#! /usr/bin/perl

# Copyright (c) 2005 Michael H. Burkhardt, All rights reserved.
# 
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in the
#    documentation and/or other materials provided with the distribution.
# 3. All advertising materials mentioning features or use of this software
#    must display the following acknowledgement:
# 	This product includes software developed by Michael H. Burkhardt
# 4. The name of Michael H. Burkhardt may not be used to endorse or promote
#    products derived from this software without specific prior written
#    permission.
# 
# THIS SOFTWARE IS PROVIDED BY MICHAEL H. BURKHARDT ``AS IS'' AND
# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED.  IN NO EVENT SHALL MICHAEL H. BURKHARDT BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF

# SUCH DAMAGE.
use Getopt::Std;
getopts('eo:',\%opt);

# GLOBAL VARIABLES
my @mega;
my $megalen;
my $sow = "ttttttttttttttttaaaaaaaaaaaaaaaaiiiiiiiissssssssoooooooccccccmmmmffffppppwwwwbdeghjklnqruvxyz";
$sowlen = length($sow);
my $eow = "eeeeeeeeeeeeeeeeeeessssssssssssssdddddddddtttttttttnnnnnnnnyyyyyyyrrrrrrrooooolllllffffabcghijkmpqsuvwxyz";
$eowlen = length($eow);
$outfile = ( $opt{'o'} ) ? $opt{'o'} : "outfile.txt";

# USAGE
$USAGE = <<EOT;

Write random text data to a file. This is useful for

Usage: mkbigfile [-e] [-o OUTFILE] SIZE

where
-e       output random text that mimics English text in character frequency
-o FILE  output results to FILE (default is outfile.txt)
SIZE     is the minimum file size in MB (2048 MB max)

EOT

# MAIN PROGRAM
initMega();

$MB = 1048576;
$megs2write = shift(@ARGV) or die "$USAGE\n";
if ( -f $outfile ) { die "File exists\n"; }
if ( $megs2write > 2048 ) { die "Let's don't get crazy now.\n"; }

$bytes2write = int($MB * $megs2write);

print "Attempting to write ${bytes2write} bytes to ${outfile}\n";

open(OUT,">${outfile}");
$byteswritten = 0;
while ( $byteswritten < $bytes2write )
{
   $r = ( $opt{'e'} ) ? generateLineEng() : randomString();
   $byteswritten += length($r);
   print OUT $r, "\n";
}
close(OUT);

# INITIALIZE THE MEGASTRING
sub initMega()
{
   my @alphabet = qw/ a b c d e f g h i j k l m n o p q r s t u v w x y z /;
   my @freq = qw/ 82 15 28 43 127 22 20 61 70 2 8 40 24 67 75 19 1 60 63 91 28 10 24 2 20 1 /;
   my $i;
   my $j;

   for ( $i = 0 ; $i < scalar(@alphabet) ; $i++ )
   {
      for ( $j = 0 ; $j < $freq[$i] ; $j++ )
      {
         push(@mega,$alphabet[$i]);
      }
   }
   push(@mega,1,2,3,4,5,6,7,8,9,0);
   $megalen = scalar(@mega);
}

# generateLine()
# generate a line of text that looks like English
sub generateLineEng()
{
   $line = "";
   while ( length($line) < 80 )
   {
      if ( length($line) > 0 ) { $line .= " "; }
      $wordlen = int(rand() * 5) + 1;
      $line .= substr($sow,int(rand() * $sowlen),1);
      for ( $j = 0 ; $j < $wordlen ; $j++ )
      {
         $line .= $mega[int(rand() * $megalen)];
      }
      $line .= substr($eow,int(rand() * $eowlen),1);
   }
   return(substr($line,0,79));
}

# randomString()
# generate a line of random text 75 characters long
sub randomString()
{
   $rstr = "";
   for ( $i = 0 ; $i < 79 ; $i++ )
   {
      $rstr .= chr(32 + int(95 * rand()));
   }
   return($rstr);
}