#!/usr/bin/perl -w
use strict;

# This program will insert all or part of one
# file inside of another

use List::Util qw(min);

# check the arguments
if (@ARGV < 2 )
    {
    die "Usage: insert.pl infile outfile [ startin [ startout [ endin ]]]\n";
    }

# open the files
open ( FILOLD, '<', "$ARGV[0]" )
    or die "Can't open $ARGV[0] for reading.\n";

open ( FILNEW, '+<', "$ARGV[1]" )
    or die "Can't open $ARGV[1] for writing.\n";

# see what we want to copy
my $start = 0;
if (@ARGV >= 3 )
    {
    seek(FILOLD, $ARGV[2], 0)
        or die "Can't seek to position $ARGV[2] in $ARGV[0].\n";
    $start = $ARGV[2];
    }

if (@ARGV >= 4 )
    {
    seek(FILNEW, $ARGV[3], 0)
        or die "Can't seek to position $ARGV[3] in $ARGV[1].\n";
    }

my $end = (stat(FILOLD))[7];
if (@ARGV == 5 )
    {
    $end = min($ARGV[4], $end);
    }

my $bytes = $end - $start;

# do it
while ($bytes > 0)
    {
    read FILOLD, my ($buffer), min(1024, $bytes);
    print FILNEW $buffer;
    $bytes -= 1024;
    }

# close the files
close FILOLD;
close FILNEW;