Provides methods and properties for compressing and decompressing streams using the Deflate algorithm.
Public Class DeflateStream _ Inherits Stream
Dim instance As DeflateStream
public class DeflateStream : Stream
public ref class DeflateStream : public Stream
public class DeflateStream extends Stream
This class represents the Deflate algorithm, an industry standard algorithm for lossless file compression and decompression. It uses a combination of the LZ77 algorithm and Huffman coding. Data can be produced or consumed, even for an arbitrarily long, sequentially presented input data stream, using only previously bound amount of intermediate storage. The format can be implemented readily in a manner not covered by patents. For more information, see RFC 1951. "DEFLATE Compressed Data Format Specification version 1.3." This class cannot be used to compress files larger than 4 GB.
This class does not inherently provide functionality for adding files to or extracting files from .zip archives. For an example of manipulating compressed file archives, see Compression Application Sample.
The GZipStream class uses the gzip data format, which includes a cyclic redundancy check value for detecting data corruption. The gzip data format uses the same compression algorithm as the DeflateStream class.
The compression functionality in DeflateStream and GZipStream is exposed as a stream. Data is read in on a byte-by-byte basis, so it is not possible to perform multiple passes to determine the best method for compressing entire files or large blocks of data. The DeflateStream and GZipStream classes are best used on uncompressed sources of data. If the source data is already compressed, using these classes may actually increase the size of the stream.
The following code example shows how to use the DeflateStream class to compress and decompress a file.
Imports System Imports System.IO Imports System.IO.Compression Public Class DeflateTest Shared msg As String Public Shared Function ReadAllBytesFromStream(stream As Stream, buffer() As Byte) As Integer ' Use this method is used to read all bytes from a stream. Dim offset As Integer = 0 Dim totalCount As Integer = 0 While True Dim bytesRead As Integer = stream.Read(buffer, offset, 100) If bytesRead = 0 Then Exit While End If offset += bytesRead totalCount += bytesRead End While Return totalCount End Function 'ReadAllBytesFromStream Public Shared Function CompareData(buf1() As Byte, len1 As Integer, buf2() As Byte, len2 As Integer) As Boolean ' Use this method to compare data from two different buffers. If len1 <> len2 Then msg = "Number of bytes in two buffer are different" & len1 & ":" & len2 MsgBox(msg) Return False End If Dim i As Integer For i = 0 To len1 - 1 If buf1(i) <> buf2(i) Then msg = "byte " & i & " is different " & buf1(i) & "|" & buf2(i) MsgBox(msg) Return False End If Next i msg = "All bytes compare." MsgBox(msg) Return True End Function 'CompareData Public Shared Sub DeflateCompressDecompress(filename As String) msg = "Test compression and decompression on file " & filename MsgBox(msg) Dim infile As FileStream Try ' Open the file as a FileStream object. infile = New FileStream(filename, FileMode.Open, FileAccess.Read, FileShare.Read) Dim buffer(infile.Length - 1) As Byte ' Read the file to ensure it is readable. Dim count As Integer = infile.Read(buffer, 0, buffer.Length) If count <> buffer.Length Then infile.Close() msg = "Test Failed: Unable to read data from file" MsgBox(msg) Return End If infile.Close() Dim ms As New MemoryStream() ' Use the newly created memory stream for the compressed data. Dim compressedzipStream As New DeflateStream(ms, CompressionMode.Compress, True) compressedzipStream.Write(buffer, 0, buffer.Length) ' Close the stream. compressedzipStream.Close() msg = "Original size: " & buffer.Length & ", Compressed size: " & ms.Length MsgBox(msg) ' Reset the memory stream position to begin decompression. ms.Position = 0 Dim zipStream As New DeflateStream(ms, CompressionMode.Decompress) Dim decompressedBuffer(buffer.Length + 100) As Byte ' Use the ReadAllBytesFromStream to read the stream. Dim totalCount As Integer = DeflateTest.ReadAllBytesFromStream(zipStream, decompressedBuffer) msg = "Decompressed " & totalCount & " bytes" MsgBox(msg) If Not DeflateTest.CompareData(buffer, buffer.Length, decompressedBuffer, totalCount) Then msg = "Error. The two buffers did not compare." MsgBox(msg) End If zipStream.Close() Catch e As Exception msg = "Error: The file being read contains invalid data." MsgBox(msg) End Try End Sub 'DeflateCompressDecompress Public Shared Sub Main(ByVal args() As String) Dim usageText As String = "Usage: DeflateTest <inputfilename>" 'If no file name is specified, write usage text. If args.Length = 0 Then Console.WriteLine(usageText) Else If File.Exists(args(0)) Then DeflateCompressDecompress(args(0)) End If End If End Sub 'Main End Class 'DeflateTest
