Read and write of binary files

General Discussion Other

alepoc69

Read and write of binary files

in General Discussion • Other • 2 years ago

Hi.

I want to save on file a set of unbufferized records (1 int + 4 floats each). Their number ranges from half a million records to several millions.

To save these data I used FileOutputStream and writeInt/writeFloat but they are incredibly slow. Using a text file with the readable data instead and converting them when necessary is far faster. This puzzles me because I don't know anything about Java's file classes.

Can you redirect me on a snippet to solve this problem? I couldn't find anything in the forum.

Thank you

Alex

Replies(5)

anonuser2

Re: Read and write of binary files

2 years ago

Using a buffered output resulted in a much much faster file write for me. Try something like the following and see if it helps. I think there may be a simpler (faster?) way to write float arrays by using ObjectOutputStream, but this will work.

import java.io.DataOutputStream;
import java.io.BufferedOutputStream;
import java.io.FileOutputStream;
String fileName = ""; // fill in
try {
FileOutputStream fstream = new FileOutputStream(fileName);
BufferedOutputStream bstream = new BufferedOutputStream(fstream);
DataOutputStream dstream = new DataOutputStream(bstream);
// output your data here
for(int i = 0; i < 1000; i++) {
dstream.writeFloat(0.5);
dstream.writeFloat(0.5);
dstream.writeInt(2);
}
dstream.close();
}
catch(FileNotFoundException e) {
println("File not found exception: " + fileName);
}
catch(IOException e) {
println("IOException");
}

alepoc69

Re: Re: Read and write of binary files

2 years ago

Great!

The writing overload is now negligible.

Thank you very much for your help!

Alex

10dot6um

Re: Read and write of binary files

1 year ago

I was just trying anonuser2's sample on my Windows 7 box.

Unfortunately, no file gets written if I start the code from within processing. If I export the application and start the exe: the file gets written!

I tried it with settings "run as administrator" and with "xp sp3 compatibility"...

Any ideas?

Thanks and cheers!

PhiLho

Re: Read and write of binary files

1 year ago

The code above wrote a 12 KiB on my Windows 7 system.
I used an absolute path to be sure of where the file get written...

10dot6um

Re: Read and write of binary files

1 year ago

With an absolut path it works. I just tried it without a path and just with a filename...

Thanks a lot for helping!

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