BinaryReader.ReadDouble Méthode

Définition

Espace de noms:

System.IO

Assembly:

System.Runtime.dll

Source:

BinaryReader.cs

Lit une valeur à virgule flottante de 8 octets dans le flux actuel et avance la position actuelle du flux de huit octets.

public:
 virtual double ReadDouble();

public virtual double ReadDouble ();

abstract member ReadDouble : unit -> double
override this.ReadDouble : unit -> double

Public Overridable Function ReadDouble () As Double

Retours

Double

Valeur à virgule flottante de 8 octets lue dans le flux actuel.

Exceptions

EndOfStreamException

La fin du flux est atteinte.

ObjectDisposedException

Le flux est fermé.

IOException

Une erreur d'E/S s'est produite.

Exemples

L’exemple de code suivant montre comment lire et écrire Double des données en mémoire à l’aide des BinaryReader classes et BinaryWriter au-dessus de la MemoryStream classe. MemoryStream lit et écrit Byte uniquement des données.

using namespace System;
using namespace System::IO;
int main()
{
   int i;
   const int arrayLength = 1000;
   
   // Create random data to write to the stream.
   array<double>^dataArray = gcnew array<double>(arrayLength);
   Random^ randomGenerator = gcnew Random;
   for ( i = 0; i < arrayLength; i++ )
   {
      dataArray[ i ] = 100.1 * randomGenerator->NextDouble();

   }
   BinaryWriter^ binWriter = gcnew BinaryWriter( gcnew MemoryStream );
   try
   {
      
      // Write data to the stream.
      Console::WriteLine( "Writing data to the stream." );
      i = 0;
      for ( i = 0; i < arrayLength; i++ )
      {
         binWriter->Write( dataArray[ i ] );

      }
      
      // Create a reader using the stream from the writer.
      BinaryReader^ binReader = gcnew BinaryReader( binWriter->BaseStream );
      
      // Return to the beginning of the stream.
      binReader->BaseStream->Position = 0;
      try
      {
         
         // Read and verify the data.
         i = 0;
         Console::WriteLine( "Verifying the written data." );
         for ( i = 0; i < arrayLength; i++ )
         {
            if ( binReader->ReadDouble() != dataArray[ i ] )
            {
               Console::WriteLine( "Error writing data." );
               break;
            }

         }
         Console::WriteLine( "The data was written and verified." );
      }
      catch ( EndOfStreamException^ e ) 
      {
         Console::WriteLine( "Error writing data: {0}.", e->GetType()->Name );
      }

   }
   finally
   {
      binWriter->Close();
   }

}

using System;
using System.IO;

class BinaryRW
{
    static void Main()
    {
        int i;
        const int arrayLength = 1000;

        // Create random data to write to the stream.
        Random randomGenerator = new Random();
        double[] dataArray = new double[arrayLength];
        for(i = 0; i < arrayLength; i++)
        {
            dataArray[i] = 100.1 * randomGenerator.NextDouble();
        }

        using(BinaryWriter binWriter =
            new BinaryWriter(new MemoryStream()))
        {
            // Write the data to the stream.
            Console.WriteLine("Writing data to the stream.");
            for(i = 0; i < arrayLength; i++)
            {
                binWriter.Write(dataArray[i]);
            }

            // Create a reader using the stream from the writer.
            using(BinaryReader binReader =
                new BinaryReader(binWriter.BaseStream))
            {
                try
                {
                    // Return to the beginning of the stream.
                    binReader.BaseStream.Position = 0;

                    // Read and verify the data.
                    Console.WriteLine("Verifying the written data.");
                    for(i = 0; i < arrayLength; i++)
                    {
                        if(binReader.ReadDouble() != dataArray[i])
                        {
                            Console.WriteLine("Error writing data.");
                            break;
                        }
                    }
                    Console.WriteLine("The data was written " +
                        "and verified.");
                }
                catch(EndOfStreamException e)
                {
                    Console.WriteLine("Error writing data: {0}.",
                        e.GetType().Name);
                }
            }
        }
    }
}

open System
open System.IO

let arrayLength = 1000

// Create random data to write to the stream.
let randomGenerator = Random()
let dataArray = 
    Array.init arrayLength (fun _ -> 100.1 * randomGenerator.NextDouble())
do
    use binWriter = new BinaryWriter(new MemoryStream())
    // Write the data to the stream.
    printfn $"Writing data to the stream."
    for num in dataArray do
        binWriter.Write num

    // Create a reader using the stream from the writer.
    use binReader = new BinaryReader(binWriter.BaseStream)
    try
        // Return to the beginning of the stream.
        binReader.BaseStream.Position <- 0

        // Read and verify the data.
        printfn "Verifying the written data."
        for num in dataArray do
            if binReader.ReadDouble() <> num then
                printfn "Error writing data."
        printfn "The data was written and verified."
    with :? EndOfStreamException as e ->
        printfn $"Error writing data: {e.GetType().Name}."

Imports System.IO

Public Class BinaryRW

    Shared Sub Main()
    
        Dim i As Integer
        Const upperBound As Integer = 1000

        ' Create random data to write to the stream.
        Dim dataArray(upperBound) As Double
        Dim randomGenerator As New Random()
        For i = 0 To upperBound
            dataArray(i) = 100.1 * randomGenerator.NextDouble()
        Next i

        Dim binWriter As New BinaryWriter(New MemoryStream())
        Try

            ' Write data to the stream.
            Console.WriteLine("Writing data to the stream.")
            
            For i = 0 To upperBound
                binWriter.Write(dataArray(i))
            Next i

            ' Create a reader using the stream from the writer.
            Dim binReader As New BinaryReader(binWriter.BaseStream)

            ' Return to the beginning of the stream.
            binReader.BaseStream.Position = 0

            ' Read and verify the data.
            Try
                Console.WriteLine("Verifying the written data.")
                For i = 0 To upperBound
                    If binReader.ReadDouble() <> dataArray(i) Then
                        Console.WriteLine("Error writing data.")
                        Exit For
                    End If
                Next i
                Console.WriteLine("The data was written and verified.")
            Catch ex As EndOfStreamException
                Console.WriteLine("Error writing data: {0}.", _
                    ex.GetType().Name)
            End Try
        Finally
            binWriter.Close()
        End Try

    End Sub
End Class

Remarques

BinaryReader ne restaure pas la position du fichier après un échec de lecture.

BinaryReader lit ce type de données au format little endian.

Pour obtenir la liste des tâches d’E/S courantes, consultez Tâches courantes d’E/S.

Voir aussi

• Fichier et flux de données E/S
• Procédure : lire le texte d’un fichier
• Procédure : écrire du texte dans un fichier