using System; using System.IO; using System.IO.Compression; public class DeflateTest { 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 DeflateCompressDecompress(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. DeflateStream compressedzipStream = new DeflateStream(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; DeflateStream zipStream = new DeflateStream(ms, CompressionMode.Decompress); Console.WriteLine("Decompression"); byte[] decompressedBuffer = new byte[buffer.Length + 100]; // Use the ReadAllBytesFromStream to read the stream. int totalCount = DeflateTest.ReadAllBytesFromStream(zipStream, decompressedBuffer); Console.WriteLine("Decompressed {0} bytes", totalCount); if( !DeflateTest.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: DeflateTest <inputfilename>"; //If no file name is specified, write usage text. if (args.Length == 0) { Console.WriteLine(usageText); } else { if (File.Exists(args[0])) DeflateCompressDecompress(args[0]); } } }
#using <System.dll> using namespace System; using namespace System::IO; using namespace System::IO::Compression; int ReadAllBytesFromStream( Stream^ stream, array<Byte>^buffer ) { // Use this method is used to read all bytes from a stream. int offset = 0; int totalCount = 0; for ( ; ; ) { int bytesRead = stream->Read( buffer, offset, 100 ); if ( bytesRead == 0 ) { break; } offset += bytesRead; totalCount += bytesRead; } return totalCount; } bool CompareData( array<Byte>^buf1, int len1, array<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; } void DeflateCompressDecompress( String^ filename ) { Console::WriteLine( "Test compression and decompression on file {0}", filename ); FileStream^ infile; try { // Open the file as a FileStream object. infile = gcnew FileStream( filename,FileMode::Open,FileAccess::Read,FileShare::Read ); array<Byte>^buffer = gcnew array<Byte>((int)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 = gcnew MemoryStream; // Use the newly created memory stream for the compressed data. DeflateStream ^ compressedzipStream = gcnew DeflateStream( 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; DeflateStream ^ zipStream = gcnew DeflateStream( ms,CompressionMode::Decompress ); Console::WriteLine( "Decompression" ); array<Byte>^decompressedBuffer = gcnew array<Byte>(buffer->Length + 100); // Use the ReadAllBytesFromStream to read the stream. int totalCount = ReadAllBytesFromStream( zipStream, decompressedBuffer ); Console::WriteLine( "Decompressed {0} bytes", totalCount ); if ( !CompareData( buffer, buffer->Length, decompressedBuffer, totalCount ) ) { Console::WriteLine( "Error. The two buffers did not compare." ); } zipStream->Close(); } 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." ); } } int main() { array<String^>^args = Environment::GetCommandLineArgs(); String^ usageText = "Usage: DeflateTest <inputfilename>"; //If no file name is specified, write usage text. if ( args->Length == 1 ) { Console::WriteLine( usageText ); } else { if ( File::Exists( args[ 1 ] ) ) DeflateCompressDecompress( args[ 1 ] ); } }
Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune
The Deflate compression algorithm is what is used to compress data in .zip files. But the DeflateStream class doesn't handle full zip files. Also, this DeflateStream class does not support different compression levels, and its compression capability is not very good. Some previously compressed data streams can actually inflate in size, some by as much as 60%. This is a known problem, and has been reported to Microsoft, though the company has not acknowledged the need to fix it. https://connect.microsoft.com/VisualStudio/feedback/ViewFeedback.aspx?FeedbackID=93636 There is a 3rd party library, though, that provides a more effective DeflateStream, and can also read and write .zip files: DotNetZip. Find DotNetZip at: http://www.codeplex.com/DotNetZipDotNetZip is written in C#, but you can use it from any language. The DeflateStream class in DotNetZip is a good replacement for the built-in one. It never inflates the size of a compressed stream. As well, DotNetZip includes classes for directly manipulating ZIP files, which the .NET BCL lacks. DotNetZip works in Winforms apps, console apps, ASP.NET apps, anything you write in .NET. It is open source, and free to use in any application.