segui il caricamento in corso di enormi file XML

Question

Provo a seguire lo stato di caricamento dei grandi file XML (non sono il fornitore di questi file) in dotnet (C#, framework 3.5 SP1): da 1 MB a 300 MB su un condivisione di file di rete.

Io uso un XmlReader per il caricamento scopo invece del metodo diretto XmlDocument.Load per accelerare il processo di caricamento.

Tra l'altro non ho trovato da nessuna parte su Internet/documento su come seguire questo progresso di caricamento: nessun delegato/evento sembra esistere. C'è un modo per eseguire questa attività? Avere il tipo di funzione per scopi di salvataggio XML potrebbe essere un piacere avere.

Grazie

Answer 1

Supponendo che si sta leggendo da un ruscello qui è un (non perfetta) esempio di come farlo ... Fondamentalmente ProgressStreamWrapper avvolge il flusso di file e genera un evento ogni volta che viene cambiata la posizione.

class Program 
{ 
    static void Main(string[] args) 
    { 
     Console.WriteLine("Reading big file..."); 

     FileStream fileStream = File.OpenRead("c:\\temp\\bigfile.xml"); 
     ProgressStreamWrapper progressStreamWrapper = new ProgressStreamWrapper(fileStream); 
     progressStreamWrapper.PositionChanged += (o, ea) => Console.WriteLine((double) progressStreamWrapper.Position/progressStreamWrapper.Length * 100 + "% complete"); 
     XmlReader xmlReader = XmlReader.Create(progressStreamWrapper); 

     while (xmlReader.Read()) 
     { 
      //read the xml document 
     } 

     Console.WriteLine("DONE"); 
     Console.ReadLine(); 
    } 
} 


public class ProgressStreamWrapper : Stream, IDisposable 
{ 
    public ProgressStreamWrapper(Stream innerStream) 
    { 
     InnerStream = innerStream; 
    } 

    public Stream InnerStream { get; private set; } 

    public override void Close() 
    { 
     InnerStream.Close(); 
    } 

    void IDisposable.Dispose() 
    { 
     base.Dispose(); 
     InnerStream.Dispose(); 
    } 

    public override void Flush() 
    { 
     InnerStream.Flush(); 
    } 

    public override IAsyncResult BeginRead(byte[] buffer, int offset, int count, AsyncCallback callback, object state) 
    { 
     return InnerStream.BeginRead(buffer, offset, count, callback, state); 
    } 

    public override int EndRead(IAsyncResult asyncResult) 
    { 
     int endRead = InnerStream.EndRead(asyncResult); 
     OnPositionChanged(); 
     return endRead; 
    } 

    public override IAsyncResult BeginWrite(byte[] buffer, int offset, int count, AsyncCallback callback, object state) 
    { 
     return InnerStream.BeginWrite(buffer, offset, count, callback, state); 
    } 

    public override void EndWrite(IAsyncResult asyncResult) 
    { 
     InnerStream.EndWrite(asyncResult); 
     OnPositionChanged(); ; 
    } 

    public override long Seek(long offset, SeekOrigin origin) 
    { 
     long seek = InnerStream.Seek(offset, origin); 
     OnPositionChanged(); 
     return seek; 
    } 

    public override void SetLength(long value) 
    { 
     InnerStream.SetLength(value); 
    } 

    public override int Read(byte[] buffer, int offset, int count) 
    { 
     int read = InnerStream.Read(buffer, offset, count); 
     OnPositionChanged(); 
     return read; 
    } 

    public override int ReadByte() 
    { 
     int readByte = InnerStream.ReadByte(); 
     OnPositionChanged(); 
     return readByte; 
    } 

    public override void Write(byte[] buffer, int offset, int count) 
    { 
     InnerStream.Write(buffer, offset, count); 
     OnPositionChanged(); 
    } 

    public override void WriteByte(byte value) 
    { 
     InnerStream.WriteByte(value); 
     OnPositionChanged(); 
    } 

    public override bool CanRead 
    { 
     get { return InnerStream.CanRead; } 
    } 

    public override bool CanSeek 
    { 
     get { return InnerStream.CanSeek; } 
    } 

    public override bool CanTimeout 
    { 
     get { return InnerStream.CanTimeout; } 
    } 

    public override bool CanWrite 
    { 
     get { return InnerStream.CanWrite; } 
    } 

    public override long Length 
    { 
     get { return InnerStream.Length; } 
    } 

    public override long Position 
    { 
     get { return InnerStream.Position; } 
     set 
     { 
      InnerStream.Position = value; 
      OnPositionChanged(); 
     } 
    } 

    public event EventHandler PositionChanged; 

    protected virtual void OnPositionChanged() 
    { 
     if (PositionChanged != null) 
     { 
      PositionChanged(this, EventArgs.Empty); 
     } 
    } 

    public override int ReadTimeout 
    { 
     get { return InnerStream.ReadTimeout; } 
     set { InnerStream.ReadTimeout = value; } 
    } 

    public override int WriteTimeout 
    { 
     get { return InnerStream.WriteTimeout; } 
     set { InnerStream.WriteTimeout = value; } 
    } 
} 

Answer 2

Come utilizzare DataSet.Read()?

o,

// Create the document. 
     XmlDocument doc = new XmlDocument(); 
     doc.Load(file); 

