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# XML Stream Lint Example

Files:

- xml/xmlstreamlint/main.cpp

The XML Stream Lint example provides a simple command line utility that accepts a file name as its single argument and writes it to the standard output file.

The specified file is parsed using an QXmlStreamReader object and written to the standard output file using an QXmlStreamWriter object. If the file does not contain a well-formed XML document or the use of namespaces in the document is incorrect, a description of the error is printed to the standard error file and will appear in the console.

## Basic Operation

The main function of the example opens the file specified by the user for input (`inputFile`), and it uses QFile to access the standard output file.

Reading XML is handled by an instance of the QXmlStreamReader class, which operates on the input file object; writing is handled by an instance of QXmlStreamWriter operating on the output file object:

     #include <QXmlStreamReader>

     /*!
      \short This class exists for the solve purpose of creating a translation context.
      */
     class XmlStreamLint
     {
     public:
         Q_DECLARE_TR_FUNCTIONS(XmlStreamLint);
     };

     int main(int argc, char *argv[])
     {
         enum ExitCode
         {
             Success,
             ParseFailure,
             ArgumentError,
             WriteError,
             FileFailure
         };

         QCoreApplication app(argc, argv);

         QTextStream errorStream(stderr);

         if (argc != 2)
         {
             errorStream << XmlStreamLint::tr(
                            "Usage: xmlstreamlint <path to XML file>\n");
             return ArgumentError;
         }

         QString inputFilePath(QCoreApplication::arguments().at(1));
         QFile inputFile(inputFilePath);

         if (!QFile::exists(inputFilePath))
         {
             errorStream << XmlStreamLint::tr(
                            "File %1 does not exist.\n").arg(inputFilePath);
             return FileFailure;

         } else if (!inputFile.open(QIODevice::ReadOnly)) {
             errorStream << XmlStreamLint::tr(
                            "Failed to open file %1.\n").arg(inputFilePath);
             return FileFailure;
         }

         QFile outputFile;
         if (!outputFile.open(stdout, QIODevice::WriteOnly))
         {
             errorStream << XmlStreamLint::tr("Failed to open stdout.");
             return WriteError;
         }

         QXmlStreamReader reader(&inputFile);
         QXmlStreamWriter writer(&outputFile);

The work of parsing and rewriting the XML is done in a while loop, and is driven by input from the reader:

         while (!reader.atEnd())
         {
             reader.readNext();

             if (reader.error())
             {
                 errorStream << XmlStreamLint::tr(
                                "Error: %1 in file %2 at line %3, column %4.\n").arg(
                                    reader.errorString(), inputFilePath,
                                    QString::number(reader.lineNumber()),
                                    QString::number(reader.columnNumber()));
                 return ParseFailure;

If more input is available, the next token from the input file is read and parsed. If an error occurred, information is written to the standard error file via a stream, and the example exits by returning a non-zero value from the main function.

             } else
                 writer.writeCurrentToken(reader);
         }

         return Success;
     }

For valid input, the writer is fed the current token from the reader, and this is written to the output file that was specified when it was constructed.

When there is no more input, the loop terminates, and the example can exit successfully.