Okay, knowing that the bit patterns are byte aligned and the records are 384 bytes each makes thing much easier. The following program should do the trick quite efficiently.
#! perl -slw
use strict;
use bytes; ## Force byte semantic rather than (unicode) character sema
+ntics.
## Maybe unnecessary, but it won't hurt.
## Using ':raw' is (roughly) equivalent to using [binmode]
open IN, '< :raw', $ARGV[ 0 ] or die "$ARGV[ 0 ] : $!";
open OUT, '> :raw', $ARGV[ 1 ] or die "$ARGV[ 1 ] : $!";
local $/ = \384; ## Read file in 384 byte chunks.
## The only magic here is that
## a) we are reading the file in 384 byte chunks
## b) The unpack format extracts just the bits we wish to retain
## from the exact offsets we need.
## x2 - skips the xF4 x?? bytes
## A190 - returns the 190 bytes we need to retain
## x2 - skips the second xF4 x?? bytes
## A58 - returns the next 58 bytes.
## - the remaining 132 bytes from the buffer are discar
+ded.
while( <IN> ) {
print OUT unpack 'x2 A190 x2 A58', $_;
}
close IN;
close OUT;
In theory, the following 'one-liner' (I've wrapped it to save PM the bother) would also work.
If you have the time/patience/enthusiasm to try it, I'd love to know if it does.
You will have to twiddle the "s -v- 's issue if you're on a non-Win32 platform.
perl -C0 -mbytes -e"BEGIN{$/=\384}"
-ne"print unpack 'x2 A190 x2 A58', $_" <infile >outfile
Examine what is said, not who speaks.
"Efficiency is intelligent laziness." -David Dunham
"Think for yourself!" - Abigail
"Memory, processor, disk in that order on the hardware side. Algorithm, algorithm, algorithm on the code side." - tachyon
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