#
# demonstrate the sysread (and read) problem and correction.  we really only need a small
# file to demonstrate the problem....
#

use strict;

my $test_file="sysread_test_file.txt";       # change name to test size/length differences

#
# create the test file
#
sub create_test_file
{
    return if -e $test_file;               # we do not want to create if it already exists....
    open TOUT,">$test_file";
    #
    # write a small file with an extra line missing the EOL.
    #
    for (my $line=0;$line<1000;$line++)
    {
        print TOUT "qwertyuiopasdfghjklzxcvbnm1234567890qwertyuiopasdfghjklzxcvbnm1234567890qwertyuiopasdfghjklzxcvbnm1234567890\n";
    }
    print TOUT "qwertyuiopasdfghjklzxcvbnm1234567890qwertyuiopasdfghjklzxcvbnm1234567890qwertyuiopasdfghjklzxcvbnm1234567890";      # no EOL!
    close TOUT;
}

sub test_while_variable
{
    my $linecount=0;
    open TIN,"<$test_file";
    while (<TIN>)
    {
        $linecount++;
    }
    close TIN;
    print "test_while_variable: $linecount\n";
}

sub test_block_read($)
{
    my $block_size=$_[0];
    open TIN,"<$test_file";
    binmode TIN;
    my ($data, $n);
    my $newlinecount=0;
    while ((read TIN, $data, $_[0]) != 0)
    {
        $newlinecount+=($data =~ tr/\012//);
    }
    close(TIN);
    print "test_block_read: $newlinecount\n";
}

sub test_fixed_block_read($)
{
    my $block_size=$_[0];
    open TIN,"<$test_file";
    binmode TIN;
    my ($data, $n);
    my $newlinecount=0;
    while ((read TIN, $data, $_[0]) != 0)
    {
        $newlinecount+=($data =~ tr/\012//);
    }
    close(TIN);
    $newlinecount++ if $data !~ /\012$/;
    print "test_fixed_block_read: $newlinecount\n";
}

sub test_block_sysread($)
{
    my $block_size=$_[0];
    open TIN,"<$test_file";
    my ($data, $n);
    my $newlinecount=0;
    while ((sysread TIN, $data, $_[0]) != 0)
    {
        $newlinecount+=($data =~ tr/\012//);
    }
    close(TIN);
    print "test_block_sysread: $newlinecount\n";
}

sub test_fixed_block_sysread($)
{
    my $block_size=$_[0];
    open TIN,"<$test_file";
    my ($data, $n);
    my $newlinecount=0;
    while ((sysread TIN, $data, $_[0]) != 0)
    {
        $newlinecount+=($data =~ tr/\012//);
    }
    close(TIN);
    $newlinecount++ if $data !~ /\012$/;
    print "test_fixed_block_sysread: $newlinecount\n";
}

#
# do the test
#

create_test_file;         # create the test file if not already present
test_while_variable;
test_block_read 4096;
test_fixed_block_read 4096;
test_block_sysread 4096;
test_fixed_block_sysread 4096;
exit 0;