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GZipStream.Flush Method

Note: This method is new in the .NET Framework version 2.0.

Flushes the contents of the internal buffer of the current GZipStream object to the underlying stream.

Namespace: System.IO.Compression
Assembly: System (in system.dll)

public override void Flush ()
public void Flush ()
public override function Flush ()

Exception typeCondition

ObjectDisposedException

The stream is closed.

When writing using the Write method, the data may not be written to the actual stream since writing the data back in chunks can provide better performance. Calling the Flush method forces the data to be written.

The following code example shows how to use the GZipStream class to compress and decompress a file.

using System;
using System.IO;
using System.IO.Compression;

public class GZipTest
{
	public static int ReadAllBytesFromStream(Stream stream, byte[] buffer) 
	{
	// Use this method is used to read all bytes from a stream.
	int offset = 0;
	int totalCount = 0;
		while (true) 
		{
		int bytesRead = stream.Read(buffer, offset, 100); 
			if ( bytesRead == 0) 
			{
			break; 
			}
	offset += bytesRead;
	totalCount += bytesRead; 
		}
	return totalCount;
	} 

	public static bool CompareData(byte[] buf1, int len1, byte[] buf2, int len2) 
	{
		// Use this method to compare data from two different buffers.
		if (len1 != len2) 
		{ 
		Console.WriteLine("Number of bytes in two buffer are different {0}:{1}", len1, len2);
		return false;
		}

		for ( int i= 0; i< len1; i++) 
		{
			if ( buf1[i] != buf2[i]) 
			{
			Console.WriteLine("byte {0} is different {1}|{2}", i, buf1[i], buf2[i]);
			return false;
			}
		}
	Console.WriteLine("All bytes compare.");
	return true; 
	}

	public static void GZipCompressDecompress(string filename)
	{
	Console.WriteLine("Test compression and decompression on file {0}", filename);
	FileStream infile;
		try
		{
		// Open the file as a FileStream object.
		infile = new FileStream(filename, FileMode.Open, FileAccess.Read, FileShare.Read);
		byte[] buffer = new byte[infile.Length];
		// Read the file to ensure it is readable.
		int count = infile.Read(buffer, 0, buffer.Length);
			if ( count != buffer.Length) 
			{
			infile.Close();
			Console.WriteLine("Test Failed: Unable to read data from file"); 
			return;
			}
		infile.Close();
		MemoryStream ms = new MemoryStream();
		// Use the newly created memory stream for the compressed data.
		GZipStream compressedzipStream = new GZipStream(ms , CompressionMode.Compress, true);
		Console.WriteLine("Compression");
		compressedzipStream.Write(buffer, 0, buffer.Length);
		// Close the stream.
		compressedzipStream.Close();
		Console.WriteLine("Original size: {0}, Compressed size: {1}", buffer.Length, ms.Length);

		// Reset the memory stream position to begin decompression.
		ms.Position = 0;
		GZipStream zipStream = new GZipStream(ms, CompressionMode.Decompress);
		Console.WriteLine("Decompression");
		byte[] decompressedBuffer = new byte[buffer.Length + 100];
		// Use the ReadAllBytesFromStream to read the stream.
		int totalCount = GZipTest.ReadAllBytesFromStream(zipStream, decompressedBuffer);
		Console.WriteLine("Decompressed {0} bytes", totalCount);

		if( !GZipTest.CompareData(buffer, buffer.Length, decompressedBuffer, totalCount) ) 
		{
		Console.WriteLine("Error. The two buffers did not compare.");
		}
	zipStream.Close(); 
		} // end try
		catch (InvalidDataException)
		{
			Console.WriteLine("Error: The file being read contains invalid data.");
		}
		catch (FileNotFoundException)
		{
			Console.WriteLine("Error:The file specified was not found.");
		}
		catch (ArgumentException)
		{
			Console.WriteLine("Error: path is a zero-length string, contains only white space, or contains one or more invalid characters");
		}
		catch (PathTooLongException)
		{
			Console.WriteLine("Error: The specified path, file name, or both exceed the system-defined maximum length. For example, on Windows-based platforms, paths must be less than 248 characters, and file names must be less than 260 characters.");
		}
		catch (DirectoryNotFoundException)
		{
			Console.WriteLine("Error: The specified path is invalid, such as being on an unmapped drive.");
		}
		catch (IOException)
		{
			Console.WriteLine("Error: An I/O error occurred while opening the file.");
		}
		catch (UnauthorizedAccessException)
		{
			Console.WriteLine("Error: path specified a file that is read-only, the path is a directory, or caller does not have the required permissions.");
		}
		catch (IndexOutOfRangeException)
		{
			Console.WriteLine("Error: You must provide parameters for MyGZIP.");
		}
	}
	public static void Main(string[] args)
	{
		string usageText = "Usage: MYGZIP <inputfilename>";
		//If no file name is specified, write usage text.
		if (args.Length == 0)
		{
			Console.WriteLine(usageText);
		}
		else
		{
			if (File.Exists(args[0]))
				GZipCompressDecompress(args[0]);
		}
	}
}
	

import System.*;
import System.IO.*;
import System.IO.Compression.*;

