G-ZIP

[Chase Preuninger]

How do you set the compression level of a G-ZIP output stream (0-9)?

 

[Roedy Green]

How do you set the compression level of a G-ZIP output stream (0-9)?

Think that is a feature of ZIP, not GZIP.

 

[Arne Vajhøj]

How do you set the compression level of a G-ZIP output stream (0-9)?

It is a bit complicated, because they have protected the API
for that.

But see at the code below for how to workaround it. It should
also be noted that the default level seems to be 6 and that
it will be fine for most usage.

Arne

================================================

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.iutputStream;
import java.util.zip.GZIPOutputStream;

public class GZipFun {
public static void gzip(String infnm, String outfnm) throws
IOException {
FileInputStream is = new FileInputStream(infnm);
GZIPOutputStream os = new GZIPOutputStream(new
FileOutputStream(outfnm));
byte[] b = new byte[100000];
int n;
while((n = is.read(b)) > 0) {
os.write(b, 0, n);
}
os.close();
is.close();
}
public static void xgzip(String infnm, String outfnm, int level)
throws IOException {
FileInputStream is = new FileInputStream(infnm);
XGZIPOutputStream os = new XGZIPOutputStream(new
FileOutputStream(outfnm));
os.setLevel(level);
byte[] b = new byte[100000];
int n;
while((n = is.read(b)) > 0) {
os.write(b, 0, n);
}
os.close();
is.close();
}
public static void main(String[] args) throws Exception {
gzip("C:\\z.txt", "C:\\z.txt.gz");
for(int i = 0; i < 10; i++) {
xgzip("C:\\z.txt", "C:\\z.txt.gz" + i, i);
}
}
}

class XGZIPOutputStream extends GZIPOutputStream {
public XGZIPOutputStream(OutputStream out) throws IOException {
super(out);
}
public void setLevel(int level) {
def.setLevel(level);
}
}

 

[Chase Preuninger]

Thanks, the reason I want the level is that I'm writing a compression
program where the user gets to choose the level. I ended up however
just using a deflateroutputstream and passing it a custom deflater.

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