GZIP file format specification version 4.3
Can GZip compression (via .net) increase file size?
Yes. It can. It has been fixed in .net 4.
The compression algorithms for the System.IO.Compression..::.DeflateStream and System.IO.Compression..::.GZipStream classes have improved so that data that is already compressed is no longer inflated. This results in much better compression ratios. Also, the 4-gigabyte size restriction for compressing streams has been removed.
How does GZipStream determine the size of compressed data
Compress byte array
using System.IO;
using System.IO.Compression;
using System.Text;
class Program
{
static void Main()
{
byte[] text = Encoding.ASCII.GetBytes(new string('A', 10000));
byte[] compress = Compress(text);
File.WriteAllBytes("compress.gz", compress);
}
public static byte[] Compress(byte[] raw)
{
using (MemoryStream memory = new MemoryStream())
{
using (GZipStream gzip = new GZipStream(memory,
CompressionMode.Compress, true))
{
gzip.Write(raw, 0, raw.Length);
}
return memory.ToArray();
}
}
}
Decompress byte array
using System;
using System.IO;
using System.IO.Compression;
class Program
{
static void Main()
{
byte[] file = File.ReadAllBytes("C:\\filename.gz");
byte[] decompressed = Decompress(file);
Console.WriteLine(file.Length);
Console.WriteLine(decompressed.Length);
}
static byte[] Decompress(byte[] gzip)
{
using (GZipStream stream = new GZipStream(new MemoryStream(gzip), CompressionMode.Decompress))
{
const int size = 4*1024;
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();
}
}
}
}
Compress and decompress
public static void Compress(String fileSource, String fileDestination, int buffsize)
{
using (var fsInput = new FileStream(fileSource, FileMode.Open, FileAccess.Read))
{
using (var fsOutput = new FileStream(fileDestination, FileMode.Create, FileAccess.Write))
{
using (var gzipStream = new GZipStream(fsOutput, CompressionMode.Compress))
{
var buffer = new Byte[buffsize];
int h;
while ((h = fsInput.Read(buffer, 0, buffer.Length)) > 0)
{
gzipStream.Write(buffer, 0, h);
}
gzipStream.Flush();
}
}
}
}
public static void Decompress(String fileSource, String fileDestination, int buffsize)
{
using (var fsInput = new FileStream(fileSource, FileMode.Open, FileAccess.Read))
{
using (var fsOutput = new FileStream(fileDestination, FileMode.Create, FileAccess.Write))
{
using (var gzipStream = new GZipStream(fsInput, CompressionMode.Decompress))
{
var buffer = new Byte[buffsize];
int h;
while ((h = gzipStream.Read(buffer, 0, buffer.Length)) > 0)
{
fsOutput.Write(buffer, 0, h);
}
}
}
}
}
public static void Compress(string inFileName)
{
int dataPortionSize = Environment.SystemPageSize / threadNumber;
try
{
FileStream inFile = new FileStream(inFileName, FileMode.Open);
FileStream outFile = new FileStream(inFileName + ".gz", FileMode.Append);
int _dataPortionSize;
Thread[] tPool;
Console.Write("Compressing...");
while (inFile.Position < inFile.Length)
{
Console.Write(".");
tPool = new Thread[threadNumber];
for (int portionCount = 0;
(portionCount < threadNumber) && (inFile.Position < inFile.Length);
portionCount++)
{
if (inFile.Length - inFile.Position <= dataPortionSize)
{
_dataPortionSize = (int)(inFile.Length - inFile.Position);
}
else
{
_dataPortionSize = dataPortionSize;
}
dataArray[portionCount] = new byte[_dataPortionSize];
inFile.Read(dataArray[portionCount], 0, _dataPortionSize);
tPool[portionCount] = new Thread(CompressBlock);
tPool[portionCount].Start(portionCount);
}
for (int portionCount = 0; (portionCount < threadNumber) && (tPool[portionCount] != null); )
{
if (tPool[portionCount].ThreadState == ThreadState.Stopped)
{
BitConverter.GetBytes(compressedDataArray[portionCount].Length+1)
.CopyTo(compressedDataArray[portionCount], 4);
outFile.Write(compressedDataArray[portionCount], 0, compressedDataArray[portionCount].Length);
portionCount++;
}
}
}
outFile.Close();
inFile.Close();
}
catch (Exception ex)
{
Console.WriteLine("ERROR:" + ex.Message);
}
}
public static void CompressBlock(object i)
{
using (MemoryStream output = new MemoryStream(dataArray[(int)i].Length))
{
using (GZipStream cs = new GZipStream(output, CompressionMode.Compress))
{
cs.Write(dataArray[(int)i], 0, dataArray[(int)i].Length);
}
compressedDataArray[(int)i] = output.ToArray();
}
}
public static void Decompress(string inFileName)
{
try
{
FileStream inFile = new FileStream(inFileName, FileMode.Open);
FileStream outFile = new FileStream(inFileName.Remove(inFileName.Length - 3), FileMode.Append);
int _dataPortionSize;
int compressedBlockLength;
Thread[] tPool;
Console.Write("Decompressing...");
byte[] buffer = new byte[8];
while (inFile.Position < inFile.Length)
{
Console.Write(".");
tPool = new Thread[threadNumber];
for (int portionCount = 0;
(portionCount < threadNumber) && (inFile.Position < inFile.Length);
portionCount++)
{
inFile.Read(buffer, 0, 8);
compressedBlockLength = BitConverter.ToInt32(buffer, 4);
compressedDataArray[portionCount] = new byte[compressedBlockLength+1];
buffer.CopyTo(compressedDataArray[portionCount], 0);
inFile.Read(compressedDataArray[portionCount], 8, compressedBlockLength - 8);
_dataPortionSize = BitConverter.ToInt32(compressedDataArray[portionCount], compressedBlockLength - 4);
dataArray[portionCount] = new byte[_dataPortionSize];
tPool[portionCount] = new Thread(DecompressBlock);
tPool[portionCount].Start(portionCount);
}
for (int portionCount = 0; (portionCount < threadNumber) && (tPool[portionCount] != null); )
{
if (tPool[portionCount].ThreadState == ThreadState.Stopped)
{
outFile.Write(dataArray[portionCount], 0, dataArray[portionCount].Length);
portionCount++;
}
}
}
outFile.Close();
inFile.Close();
}
catch (Exception ex)
{
Console.WriteLine("ERROR:" + ex.Message);
}
}
public static void DecompressBlock(object i)
{
using (MemoryStream input = new MemoryStream(compressedDataArray[(int)i]))
{
using (GZipStream ds = new GZipStream(input, CompressionMode.Decompress))
{
ds.Read(dataArray[(int)i], 0, dataArray[(int)i].Length);
}
}
}