// load an earth file, and support all or our example command-line options// and earth file <external> tags    osg::Node* node = MapNodeHelper().load(arguments, &viewer);

  1 ReaderWriter::ReadResult Registry::read(const ReadFunctor& readFunctor)
  2 {
  　　　　　　　　　　　　　......关于osga和zip文件的
 52     // first attempt to load the file from existing ReaderWriter's第一次尝试从现有ReaderWriter的加载文件
 53     AvailableReaderWriterIterator itr(_rwList, _pluginMutex);
 54     for(;itr.valid();++itr)
 55     {
 56         ReaderWriter::ReadResult rr = readFunctor.doRead(*itr);
 57         if (readFunctor.isValid(rr))
 58             return rr;
 59         else results.push_back(rr);
 60     }
 61
 62     // check loaded archives.检查加载的档案
 63     AvailableArchiveIterator aaitr(_archiveCache, _archiveCacheMutex);
 64     for(;aaitr.valid();++aaitr)
 65     {
 66         ReaderWriter::ReadResult rr = readFunctor.doRead(*aaitr);
 67         if (readFunctor.isValid(rr))
 68             return rr;
 69         else
 70         {
 71             // don't pass on FILE_NOT_FOUND results as we don't want to prevent non archive plugins that haven't been
 72             // loaded yet from getting a chance to test for the presence of the file.
 73             if (rr.status()!=ReaderWriter::ReadResult::FILE_NOT_FOUND) results.push_back(rr);
 74         }
 75     }
 76
 77     // now look for a plug-in to load the file.现在寻找一个插件加载文件!!!
 78     std::string libraryName = createLibraryNameForFile(readFunctor._filename);
 79     if (loadLibrary(libraryName)!=NOT_LOADED)
 80     {
 81         for(;itr.valid();++itr)
 82         {
 83             ReaderWriter::ReadResult rr = readFunctor.doRead(*itr);
 84             if (readFunctor.isValid(rr))
 85                 return rr;
 86             else results.push_back(rr);
 87         }
 88     }
 89
 90     //If the filename contains a server address and wasn't loaded by any of the plugins, try to find a plugin which supports the server
 91     //protocol and supports wildcards. If not successfully use curl as a last fallback
 92     if (containsServerAddress(readFunctor._filename))
 93     {
 94         ReaderWriter* rw = getReaderWriterForProtocolAndExtension(
 95             osgDB::getServerProtocol(readFunctor._filename),
 96             osgDB::getFileExtension(readFunctor._filename)
 97         );
 98
 99         if (rw)
100         {
101             return readFunctor.doRead(*rw);
102         }
103         else
104         {
105             return  ReaderWriter::ReadResult("Warning: Could not find the .curl plugin to read from server.");
106         }
107     }
108
109     if (results.empty())
110     {
111         return ReaderWriter::ReadResult("Warning: Could not find plugin to read objects from file \""+readFunctor._filename+"\".");
112     }
113
114     // sort the results so the most relevant (i.e. ERROR_IN_READING_FILE is more relevant than FILE_NOT_FOUND) results get placed at the end of the results list.
115     std::sort(results.begin(), results.end());
116     ReaderWriter::ReadResult result = results.back();
117
118     if (result.message().empty())
119     {
120         switch(result.status())
121         {
122             case(ReaderWriter::ReadResult::FILE_NOT_HANDLED): result.message() = "Warning: reading \""+readFunctor._filename+"\" not supported."; break;
123             case(ReaderWriter::ReadResult::FILE_NOT_FOUND): result.message() = "Warning: could not find file \""+readFunctor._filename+"\"."; break;
124             case(ReaderWriter::ReadResult::ERROR_IN_READING_FILE): result.message() = "Warning: Error in reading to \""+readFunctor._filename+"\"."; break;
125             default: break;
126         }
127     }
128
129     return result;
130 }