+BaseName+__T("_*_cc.smi"), Dir::Include_Files);

                        List+=Dir::GetAllFileNames(Test.Path_Get()+PathSeparator+BaseName+__T("_*_cc.srt"), Dir::Include_Files);

                        List+=Dir::GetAllFileNames(Test.Path_Get()+PathSeparator+BaseName+__T("_*_cc.stl"), Dir::Include_Files);

                        for (size_t Pos=0; Pos<List.size(); Pos++)

                            Dxw+=" <clip file=\""+List[Pos].To_UTF8()+"\" />\r\n";

                    }



                    if (!Dxw.empty())

                    {

                        Dxw.insert(0, "<?xml version=\"1.0\" encoding=\"UTF-8\" ?>\r\n"

                                "<indexFile xmlns=\"urn:digimetrics-xml-wrapper\" xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xsi:schemaLocation=\"urn:digimetrics-xml-wrapper DMSCLIP.XSD\">\r\n"

                                " <clip source=\"main\" file=\""+FileName(Config.File_Names[0]).Name_Get().To_UTF8()+"."+FileName(Config.File_Names[0]).Extension_Get().To_UTF8()+"\" />\r\n");

                        Dxw.append("</indexFile>\r\n");

                        Config.File_FileNameFormat_Set(__T("Dxw"));

                    }

                }

				//为空

                if (Dxw.empty())

                {

                    CS.Enter();

                    if (Reader)

                    {

                        CS.Leave();

                        return; //There is a problem

                    }

                    Reader=new Reader_File();

                    CS.Leave();

					//测试格式

                    Reader->Format_Test(this, Config.File_Names[0]);

                }

                else

                {

					//初始化Buffer

                    Open_Buffer_Init(Dxw.size(), FileName(Config.File_Names[0]).Path_Get()+PathSeparator+FileName(Config.File_Names[0]).Name_Get());

                    Open_Buffer_Continue((const int8u*)Dxw.c_str(), Dxw.size());

                    Open_Buffer_Finalize();

                }

            #else //defined(MEDIAINFO_REFERENCES_YES)

                CS.Enter();

                if (Reader)

                {

                    CS.Leave();

                    return; //There is a problem

                }

                Reader=new Reader_File();

                CS.Leave();



                Reader->Format_Test(this, Config.File_Names[0]);

            #endif //defined(MEDIAINFO_REFERENCES_YES)



            #if MEDIAINFO_NEXTPACKET

                if (Config.NextPacket_Get())

                    return;

            #endif //MEDIAINFO_NEXTPACKET

        }

    #endif //MEDIAINFO_FILE_YES



    CS.Enter();

    Config.State_Set(1);

    CS.Leave();

}

我们可以看出，MediaInfo支持流媒体协议作为输入源（例如mms），但前提是要使用相应的库（libmms，或者libcurl）。它会首先查找文件路径中有没有“://”，判断是否是流媒体输入。

大多数情况下，我们使用本地文件路径作为输入源。这是我们就进入了代码中“#if defined(MEDIAINFO_FILE_YES) "部分下面的代码。具体每块代码的左右都写在代码注释中了，不再细说。最后使用 Reader_File的Format_Test()测试输入文件的格式。

看一下Reader_File的Format_Test()的源代码：

//用于测试文件格式

size_t Reader_File::Format_Test(MediaInfo_Internal* MI, String File_Name)

{

    //std::cout<<Ztring(File_Name).To_Local().c_str()<<std::endl;

	

    //With Parser MultipleParsing

    /*

    MI->Open_Buffer_Init((int64u)-1, File_Name);

    if (Format_Test_PerParser(MI, File_Name))

         return 1;

    return 0; //There is a problem

    */



    //Get the Extension

	//文件后缀

    Ztring Extension=FileName::Extension_Get(File_Name);

    Extension.MakeLowerCase();



    //Search the theorical format from extension

    InfoMap &FormatList=MediaInfoLib::Config.Format_Get();

    InfoMap::iterator Format=FormatList.end();

    if (!MI->Config.File_ForceParser_Get().empty())

        Format=FormatList.find(MI->Config.File_ForceParser_Get());

    if (Format==FormatList.end())

    {

        Format=FormatList.begin();

        while (Format!=FormatList.end())

        {

            const Ztring &Extensions=FormatList.Get(Format->first, InfoFormat_Extensions);

            if (Extensions.find(Extension)!=Error)

            {

                if(Extension.size()==Extensions.size())

                    break; //Only one extenion in the list

                if(Extensions.find(Extension+__T(" "))!=Error

                || Extensions.find(__T(" ")+Extension)!=Error)

                    break;

            }

            ++Format;

        }

    }

    if (Format!=FormatList.end())

    {

        const Ztring &Parser=Format->second(InfoFormat_Parser);

        if (MI->SelectFromExtension(Parser))

        {

            //Test the theorical format

            if (Format_Test_PerParser(MI, File_Name)>0)

                 return 1;

        }

    }

	//遍历所有支持格式，测试格式

    size_t ToReturn=MI->ListFormats(File_Name);

    return ToReturn;

}

可以看出，最后遍历了所有支持的格式，试图找出合适的格式。

 

至此Open()函数的分析完毕。