Re: [Jython-users] File write and read

[Kent J. <ke...@td...>]

Lauri Lehtinen wrote:
> Setting to use the binary mode worked!
> 
> Does any one know why java variant of this in jython performs very poorly?

The first one is using unbuffered file I/O. The second one is copying one byte at a time. You need 
to combine the two - use Buffered[Input|Output]Stream *and* use a large copy buffer.

Kent

> 
> Here the basic java variant:
> ---
> from java.net import *
> from java.io import *
> def copy(filename):
>    bi = FileInputStream(File(filename))
>    bo = FileOutputStream(File(filename+".copy"))
>    b = [1000000]
>    while 1:
>        l = bi.read(b)
>        if l == -1:
>            break
>        bo.write(b)              bo.close()
>    bi.close()
>    return 1
>           if __name__ == "__main__":          i = raw_input("Give file:")
>    copy(i)
> ---
> That berforms only about 10kB/s, here one that uses buffers and performs 
> better:
> ---
> from java.net import *
> from java.io import *
> def copy(filename):
>    bi = BufferedInputStream(FileInputStream(File(filename)))
>    bo = BufferedOutputStream(FileOutputStream(File(filename+".copy")))
>    while 1:
>        l = bi.read()
>        if l == -1:
>            break
>        bo.write(l)              bo.close()
>    bi.close()
>    return 1
>           if __name__ == "__main__":          i = raw_input("Give file:")
>    copy(i)
> ---
> This performs about 600kB/s what isn't good at all, that should be much 
> better. I tried also by using static buffer size but that performed even 
> poorly for some reason. Why the performance is so bad?
> 
> Sincerely,
> Lauri Lehtinen
>