GZip and Deflate streams...

[Finn Stampe Mikkelsen]

Hi

I've tried below code, working with the SelfPaced Training Kit for FrameWork
2.0 (MS) and also tried to play around with the classes otherwise.. I can't
seem to get a result that actually compresses any data...

I have tried with files from around 1mb up to the below file of 250mb and
there always seems to be the same result. The files come out with a bigger
size, actually proportionat to the initial size..

Whats up with that?? What am I and aparrently MS doing wrong, since they
claim that the below code will shrink the sourcefile...

FileStream sourceFile =
File.OpenRead(@"Y:\DaffReport_20-04-2010.csv");
FileStream destFile =
File.Create(@"Y:\DaffReport_20-04-2010.zip");

//GZipStream compStream = new GZipStream(destFile,
CompressionMode.Compress);
DeflateStream compStream = new DeflateStream(destFile,
CompressionMode.Compress);

int theByte = sourceFile.ReadByte();

while (theByte != -1)
{
compStream.WriteByte((byte)theByte);
theByte = sourceFile.ReadByte();
}

sourceFile.Close();
destFile.Close();

/Finn
--
Der er 10 slags mennesker - Dem som forstår binær og dem som ikke gør.
There are 10 kinds of people. Those who understand binary and those who
don't.
Es gibt 10 Arten von Menschen. Die, die Binär verstehen, bzw. die, die es
nicht tuhen.

 

[Arne Vajhøj]

I've tried below code, working with the SelfPaced Training Kit for
FrameWork 2.0 (MS) and also tried to play around with the classes
otherwise.. I can't seem to get a result that actually compresses any
data...

I have tried with files from around 1mb up to the below file of 250mb
and there always seems to be the same result. The files come out with a
bigger size, actually proportionat to the initial size..

Whats up with that?? What am I and aparrently MS doing wrong, since they
claim that the below code will shrink the sourcefile...

FileStream sourceFile = File.OpenRead(@"Y:\DaffReport_20-04-2010.csv");
FileStream destFile = File.Create(@"Y:\DaffReport_20-04-2010.zip");

//GZipStream compStream = new GZipStream(destFile,
CompressionMode.Compress);
DeflateStream compStream = new DeflateStream(destFile,
CompressionMode.Compress);

int theByte = sourceFile.ReadByte();

while (theByte != -1)
{
compStream.WriteByte((byte)theByte);
theByte = sourceFile.ReadByte();
}

sourceFile.Close();
destFile.Close();

Those compression classes has a bug/feature where it only compresses
when you call Write with large byte arrays and not WriteByte with a
single byte.

So either you call Write with a byte array or you wrap the
stream with a BufferedStream.

Arne

 

[Arne Vajhøj]

Those compression classes has a bug/feature where it only compresses
when you call Write with large byte arrays and not WriteByte with a
single byte.

So either you call Write with a byte array or you wrap the
stream with a BufferedStream.

Example:

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

namespace E
{
public class DeflateTest
{
public void WithOneByte(string fromfnm, string tofnm)
{
using(FileStream fromf = File.OpenRead(fromfnm))
using(FileStream tof = File.Create(tofnm))
using(DeflateStream cmp = new DeflateStream(tof,
CompressionMode.Compress))
{
int c;
while((c = fromf.ReadByte()) >= 0)
{
cmp.WriteByte((byte)c);
}
}
}
public void WithBuffer(string fromfnm, string tofnm)
{
using(FileStream fromf = File.OpenRead(fromfnm))
using(FileStream tof = File.Create(tofnm))
using(DeflateStream cmp = new DeflateStream(tof,
CompressionMode.Compress))
{
byte[] b = new byte[100000];
int n;
while((n = fromf.Read(b, 0, b.Length)) > 0)
{
cmp.Write(b, 0, n);
}
}
}
public void WithCombo(string fromfnm, string tofnm)
{
using(FileStream fromf = File.OpenRead(fromfnm))
using(FileStream tof = File.Create(tofnm))
using(DeflateStream cmp = new DeflateStream(tof,
CompressionMode.Compress))
using(BufferedStream buf = new BufferedStream(cmp))
{
int c;
while((c = fromf.ReadByte()) >= 0)
{
buf.WriteByte((byte)c);
}
}
}
public void WithComboX(string fromfnm, int bufsiz, string tofnm)
{
using(FileStream fromf = File.OpenRead(fromfnm))
using(FileStream tof = File.Create(tofnm))
using(DeflateStream cmp = new DeflateStream(tof,
CompressionMode.Compress))
using(BufferedStream buf = new BufferedStream(cmp, bufsiz))
{
int c;
while((c = fromf.ReadByte()) >= 0)
{
buf.WriteByte((byte)c);
}
}
}
public static void Main(string[] args)
{
DeflateTest gzt = new DeflateTest();
gzt.WithOneByte(@"C:\foobar.txt", @"C:\foobar.gz1");
gzt.WithBuffer(@"C:\foobar.txt", @"C:\foobar.gz2");
gzt.WithCombo(@"C:\foobar.txt", @"C:\foobar.gz3");
gzt.WithComboX(@"C:\foobar.txt", 256, @"C:\foobar.gz4");
gzt.WithComboX(@"C:\foobar.txt", 16, @"C:\foobar.gz5");
}
}
}


20-04-2010 20:49 3.863 foobar.gz1
20-04-2010 20:49 2.210 foobar.gz2
20-04-2010 20:49 2.210 foobar.gz3
20-04-2010 20:49 2.221 foobar.gz4
20-04-2010 20:49 2.465 foobar.gz5
04-04-2005 15:28 4.351 foobar.txt

Arne