public class GZipTest
{
    public static int ReadAllBytesFromStream(Stream stream, ubyte buffer[])
    {
        // Use this method is used to read all bytes from a stream.
        int offSet = 0;
        int totalCount = 0;
        while (true) {
            int bytesRead = stream.Read(buffer, offSet, 100);
            if (bytesRead == 0) {
                break;
            }
            offSet += bytesRead;
            totalCount += bytesRead;
        }
        return totalCount;
    } //ReadAllBytesFromStream

    public static boolean CompareData(ubyte buf1[], int len1, 
        ubyte buf2[], int len2)
    {
        // Use this method to compare data from two different buffers.
        if (len1 != len2) {
            Console.WriteLine("Number of bytes in two buffer are "
                + "different {0}:{1}", System.Convert.ToString(len1), 
                System.Convert.ToString(len2));
            return false;
        }
        for (int i = 0; i < len1; i++) {
            if (!(buf1.get_Item(i).Equals(buf2.get_Item(i)))) {
                Console.WriteLine("byte {0} is different {1}|{2}", 
                    System.Convert.ToString(i), 
                    System.Convert.ToString(buf1.get_Item(i)), 
                    System.Convert.ToString(buf2.get_Item(i)));
                return false;
            }
        }
        Console.WriteLine("All bytes compare.");
        return true;
    } //CompareData

    public static void GZipCompressDecompress(String fileName)
    {
        Console.WriteLine("Test compression and decompression on file {0}",
            fileName);
        FileStream inFile;
        try {
            // Open the file as a FileStream object.
            inFile = new FileStream(fileName, FileMode.Open, 
                FileAccess.Read, FileShare.Read);
            ubyte buffer[] = new ubyte[(ubyte)inFile.get_Length()];

            // Read the file to ensure it is readable.
            int count = inFile.Read(buffer, 0, buffer.length);
            if (count != buffer.length) {
                inFile.Close();
                Console.WriteLine("Test Failed: Unable to read data from file");
                return;
            }
            inFile.Close();
            MemoryStream ms = new MemoryStream();

            // Use the newly created memory stream for the compressed data.
            GZipStream compressedZipStream = 
                new GZipStream(ms, CompressionMode.Compress, true);
            Console.WriteLine("Compression");
            compressedZipStream.Write(buffer, 0, buffer.length);

            // Close the stream.
            compressedZipStream.Close();
            Console.WriteLine("Original size: {0}, Compressed size: {1}", 
                System.Convert.ToString(buffer.length), 
                System.Convert.ToString(ms.get_Length()));

            // Reset the memory stream position to begin decompression.
            ms.set_Position(0);
            GZipStream zipStream = 
                new GZipStream(ms, CompressionMode.Decompress);
            Console.WriteLine("Decompression");
            ubyte decompressedBuffer[] = new ubyte[buffer.length + 100];

            // Use the ReadAllBytesFromStream to read the stream.
            int totalCount = GZipTest.ReadAllBytesFromStream(zipStream, 
                decompressedBuffer);
            Console.WriteLine("Decompressed {0} bytes", 
                System.Convert.ToString(totalCount));
            if (!(GZipTest.CompareData(buffer, buffer.length, 
                decompressedBuffer, totalCount))) {
                Console.WriteLine("Error. The two buffers did not compare.");
            }
            zipStream.Close();
        } 
        catch (InvalidDataException exp) {
            Console.WriteLine("Error: The file being read contains"
                + " invalid data.");
        }
        catch (FileNotFoundException exp) {
            Console.WriteLine("Error:The file specified was not found.");
        }
        catch (ArgumentException exp) {
            Console.WriteLine("Error: path is a zero-length string, contains "
                + "only white space, or contains one or more invalid characters");
        }
        catch (PathTooLongException exp) {
            Console.WriteLine("Error: The specified path, file name, or both "
                + "exceed the system-defined maximum length. For example, on"
                + " Windows-based platforms, paths must be less than 248 "
                + "characters, and file names must be less than 260 characters.");
        }
        catch (DirectoryNotFoundException exp) {
            Console.WriteLine("Error: The specified path is invalid, such"
                + " as being on an unmapped drive.");
        }
        catch (IOException exp) {
            Console.WriteLine("Error: An I/O error occurred while "
                + "opening the file.");
        }
        catch (UnauthorizedAccessException exp) {
            Console.WriteLine("Error: path specified a file that is read-only,"
                + " the path is a directory, or caller does not have"
                + " the required permissions.");
        }
        catch (IndexOutOfRangeException exp) {
            Console.WriteLine("Error: You must provide parameters for MyGZIP.");
        }
    } //GZipCompressDecompress

    public static void main(String[] args)
    {
        String usageText = "Usage: MYGZIP <inputfilename>";

        //If no file name is specified, write usage text.
        if (args.length == 0) {
            Console.WriteLine(usageText);
        }
        else {
            if (File.Exists(args[0])) {
                GZipCompressDecompress(args[0]);
            }
        }
    } //main
} //GZipTest

Windows 98, Windows 2000 SP4, Windows Millennium Edition, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0

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