hi..

I have a binary data which is represented in data block and each of data block have a block header and data records. The block header have an variables to inform number of the records in the blocks either 2 or 3 records.

The block length for 3 records (including block header) is 890 bytes and block length for 2 data records (including block header) is 604 bytes.

Based on that, I want to append a DUMMY data for any block with 2 record in the blocks and make it as 3 blocks.

But, my program did not work as I plan and might be the offset variables is not calculated properly. Hopefully somebody could help me.. 

use constant BLOCKHDR => 28;
use constant BLOCKDATA => 4;
use constant CDRLENGTH => 286*3;
use constant BLOCKLEN  => BLOCKHDR + BLOCKDATA + CDRLENGTH;

if ($fname) {
        open (OUTPUT, ">$fname.tmp");
        open (DATA, "$fname");
        binmode DATA;
        $offset = 0;
        while (read(DATA, $data, BLOCKLEN, $offset)) {
                my $blockhdr = unpack "H*", substr($data, 0, BLOCKHDR)
+;
                my $blockdt  = unpack "H*", substr($data, BLOCKHDR, BL
+OCKDATA);
                my $cdrdata  = unpack "H*", substr($data, BLOCKHDR+BLO
+CKDATA, CDRLENGTH);

                my $total_record = hextoint(reverse_str(substr($blockd
+t,4)));
                print "TEST $offset\n";

                if ($total_record eq 3) {
                        #printf (OUTPUT "%s", pack("H*", $blockhdr . $
+blockdt . $cdrdata));
                        $offset += BLOCKLEN;
                        #printf ("%s\n", $blockhdr . $blockdt . $cdrda
+ta);
                        printf ("TEST1: $t_cdr - $offset - $blockhdr -
+ $blockdt\n");
                } else {
                        #printf (OUTPUT "%s", pack("H*", $blockhdr . $
+blockdt . $cdrdata . DUMMYCDR));
                        $offset += BLOCKLEN;
                        $offset -= 286;
                        printf ("TEST2: $t_cdr - $offset - $blockhdr -
+ $blockdt\n");
                }

        }

        close(DATA);
        close(OUTPUT);
} else {
        usage();
}

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In reply to How to read number of block in binary files? by bh_perl

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