C# Decompress GZIP

Decompress a GZIP byte array using GZipStream. Test the size of the expanded data.

Decompress GZIP. GZIP data is often decompressed before use. A byte array containing GZIP bytes can be translated into one with the original representation of bits. It is possible to use a wrapper method around the GZipStream and other streams.Compress Data

This program receives a byte array that contains GZIP data and transform it into a byte array that contains the original representation of bytes. We use a specific GZIP-compressed file on the C:\ directory.

Decompress: Here the GZipStream object is first instantiated. The backing store is a MemoryStream wrapped around the GZIP buffer.

GZipStream: The second argument to the GZipStream is the CompressionMode.Decompress enumerated constant.

Next: A byte array is allocated. We use the value 4096 because arrays that are powers of 2 are better aligned on memory caches and therefore faster.

Then: The GZIP array is read from the GZipStream and decompressed. This is written to the MemoryStream.

MemoryStream

C# program that decompresses GZIP file using System; using System.IO; using System.IO.Compression; class Program { static void Main() { // Open a compressed file on disk. // ... Then decompress it with the method here. // ... Then write the length of each array. byte[] file = File.ReadAllBytes("C:\\perlgzips\\~stat.gz"); byte[] decompressed = Decompress(file); Console.WriteLine(file.Length); Console.WriteLine(decompressed.Length); } static byte[] Decompress(byte[] gzip) { // Create a GZIP stream with decompression mode. // ... Then create a buffer and write into while reading from the GZIP stream. using (GZipStream stream = new GZipStream(new MemoryStream(gzip), CompressionMode.Decompress)) { const int size = 4096; byte[] buffer = new byte[size]; using (MemoryStream memory = new MemoryStream()) { int count = 0; do { count = stream.Read(buffer, 0, size); if (count > 0) { memory.Write(buffer, 0, count); } } while (count > 0); return memory.ToArray(); } } } } Output (Please change the filename in the program to a GZIP file.) 9106 36339

Usage. This code reads in a byte array and then decompresses that array to another byte array. Because GZIP compression is often used for websites, you can store web pages as byte arrays in compressed form and then decompress them when required.

Tip: Because the GZIP version is more compact, this form can be used to store the pages on the disk.

Decompress web page. This C# console program decompresses web pages in GZIP format. It uses types from System.IO, System.IO.Compression and System.Net namespaces. When you pass it a URL from the command line, it will download the page in GZIP form.

Next: It passes that byte array to the Decompress method. Finally it converts that byte array to a string.

Convert String, Byte Array WebClient

Info: The compressed page from the example required 15,228 bytes. The expanded form required 56,362 bytes (several times larger).

Note: Getting the GZIP page with the WebClient would enhance network (and likely overall) performance.

C# program that decompresses web pages using System; using System.IO; using System.IO.Compression; using System.Net; class Program { static byte[] Decompress(byte[] gzip) { using (GZipStream stream = new GZipStream(new MemoryStream(gzip), CompressionMode.Decompress)) { const int size = 4096; byte[] buffer = new byte[size]; using (MemoryStream memory = new MemoryStream()) { int count = 0; do { count = stream.Read(buffer, 0, size); if (count > 0) { memory.Write(buffer, 0, count); } } while (count > 0); return memory.ToArray(); } } } static void Main(string[] args) { try { Console.WriteLine("*** Decompress web page ***"); Console.WriteLine(" Specify file to download"); Console.WriteLine("Downloading: {0}", args[0]); // Download url. using (WebClient client = new WebClient()) { client.Headers[HttpRequestHeader.AcceptEncoding] = "gzip"; byte[] data = client.DownloadData(args[0]); byte[] decompress = Decompress(data); string text = System.Text.ASCIIEncoding.ASCII.GetString(decompress); Console.WriteLine("Size from network: {0}", data.Length); Console.WriteLine("Size decompressed: {0}", decompress.Length); Console.WriteLine("First chars: {0}", text.Substring(0, 5)); } } finally { Console.WriteLine("[Done]"); Console.ReadLine(); } } } Output [Argument = http://en.wikipedia.org/] *** Decompress web page *** Specify file to download Downloading: http://en.wikipedia.org/ Size from network: 15228 Size decompressed: 56362 First chars: <!DOC [Done]

Summary. We decompressed an array of GZIP bytes into an array of the original bytes. The C# method shown receives a GZIP byte array and returns the original byte array. The method translates the two arrays using stream interfaces.

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C# Decompress GZIP

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