UnmanagedMemoryStream.ReadByte 方法

定義

命名空間:

System.IO

組件:

netstandard.dll, System.Runtime.dll

來源:

UnmanagedMemoryStream.cs

從串流讀取一個位元組，並將串流中的位置往前推進一個位元組，若在串流末端則返回 -1。

public:
 override int ReadByte();

public override int ReadByte();

override this.ReadByte : unit -> int

Public Overrides Function ReadByte () As Integer

傳回

Int32

未簽名位元組投射到 Int32 物件，若在串流結束則投射為 -1。

例外狀況

ObjectDisposedException

溪流已經關閉。

NotSupportedException

底層記憶體不支援讀取。

-或-

目前的位置是在溪流的盡頭。

範例

以下程式碼範例示範如何使用類別讀取與寫入未管理記憶體 UnmanagedMemoryStream 。 使用類別 Marshal 分配與取消管理的記憶體區塊。 在此範例中，物件 UnmanagedMemoryStream 會傳給一個方法，該方法在嘗試讀取並顯示內容給主控台前檢查該 CanRead 屬性。

// Note: You must compile this sample using the unsafe flag.
// From the command line, type the following: csc sample.cs /unsafe
using System;
using System.IO;
using System.Runtime.InteropServices;
using System.Text;

unsafe class Program
{
    static void Main()
    {
        // Create some data to write.
        byte[] text = UnicodeEncoding.Unicode.GetBytes("Data to write.");

        // Allocate a block of unmanaged memory.
        IntPtr memIntPtr = Marshal.AllocHGlobal(text.Length);

        // Get a byte pointer from the unmanaged memory block.
        byte* memBytePtr = (byte*)memIntPtr.ToPointer();

        UnmanagedMemoryStream writeStream =
            new UnmanagedMemoryStream(
            memBytePtr, text.Length, text.Length, FileAccess.Write);

        // Write the data.
        WriteToStream(writeStream, text);

        // Close the stream.
        writeStream.Close();

        // Create another UnmanagedMemoryStream for reading.
        UnmanagedMemoryStream readStream =
            new UnmanagedMemoryStream(memBytePtr, text.Length);

        // Display the contents of the stream to the console.
        PrintStream(readStream);

        // Close the reading stream.
        readStream.Close();

        // Free up the unmanaged memory.
        Marshal.FreeHGlobal(memIntPtr);
    }

    public static void WriteToStream(UnmanagedMemoryStream writeStream, byte[] text)
    {
        // Verify that the stream is writable:
        // By default, UnmanagedMemoryStream objects do not have write access,
        // write access must be set explicitly.
        if (writeStream.CanWrite)
        {
            // Write the data, byte by byte
            for (int i = 0; i < writeStream.Length; i++)
            {
                writeStream.WriteByte(text[i]);
            }
        }
    }

    public static void PrintStream(UnmanagedMemoryStream readStream)
    {
        byte[] text = new byte[readStream.Length];
        // Verify that the stream is writable:
        // By default, UnmanagedMemoryStream objects do not have write access,
        // write access must be set explicitly.
        if (readStream.CanRead)
        {
            // Write the data, byte by byte
            for (int i = 0; i < readStream.Length; i++)
            {
                text[i] = (byte)readStream.ReadByte();
            }
        }

        Console.WriteLine(UnicodeEncoding.Unicode.GetString(text));
    }
}

備註

使用此方法可從串流中回傳整數值。