Re: How to search in a file efficiently (=fast !) for a certain hex value ?

From:

Knute Johnson <nospam@rabbitbrush.frazmtn.com>

Newsgroups:

comp.lang.java.programmer

Date:

Sun, 06 Jan 2008 13:48:56 -0800

Message-ID:

<47814cc6$0$1606$b9f67a60@news.newsdemon.com>

Mark Thornton wrote:

Mark Space wrote:

Ulf Meinhardt wrote:

How can I efficiently (!) and fast search a file for a given hex
value (e.g. x'6A')
resp. how can I count the number of occurencies in a given hex value ?

Ulf

You could spawn several threads, each searching a specific region of
the file.

This loads more of the file into memory at once, loads up the IO
subsystem with IO requests so it can organize the requests and load bits

It might on some operating systems. To get this effect on Windows you
have to open the file multiple times. All the file read methods are
synchronized in Sun's current Windows implementation so that only one
read occurs at a time on a given
FileChannel/RandomAccessFile/FileInputStream. Rather disappointing.

Mark Thornton

Just for my curiosity is this documented somewhere or did you glean this
from the source code?

Thanks,

--

Knute Johnson
email s/nospam/knute/

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