     // Loop through all the nodes, and create the list of Product objects . 
     List<Product> products = new List<Product>(); 

     foreach (XmlElement element in doc.DocumentElement.ChildNodes) 
     { 
      Product newProduct = new Product(); 
      newProduct.ID = Int32.Parse(element.GetAttribute("ID")); 
      newProduct.Name = element.GetAttribute("Name"); 

      // If there were more than one child node, you would probably use 
      // another For Each loop here and move through the 
      // Element.ChildNodes collection. 
      newProduct.Price = Decimal.Parse(element.ChildNodes[0].InnerText); 

      products.Add(newProduct); 
     } 

Answer 3

Con le pale incorporati non c'è molto; potresti comunque scrivere uno stream di intercettazione, caricare il tuo documento da questo stream ed esporre lo Position tramite eventi? Ad esempio, genera un evento nel metodo Read (a intervalli)?

---

Ecco un esempio che supporta gli aggiornamenti sia in fase di lettura e scrittura:

using System; 
using System.IO; 
using System.Xml; 
class ChattyStream : Stream 
{ 
    private Stream baseStream; 
    public ChattyStream(Stream baseStream) 
    { 
     if (baseStream == null) throw new ArgumentNullException("baseStream"); 
     this.baseStream = baseStream; 
     updateInterval = 1000; 
    } 
    public event EventHandler ProgressChanged; 
    protected virtual void OnProgressChanged() 
    { 
     var handler = ProgressChanged; 
     if (handler != null) handler(this, EventArgs.Empty); 
    } 
    private void CheckDisposed() 
    { 
     if (baseStream == null) throw new ObjectDisposedException(GetType().Name); 
    } 
    protected Stream BaseStream 
    { 
     get { CheckDisposed(); return baseStream; } 
    } 
    int pos, updateInterval; 
    public int UpdateInterval 
    { 
     get { return updateInterval; } 
     set 
     { 
      if (value <= 0) throw new ArgumentOutOfRangeException("value"); 
      updateInterval = value; 
     } 
    } 

    protected void Increment(int value) 
    { 
     if (value > 0) 
     { 
      pos += value; 
      if (pos >= updateInterval) 
      { 
       OnProgressChanged(); 
       pos = pos % updateInterval; 
      } 
     } 
    } 
    public override int Read(byte[] buffer, int offset, int count) 
    { 
     int result = BaseStream.Read(buffer, offset, count); 
     Increment(result); 
     return result; 
    } 
    public override void Write(byte[] buffer, int offset, int count) 
    { 
     BaseStream.Write(buffer, offset, count); 
     Increment(count); 
    } 
    public override void SetLength(long value) 
    { 
     BaseStream.SetLength(value); 
    } 
    public override void Flush() 
    { 
     BaseStream.Flush(); 
    } 
    public override long Position 
    { 
     get { return BaseStream.Position; } 
     set { BaseStream.Position = value; } 
    } 
    public override long Seek(long offset, SeekOrigin origin) 
    { 
     return BaseStream.Seek(offset, origin); 
    } 
    public override long Length 
    { 
     get { return BaseStream.Length; } 
    } 
    public override bool CanWrite 
    { 
     get { return BaseStream.CanWrite; } 
    } 
    public override bool CanRead 
    { 
     get { return BaseStream.CanRead; } 
    } 
    public override bool CanSeek 
    { 
     get { return BaseStream.CanSeek; } 
    } 
    protected override void Dispose(bool disposing) 
    { 
     if (disposing && baseStream != null) 
     { 
      baseStream.Dispose(); 
     } 
     baseStream = null; 
     base.Dispose(disposing); 
    } 
    public override void Close() 
    { 
     if (baseStream != null) baseStream.Close(); 
     base.Close(); 
    } 
    public override int ReadByte() 
    { 
     int val = BaseStream.ReadByte(); 
     if (val >= 0) Increment(1); 
     return val; 
    } 
    public override void WriteByte(byte value) 
    { 
     BaseStream.WriteByte(value); 
     Increment(1); 
    } 

} 
static class Program 
{ 
    static void Main() 
    { 
     /* invent some big data */ 
     const string path = "bigfile"; 
     if (File.Exists(path)) File.Delete(path); 
     using (var chatty = new ChattyStream(File.Create(path))) 
     { 
      chatty.ProgressChanged += delegate 
      { 
       Console.WriteLine("Writing: " + chatty.Position); 
      }; 
      using (var writer = XmlWriter.Create(chatty)) 
      { 
       writer.WriteStartDocument(); 
       writer.WriteStartElement("xml"); 
       for (int i = 0; i < 50000; i++) 
       { 
        writer.WriteElementString("add", i.ToString()); 
       } 
       writer.WriteEndElement(); 
       writer.WriteEndDocument(); 
      } 
      chatty.Close(); 
     } 


     /* read it */ 

     using (var chatty = new ChattyStream(File.OpenRead("bigfile"))) 
     { 
      chatty.ProgressChanged += delegate 
      { 
       Console.WriteLine("Reading: " + chatty.Position); 
      }; 

      // now read "chatty" with **any** API; XmlReader, XmlDocument, XDocument, etc 
      XmlDocument doc = new XmlDocument(); 
      doc.Load(chatty); 
     } 
    } 
}